Building a 100% Renewable Energy System Globally

The Technological Imperative for Securing a Liveable [sic] Future

Alan Reed

Synopsis: Technology is an extended tool that humanity can use for good or ill. How can we put technology in service of humanity and the global ecosystem to help secure a liveable [sic] future on Earth? We must transition to 100% renewable energy (RE) systems globally. This article describes how 100% RE systems can provide reliable energy globally 365×24 for power, heat, transport, and industry. We should reduce our energy consumption via energy efficiency and energy sufficiency measures in parallel so that we will need to build less RE capacity and can shut down fossil fuel combustion faster. In order to keep the world on track for the goals of the 2015 Paris Agreement, the 2022 reports from IPCC, IEA, and UNEP demand the deployment of as much RE as possible by 2030 along with energy efficiency/energy sufficiency measures. There is no feasible alternative to 100% RE for powering ecological living on Earth: Let’s make it our tool and perfect it together.

Table of Contents

A. Redirecting technology to support ecological living

We humans created techniques and tools for sustaining and thriving everywhere on Earth except Antarctica. We did this by acting as close-knit actively participating communities who gained and utilized knowledge about our local ecosystems. We respected our ecosystem as the basis for our livelihood, and we developed the necessary skills and tools. Gradually, however, we started regarding nature as a nearly infinite resource to be exploited, and we lost this respect. By developing technology to utilize the energy from ancient sunshine that was captured millions of years ago in fossil fuels, we mechanized and accelerated the destruction of all of Earth’s ecosystems, even Antarctica.

How can we take responsibility to solve the climate crisis? We must resurrect our ancient respect for the ecosystem. We must function as actively participating communities at local, regional, and global levels to rethink, redesign, and change how we generate and consume energy so that we live in harmony with the ecosystem. Many of these solutions will be non-technical and involve more ecologically friendly ways of living. Just as crucially, we need to redirect energy technology to be a tool that supports our ecological living on Earth.

That we must resurrect our ancient respect for the ecosystem, a respect which Indigenous peoples still have, and function as actively participating communities, was emphasized in connection with the 2022 IPCC report on climate change mitigation.¹ Diana Ürge-Vorsatz, a Vice-Chair for the report, explained:

We show that preserving ecosystems and preserving some of the land in its original ecosystem status is very important, in fact one of the most important options for how we can reduce emissions from our land. What we also show is that any option that we want to implement will have negative impacts on some consumer groups or some stakeholders or some parts of businesses or society. In order to manage these, the best option is to involve these stakeholders from the beginning of planning these actions. We emphasize that Indigenous peoples are especially important to involve; they can also provide special wisdom to us which we can benefit from when we plan these opportunities.²

B. Reducing our energy consumption

Reducing our energy consumption will enable us to stop using fossil fuels more quickly and reduce the amount of renewable energy generation capacity that is needed to decarbonize our energy supply. We need to pursue energy efficiency and energy sufficiency. Energy efficiency involves increasing the efficiency of energy usage for a given purpose, for instance, with energy-efficient appliances and lighting, and insulation of buildings. Energy sufficiency involves reducing or altering our activities that require the usage of energy. This could involve individual choices such as setting the thermostat for less heating or cooling and buying local food. Additionally, it could involve collective actions such as expanding public transportation.

The Low Energy Demand (LED) scenario created by Grubler et al.³ shows how energy efficiency and energy sufficiency measures together could reduce the global final energy demand by 40% by 2050 “despite rising population, income and activity.” The LED scenario shows a rich set of possibilities, some non-technological and some technological, for increasing the efficiency of end-use energy services, which would be key to addressing both the climate crisis and the United Nations Sustainable Development Goals.

The 2022 IPCC report provides a detailed investigation of reduction of consumption and energy demand, reaching the following conclusions:

The indicative potential of demand-side strategies across all sectors to reduce emissions is 40-70% by 2050 (high confidence). . . . The greatest Avoid potential comes from reducing long-haul aviation and providing short-distance low-carbon urban infrastructures. The greatest Shift potential would come from switching to plant-based diets. The greatest Improve potential comes from within the building sector, and in particular increased use of energy efficient end-use technologies and passive housing. 4

This would be energy efficiency and energy sufficiency in action.

C. The emergence of RE technology as a competitive solution

In 1990, there was a good basis for saying that renewable energy (RE) could not supply our global energy needs. Around this time, Germany and Denmark set up visionary policies to promote the development of solar and wind energy. These policies sparked the initial spike in market demand needed to fuel the industrialization of renewable energy technology. Many other countries including the US and China later followed with analogous measures to promote deployment of RE. In the meantime, the drive towards renewable energy is self-sustainable, as solar and wind energy are already cheaper than fossil fuel technologies in many places around the world, even without including the “externalities” that are the hidden cost to society of the fossil fuel pollution as well as carbon dioxide and methane emissions.

Today, there is ample basis to say that RE can serve as the basis for our global energy system. Research performed over the last fifteen years indicates that building 100% RE systems will not only be feasible but also economically viable and will provide increased energy security globally. The key is to take a multi-faceted approach that is tailored to the locally available resources and energy needs with participation of members of the local community in designing the solution. For instance, Christian Breyer,⁵ from Lappeenranta University of Technology (LUT) in Finland declared that “100% renewable energy is the core of any climate crisis survival strategy, while reducing air pollution, supporting a peaceful world, based on practically unlimited, and low-cost and sustainable energy for all.”

D. Building reliable 100% RE systems everywhere on Earth

For most local areas of the world, the primary energy sources for a 100% RE system will be solar photovoltaic (PV) and wind energy. Solar is generally by far the most available energy source in the “sunbelt” between thirty-five degrees latitude north and thirty-five degrees south of the equator where three-fourths of the world’s population lives, whereas wind becomes more available in the higher latitudes. In some areas with rich hydropower and/or geothermal resources, these resources may be primary energy sources as well. Concentrating solar-thermal power (CSP) is an option in hot, sunny regions, but globally will make a minor contribution compared to solar PV. Smaller contributions at suitable locations may also be made by ocean power driven by tides or waves. These are all examples of renewable energy harvesting.

Of these sources, solar PV, wind, run-of-river hydro, and ocean energy are variable or intermittent and need to be balanced by other sources. On the other hand, reservoir hydropower, geothermal, and CSP are at least partially dispatchable; thus, their power production can be ramped up or down according to the needs of the overall electrical grid, within certain limits: The rate of water released from a reservoir can be varied for dispatchable power. The heat collected by CSP can be utilized for generating electricity for dispatchable power after sunset, and thus CSP can be very useful for balancing the grid in the evening hours. The conversion of geothermal heat to power can also be dispatched to some degree. Note that geothermal and CSP can also be utilized directly for heat as well. One caveat: There are significant limits to the environmentally responsible expansion of reservoir hydropower since the natural flow of rivers is interrupted and landscapes are flooded.

In addition to harvesting RE from the above-mentioned sources, RE power and heat can be generated by combustion of locally available biowaste, biogas, or biofuels. Biowaste consists of agricultural wastes such as residues, biomass, or animal waste that would otherwise need to be disposed of. Biogas consists primarily of methane produced by biological decomposition that would otherwise escape as a greenhouse gas. The amount of available biowaste and biogas, once all local sources are being collected, will be relatively constant from year to year and cannot be further expanded; it should not be exported, but used as a local resource. By contrast, biofuels are produced from intentionally grown crops. Two major caveats about biofuels: (1) We should avoid competition for land between bioenergy crops and food crops. If bioenergy is utilized, the bioenergy crops should be grown on land that is not suitable for food production. (2) Many types of biofuels are neither energy efficient nor environmentally efficient when their entire production and usage lifecycle is considered. Indeed, some types of energy crops might be net emitters of CO2 when land usage changes and the balance between plant growth and plant decay in the fields are considered—those energy crops cannot be regarded as fully renewable fuels. We will return to the topic of bioenergy near the end of this article.

How do we balance the grid, so that the power supplied across the grid equals the power demand on a moment-to-moment basis? There is a rich menu of capabilities that can be exploited, whereby the exact mix of these will depend not only on the local energy resources but also the energy consumption needs. Strategies are needed to balance the grid at four timescales⁶:

1. Sub-seconds to minute: Grid-forming inverters that can regulate system voltages and frequencies through local decentralized control⁷; synchronous condensers that provide reactive power and inertia; batteries providing synthetic inertia; and pumped hydro for mechanical inertia and rapid balancing in tenths of seconds.
2. Hours to days to weeks: Electrochemical storage (many types of batteries); mechanical storage (pumped hydro, gravity based, compressed air, liquid air, liquid CO2); thermal energy storage (multiple types); demand-side management; additional flexibility via coupling with other energy sectors (described below); and interconnections over larger areas to smooth out local weather.
3. Seasonal: Balance solar with wind, which generally have opposite seasonal variations; energy sector coupling; and combustion of renewable fuels, including biomass, biogas, biofuels, and synthetic fuels produced via “Power-to-X” (described below).
4. Interannual: The variability of solar generation from year to year is low, and the impact of climate change on solar generation is expected to be low. However, reservoir hydroelectric power and nuclear fission power can be significantly affected from year to year by droughts, as happened in 2022.

Of the four timescales, the only challenge that has high complexity is the seasonal timescale, especially in the case of higher latitude locations. At lower latitudes, where most of the world’s population lives, the seasonal variations of solar energy are much less. Forecasting capability is an essential aid in advance planning for balancing the grid on these timescales, namely a sophisticated daily/hourly prediction of energy generation and demand according to local seasonal conditions and detailed weather forecasting.

What about energy needs for heat and transportation? If the end application is heat, there is another way to ensure 365×24 availability besides converting stored power back to electricity and using that to produce heat: Energy from renewable electricity can be stored in the form of thermal energy storage (TES). When heat is needed at a later time, heat can be extracted directly from TES at very high efficiency compared to converting the heat energy from TES back to electricity and then using that electricity to produce heat. If the end application is transportation, there are two possibilities: For electric vehicles, RE is stored in the vehicle’s batteries via charging for later use. For vehicles with combustion engines, they can be powered with renewable fuels, which are produced from RE via Power-to-X, or from biomass or from bioenergy crops, as will be described in later sections. As will be explained further below, coupling the electricity energy sector with the heat and transportation sectors will make it easier to achieve 100% renewable electricity. Each energy sector will benefit from the coupling.

Further, local energy efficiency and sufficiency programs to enable community participation will be indispensable for achieving success. Without close community participation, 100% RE projects are at risk of failure due to insufficient buy-in. Reduction of energy demand via efficient buildings and appliances is much cheaper than building additional RE capacity to power inefficient energy usage. Even more importantly, the design of the local 100% RE system will best fit the needs of the local population if they provide detailed input about their needs and the locally available resources relevant for 100% RE system components. 100% RE should not be experienced as a huge gorilla on our backs, but as a community project to most efficiently provide the energy needed for the needs of the local population.

Without community energy efficiency and sufficiency programs, increases in energy demand may outstrip available RE even after large amounts of RE are added, requiring continued reliance on fossil fuels to make up the difference. This makes clear that there must be a locally agreed upon plan for shutting down fossil fuel energy as the RE system is expanded.

Let us summarize this catalog of components and measures for a 100% RE system to meet instantaneous energy demand:

Components of a 100% renewable energy system plus accompanying measures
Energy Harvesting	Solar PV: on land, above water; Wind: onshore, offshore; Hydropower: run-of-river, reservoir; Geothermal; Concentrating Solar-Thermal Power (CSP); Ocean (tide, wave)
Energy Storage	Short-term: Batteries (many types), Pumped Hydro Energy Storage Medium-term: Batteries, Mechanical Storage, Thermal Energy Storage, Renewable Fuels Long-term: Renewable Fuels, including local Hydrogen Gas Storage Thermal Energy Storage (TES): Extract heat directly from TES for heat applications
Renewable Fuels	Renewable fuels can be used for generating power or heat, or for transportation. Hydrogen and other synthetic fuels: Produced via excess solar/wind electricity. Biowaste and Biogas: Wastes from agricultural processes. Biofuels: Produced from crops; see caveats in text.
Demand Flexibility	Measures to shift energy demand for consumers, businesses, institutions to timeframes when more energy is available, to better match to energy supply.
Sector Coupling	Coupling energy demand between the electricity, transport, heat, and industry sectors, enabling opportunities for synergies and load balancing.
Grid Stability Tools	Technology and controls for balancing the grid on a sub-second timescale which are redesigned for handling variable RE instead of conventional power generator turbines.
Forecasting	Daily/hourly prediction of energy generation and demand as aid in advance planning.
Energy Efficiency & Sufficiency	Concerted energy efficiency and sufficiency programs must run in parallel to the RE buildout, especially efficient and sufficient buildings and appliances; this reduces the amount of RE capacity needed.
Community participation	100% RE is not a “pure technology” change-out and requires active local participation and input in the planning/design process and the stages of roll out.

Matching energy demand and supply on the electrical grid is a complex task, and how to do this for a 100% RE system is a field of active research. Reaching such a goal for any local or regional electrical grid can only be achieved with detailed advance planning and multiple years of implementation during which, on a step-by-step basis, RE steadily increases and fossil fuel sources steadily taper to zero. An essential part of the planning process involves simulations of the energy system taking into account weather variations that will affect both energy demand and solar/wind energy production.

To meet this challenge, the National Renewable Energy Lab (NREL), together with the Department of Energy’s Office of Energy Efficiency and Renewable Energy, has set up a platform called Advanced Research on Integrated Energy Systems, or ARIES.⁸ The ARIES research platform has been built to “match the complexity of the modern energy system” to help “understand the impact and get the most value from the millions of new devices—like electric vehicles, renewable generation, energy storage, and grid-responsive building technologies that are being connected to the grid on a daily basis.” NREL has physically set up and demonstrated a 100% RE electricity system at one of its main campuses and showed that it can be started up from an electrical blackout situation.⁹ In turn, these real-life demonstrations with modern equipment inform the model building on their supercomputer.

In 2024, the island of Maui is likely to become the world’s first interconnected electric transmission grid that will run for longer periods on predominately solar/wind-powered 100% RE on an instantaneous basis. NREL is developing and validating tools that will ensure 100% reliability of the grid on multiple timescales.¹⁰ NREL modelled Maui’s entire transmission system including transformers, lines, solar/wind/storage systems, and inverters at a sub-second scale. They found several technical options for maintaining grid stability as the system approaches 100% RE that worked well in the simulation. These simulations were then augmented by setting up a system with real hardware at an NREL campus and replicating the conditions that the energy system in Maui will experience. High levels of wind and solar change the dominant physics of the grid regarding reliability and the controls needed to stabilize the grid down to a sub-second level. Given this, it is not surprising that many grid operators view RE as uncontrollable. NREL, based on its research, pushes back against this view: “One thing is certain, however: Renewables alone can provide the services necessary to maintain the grid. Operators just need the tools to properly manage them.” Providing those needed tools for managing stability of a 100% RE grid is part of NREL’s work.

Hawaii and NREL are collaborating on how to transition the electrical grid of each island to 100% RE with the help of the ARIES platform mentioned above. In 2021, Kauai achieved 69.5% renewable electricity,¹¹ Maui 50%, Hawaii 60%, and Oahu 33%.¹² Even though Kauai had the highest percentage of RE, it also led the State of Hawaii in reliability for the third straight year in 2021 with a system availability of 99.985%. From 2018 to 2020, the electric rates in Kauai dropped by about 10% while the amount of RE increased from 43% to 67%. In 2021, oil prices skyrocketed but the Kauai Island Utility Cooperative (KIUC) was able to achieve substantial stability of electric rates with an increase of only 5% due to KIUC’s long-term power purchase agreements for RE. Kauai’s electricity generation mix was 30% utility solar, 15% customer solar, 14% hydro, 11% biomass, and 30% fossil fuel. For Oahu/Hawaii/Maui, served by Hawaiian Electric, the RE sources were 45% customer-sited, grid-connected solar and wind, 22% utility wind, 12% utility solar, 12% biomass, 6% geothermal, 2% biofuels, and 1% hydro. All Hawaiian islands have a healthy mix of customer-owned and utility-owned solar PV and wind energy plus other RE sources.

The City of Los Angeles has set a goal of 100% RE electricity by 2045 including electrifying the building and transportation sectors. Under the direction of the Los Angeles Department of Water and Power (LADWP), NREL, along with two universities, produced the “Los Angeles 100% Renewable Energy Study” (LA100).¹³ The study involved three years of work and over one hundred million simulations to evaluate how the LA power system could evolve. It involved LA community members every step of the way. The model included every building in the city. A priority was placed on reliability of the power grid even in the face of extreme events, such as heat waves or wildfires. One big constraint for the study was the requirement that LADWP be self-sufficient for power generation and not be dependent on energy imports to maintain reliability. LADWP, the largest municipal power company in the United States, serves more than four million residents.

Multiple pathways for achieving reliable, 100% renewable electricity supply are identified by the LA100 study. Between 69% and 87% of LA’s energy would be provided by solar and wind. A key element for maintaining reliability would involve renewably produced and stored fuels that can provide essential generation capacity within a few minutes and run for hours or days. The study concluded that 100% RE can be achieved without negative economic effects for LA. If LA follows the plan, significant emissions reductions of 76% or more can be achieved by 2030.

Environmental justice is a key concern for the study, which devotes one hundred pages to the steps that should be taken to ensure a just transition and the potential benefits for disadvantaged communities: “All communities will share in the benefits of the clean energy transition—but improving equity in participation and outcomes will require intentionally designed policies and programs.” It also includes “customer-oriented actions” that complement the transition to RE electricity: (a) energy efficiency which among other benefits, lowers energy burden for low-income residents; (b) greater electrification reduces pollution, contributes to higher public health (especially for low-income neighborhoods), further lowers greenhouse gas emissions, and helps to reduce the electricity rates; and (c) customer demand flexibility, which supports electrical reliability and helps contain the costs of the transition to RE and the expanded electrification.

While the study is specifically tailored for Los Angeles, there are many insights in it that could apply in a qualitative manner to other large cities or local regions. Having performed such a “brute force” simulation, NREL is now considering what simplifications of the modelling methods could be made in future studies to obtain useful results more rapidly.

E. Denmark’s path towards 100% RE involves sector coupling and intense collaboration

Denmark met 49.9% of its electricity consumption by wind and solar power in 2020, up from 40% in 2015 and less than 20% in 2010.¹⁴ Since another 14% of Denmark’s electricity in 2020 was generated from biomass, the country’s electricity has already reached 64% RE. Notably, for the first time on September 15, 2019, wind power exceeded electricity demand by 30% in Denmark for twenty-four consecutive hours. Importantly, Danish security of electricity supply was “in top European class” again in 2020, remaining at an availability rate of 99.996%, a level that has been maintained for Denmark since 2008.

Denmark is targeting 100% electricity from renewables by 2030. Energinet, the Danish transmission system operation (TSO) responsible for the grid, explains that there are two keys to achieving this. First, the electricity grid needs to be modernized and expanded, as more and more electricity is being generated by decentralized facilities. They have detailed plans for how to do this. The second key is that 100% RE “can only be achieved with a comprehensive sector coupling.” Quoting from another report,

Leaders at Energinet explain the necessity of intense collaboration within Denmark as well as globally¹⁵:

This is the “can do” collaborative and innovative spirit that is needed to set up a 100% RE system, and which truly regards the climate crisis as a crisis.

F. RE can power our global energy needs across all sectors

The electricity sector only accounts for around 20% of global final energy usage. As shown above, major strides are being made towards 100% RE electricity. RE penetration in other sectors, such as power, heat, transport, and industry has proceeded more slowly. This raises the question of how do we go from 100% RE electricity to a 100% RE system covering all sectors of energy needs? There are three key principles to accomplishing this:

1. Electrification: Electrification of the heat, transport, and industrial energy sectors where possible, and ensuring that these are powered with 100% RE electricity.
2. Sector coupling: Coupling the power, heat, transport, and industrial sectors together via Power-to-X, energy storage, and other measures. This accomplishes two main purposes: (a) providing RE for the portions of the heat, transport, and industrial sectors that cannot be electrified; (b) increasing the overall efficiency, reliability, and affordability of the resulting 100% RE system, which will also decrease the cost of providing 100% renewable electricity at all times of the day and year.
3. Primary energy utilization efficiency: Without any change in energy usage profile, primary global energy demand is cut in half due to the much higher efficiency of an energy system based on RE and maximum electrification vs. our current energy system based primarily on the combustion of fossil fuels.

LUT University in Finland and the Energy Watch Group from Germany published a study in 2019¹⁶ with a further exposition provided in 2021¹⁷ (the EWG/LUT study, also called the LUT model) showing that a 100% global RE system can be accomplished by 2050—the study covers the power, heat, transport, and desalination sectors. It has several key features that are environmentally sound: (a) no usage of energy crops for biofuels which would compete for agricultural land with food production or interfere with ecosystems; (b) no building of large new hydropower that might have negative environmental effects; and (c) no dependence on underground storage of CO2.

The modelling included the existing renewable energy potential and technologies, and the requirement of a secure energy supply at every hour throughout the year. Least-cost optimization was performed among the renewable energy sources available in each local region for each hour of the year 365×24 based on historical weather information. The resulting model energy system in 2050, with zero CO2 emissions, is slightly lower in overall energy cost in 2050 than the current fossil-fuel based global energy system. It involves a global mix of primary energy generation of 69% solar energy, 18% wind power, 3% hydropower, 6% bioenergy from wastes and residues, and 2% geothermal energy. Thus, the global energy system overall would be 87% solar and wind; for electrical power alone, it would be 96% solar and wind.

Moreover, it would be a fair, inclusive, and just energy transition. Renewable energy would be produced almost exclusively from decentralized local and regional generation. This reduces energy supply dependencies between countries and ensures the most reliable energy supply in the face of possible trade or weather disruptions. Further, there is a significant increase in energy-related jobs globally compared to today’s fossil-fuel energy system. This transition eliminates international energy dependencies, mainly because renewable energy resources are well distributed across the world. As a result, it will be easier to mitigate international energy resource-based conflicts and find paths towards peace and increased welfare globally. This opens prospects for greater economic activity in every region. Alone the phase-out of biomass for cooking will drastically improve health in least developed and developing countries. The Global South would experience a major uplift in their living standards since these countries have excellent solar conditions year-round. This will present to the Global South the opportunity to leapfrog developed countries in achieving a sustainable future.

Not just the EWG/LUT model, but other studies using different models and assumptions come to a similar conclusion. An Oxford University study by Way et al.¹⁸ published in 2022 concludes, “Compared to continuing with a fossil fuel-based system, a rapid green energy transition will likely result in overall net savings of many trillions of dollars—even without accounting for climate damages or co-benefits of climate policy.” Their method was based on probabilistic cost forecasting methods that they validated by testing more than fifty technologies. They emphasize that a rapid transition to 100% RE by 2050 “is likely to be beneficial, even if climate change were not a problem,” with 80% probability of being cheaper than continuing with a fossil fuel-based system and savings of $5 to $15 trillion. Adding in a social cost of carbon, the total expected savings by 2070 for a rapid transition by 2050 to 100% RE are estimated at $31-$255 trillion. From their analysis, they conclude that “a greener, healthier, and safer global energy system is also likely to be cheaper.”

How would the balancing of electricity and heat needs be provided reliably by 100% RE systems in practice? There are two main carbon-neutral technologies in usage today for short-term balancing of the grid: Large-scale pumped hydro with typical discharge times of four to sixteen hours, which has geographical limitations since two bodies of water at different elevations are needed, and lithium-ion (Li-ion) batteries with typical discharge times of four to eight hours. In optimal operation, Li-ion batteries deliver power (kW) and energy (kWh) as a bundle, preventing the flexibility of independently scaling power and energy capacity, and become too expensive for longer durations. By contrast, long duration energy storage (LDES), overcomes these limitations by providing long duration energy services economically, whereby power and energy capacity can be independently scaled. LDES is competitive for durations longer than eight hours: electrochemical storage (aqueous flow batteries, metal anode batteries, hybrid flow batteries), mechanical storage (novel pumped hydro, gravity based, compressed air, liquid air, liquid CO2), TES (sensible heat, latent heat, thermochemical heat), and chemical storage (production of renewable fuels via Power-to-X). Li-ion batteries and traditional pumped hydro storage are not included in LDES. Depending on the specific technology, these are suitable for eight to twenty-four hours to days to weeks and, in the case of chemical storage, for months or multiple seasons. For added flexibility, many forms of LDES allow the charging power level and method to be designed independently of the discharging power level and method. Some of these technologies, such as compressed air energy storage (CAES), latent heat based on aluminum alloys, and hybrid flow batteries are already commercially deployed. Others such as liquid CO2 and liquid air are in the pilot phase of development; additional ones are in the R&D stage. Compared to traditional pumped hydro storage, LDES has a dramatically smaller land footprint.

How a globally deployed landscape of LDES technologies could work in practice is being researched and modeled in detail by the LDES Council,¹⁹ which was formed at COP26 in November 2021. The council currently consists of sixty-four companies who are technology providers, low-carbon energy system integrators, equipment manufacturers, and customers from the industrial and services sectors. The LDES Council projects that by 2040 LDES technology deployment will potentially store up to 10% of all electricity consumed globally (in the United States alone up to 15%) and avoid 10-15% of today’s power sector emissions. They explain how LDES will play a crucial role in decarbonizing the power sector at a manageable cost: LDES deployment in the United States could reduce the cost of decarbonizing the power system by about $35 billion annually by 2040. By optimizing the usage of existing grid lines, LDES could significantly reduce the buildout of transmission and distribution lines. Renewable power-purchase agreements (RE PPAs) could use LDES to ensure that businesses will be able to procure 100% renewable electricity. LDES could also support isolated grids on islands and support large power users at remote locations.

With TES, net-zero heat systems could be accomplished globally: heat from TES would be extracted directly as heat without first converting it back to electricity. In the LDES Council’s model, TES for heat storage plus LDES for power storage has the potential to grow in total capacity by 2040 to eight terawatts to support a global net zero power and net zero heat system. The total estimated capital investment needed by 2040 for this to occur is $3.6 trillion. Since the LDES/TES capacity would reduce overall energy system costs by up to $540 billion per year, this investment would pay for itself within about eight years. The details of how LDES and TES would work are explained in the LDES Council reports, which strongly support the feasibility of 100% RE systems and explain what needs to be done to promote the development and deployment of these technologies. At COP 27, the LDES Council made a presentation on net zero heat. They explained that there are a number of use cases for installation of LDES and TES that already have a high positive return on investment. For instance, they presented use cases for TES deployments in Europe that could be implemented by the winter of 2023­2024 to reduce dependency on natural gas for heating, which is needed in view of Russia’s war on Ukraine. Thus, LDES/TES could make big contributions to energy security, as well as reduce the costs of the energy system and accelerate decarbonization.

A key factor in the feasibility and cost-effectiveness of the global 100% RE system is electrification, which leads to huge energy efficiency gains—overall by a factor of two over the current fossil fuel system. How? The basic principle becomes obvious, for instance, when you compare an electric car to a gasoline car: An electric car can accelerate immediately and efficiently via flow of electrical energy to an electric motor. The gasoline car must first combust its fuel and convert as much of the resulting energy as possible via a much more complex drive train into mechanical motion of the wheels, while losing most of the energy of combustion in the form of heat. Thus, electrical energy can be converted into mechanical motion much more efficiently compared to thermal energy from combustion of fossil fuels.

The enormous efficiency gains via electrification are explained in a white paper by the German Federal Ministry for Economic Affairs and Energy²⁰: Fossil-fuel condensing power stations are only about 40% efficient on average—60% of the fossil fuel energy content goes to waste. While heating with natural gas has an efficiency of about 85%, conversion to electric heat pumps powered by RE can lead to an efficiency of 340% through the capture of ambient heat. Internal combustion engines convert only about 25-40% of the energy of the fuel into vehicle propulsion, compared to 80% energy efficiency for electric mobility. (See Figure 18 from the white paper below.)

Figure 18 in An Electricity Market for Germany’s Energy Transition: White Paper by the Federal Ministry for Economic Affairs and Energy, Berlin, July 2015.

The EWG/LUT study authors emphasize that there are four “key enabling technologies for survival of human civilization” that enable the complete phase-out of fossil fuels; we have added LDES to the third item:

Key technologies that enable the complete phase-out of fossil fuels
Solar PV	Accessible everywhere – no resource conflicts – highly modular technology
Wind Energy	Accessible in all world regions – no resource conflicts – modular technology
Li-ion batteries, LDES, and Electric Vehicles	Li-ion batteries and LDES convert RE into flexible 24×7 technology – highly modular technology; electric vehicles will become least-cost mobility solution
Power-to- X	Covering demand for gaseous and liquid fuels as well as chemical feedstock

Of these four enabling technologies, Power-to-X is less well known and deserves close attention. It involves using renewable power to produce a wide variety of fuels, as well as feedstocks for chemical, metals, and agricultural industries, utilizing only air and water:

• Air: The carbon incorporated in the fuels/feedstocks is obtained from air via direct air capture (DAC), and the nitrogen is obtained via nitrogen fixation from air using the Haber-Bosch process.
• Water: The hydrogen incorporated in the fuels/feedstocks is obtained from water. As water source, seawater, after desalination using RE, can be utilized.

Some of the main fuels and chemical feedstocks that can be produced with renewable power, as possible values of “X” in “Power-to-X,” are shown below.

Molecule/Substance and Usage	How produced from renewable power
Hydrogen (H2) – fuel or feedstock	Electrolysis of seawater
Ammonia (NH3) – fuel or feedstock	Electrolysis of seawater + Nitrogen fixation from air via Haber-Bosch Process
Methane (CH4) – fuel or feedstock	Electrolysis of seawater + CO2 from DAC + Methanation reaction
Gasoline, Diesel, Marine Fuel Oil, Jet Fuel – fuel; Olefins, Naphtha, Waxes – feedstock	Electrolysis of recycled water + CO2 from DAC + conversion of CO2 to CO + Fischer-Tropsch Process
Methanol, Dimethyl Ether, Ethanol – feedstock or fuel; Acetic Acid – feedstock	Electrolysis of seawater + CO2 from DAC + various chemical reaction processes

All these fuels are carbon neutral: Burning hydrogen fuel produces water. Burning ammonia fuel produces water and nitrogen gas. Burning carbon-based fuels produced by RE and various chemical reactions produces CO2 and water, but these fuels are carbon-neutral because the carbon released in the burning of the fuel was previously captured from the air. Furthermore, there is an option for flexible seasonal energy storage by storing the energy from excess renewable electricity in the form of fuels that can later be utilized for energy in a different season when less solar or wind energy is available. Note that some of these fuels, for instance methane, could also be produced as biogas from fermentation of agricultural waste, including from farm animals, or plant biomass that would otherwise be waste that needs to be disposed of.

G. Running shipping, aviation, and heavy industry on RE

For transport, lighter vehicles such as cars and small trucks can be electrified and powered using renewable electricity. Smaller boats and airplanes travelling shorter to medium distances could also be electrified. However, there will be a breaking point where the usage of batteries becomes impossible, impractical, or too expensive due to the lower energy density compared with gaseous and liquid fuels produced via Power-to-X or as biofuels. This might be the case for larger land vehicles and mobile equipment operating in areas without access to charging stations. This would be the case for long-haul shipping and aviation where energy-dense fuel is required. Exactly which renewable fuels would be best for which types of vehicles is the subject of current debate and research. For instance, some options for long-distance shipping are ammonia, methanol, hydrogen, and carbon-based synthetic fuels. In the EWG/LUT study cited above, heavy transport, shipping, and aviation are modelled using Power-to-X fuels according to a least-cost model that includes the full costs of producing these fuels, including the direct air capture of CO2 as carbon source and usage of seawater as hydrogen source.

The world’s leading ocean shipping company Maersk, which emitted thirty-four million tons of CO2 from about seven hundred ships in 2020 and aims to be carbon-neutral by 2050, has decided upon green methanol for its future fuel. In December 2021, Maersk announced²¹ the design for eight methanol-powered container ships on order that will be going into operation starting early 2024. The new design will be 20% more energy efficient per transported container; together the eight ships will save about one million tons of CO2 emissions per year. Now the challenge is to source the ten thousand tons of green methanol needed annually to power each of these ships. Already there is an agreement with the company European Energy²² to produce the fuel for the first ship in 2024 through a Power-to-Methanol plant in Denmark: wind/solar energy will power water electrolysis, producing hydrogen that will be combined with biogenic CO2 from biowaste to create methanol. This will be done utilizing some of the excess renewable electricity available in Denmark that Energienet previously spoke about exploiting for Power-to-X and energy sector coupling.

Transformation of heavy industry is a different matter altogether. For instance, in the production of steel and cement, there is not only a release of CO2 due to the burning of fossil fuels to provide the intense heat needed, but also a release of CO2 due to the chemical reactions currently used to produce steel and cement. Thus, by simply replacing the energy input by RE instead of fossil fuels, the current industrial processes will still release vast quantities of CO2. The production of each ton of steel results in about 1.8 tons of CO2 emissions; in the aggregate, the production of steel accounts for 7­9% of all fossil fuel emissions.

The push for net zero heavy industry is especially strong in Europe. The European Union²³ (EU) as well as the non-EU countries United Kingdom, Switzerland, and Norway have official policies of achieving net zero by 2050, with action plans being formulated to guide the implementation. The EU has published a “Masterplan for a Competitive Transformation of EU Energy-intensive Industries Enabling a Climate-neutral, Circular Economy by 2050,”²⁴ which identifies detailed steps towards achieving this transformation.

For steel, the key will be the decarbonization of the reduction of iron ore to form iron metal. Currently, carbon sources in the form of coal, coke, or natural gas are used to react with the oxygen bonded within iron ore, producing iron metal and CO2. To avoid the release of CO2, R&D work is underway on an alternative that will utilize renewable hydrogen, so that the hydrogen reacts with the oxygen bonded within the iron ore to produce iron metal plus water. If adopted, this would involve significant redesign of the entire steel-making process. The German steelmaker Thyssen-Krupp, which has set the goal of becoming carbon neutral by 2050, is building an electrolysis plant that will provide fifty thousand tons of hydrogen per year, enough to supply its first plant for direct reduction of iron ore with hydrogen.²⁵ Using this process, the company could by 2050 avoid emissions of twenty million tons of CO2 per year, or about 2.5% of Germany’s CO2 emissions. The Swedish steelmaker SSAB, in collaboration with the iron ore producer LKAB and the energy firm Vattenfall,²⁶ aims to produce and sell the world’s first fossil-free steel in 2026.²⁷ They are currently building a pilot plant. SSAB is also collaborating with Volvo on fossil-free steel for the automotive industry.²⁸

In cement production, about half of the CO2 released occurs in the calcination process where limestone (CaCO3) is heated under low oxygen conditions and decomposes into lime (CaO) and CO2. In this case, CO2 is a non-energetic emission as its atoms were originally contained in the limestone rock, instead of coming from fossil fuels. There are two approaches, or a combination of these two approaches, that can be pursued to decarbonize these CO2 emissions in cement production: (a) capture the CO2 and reuse it for other industrial processes, such as creating other materials or carbon-based fuels (Power-to-X) or store the CO2; and (b) change the chemistry of cement production—there are multiple initiatives in this direction.

The other half of the CO2 emissions released in cement production comes from fossil fuel inputs for energy and heating. Possible alternatives to fossil fuels are waste or biomass as fuel, green hydrogen as fuel, or switching to renewable electricity as the heat source. One cement manufacturer with active development towards green cement and a 2050 target to be carbon-neutral globally is German-based Heidelberg Cement.²⁹ Its subsidiary Hanson in the United Kingdom has successfully operated a cement kiln at Ribblesdale using a mix of net zero fuels as part of a world first demonstration project using hydrogen technology.³⁰ If implemented for the entire site, this technology could save 180 thousand tons of CO2 emissions at Ribblesdale alone, compared to the current usage of coal.

What are the prospects for the chemical industry? The world’s largest chemical company BASF announced in 2021 its plan to reduce CO2-equivalent emissions by 25% in 2030 compared with 2018 levels and to achieve net zero emissions by 2050.³¹ If accomplished, this would result in the elimination of twenty-two million tons of CO2-equivalent emissions per year. Key technologies being developed by BASF to eliminate these emissions, some in collaboration with external partners,³² include the following: (a) electrically heated steam cracker running on RE—the furnace runs at 850⁰C and converts naphtha to raw olefins; (b) methane pyrolysis,³³ an alternative means to produce hydrogen gas that uses 80% less electricity than water electrolysis; (c) utilization of green hydrogen for production of ammonia and other chemicals; (d) “Power-to-Steam” using RE to produce the steam needed as heat input for chemical processes; (e) electric heat pumps and steam compressors to use waste heat from chemical plants for steam production on a scale that has never been realized before; (f) off-shore wind energy—partnerships with energy companies for building and operating gigawatt scale wind farms in the North Sea³⁴ as the source for green electricity for electrification of chemical production in Germany and for production of green hydrogen; and (g) circular economy—renewable-based and bio-based feedstocks, recycled-based feedstocks, enable recyclability and/or biodegradability.

Another German chemical company, Covestro, is now offering the world’s first climate-neutral grade of polycarbonate, an engineering plastic, using renewable electricity.³⁵ For polymer production in Germany and China, Covestro is gradually replacing fossil feedstock with alternative feedstock consisting of plant waste, residual fats and vegetable oils, and recycling of CO2 as a raw material.³⁶ As a further step towards the circular economy, the company also recently started selling recycled polycarbonate.

Many efforts to decarbonize heavy industry and to develop Power-to-X capabilities that could support these efforts are currently at pilot plant stage or need to be scaled up and reduced in cost. Billions of dollars of investment and continual progress is occurring not only in Europe but also in North America, Asia, Australia, South America, ³⁷ and Africa.³⁸ What is still holding back even more rapid investment and development of Power-to-X and the decarbonization of industry is the increased costs of many of these technologies for industrial processes compared to the use of fossil fuels, so that it is hard for companies to go green yet stay in business. For instance, the production of some commodity chemicals might cost 20% more using RE vs. fossil fuel energy. Therefore, an even playing field is needed globally, for instance recognizing the harmful externalities of fossil fuels via pricing for carbon emissions instead of de facto economically rewarding companies and countries who produce CO2 emissions. The second bottleneck is the availability of renewable electricity and green hydrogen at the scales needed for industrial plants, which explains why some industrial companies are signing contracts for large-scale wind and solar energy.

In summary, it is true that in contrast to the case of the electrical grid where we already have the technologies developed we need to provide 100% renewable electricity, we still need to develop many technologies to transition shipping, aviation, and heavy industry to 100% RE. However, we are making progress towards solutions. In many areas, R&D is proceeding, including through many pilot plants in planning, under construction, or in early operation. This R&D work needs to continue and be intensified. If there are some industries that cannot be decarbonized, we should then find alternatives to these industrial activities or shut them down.

H. Critical metals availability will not hinder the transition to 100% RE

Deployment of solar PV will not be hindered by lack of availability of critical metals. The only critical metal needed is silver, which is used for solar cell contacts. Fortunately, the silver usage per watt in a solar cell has been greatly reduced over the last few years. Also, silver could be replaced by copper or aluminum as conductor if necessary.

Deployment of wind energy will, also, not be hindered by the lack of availability of critical metals. Roughly 80% of wind turbines do not contain critical materials. About 20% of wind turbines contain direct-drive permanent magnet generators. The permanent magnet eliminates the gearbox, which means fewer moving parts and reduced need for maintenance. These are attractive for offshore wind farms, which are harder to access for servicing. The rare earth metals neodymium and dysprosium are employed for these magnets. These are in critical supply, but there are other potential alternatives.

The lack of availability of critical metals will be a problem for manufacturing the batteries needed for a 100% RE system. The most energy-dense battery types in general usage are Li-ion batteries that utilize nickel, manganese, and cobalt in varying proportions for stabilizing the cathode; these are called NMC batteries for short. Of these four metals, lithium, cobalt, and nickel are in critical supply; moreover, there are human rights concerns regarding cobalt supply. First, are there alternatives to using cobalt and nickel? Yes, lithium iron phosphate (LFP) batteries contain only one critical metal, namely lithium. LFP batteries have advantages in cost, safety, and usable life over nickel-based lithium batteries, but they are less energy dense meaning that LFP batteries are heavier than NMC batteries per unit of energy stored. The additional weight of LFP batteries is not a problem in stationary applications and it is tolerable in many mobile applications as shown by their use by Tesla and others in some lower-cost electrical vehicles. In 2021-2022, several companies, including Tesla, FREYR (Norway), and ElevenEs (Serbia) announced that they are setting up large-scale production of grid-scale LFP batteries.³⁹ Thus, for grid-scale LFP batteries, the supply of lithium is the only critical metal that would potentially constrain production.

Many alternatives to using lithium for stationary batteries are being researched or developed, and some have already been commercially deployed at small scales. These include vanadium flow redox batteries, sodium sulfur batteries, and zinc bromide batteries, each with unique advantages and disadvantages compared to Li-ion batteries. A new alternative that could directly compete with Li-ion batteries, not only for stationary but also for mobile applications such as electric vehicles, are sodium-ion batteries which do not contain any critical metals such as lithium, cobalt, or nickel. Sodium is the sixth-most abundant element on Earth. In 2021, the world’s largest battery manufacturer, CATL in China, announced⁴⁰ that it has started industrial deployment and will set up a supply chain for sodium-ion batteries in 2023. This plan was confirmed by CATL in October 2022. CATL is also developing hybrid sodium-ion/Li-ion battery systems that predominantly use sodium but combine the advantages of both types. Regardless of whether this specific venture is successful, much progress towards sodium-based batteries, as well as other alternatives utilizing alternative non­critical materials, is being made by other groups globally.

As previously discussed, Li-ion batteries are only suitable for balancing the electrical grid for up to four to eight hours. For longer durations, there are many LDES technologies available or in pilot. Most LDES technologies involve only materials that are abundant; the exceptions are vanadium in vanadium flow batteries and magnetic materials for electric generators, neither of which is experiencing supply constraints at present.

When critical materials are either in short supply or their mining or processing causes significant environmental damage, we need to apply one or more of these strategies:

Mitigation of availability and sustainability issues for critical materials needed for RE
Mitigation Strategy	Examples
Find alternative materials that are more abundant, or easier to access/mine, without significant degradation of performance.	Many new battery technologies/chemistries in R&D use materials that are much more abundant.
Find new sources globally, develop these in an environmentally sustainable fashion, and recycle materials.	R&D on extracting lithium in a more environmentally friendly way than current sources; development of recycling processes.
Improve the environmental footprint of current mining operations.	Efforts to utilize the mine tailings for building materials, or to mine the tailings for rare earths.
Consider alternative materials that work well and are more plentiful but provide less performance.	Using iron phosphate in Li-ion batteries for electric cars, instead of nickel/manganese/cobalt.

I. Being creative in using land and other surfaces for solar PV

Solar PV is typically deployed either on rooftops of buildings, or, at larger scale, mounted directly on the ground. However, there are other possibilities: (a) agrivoltaics that integrate solar PV with agriculture, and (b) solar photovoltaics that float on bodies of water.

Agrivoltaics are being researched and promoted by NREL in the United States⁴¹ and by the Frauenhofer Institute for Solar Energy Systems (ISE) in Germany.⁴² There are a large variety of configurations for agrivoltaics that can be customized according to the specific crops and the local climate conditions. For instance, bifacial solar panels that can be mounted vertically as east/west-facing instead of tilted as south-facing as is typical now in solar farms. Such vertically mounted bifacial solar panels have a much smaller land footprint, which allows the land between them to be utilized, yet the solar production per panel is at least as high as for monofacial panels. Another configuration is bifacial solar panels that are raised up higher and can be adjusted automatically to either be vertical, at an angle, or fully horizontal depending on what degree of sunlight or shading is currently most beneficial for the crops. Beyond the ability to use the land between bifacial panels, and in the case of raised panels underneath them, there are other advantages of agrivoltaics such as shading of the crops as shelter from intense sunlight and a lower temperature of solar panels due to the cooling effect of the proximate vegetation and soil. The lower temperature of the solar panels results in higher power production on hot days than panels on a typical solar farm with gravel underneath, which radiates heat to the panels.

Frauenhofer ISE explains that agrivoltaics defuse the land-use conflict between solar farms and agriculture. For instance, compare the following two situations: (a) grow potatoes on one field and use an identically sized neighboring field for a solar farm; vs. (b) raised solar panels installed on one field and grow potatoes on that same field. Research has shown that case (b), which uses only half the land area of case (a), has a potato yield of 103% of case (a) and produces 83% of the solar power as case (a). Thus, the land efficiency for case (b) totals 186%. In Germany, it is beneficial to grow berries underneath solar panels, as they are protected from too much sun as well as from hailstorms and extreme rainfall. Currently, a five-year project is running in Germany to research how agrivoltaics could help counteract the negative effects of climate change on growing fruit.

Another win-win proposition for agriculture and solar is the installation of solar panels over irrigation canals. McKuin et al.⁴³ find that putting solar over California’s four thousand miles of canals would provide up to 82% evaporation savings and save enough water annually to irrigate fifty thousand acres of farmland or supply the residences of two million people with water. The 13 GW of solar energy capacity installed over the canals would correspond to about one-sixth of California’s current installed capacity. The panels would also curtail the growth of aquatic weeds, resulting in an annual reduction in canal maintenance costs of as much as $40,000 per mile. The water vapor from the canal would cool the panels and therefore significantly increase their power production compared to ground-mounted panels in a solar farm. Overall, the financial benefits of “over-canal solar” significantly exceed the additional cost for the cable structures needed to support the panels over the canal. As follow-up, the State of California is funding the $20 million Project Nexus that will install solar panel canopies over various sections of Turlock Irrigation District’s (TID) irrigation canals.⁴⁴ This will serve as a proof of concept to pilot and further study solar-over-canal design and co-benefits and will be completed by 2024. India has been pioneering over-canal solar since 2012 and has gained knowledge and experience in using this approach.⁴⁵

Floating solar photovoltaics (FPV) can be implemented on water. Initial installations of FPV have mainly been on artificial water bodies such as reservoirs, irrigation ponds, and treated wastewater storage ponds.⁴⁶ NREL has determined that a great symbiosis is possible between hydroelectric dams and FPV⁴⁷: The water cools the panels, so that they produce more power in hot weather than ground-mounted solar. The shade from the floating panels reduces evaporation of the reservoir and thus helps retain more capacity for the hydroelectric dam to produce electricity in the drier months. The FPV installation in these reservoirs can take advantage of the already existing power line connections for the hydroelectric dams. Also, when there is excess solar PV power generation, it can be used for pumped hydro energy storage. NREL is setting up international collaborations to further advance FPV technology and deployment.

The largest FPV farms are in China, which has at least 2 GW of installed capacity already. Examples are a 70 MW installation on a flooded area above a collapsed coal mine, and a 550 MW farm on an enclosed pond adjoining the sea in water of high salt content, which has dual usage as a fishpond.⁴⁸ South Korea is building a 2.1 GW FPV farm near a tidal flat on the coast of the Yellow Sea.

Agrivoltaics and FPV are just two examples of the rapidly developing field of integrated photovoltaics, which includes integrating PV into building envelopes, above roadways, on noise barriers and walls, and on vehicles.⁴⁹ With these innovations regarding spatial deployment of solar PV, it is unlikely that space will be a constraint. Most importantly, the evolving “toolset” of integrated PV provides a richer variety of technical solutions that can be explored with community involvement, promoting local collaboration to find the best land and water use solutions in symbiosis with solar PV.

J. Nuclear energy is not needed for baseload power to supplement RE

Conventional electrical grids depend on three types of power plants called “baseload,” “load-following,” and “peaker” plants. Baseload plants, e.g., large coal, gas, or nuclear plants, provide a relatively constant output at near full power for longer periods 24×7. Load-following plants typically run during the day or early evening, and their energy output can be changed to follow changes in energy demand. Peaker plants provide the most expensive energy and are only operated when there is an additional peak demand beyond what the baseload and load-following plants can handle, e.g., on very hot days in summer or cold days in winter.

By contrast, in a 100% RE system, the amount of power provided by each source is constantly varying. On sunny or windy days, the total solar PV and wind energy generation may exceed power demand on the grid. When this occurs, the excess energy can be sent to short-, medium- or long-term storage, or used for energy sector coupling, i.e., for Power-to-X to create fuels, such as hydrogen, methane, and liquid fuels that can be stored (RE fuels). When the total solar and wind production is low or zero, some of this stored energy can be converted back to electrical power, and/or RE fuels can be used to generate electricity. Further, through demand flexibility and energy sector coupling, energy demand can be shifted to times when excess solar and wind energy is likely to be available.

Thus, a 100% RE-based electrical power system is possible, and in such a system no “baseload” fossil fuel or nuclear power supply would be needed. This is good news and here follows some of the reasons why.

The economics of the current generation of nuclear plants assumes that they will produce at 90% capacity, i.e., that they can sell electricity to the grid 90% of the time. Therefore, the current nuclear plants are used to provide baseload power. The role of nuclear plants would need to change in an RE-based system. The nuclear plants would continue to produce constant energy, but the need for this energy would vary based on the amount of energy supplied by RE. When the energy from the nuclear is not needed for the grid, it could be used for Power-to-X. The nuclear industry is aware of how the role of nuclear will change. Nuclear reactors currently being developed, such as small modular reactors (SMRs), are being designed to be load-following energy sources and be coupled with Power-to-X technology to produce heat, hydrogen, methane, and liquid fuels such as gasoline, jet fuel, and marine fuel. How to make this happen is the subject of active research. The International Atomic Energy Agency (IAEA) holds regular discussions on this topic.⁵⁰ The US Department of Energy set up the program “Nuclear-Renewable Hybrid Energy Systems” (N-R HES), which is driven primarily by Idaho National Laboratory and NREL.⁵¹ Therefore, if nuclear fission is set up as a load-following generation source which sends electricity to the grid when it is needed but then utilizes it for Power-to-X production otherwise, it can easily be integrated into an overall 100-x% RE + x% nuclear energy system, where x is, say, 5 to 10%.

Although it will be possible to build 100% RE systems without using nuclear fission sources, could nuclear fission make it easier or faster to achieve a carbon-neutral grid?

The answer is no: Usage of nuclear fission beyond utilizing already existing nuclear plants until end of life will not help achieve the energy transition any faster or more cheaply. Rather, excessive investment in nuclear fission could be a distraction that diverts investment from 100% RE systems, and thus could delay progress on carbon neutrality.

Current nuclear fission technology is currently more expensive than RE and is becoming more expensive. This is the case not even counting the cost of government liability insurance guarantees or of long-term handling of the resultant nuclear waste. Additionally, nuclear fission plants have very long build times. This is because nuclear fission is not a modular technology such as solar PV, wind, or batteries that can achieve strong “learning curves” with continual cost improvements. Nevertheless, there is an attempt to make nuclear a modular technology. Much hope is being placed in designing Small Modular Reactors (SMRs) that are intended to be mass produced and sold globally. However, it is doubtful that it will be possible to achieve standardization of reactor design and regulatory framework or large global demand for new nuclear plants even if this standardization were to occur. All of this would be needed to drive down costs via assembly-line mass production for global sales and operations, such as has happened with widebody aircraft produced by Airbus and Boeing which are sold and operated globally and are approved by all national aviation regulatory bodies.

A detailed study conducted by the Institute of Safety and Risk Sciences at the University of Natural Resources and Life Sciences in Vienna⁵² concludes that

Uranium is a finite resource. As of 2015, the world’s reserve of uranium resources would suffice to power the entire world at 2015 electricity consumption level for only thirteen years.⁵³

The 2022 IEA report on “Nuclear Power and Secure Energy Transitions,”⁵⁴ while concluding with the idea that SMRs might see large-scale deployment in the 2040s, acknowledges the following: “The prospects for the deployment of SMRs and the degree to which they could contribute to achieving net zero goals remain uncertain. Most SMR concepts have yet to be demonstrated and new nuclear plants have typically had long lead-times.”

In summary, we do not need nuclear fission energy to create a decarbonized global energy system; renewables would be sufficient as described in this article. Nuclear fission energy will not speed up the decarbonization of our energy system, but could divert much needed investments and government incentives/subsidies/R&D money away from addressing the climate crisis more effectively via RE.

In view of the above information, it is no wonder that the total global investment in non-hydro renewable electricity capacity exceeded US$300 billion in 2020, “almost 17 times the reported global investment decisions for the construction of nuclear power of around US$18 billion for 5 GW,” and that the share in global electrical power generation from non-hydro renewables at 10.7% already exceeded that from nuclear at 10.1%.⁵⁵ Based on its comprehensive analysis, the World Nuclear Industry Status Report 2021 concludes that it is likely that “nuclear power will be permanently destined to be found only in niche markets of a handful of countries.”

One small note about nuclear fusion energy, which involves fusing small nuclei together to release tremendous energy as continually happens in the sun: If fusion energy becomes available and economical someday, it should also be possible to integrate fusion energy plants into a 100%, or 100-x% RE system and coupled with Power-to-X: We will not need fusion energy for baseload power, but fusion energy could be used on the grid to meet energy demand on the grid beyond what RE can supply and, when not so needed, to produce heat or RE fuels.

K. CCS will not make the burning of fossil fuels “clean”

There have been great efforts made, including billions of dollars spent, to capture and sequester the CO2 produced by burning fossil fuels. Such fossil fuel “carbon capture and sequestration,” or more commonly “carbon capture and storage” (CCS) plants have also been proposed as baseload power for carbon-neutral power grids. Note however, that fossil fuel CCS plants would be significantly more expensive to build and to operate than conventional fossil fuel power generation plants due to the equipment and operational processes needed to continually capture and store enormous volumes of CO2. Also, such fossil fuel CCS plants would lead to higher consumption of fossil fuels and thus a higher fuel cost to produce the same amount of power because of the energy needed for CCS. Both factors would increase the levelized cost of energy for coal and natural gas power generation compared to today’s non-CCS fossil fuel generation plants.

An alternative to CCS is “carbon capture and utilization” (CCU), where the captured CO2 is utilized for some other industrial or chemical process instead of storing it underground. Sometimes, CCS and CCU are collectively called “CCUS.” The oil industry has been practicing CCU for decades by capturing CO2 and injecting it underground for enhanced oil recovery. This is a process that results overall in significantly more CO2 being released to the atmosphere, estimated at 1.4 to 4.7 times more than is being injected into the ground,⁵⁶ yet oil companies receive tax credits from the US government for this net CO2 release which exacerbates climate change.

There are significant remaining hurdles to solve for fossil fuel combustion CCS,⁵⁷ such as “cost, technical feasibility of long-term sequestration without leakage, . . ., other air pollutants from combustion and imperfect capture when capturing from power plants, lower energy efficiency, regulatory issues, public acceptance of sequestration facilities, and systems integration.” Even if fossil fuel combustion CCS did work, it would lead to increased extraction and combustion of fossil fuels because additional energy would be needed for operating CCS. Not only is fossil fuel CCS not needed for baseload or load following in a 100% carbon-neutral energy power grid, but CCS plants would increase the cost of electricity over that of a 100% RE system.

Solar PV and wind energy combined with energy storage provides a much better option for reducing CO2 emissions than fossil fuel power plants with CCS, according to the research of Sgouridis et al.⁵⁸: “We conclude that it is more valuable, energetically, to invest the available energy resources directly into building new renewable electricity (and storage) capacity rather than building new fossil fuel power plants with CCS.”

All coal CCS projects in the United States have failed, as documented by a 2021 GAO report.⁵⁹ All eight projects were dropped due to economic factors including lower natural gas prices and uncertainty about the carbon markets that affected the economic viability of coal CCS. There is one remaining fossil fuel combustion CCS/CCU project that is still in operation globally, in Canada: The Boundary Dam Power Station in Saskatchewan, a relatively small 115 MW coal power plant, with the CO2 being partly used for enhanced oil recovery (CCU) and partly stored underground (CCS). The goal was to capture 90% of the plant’s emissions, but it has captured on average only 44%.⁶⁰ Thus, there has been no demonstration of “clean coal.”

If CCS is going to make any significant contribution to climate change, operations would have to be scaled up by a factor of one thousand from a few million tons per year globally today to multiple gigatons per year by 2050, as noted by Creutzig et al.⁶¹ Although solar PV has sustained a cumulative growth rate for more than twenty-five years that is around that magnitude, it is extremely unlikely that CCS technology deployment could experience such rapid growth: CCS is not a modular technology like solar PV that can be mass produced in a factory and then mounted on a field or on top of a roof. Each CCS project is unique, involving engineering how to best capture CO2 from a particular gas stream (fossil fuel combustion or industrial process such as steel/cement), where and how to store it in the local geologic formations, and how to monitor leakages. Although the first CCS/CCU operation for enhanced oil recovery went live in 1996, and many billions of dollars have been invested globally over 25 years, no fossil fuel CCS has been deployed through 2021 except for the small plant in Saskatchewan.

There is no “market” for CCS. CCS as an economic activity does not bring direct value, while investment in RE technology does: CCS consumes useful energy; RE technology provides useful energy. CCS does not produce anything useful, and thus its business case will depend on government regulations and complex carbon accounting that is open to dispute for such purposes as carbon pricing, taxing carbon, and cap-and-trade mechanisms.

In summary, fossil fuel combustion CCS is a mere mirage: Such CCS plants aiming to capture and store CO2 underground from power plants have been a failure so far, and there are no reasonable prospects for fossil fuel plants with CCS to become cost competitive with RE sources and a 100% RE system that balances energy supply and demand. Nevertheless, CCS might be a needed niche solution when there is no other way to avoid CO2 emissions from industrial processes, such as cement production and waste incineration, which release large amounts of CO2.

L. BECCS will not produce energy efficiently or draw down carbon from the atmosphere

If we develop a global 100% RE energy system, which would be possible as is described in this article, and we fully stop the combustion of fossil fuels, what if the CO2 levels in the Earth’s atmosphere are too high to stabilize the global climate at some level, say 1.5⁰C global temperature rise? Yes, it is very likely that due to our procrastination as a species in shutting down combustion of fossil fuels, we will not be able to stay at a level of 1.5⁰C or even 2⁰C global-average temperature rise. If this is the case, what would be the best way to reduce CO2 levels? Bioenergy with carbon capture and storage (BECCS) is one of the main solutions that has been favored by IPCC, IEA, and some other prominent organizations over the last decade.

In theory BECCS would produce energy and at the same time results in negative emissions. Crops are grown absorbing “Y” amounts of CO2 from air; the crops are burned to produce energy, Y amount of CO2 is released in the process; then using CCS, taking a very optimistic efficiency of 90% for CCS, 90% of the Y amount of CO2 is captured and permanently stored. According to this calculation, since – Y + Y – 0.9Y = – 0.9Y and in the process energy is produced, BECCS yields positive energy and negative CO2.

The first problem with BECCS is that it is a very inefficient means of producing energy. Sgouridis et al.⁶² conclude that BECCS is not an economical method for production of electricity compared to a RE system consisting mainly of solar, wind, and storage. They stated that “biomass-based, negative emission technologies” such as BECCS would be “an energetically intensive carbon management tool rather than an energy resource.”

The second problem with BECCS is that the accounting for CO2 emissions is very complex and variable according to local farming and other conditions, and subject to dispute. In addition to the “Y” carbon counted in the theoretical example of BECCS above, we need to consider: (a) Land usage changes: How much carbon was stored in the forest, grassland, shrubland, wetland, or other ecosystem type—including both biomass and soil organic carbon stocks–before conversion to cropland vs. afterwards? In general, there is a large net release of carbon that had been stored in the original biosystem over many decades or centuries. (b) Farming: How much carbon is emitted in planting, growing, cultivating, and harvesting the crops? (c) Biofuel production: How much carbon is released in building the biofuel plant and using it to convert the harvested crops to biofuel? (d) Transportation: How much carbon is emitted in transporting the biofuel to the energy plant? (e) Energy plant: What are the carbon emissions associated with building, maintaining, and running the energy plant? And, also, (f) Storage infrastructure: What are the emissions associated with building and operating the infrastructure for capturing the CO2, transporting it to the storage site, and storing it? After including all of these additional CO2 emissions, there may be no negative emissions as a result of BECCS and, as discussed below, significant positive emissions.

There is a third problem with BECCS, which is a problem in general for bioenergy, as pointed out in a study by van de Ven et al. ⁶³ They compared the land usage and land use change emissions impacts for a solar energy farm vs. cultivation of bioenergy crops and found that the land use requirements for solar energy are an order of magnitude less. They calculated the CO2 payback period and found that the payback period for bioenergy of about four years is significantly higher than for solar energy, which is less than eight months. This is not to say that there should be no bioenergy crops, since bioenergy fuels can be used, e.g., for aviation or for generating electricity when solar energy is not available, but this study makes clear that it does not make sense to expand bioenergy crops for purposes that solar PV could fulfil more efficiently.

The potential consequences of inaccurate carbon accounting for BECCS processes are not abstract but rather have real consequences. The scale of the potential error created by overly optimistic model projections used by IPCC through 2019 about BECCS carbon removal is staggering: Due to the large-scale BECCS deployment proposed for holding Earth to a 1.5⁰C temperature rise, McLaren⁶⁴ estimates unanticipated net additions of 371 to 545 gigatons carbon to the atmosphere by 2100, which could cause an additional 1.4⁰C increase in global temperature. This would mean that, instead of a targeted 1.5⁰C rise, there would be a 2.9⁰C rise in global temperature due to BECCS. A much better approach would be to have separate targets for emissions reductions and negative emissions, as proposed by McLaren et al.⁶⁵

Let us consider an actual bioenergy supply chain managed by the United Kingdom company Drax,⁶⁶ which is subsidized by the UK government. Wood pellets are produced from trees harvested from loblolly pine plantations in the US Southeast, which are shipped to the UK and burned as fuel in power plants. Drax has a project to turn their power plant into a BECCS facility by capturing the CO2 emissions and sequestering them underneath the North Sea via a pipeline, with the goal of eight million tons of negative carbon emissions by 2030. NRDC modelled every step involved in this BECCS process,⁶⁷ including CO2 emissions both in the US and the UK. They made the generous assumption of a 95% capture rate for the CO2 emissions from the power plant, which is overly optimistic in view of the 44% average capture rate of the coal CCS plant in Saskatchewan. Nevertheless, NRDC’s model calculates the net emissions for this BECCS process as 80% of the emissions that come from a coal power plant that does not have CCS installed. That is, this BECCS process is strongly carbon positive, not carbon negative, and almost as bad as burning coal. The conclusion is that “bioenergy does not even maintain carbon sequestration levels [of the forests]; cutting and burning forests in the southeastern United States leads to a net shift of carbon from the land to the air that lasts for decades.”

In addition to these drawbacks, the deployment of BECCS at the scale envisioned in many models used by IPCC will result in increasing conflicts in land usage with needs for biodiversity and for food production, which could push up the cost of both food and bioenergy crops. Regarding the overall possible role of BECCS in decarbonization, Fajardy et al.⁶⁸ conclude as follows:

In summary, BECCS using energy crops is unnecessary in a 100% RE system and could in many cases even lead to increased CO2 emissions. If we still need to draw down CO2 from the atmosphere, natural carbon sinks such as rewilding should be considered.

BECCS might be a niche solution for situations where the carbon math works well, but if we attempt to scale it up to be a very significant contributor to reducing atmospheric CO2, it will backfire: It may instead cause environmental destruction of ecosystems and increase atmospheric CO2 while being less economically and energy inefficient than a 100% RE system that excludes energy crops. Finally, there is also the risk that BECCS would be used as a public relations fig leaf for continuing to burn fossil fuels, i.e., engaging in mass-scale BECCS in a futile attempt to clean up the mess we create when combusting fossil fuels.

M. The IPCC and IEA see RE technology deployment as key for rapid decarbonization

The IPCC Sixth Assessment Report, Working Group III “Mitigation of Climate Change” (IPCC AR6 WG3) was finalized and released in April 2022.⁶⁹ Compared to the previous SR1.5 report from 2019, and the Fifth Assessment Report IPCC AR5 WG3 from 2014, the IPCC AR6 WG3 report views the prospects for rapid transition to RE much more favorably and highlights RE as the most promising technology for decarbonizing of energy supply. To quote from page TS-25 of the Technical Summary, which compares the AR6 conclusions (2022) to those from AR5 (2014):

Thus, in the intervening eight years from AR5 in 2014, RE developed much more quickly than the IPCC had anticipated, both in economics and scale of deployment, whereas nuclear fission and CCS had not progressed significantly. This is because, as explained in the previous sections, nuclear fission and CCS are very expensive and hard to scale up, whereas RE technology is easily scalable and is dropping in price due to the modular technology and rapid innovation cycles. Indeed, section B.4.1 on page SPM-12 of the Summary for Policymakers (SPM) states:

In the last sentence above, “multiple large-scale mitigation technologies” include nuclear fission and CCS, and this statement confirms our conclusions that it will be very hard to achieve “learning” for nuclear fission and CCS, i.e., continuous improvement of the technology, and, by reason of lack of mass-scale production and deployment, large reductions in cost.

The IPCC report indicates that wind and solar energy have the biggest potential to reduce net emissions by 2030. This is shown in the excerpt from Figure SPM.7 for the Energy Sector below. Compare, in particular, the potential emissions reduction via solar and wind vs. bioelectricity (bioenergy), nuclear, CCS, and bioelectricity with CCS (BECCS) in terms of magnitude (gigatons CO2-equivalent per year) and color (net lifetime cost per ton of CO2-equivalent avoided):

Excerpt from Figure SPM.7 (Energy sector): Overview of mitigation options and their estimated ranges of costs and potentials in 2030. Reproduced from IPCC AR6 WG3, Summary for Policymakers, page SPM-50.⁷⁰

The conclusion from the IPCC report, as indicated in the full version of Figure SPM.7 covering all mitigation options, is that we should do the following on a massive global scale: (a) deploy solar and wind energy; (b) implement energy efficiency improvements and other measures to reduce energy consumption; (c) leave natural ecosystems as natural ecosystems; and (d) reduce methane (CH4) emissions from fossil fuel activities and from waste. The good news is that we can perform these four measures in parallel to each other and start action immediately. The IPCC AR6 WG3 report is a plea for action, “The evidence is clear: the time for action is now.” Moreover, “We are at a crossroads. The decisions we make now can secure a liveable future. We have the tools and know-how required to limit warming.”⁷¹

In October 2022, IEA released the World Energy Outlook 2022,⁷² which includes three scenarios: Stated Policies Scenario (STEPS), Announced Pledges Scenario (APS), and Net Zero Emissions by 2050 Scenario (NZE). Compared to the global emissions of CO2 in 2021 of thirty-seven gigatons, in 2050 these scenarios lead to net emissions of thirty-two gigatons (STEPS), twelve gigatons (APS), and zero (NZE). The gap between STEPS and APS is the “implementation gap” showing that current policies do not match the announced pledges (aspirational targets) of governments. The gap between APS and NZE, however, is the “ambition gap” showing that the current pledges do not lead to a net-zero energy system by 2050. As summarized in the IEA press release, RE technology is poised to help us leap past both the implementation and the ambition gaps:

Quoting further, a huge increase in clean energy investment—which is USD 1.3 trillion per year today—is needed by 2030, especially clean energy investment in developing economies:

The executive summary in the IEA WEO report concludes that the 2022 energy crisis, which was created by Russia’s invasion of Ukraine, “promises to be a historic turning point towards a cleaner and more secure energy system”:

Indeed, in connection with the spike in energy prices due to Russia’s war against Ukraine, the TEA WEO report notes that: “Tn the most affected regions, higher shares of renewables were correlated with lower electricity prices, and more efficient homes and electrified heat provided an important buffer for some—but far from enough— consumers.” Clearly, RE, energy efficiency, and electrified heat promote energy security.

What is striking in the IEA report, considering that the IEA has historically been strongly influenced by fossil fuel interests and continually underestimated the potential of RE, is the open admission of the world’s fundamental energy insecurity due to dependence on fossil fuels and the call for a broad coalition to build a sustainable energy system that leaves fossil fuels in the ground.

Thus, both IPCC and IEA see that further acceleration in the rapid deployment of RE technology is the biggest driver for achieving progress in decarbonizing the energy system in the near team. How do their 2050 net zero emissions scenarios compare with our 100% RE (or 100-x% RE + x% nuclear fission) scenario that we are promoting in this article? They rely on a large expansion of bioenergy and continued combustion of significant amounts of coal, oil, and natural gas coupled with CCS and carbon dioxide removal (CDR) to remove the resulting CO2 emissions, whereas this article does not.

N. Alternatives to the reliance of the IPCC and IEA on BECCS, CDR, and CCS

The IPCC AR6 WG3 team assessed 1686 model scenarios, sixteen of which involve net zero emissions from the energy sector by 2050. The median IPCC net zero 2050 scenario requires seventeen gigatons of CCS and twelve gigatons of energy sector CDR from BECCS and DAC in order to mitigate fossil fuel combustion. The IEA NZE requires six gigatons of CCS and 1.4 gigatons of energy sector CDR. Regarding bioenergy, the IEA NZE and IPCC median scenarios see a biomass usage of 1.4 and 3.5 times higher than 2021, respectively. As explained in previous sections, these large amounts of CCS and BECCS will not be achievable, certainly not by 2050 if at all. Why do the IPCC and IEA models lead to such a strong dependency on CCS, CDR (including BECCS) and bioenergy? It is because the models used by IPCC and IEA do not adequately represent the potential of 100% RE systems, as we will explain in a later section.

Let us look at the energy mix in IEA NZE scenario, which calls for a higher percentage of RE than the IPCC scenarios: 70% of total energy supply is from RE (39% solar/wind, 6% hydro, 19% bioenergy, 6% other RE), 13% from fossil fuel combustion, and 12% from nuclear fission. For electricity generation, 88% is from RE (71% solar/wind, 11% hydro, 4% bioenergy), 2% hydrogen and ammonia (most via RE and Power-to-X), 8% from nuclear fission, and 2% from fossil fuel combustion.

We should not depend on CCS or CDR to make our global energy system carbon neutral by offsetting emissions from continued use of fossil fuels: Rather, we should create a global 100% RE system that does not emit any CO2, except for the combustion of renewable fuels that contain carbon captured from atmospheric CO2. Instead, CDR measures, such as natural carbon sinks, should be used exclusively to reduce CO2 global emissions that are in excess of the IPCC’s “carbon budget” for keeping global warming to 1.5⁰C or 2⁰C. Further, we should use CDR to compensate for:

• non-energetic emissions of CO2 from land use, land use change, forestry, and, to the extent unavoidable, industry, and
• non-CO2 emissions of the other primary greenhouse gases
  • methane (CH4)
  • nitrous oxide (N2O)
  • fluorinated gases including hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3)—these are the fastest increasing and the most potent and longest lasting class of greenhouse gases

A further reason for accelerating the transition to 100% RE without depending on BECCS, CDR, or CCS to enable continued combustion of fossil fuels, is that the IPCC is being scientifically conservative in its projections of future global warming. CDR measures are needed to, and must be reserved for, addressing issues that we cannot be solved by decarbonizing our energy system.

As RE technology and deployment progresses rapidly, the IPCC and IEA assessments are recognizing these RE trends with a lag time. As we move further towards 100% RE (or 100-x% RE + x% nuclear fission), the contribution of fossil fuel combustion, CCS, and BECCS in the IPCC and IEA models will continue to decline, and the contribution of RE will increase. Aside from this caveat about their lag time in recognizing the potential of RE, the IPCC AR6 WG3 and the IEA WEO 2022 reports provide a solid basis of information about how we can tackle the climate crisis in a multifaceted manner. I encourage you to read at least the executive summaries of these reports and also the UNEP report reviewed below.

O. UNEP’s advocacy of RE

That a rapid expansion of RE is absolutely necessary is underscored by the Emissions Gap Report 2022 of the UN Environment Programme (UNEP).⁷³ Here are some of the report’s recommendations for immediate actions: National governments should “remove barriers to the expansion of renewables” and “adapt market rules of electricity system for high shares of renewables.” Subnational governments should “set 100 per cent renewable targets.” Businesses should “support a 100 per cent renewable future.” Citizens should “purchase 100 per cent renewable electricity.” Another recommendation towards a global RE system regards hydrogen: “International cooperation and coordination is important to develop a market for hydrogen from renewable sources, with coordinated targets, standards, and bilateral and multilateral cooperation agreements and blended finance.”

In his message about the Emissions Gap Report 2022, UN General Secretary António Guterres made clear the essential role that RE needs to play over the decade:

There is no explicit mention of nuclear energy in any of the UNEP report’s recommendations. Carbon capture is only mentioned as a tool for decarbonizing industrial processes but not for decarbonizing the energy supply. BECCS is mentioned as a technology that has “not yet been proven to work at scale.” As highlighted in this report, current policies will result in 2.8 ⁰C warming instead of the target of 1.5⁰C. UNEP is acknowledging the obvious: Besides reduction of energy demand, RE is the only tool we have for decarbonizing our global energy system that is immediately deployable and can address the global scale of the need that we have to move down from our current policies path of 2.8⁰C or more warming.

P. Responding to those who are critical or skeptical about 100% RE

Could we really run the world on 100% RE? Might 100% RE itself cause large environmental issues? Many criticisms of the viability of 100% RE have been published in the scientific literature. These articles present argumentation and model scenarios that are based on incomplete and fragmented understandings of the potential of 100% RE based systems—they have outdated information about RE costs and/or do not sufficiently represent the flexibility that a 100% RE system would have in balancing diverse types of energy sources and energy demands. Brown et al.⁷⁴ and Diesendorf and Elliston,⁷⁵ have published systematic responses to these criticisms showing the feasibility of 100% RE systems. Recently, Christian Breyer and twenty-two other researchers in the 100% RE field have addressed the criticisms of 100% RE.⁷⁶ They provide a thorough rebuttal of the claim that calculations of energy return on investment (EROI) prove that a switch from fossil fuels to renewables “would be problematic or even impossible due to limitations in fundamental energy economics.” In short, there are no fundamental scientific reasons why 100% RE systems could not replace fossil fuel energy systems.

Historically, many of the most prominent energy models such as those from IPCC and IEA have underestimated the potential of RE—even the models used in their 2022 reports. Two studies published in 2021 examine this trend and investigate the reasons for it. Xiao et al.⁷⁷ compared the costs for solar and wind energy in energy scenario studies to historical market and auction prices for solar/wind. They observed, “Virtually all consulted studies hugely overestimate the costs. In the extreme, assumed costs for 2050 are higher than observed costs for 2019. Solar PV, CSP, and offshore wind seem particularly plagued by this situation.” The second study, by Victoria et al.,⁷⁸ explained in more detail how the potential of solar PV is being underestimated, and that solar PV is positioned to be “one of the main, if not the main, energy sources in cost-optimal decarbonized scenarios.” Thus, solar PV will play a much larger role in decarbonizing the global energy system than is generally recognized in the literature or in current public discourse.

In the Oxford University study previously cited, Way et al.⁷⁹ found that

Further, they explain what the consequences of this systematic bias against RE have been: “The belief that the green energy transition will be expensive has been a major driver of the ineffective response to climate change for the past 40 years. This pessimism is at odds with past technological cost improvement trends and risks locking humanity into an expensive and dangerous energy future.”

For those concerned that 100% RE cannot replace fossil fuel usage or that it will cause enormous environmental damage, consider this: Humanity has been building and optimizing our current global energy system based on fossil fuel combustion for the last 270 years since 1750. Therefore, it is no wonder that many people have difficulty imagining we can create a better system with RE, and there is fear of change. We have been developing RE technology for only about fifty years since around 1970, and at larger scale and in earnest only for the last twenty years; and the global investments and subsidies for fossil fuels are still much higher than for RE. Nevertheless, in spite of this investment/subsidy imbalance, RE is now cost competitive with fossil fuels in many places in the world even without RE subsidies or considering the cost externalities of fossil fuels. The creativity and collaboration/competition of eight billion humans will continue to improve RE technology and its environmental sustainability and result in energy solutions that can be finely adapted to local needs and conditions everywhere.

For those who are against 100% RE, what is the alternative? Continuing to burn fossil fuels is not an alternative; there are enough remaining reserves to secure for humanity an un-liveable future with a hot-house Earth that will destroy all human civilization. As explained above, although nuclear fission energy can be integrated with 100% RE systems, it will not make it cheaper or faster to achieve a net zero global energy system; and CCS and BECCS will not enable us to continue burning fossil fuels. The IPCC AR6 WG3 report does not show any other alternative energy sources for powering a decarbonized global energy system than the ones just listed.

On the other hand, the IPCC AR6 WG3 report does strongly recommend two further tools that we have in our quiver: CDR and reduction of energy demand. Regarding CDR, as explained above, we should not use CDR to justify continued combustion of fossil fuels; rather we should use CDR to reduce the accumulated anthropogenic CO2 emissions in our atmosphere, as well as to offset anthropogenic emissions of other primary greenhouse gases.

Regarding reduction of energy demand, Jim Skea, the IPCC AR6 WG3 co-chair, explained:

That is to say, technology together with collective action will be our tools to aid in reduction of energy demand. Individual actions will not be sufficient.

Certainly, a tandem approach is possible: Reducing our energy consumption while transitioning to 100% RE for our remaining energy demand. As mentioned early in this work, the Low Energy Demand scenario of Grubler et al ⁸¹ shows how energy efficiency and energy sufficiency measures together could reduce the global final energy demand by 40% by 2050—the IPCC AR6 WG3 likewise shows how energy demand could be lowered by a similar amount. The IEA WEO 2022 report as well as the UNEP Emissions Gap Report 2022 provide many recommendations for reducing energy demand. Instead of waiting for a war or a climate disaster to force us to reduce our energy consumption at short notice, we could with collaboration across all sectors of society embark on a systematic path of right-sizing our energy demand. Whether we replace 100% of present-day fossil fuel energy with RE or only need to replace 75% or 50% of it by RE due to lower energy demand, we must still shut down all fossil fuel usage and our global energy system still has to be 100% RE (or 100-x% RE + x% nuclear fission). It’s that simple.

Q. Collaborating to advance 100% RE solutions to secure a liveable future

The prospects for achieving 100% RE to fully decarbonize our global energy system are good, and the need to do this is urgent. There are three essential actions:

• Build 100% RE: Focus on building 100% RE systems everywhere globally, including the coupling of the energy sectors power, heat, transport and industry via Power-to-X and other measures. Do not use CCS, BECCS or CDR as a fig leaf to continue fossil fuel combustion.
• Collaborate intensively: Stimulate public participation across society to build 100% RE.
• Reduce energy consumption: Implement energy efficiency and energy sufficiency measures.

Yes, there will be continued investment in nuclear fission, especially in those countries with a strong nuclear industry, and future nuclear reactors in development could be integrated into a 100-x% RE system. However, the deployment of nuclear will continue to be slow and expensive and have many hidden government subsidies such as public liability for accidents. Promotion of nuclear fission as an option will slow down the energy transition by raising expectations that it cannot fulfill and by diverting investment money and governmental support away from RE.

Yes, bioenergy crops can contribute to a fossil free future. However, before implementation or expansion of a particular bioenergy solution, we need to perform a complete carbon lifecycle analysis to assure that it is carbon neutral. If so, that bioenergy solution would be a form of RE and could easily be integrated into a 100% RE system. If not, do not proceed. Just as important, ensure that there is no competition for land between food production and bioenergy.

After shutting down fossil fuel combustion, will we still be able to consume as much energy as today—for end usage—in a future global 100% RE system? Studies such as EWG/LUT predict yes. We cannot know for sure in advance, which is why energy efficiency and energy sufficiency initiatives should be running in parallel. One factor that will greatly help is that an RE system produces electricity primarily directly from the sun or wind; this will improve the efficiency of primary energy supply by about 100% over that of a fossil-fuel-combustion based energy system where a large part of the energy is lost via heat.

In order to keep the world on track for the goals of the 2015 Paris Agreement, the 2022 reports from IPCC, IEA, and UNEP demand the deployment of as much RE as possible by 2030, along with energy efficiency/energy sufficiency measures. IPCC, IEA, and UNEP place no such expectation that significant progress towards decarbonization can be achieved with nuclear energy, CCS, or BECCS by 2030.

Let us return to our starting point. Technology is neither the villain nor the solution, but it is our tool as humans to wield in service of humanity and the global ecosystem. The biggest risk is not the technology itself, but that our thoughts and actions still tend to be short-sighted and ego-centric instead of long-sighted and eco-centric. Therefore, as we roll out RE technology on an enormous global industrial scale, we must guard against feeding and enabling our same unhealthy historical tendencies to separate ourselves from nature and from other humans and exploit them both, which have led to the climate crisis, environmental degradation, and global social injustices we can no longer avoid facing.

In assessing the role and application of technologies, each of us can and must contribute, by asking and pursuing questions such as: If a proposed technology looks like it might cause harm to fellow humans or our ecosystem, what could be done to redirect the technology to avoid these issues? If a particular RE technology or supply chain is causing harm, could it be improved or replaced with a more sustainable solution or supply chain? Instead of leveraging any environmental or social issue regarding RE to argue against RE deployment, we should leverage that issue for improving the environmental and social footprint of RE.

Therefore, let’s redirect technology in service of humanity and the global ecosystem. Let’s collaborate to advance 100% RE solutions to help secure and power a liveable future.

1 “IPCC AR6 WG3”: Intergovernmental Panel on Climate Change (IPCC), “Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change” [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY (2022): https://www.ipcc.ch/report/ar6/wg3/.

2 IPCC, “IPCC Press Conference for CLIMATE CHANGE 2022: Mitigation of Climate Change,” April 4, 2022: https://www.youtube.com/watch?v=STFoSxqFQXU&t=3s.

3 Arnulf Grubler, Charlie Wilson, Nuno Bento, Benigna Boza-Kiss, Volker Krey, David L. McCollum, Narasimha D. Rao, Keywan Riahi, Joeri Rogelj, Simon De Stercke, Jonathan Cullen, Stefan Frank, Oliver Fricko, Fei Guo, Matt Gidden, Petr Havlík, Daniel Huppmann, Gregor Kiesewetter, Peter Rafaj, Wolfgang Schoepp, Hugo Valin, “A low energy demand scenario for meeting the 1.5°C target and sustainable development goals without negative emission technologies,” Nature Energy 3, 515–527 (2018): https://doi.org/10.1038/s41560-018-0172-6.

4 See IPCC AR6 WG3 (2022). The conclusions about reduction of energy demand are summarized on pages TS-98 to TS-104 of the Technical Summary.

5 Joint Declaration of The Global 100% RE Strategy Group at CleanTech Business Club Thought Leaders on Feb. 9, 2021: https://www.youtube.com/watch?v=7r9f0Zp8Yyk.

6 Marta Victoria, Nancy Haegel, Ian Marius Peters, Ron Sinton, Arnulf Jäger-Waldau, Carlos del Cañizo, Christian Breyer, Matthew Stocks, Andrew Blakers, Izumi Kaizuka, Keiichi Komoto, Arno Smets, “Solar photovoltaics is ready to power a sustainable future,” Joule 5, 1041–1056 (2021): https://doi.org/10.1016/j.joule.2021.03.005

7 Benjamin Kroposki, Brian Johnson, Yingchen Zhang, Vahan Gevorgian, Paul Denholm, Bri-Mathias Hodge, Bryan Hannegan, “Achieving a 100% renewable grid: operating electric power systems with extremely high levels of variable renewable energy,” IEEE Power and Energy Mag 15, 61–73 (2017): https://www.researchgate.net/publication/314198578_Achieving_a_100_Renewable_Grid_Operating  Electric_Power_Systems_with_Extremely_High_Levels_of_Variable_Renewable_Energy.

8 NREL, “ARIES: Advanced Research on Integrated Energy Systems”: https://www.nrel.gov/aries ; and NREL, “ARIES: A research platform to match the complexity of the modern energy system”: https://www.nrel.gov/news/video/aries-a-research-platform-to-match-the-complexity-of-the-modern-energy-system-text.html.

9 NREL, “Resilience With 100% Renewable Power”: https://www.nrel.gov/news/video/resilience-with-100-renewable-power-text.html.

10 NREL, “NREL Methods Assist Maui in Approaching 100% Renewable Operations: New Capabilities Demonstrate How Renewables Can Stabilize and Support the Power Grid, Jul. 30, 2021: https://www.nrel.gov/news/program/2021/nrel-methods-assist-maui-in-approaching-100-renewable-operations.html ; and Connor O’Neil, “Renewables Rescue Stability as the Grid Loses Spin,” NREL, Sep. 15, 2020: https://www.nrel.gov/news/features/2020/renewables-rescue-stability-as-the-grid-loses-spin.html.

11 Kauai Island Utility Coop, “Hitting the Target: KIUC 2021 Annual Report”: https://www.kiuc.coop/sites/default/files/documents/annual_reports/AnnualReport21.pdf ; and “KIUC Spotlights Accomplishments at Annual Meeting”: https://www.kiuc.coop/kiuc-spotlights-accomplishments-annual-meeting.

12 Hawaiian Electric, “Taking Action on Climate Change Together—21/22 Sustainability Report”: https://view.hawaiianelectric.com/2021-2022-sustainability-report/page/1 ; and “Our Clean Energy Portfolio”: https://www.hawaiianelectric.com/clean-energy-hawaii/our-clean-energy-portfolio .

13 NREL, “LA100: The Los Angeles 100% Renewable Energy Study”: https://www.nrel.gov/analysis/los-angeles-100-percent-renewable-study.html; Full study: https://maps.nrel.gov/la100/.

14 Energinet website, which provides a lot of documentation: https://en.energinet.dk/; see Energinet’s video “Green Energy for a Better World”: https://en.energinet.dk/Green-Transition

15 See Energinet’s video “Green Energy for a Better World”: https://en.energinet.dk/Green-Transition ; and Energinet, “Energinet Associated Activities”: https://en.energinet.dk/About-us/Organisation/Energinet -Energy-Consultancy

16 Manish Ram, Dmitrii Bogdanov, Arman Aghahosseini, Ashish Gulagi, Solomon A. Oyewo, Michael Child, Upeksha Caldera, Kristina Sadovskaia, Javier Farfan, Larissa S.N.S. Barbosa, Mahdi Fasihi, Siavash Khalili, Bernhard Dalheimer, Georg Gruber, Thure Traber, Felix De Caluwe, Hans-Josef Fell, Christian Breyer, “Global Energy System based on 100% Renewable Energy—Power, Heat, Transport and Desalination Sectors, Study by Lappeenranta University of Technology and Energy Watch Group,” Lappeenranta, Berlin, March 2019: https://www.energywatchgroup.org/new-study-global-energy-system-based-100-renewable-energy/.

17 Dmitrii Bogdanov, Manish Ram, Arman Aghahosseini, Ashish Gulagi, Ayobami Solomon Oyewo, Michael Child, Upeksha Caldera, Kristina Sadovskaia, Javier Farfan, Larissa De Souza Noel Simas Barbosa, Mahdi Fasihi, Siavash Khalili, Thure Traber, Christian Breyer, “Low-cost renewable electricity as the key driver of the global energy transition towards sustainability,” Energy 227, 120467 (2021): https://doi.org/10.1016/j.energy.2021.120467.

18 Rupert Way, Matthew C. Ives, Penny Mealy, J. Doyne Farmer, “Empirically grounded technology forecasts and the energy transition,” Joule 6, 2057-2082 (2022): https://doi.org/10.1016/j.joule.2022.08.009  

19 Long Duration Storage (LDES) Council and McKinsey & Company, “Net-zero power: Long duration energy storage for a renewable grid,” November 2021: https://www.ldescouncil.com/assets/pdf/LDES-brochure-F3-HighRes.pdf; LDES Council and McKinsey & Company, “Net-zero heat: Long Duration Energy Storage to accelerate energy system decarbonization,” November 2022: https://www.ldescouncil.com/assets/pdf/221108_NZH_LDES%20brochure.pdf, plus presentation of this report at COP27 (November 2022): https://www.youtube.com/watch?v=DoZZwzS5x2U ; and LDES Council, “Long-duration energy storage: the piece of the puzzle to enable the energy transition” LDES Council at COP27 (November 2022): https://www.youtube.com/watch?v=u_KZXPcW29U .

20 “An electricity market for Germany’s energy transition—White Paper by the Federal Ministry for Economic Affairs and Energy,” Berlin, July 2015; see pp. 85-86 (especially Figure 18 on p. 86): https://www.bmwi.de/Redaktion/EN/Publikationen/whitepaper-electricity-market.pdf.

21 Palle Laursen, “Designing the future of our customers’ supply chains with carbon-neutral methanol vessels,” Maersk, Dec. 8, 2021: https://www.maersk.com/news/articles/2021/12/08/designing-the-future-of-our-customers-supply-chains ; “A.P. Moller – Maersk accelerates fleet decarbonisation with 8 large ocean-going vessels to operate on carbon neutral methanol,” Maersk Press Release, Aug. 24, 2021: https://www.maersk.com/news/articles/2021/08/24/maersk-accelerates-fleet-decarbonisation.

22 “Maersk secures green e-methanol for the world’s first container vessel operating on carbon neutral fuel,” Maersk Press Release, Aug. 19, 2021: https://www.maersk.com/news/articles/2021/08/18/maersk-secures-green-e-methanol; “Maersk secures green e-methanol for the world’s first container vessel operating on carbon neutral fuel,” European Energy Press Release, Aug. 19, 2021: https://europeanenergy.com/en/press-releases/2021/8/19/maersk-secures-green-e-methanol-for-the-worlds-first-container-vessel-operating-on-carbon-neutral-fuel; and “Power-to-X Solutions in European Energy,” European Energy: https://europeanenergy.com/en/power-to-x/solutions.

23 “The European Green Deal,” European Commission, Brussels, Nov. 12, 2019: https://ec.europa.eu/info/sites/default/files/european-green-deal-communication_en.pdf; and “Parliament supports European Green Deal,” European Interest, Jan. 15, 2020: https://www.europeaninterest.eu/article/parliament-supports-european-green-deal/.

24 “Masterplan for a Competitive Transformation of EU Energy-intensive Industries Enabling a Climate-neutral, Circular Economy by 2050 – Report,” European Commission, Nov. 28, 2019: https://ec.europa.eu/docsroom/documents/38403.

25 Vera Schmies, “Green hydrogen for green steel: Paving the way to Hydrogen Valley,” ThyssenKrupp AG, Jan. 28, 2021: https://engineered.thyssenkrupp.com/en/green-hydrogen-for-green-steel/.

26 HYBRIT, “SSAB, LKAB, and Vattenfall are making a unique joint effort to change the Swedish iron and steel industry fundamentally. Under the name HYBRIT, we are working together to develop the first fossil-free steel”: https://www.hybritdevelopment.se/en/.

27 SSAB, “SSAB aims to hit the market with the world’s first fossil-free steel in 2026”: https://www.ssab.com/fossil-free-steel/ssab-aims-to-hit-the-market-with-the-worlds-first-fossil-free-steel-in-2026; and see also SSAB, “SSAB is taking the lead in decarbonizing the steel industry”: https://www.ssab.com/fossil-free-steel

28 “Volvo Cars is first carmaker to explore fossil-free steel with SSAB,” Joint SSAB/Volvo Press Release, Jun. 16, 2021: https://www.ssab.com/news/2021/06/volvo-cars-is-first-carmaker-to-explore-fossilfree-steel-with-ssab.

29 Jennifer Gerholdt, “HeidelbergCement targets zero-carbon construction future with science-based target,” We Mean Business Coalition, May 13, 2019: https://www.wemeanbusinesscoalition.org/blog/heidelbergcement-targets-zero-carbon-construction-future-with-science-based-target/.

30 Hanson HeidelbergCement Group, “Fuel switching to hydrogen,” Aug. 10, 2022: https://www.hanson.co.uk/en/news-and-events/fuel-switching-to-hydrogen ; “Fuel-switching research takes next step at Ribblesdale,” Dec. 9, 2020: https://www.hanson.co.uk/en/about-us/news-and-events/fuel-switching-research-at-ribblesdale; and “Hydrogen Trial” (undated, accessed December 25, 2022) https://www.hanson.co.uk/en/socialvalue/climate/hydrogen-trial.

31 Martin Brudermüller, “BASF Capital Markets Day – Keynote: Our journey to net zero 2050,” BASF SE, Mar. 26, 2021: https://www.basf.com/global/en/investors/calendar-and-publications/calendar/2021/capital-markets-day.html; and “BASF presents roadmap to climate neutrality, March 26, 2021: https://www.basf.com/global/en/media/news-releases/2021/03/p-21-166.html.

32 “Energy and Climate Protection / Our Carbon Management / New technologies,” BASF: https://www.basf.com/global/en/who-we-are/sustainability/we-produce-safely-and-efficiently/energy-and-climate-protection/carbon-management/innovations-for-a-climate-friendly-chemical-production.html.

33 “Methane pyrolysis – Climate-friendly hydrogen for chemistry,” BASF, Oct. 6, 2021: https://www.youtube.com/watch?v=4r8o6I96Lgw (German with English subtitles). The hydrogen atoms of methane (CH4) are separated from the carbon atom, producing hydrogen gas and solid carbon using 80% less renewable electricity than water electrolysis. The solid black carbon is rather pure and could be sold for other industrial usages, for instance in building materials. This process is already in scale-up and the first commercial plant is projected for 2030. The source of methane could be natural gas or biomethane.

34 “BASF and RWE plan to cooperate on new technologies for climate protection,” Joint News Release BASF/RWE AG, May 21, 2021: https://www.basf.com/global/en/media/news-releases/2021/05/p-21-217.html; and “Vattenfall to sell 49.5% of the offshore wind farm Hollandse Kust Zuid to BASF,” Joint News Release BASF/Vattenfall, Jun. 24, 2021: https://www.basf.com/global/en/media/news-releases/2021/06/p-21-238.html.

35 “Covestro starts offering the world’s first climate- neutral polycarbonate,” Covestro Press Release, Dec. 13, 2021: https://www.covestro.com/press/covestro-starts-offering-the-worlds-first-climate–neutral-polycarbonate/.

36 “Pioneering work for the circular economy and a climate-neutral future,” Covestro Press Release, Nov. 5, 2021: https://www.covestro.com/press/pioneering-work-for-the-circular-economy-and-a-climate-neutral-future/.

37 “Construction begins on world’s first integrated commercial plant for producing CO2-neutral fuel in Chile,” Siemens Energy Press Release, Sep. 10, 2021: https://press.siemens-energy.com/global/en/pressrelease/construction-begins-worlds-first-integrated-commercial-plant-producing-co2-neutral.

38 Mohamed Adow, Amos Wemanya, Kerstin Opfer, Chigozie Nweke-Eze, Augustine B. Njamnshi, Jaime Fernandez, Stephan Singer, “Civil society perspectives on Green Hydrogen production and Power-to-X products in Africa,” Collaboration of German Watch, Power Shift Africa, ACSEA (Advancing Sustainable Energy and Access in Africa) and Brot für die Welt, Jan. 26, 2022: https://www.germanwatch.org/en/84785; “PtX Hub in Morocco: Piloting Power-to-Liquid to fuel Morocco’s energy transition,” International PtX Hub: https://ptx-hub.org/ptx-hub-in-morocco/.

39 Steve Hanley, “Tesla Transitions To LFP Battery Cells For Megapack Installations,” CleanTechnica, May 11, 2021: https://cleantechnica.com/2021/05/11/tesla-transitions-to-lfp-battery-cells-for-megapack-installations/; “FREYR joins race to make LFP batteries at gigawatt-scale in Europe,” energy Storage News, Jan. 12, 2022: https://www.energy-storage.news/freyr-joins-race-to-make-lfp-batteries-at-gigawatt-scale-in-europe/; Andy Colthorpe, “Strategic partnership formed for Europe’s first lithium iron phosphate cell gigafactory,” Oct. 22, 2021: https://www.energy-storage.news/strategic-partnership-formed-for-europes-first-lithium-iron-phosphate-cell-gigafactory/.

40 “CATL Unveils Its Latest Breakthrough Technology by Releasing Its First Generation of Sodium-ion Batteries,” CATL, Jul. 29, 2021: https://www.catl.com/en/news/665.html; “The First-generation Sodium-ion Battery Launch Event,” CATL video in Chinese with English subtitles: https://www.catl.com/en/news/685.html; Shrey Chakraborty, “CATL new patent allows anode-free sodium-ion battery density to go above 200Wh/Kg,” CarNewsChina, Jan. 13, 2022: https://carnewschina.com/2022/01/13/catl-new-patent-allows-anode-free-sodium-ion-battery-density-to-go-above-200wh-kg/; and Brian Wang, “CATL will mass produce sodium-ion batteries in 2023,” Oct. 28, 2022: https://www.nextbigfuture.com/2022/10/catl-will-mass-produce-sodium-ion-batteries-in-2023.html.

41 Agrivoltaics Homepage, Frauenhofer Institute for Solar Energy Systems: https://agri-pv.org/en/.

42 NREL, “Beneath Solar Panels, the Seeds of Opportunity Sprout – Low-Impact Development of Solar Installations Could Be Win-Win-Win for Food, Water, and Renewable Energy,” (2019): https://www.nrel.gov/news/features/2019/beneath-solar-panels-the-seeds-of-opportunity-sprout.html ; and NREL, “The Future of Agriculture Combined With Renewable Energy Finds Success at Jack’s Solar Garden, Sep. 10, 2021: https://www.nrel.gov/news/program/2021/future-of-agriculture-combined-with-renewable-energy-finds-success-at-jacks-solar-garden.html.

43 Brandi McKuin, Andrew Zumkehr, Jenny Ta, Roger Bales, Joshua Viers, Tapan Pathak, J. Elliott Campbell, “Energy and water co-benefits from covering canals with solar panels,” Nature Sustainability 4, 609–617 (2021): https://doi.org/10.1038/s41893-021-00693-8 ; and “Solar Panels Over Canals Can Save Money, Energy and Water, Study Shows,” University of California Merced Newsroom, Mar. 18, 2021: https://news.ucmerced.edu/news/2021/solar-panels-over-canals-can-save-money-energy-and-water-study-shows.

44 Turlock Irrigation District – TID Water and Power, “Project Nexus – Water and Energy Integration for the Future”: https://www.tid.org/about-tid/current-projects/project-nexus/.

45 Uma Gupta, “Solar arrays on canals,” pv magazine India, Mar. 9, 2021: https://www.pv-magazine-india.com/2021/03/09/installing-solar-atop-canals/; and Kalpana Sunder, “The ‘solar canals’ making smart use of India’s space,” BBC Future Planet, Aug. 3, 2020: https://www.bbc.com/future/article/20200803-the-solar-canals-revolutionising-indias-renewable-energy.

46 Samuel Booth, “International Applications for Floating Solar Photovoltaics,” NREL, June 2019: https://www.nrel.gov/docs/fy19osti/73907.pdf ; and Sika Gadzanku, Laura Beshilas, Ursula Grunwald, “Enabling Floating Solar Photovoltaic (FPV) Deployment: Review of Barriers to FPV Deployment in Southeast Asia,” NREL, 2019: https://www.nrel.gov/docs/fy21osti/76867.pdf.

47 Nathan Lee, Ursula Grunwald, Evan Rosenlieb, Heather Mirletz, Alexandra Aznar, Robert Spencer, Sadie Cox, “Hybrid floating solar photovoltaics-hydropower systems: Benefits and global assessment of technical potential,” Renewable Energy 162, 1415-1427 (2020): https://doi.org/10.1016/j.renene.2020.08.080 ; NREL “Untapped Potential Exists for Blending Hydropower, Floating PV,” Sep. 29, 2020: https://www.nrel.gov/news/press/2020/untapped-potential-exists-for-blending-hydropower-floating-pv.html

48 Emiliano Bellini, “Chinese fish pond hosts 550 MW solar farm,” pv magazine, Jan. 7, 2022: https://www.pv-magazine.com/2022/01/07/chinese-fish-pond-hosts-550-mw-solar-farm/.

49 Fraunhofer Institute for Solar Energy Systems ISE, “Integrated Photovoltaics – Areas for the Energy Transformation”: https://www.ise.fraunhofer.de/en/business-areas/photovoltaics/photovoltaic-modules-and-power-plants/integrated-photovoltaics.html.

50 Nicholas Watson, Alina Constantin, “IAEA Event Showcases Progress, Innovations in Nuclear Hydrogen for a Clean Energy Transition,” International Atomic Energy Agency (IAEA), Sep. 21, 2021: https://www.iaea.org/newscenter/news/iaea-event-showcases-progress-innovations-in-nuclear-hydrogen-for-a-clean-energy-transition ; and “Nuclear–Renewable Hybrid Energy Systems for Decarbonized Energy Production and Cogeneration,” IAEA-TECDOC-1885, Proceedings of a Technical Meeting Held in Vienna, Oct. 22–25, 2018, IAEA (2019). https://www.iaea.org/publications/13594/nuclear-renewable-hybrid-energy-systems-for-decarbonized-energy-production-and-cogeneration.

51 Mark Ruth, Dylan Cutler, Francisco Flores-Espino, Greg Stark, “The Economic Potential of Nuclear-Renewable Hybrid Energy Systems Producing Hydrogen,” Technical Report NREL/TP-6A50-66764, The Joint Institute for Strategic Energy Analysis, April 2017: https://www.nrel.gov/docs/fy17osti/66764.pdf; and Mark Ruth, Dylan Cutler, Francisco Flores-Espino, Greg Stark, Thomas Jenkin, “The Economic Potential of Three Nuclear-Renewable Hybrid Energy Systems Providing Thermal Energy to Industry,” Technical Report NREL/TP-6A50-66745, The Joint Institute for Strategic Energy Analysis, December 2016: https://www.nrel.gov/docs/fy17osti/66745.pdf.

52 Nikolaus Muellner, Nikolaus Arnold, Klaus Gufler, Wolfgang Kromp, Wolfgang Renneberg, Wolfgang Liebert, “Nuclear energy – The solution to climate change?,” Energy Policy 155, 112363 (2021). https://doi.org/10.1016/j.enpol.2021.112363.

53 T.W. Brown, T. Bischof-Niemz, K. Blok, C. Breyer, H. Lund, B.V. Mathiesen, “Response to ‘Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems’,” Renewable and Sustainable Energy Reviews 92, 834-847 (2018): https://doi.org/10.1016/j.rser.2018.04.113.

54 International Energy Agency, “Nuclear Power and Secure Energy Transitions: From today’s challenges to tomorrow’s clean energy systems,” Revised Version (Sept. 2022): https://www.iea.org/reports/nuclear-power-and-secure-energy-transitions.

55 The World Nuclear Industry Status Report 2021, pp. 31-32 and 290-307:
https://www.worldnuclearreport.org/IMG/pdf/wnisr2021-lr.pdf.

56 June Sekera, Andreas Lichtenberger, “Assessing Carbon Capture: Public Policy, Science, and Societal Need – A Review of the Literature on Industrial Carbon Removal,” Biophysical Economics and Sustainability 5, 14 (2020): https://doi.org/10.1007/s41247-020-00080-5.

57 See: T.W. Brown et al. (2018).

58 Sgouris Sgouridis, Michael Carbajales-Dale, Denes Csala, Matteo Chiesa, Ugo Bardi, “Comparative net energy analysis of renewable electricity and carbon capture and storage,” Nature Energy 4, 456–465 (2019): https://doi.org/10.1038/s41560-019-0365-7.

59 “CARBON CAPTURE AND STORAGE: Actions Needed to Improve DOE Management of Demonstration Projects,” US Government Accountability Office, GAO-22-105111, December 2021: https://www.gao.gov/products/gao-22-105111.

60 Carlos Anchondo, “CCS ‘red flag?’ World’s sole coal project hits snag,” Energy & Environment News, Jan. 10, 2022: https://www.eenews.net/articles/ccs-red-flag-worlds-sole-coal-project-hits-snag/; and Government of Canada, “Boundary Dam Integrated Carbon Capture and Storage Demonstration Project”: https://www.nrcan.gc.ca/energy/publications/16235.

61 Felix Creutzig, Christian Breyer, Jérôme Hilaire, Jan Minx, Glen P. Peters, Robert Socolow, “The mutual dependence of negative emission technologies and energy systems,” Energy & Environmental Science 12, 1805-1817 (2019): https://pubs.rsc.org/en/content/articlelanding/2019/ee/c8ee03682a.  

62 See: S. Sgouridis et al. (2019).

63 Dir-Jan van de Ven, Iñigo Capellan-Peréz, Iñaki Arto, Ignacio Cazcarro, Carlos de Castro, Pralit Patel, and Mikel Gonzalez-Eguino, “The potential land requirements and related land use change emissions of solar energy,” Scientific Reports 11, 2907 (2021): https://doi.org/10.1038/s41598-021-82042-5.

64 Duncan McLaren, “Quantifying the potential scale of mitigation deterrence from greenhouse gas removal techniques,” Climate Change 162, 2411-2428 (2020): https://doi.org/10.1007/s10584-020-02732-3.

65 Duncan P. McLaren, David P. Tyfield, Rebecca Willis, Bronislaw Szerszynski, Nils O. Markusson, “Beyond “Net-Zero”: A Case for Separate Targets for Emissions Reduction and Negative Emissions,” Frontiers in Climate 1, Article 4 (2019): https://doi.org/10.3389/fclim.2019.00004.

66 Drax, “BECCS and negative emissions”: https://www.drax.com/about-us/our-projects/bioenergy-carbon-capture-use-and-storage-beccs/.

67 “A Bad Biomass Bet – Why the Leading Approach to Biomass Energy with Carbon Capture and Storage isn’t Carbon Negative,” Natural Resources Defense Council (NRDC), October 2021: https://www.nrdc.org/resources/bad-biomass-bet.

68 Mathilde Fajardy, Alexandre Köberle, Niall Mac Dowell, and Andrea Fantuzzi, “BECCS deployment: a reality check,” Grantham Institute Briefing Paper No 28, Imperial College London (2019): https://www.imperial.ac.uk/grantham/publications/energy-and-low-carbon-futures/beccs-deployment-a-reality-check.php.  

69 See IPCC AR6 WG3 (2022).

70 Figure SPM.7 is reproduced in excerpt for the Energy Sector from page SPM.50 of the “Summary for Policymakers” in “Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change,” IPCC AR6 WG3 (2022). The figure and the complete figure data are available at: https://www.ipcc.ch/report/ar6/wg3/figures/summary-for-policymakers/figure-spm-7/.

71 IPCC Press Release on the IPCC AR6 WG3 report, April 4, 2022:
https://www.ipcc.ch/report/ar6/wg3/resources/press.

72 International Energy Agency, “World Energy Outlook 2022” (2022): https://www.iea.org/reports/world-energy-outlook-2022; and Press Release, Oct. 27, 2022: https://www.iea.org/news/world-energy-outlook-2022-shows-the-global-energy-crisis-can-be-a-historic-turning-point-towards-a-cleaner-and-more-secure-future

73 UN Environment Programme, “Emissions Gap Report 2022: The Closing Window – Climate Crisis calls for rapid transformation of societies” (2022): https://www.unep.org/resources/emissions-gap-report-2022; and António Guterres, “Emissions Gap Report 2022 Message” https://www.youtube.com/watch?v=mCkUcJUuCPE.

74 See T.W. Brown et al. (2018).

75 Mark Diesendorf, Ben Elliston, “The feasibility of 100% renewable electricity systems: A response to critics,” Renewable and Sustainable Energy Reviews 93, 318-330 (2018): https://doi.org/10.1016/j.rser.2018.05.042.

76 Christian Breyer, Siavash Khalili, Dmitrii Bogdanov, Manish Ram, Ayobami Solomon Oyewo, Arman Aghahosseini, Ashish Gulagi, A. A. Solomon, Dominik Keiner, Gabriel Lopez, Poul Albert Østergaard, Henrik Lund, Brian V. Mathiesen, Mark Z. Jacobson, Marta Victoria, Sven Teske, Thomas Pregger, Vasilis Fthenakis, Marco Raugei, Hannele Holttinen, Ugo Bardi, Auke Hoekstra, Benjamin K. Sovacool, “On the History and Future of 100% Renewable Energy Systems Research,” IEEE Access 10, 78176-78218 (2022): https://doi.org/10.1109/ACCESS.2022.3193402.

77 Mengzhu Xiao, Tobias Junne, Jannik Haas, Martin Klein, “Plummeting costs of renewables – Are energy scenarios lagging?,” Energy Strategy Reviews 35, 100636 (2021): https://doi.org/10.1016/j.esr.2021.100636.

78 See Marta Victoria et al. (2021).

79 See R. Way et al. (2022).

80 See “IPCC Press Conference for CLIMATE CHANGE 2022: Mitigation of Climate Change” (2022).

81 See A. Grubler et al. (2018).