Above: EDF is planning to install up to a 2MW electrolyser by the Sizewell site, which can use electricity from Sizewell B to produce hydrogen to fuel site construction traffic (Photo credit: EDF Energy)
AS NEW SOURCES OF ENERGY and advanced technologies are used, there is continuous evolution in energy supply, demand, and distribution. But most of the energy infrastructure around the world has a lot of ‘inertia’ — ie takes years or decades to replace — and long-term developments will affect the energy economy for decades to come.
Nuclear power plants are evolving too and undergoing technological advances to make them more versatile. Advanced nuclear power plants will function as part of an electricity system that is very different from the one that existed during the construction of the nuclear plants currently in use.
Another technology undergoing technical advances to become more versatile is hydrogen cogeneration, and as the energy economy evolves hydrogen production is gaining global visibility and political support.
As markets are rapidly incorporating renewable sources of energy, including wind and solar, it is becoming more difficult to sustain the supply-demand balance. Energy demand varies during the day, falling briefly in the morning and peaking in the early evening as people come home from their work. Generally, nuclear plants operate at full load but they are theoretically still capable of achieving a higher operational flexibility. It is operational flexibility that enables nuclear plants to respond dynamically to seasonal demand shifts or hourly market pricing changes.
In practice, more promising applications for nuclear, including hydrogen production and high-temperature process heat, have recently been included in the International Atomic Energy Agency’s programme. It said in 2018 that “The OECD Nuclear Energy Agency, Euratom, and the Generation IV International Forum have all expressed interest in non-electric nuclear power applications focused on advanced next-generation and revolutionary nuclear reactors”. According to the IAEA’s Ibrahim Khamis, the drivers for cogeneration include, but are not limited to, improving economics, meeting the demand for energy-intensive non-electric goods, securing energy supply for industrial complexes, accommodating seasonal fluctuations in electricity demand and matching small and medium electrical grids with accessible large-size grids.
Advantages of nuclear power and hydrogen cogeneration
Every year, about 50Mt of hydrogen are consumed worldwide. Nuclear power plants and hydrogen production systems are well aligned to give nuclear an economical advantage over traditional hydrogen production energy sources. Nuclear power plants can supply the required heat and electricity without generating any carbon emissions. Producing hydrogen will serve as energy storage and decouple power production from the consumption of electricity. The hydrogen stored can either be used as fuel for generators based on combustion or sold for other industrial purposes.
Hydrogen production was also regarded as an energy storage technology in a 2017 study (Coleman, Bragg-Sitton, & Dufek, 2017). MIT Energy Initiative (MITEI) researcher Jesse Jenkins and his colleagues at Argonne National Laboratory considered pairing renewable resources with flexible nuclear power plants. In a paper for Applied Energy Jenkins claims it makes more sense to operate a nuclear power plant at lower performance and to absorb as much free wind and sun as possible. That way nuclear operates flexibly to integrate renewable energy and reduce carbon dioxide emissions. Flexible operations improve reactor ownership revenue by reducing the amount of waste fuel, improving system quality, and reducing customer energy costs.
The development of energy storage systems for hydrogen could reduce power generation emissions in comparison to emissions generated by fossil-fuel combustion according to a paper published in journal Sustainability (Noussan, Raimondi, Scita, & Hafner, 2021). They say integrating fuel cells with hydrogen in the transport sector and using energy storage to mitigate peak power generation reduces CO2 emissions, provided that the only hydrogen combustion byproduct is water.
However, the emission of carbon from the hydrogen fuel cell lifecycle depends on the primary source of energy and the process used in hydrogen production. There may also be significant environmental impacts from the use of water in hydrogen production. However, water is generated and can be returned to the original source when the hydrogen is recombined with oxygen in a fuel cell to generate electricity.
Toxic metals, such as palladium, are used for the electrodes and catalysts in the hydrogen generation process. Hence, the disposal of used fuel cells is another aspect that must be thoroughly monitored in order to reduce the adverse effect on the environment. Recently, recycling and reprocessing of palladium has been the focus of research, with the goal of reducing its negative environmental impact.
If nuclear is considered as the primary energy source for hydrogen production, it should generate minimal emissions and have minimal impact on the environment.
A public-private US project aims to demonstrate HTSE using heat and electricity, likely at the Prairie Island Nuclear Generating Plant (Photo credit: Xcel Energy)
Challenges of nuclear power and hydrogen cogeneration
Nuclear cogeneration faces major challenges, including the disparities between nuclear and heat markets. There are also specific issues and concerns to be addressed around nuclear plant whose design has been altered so it is better suited to produce hydrogen (settlement, the time needed to plan, construction and financial risk), the demonstration of industry-specific nuclear plant and licensing of custom nuclear units.
Nuclear power generation is feasible and economically viable; however, any nuclear reactor is subject to a set of operational limitations arising from nuclear reactor physics and these are different from the technological restrictions of traditional coal or gas power plants. For example if, over the fuel irradiation cycle, the minimally stable performance of a nuclear reactor changes, production cannot ramp up or down too rapidly without loading the nuclear fuel rods and the reactor itself.
At high power levels there is surplus energy available and curtailing it is considered to be largely unfavourable to the plant. The surplus energy available would suffer if the plant were operated flexibly to accommodate demand management.
Conclusion
The potential benefits of nuclear hydrogen over other sources are significant and could result in a growing share of hydrogen production in a future global energy economy. However, nuclear hydrogen processes are technically uncertain and require comprehensive research and a strong development effort. Safety issues and the storage and delivery of hydrogen are critical areas for development to promote a prosperous hydrogen economy.
In the evaluation of the cost of green hydrogen ie that produced by electrolysis of water using low carbon power (the likely alternative, production from methane with steam reforming and carbon capture is referred to as ‘blue’ hydrogen) the analysis must account for the cost and efficiency of an electrolyser, and replacement of its stacks, the compression and storage of hydrogen, the cost of transporting hydrogen and, finally, the efficiency of dispensing hydrogen.
One of the ultimate questions pertaining to the future of hydrogen in a decarbonised world is the cost of hydrogen production from an electrolyser relative to alternative means for providing hydrogen for transport, fertilizer, industrial uses, and other things.
Accurately calculating the cost of hydrogen as a lifetime cost allows you to address different business models, such as use of hydrogen fuel for airplanes, garbage trucks, buses and other transport that cannot be accomplished with electric vehicles. You can also compare the cost of hydrogen from an electrolyser with the cost of hydrogen from a steam methane reactor; evaluate the cost and benefits of distributed hydrogen production versus centralised production; and measure the effectiveness of a strategy that produces hydrogen during periods when electricity costs are low.
Authors: Paul Lalovich, Organisational effectiveness consultant, Agile Dynamics; Ed Bodmer, Organisational effectiveness consultant, Agile Dynamics
