A new report by the OECD Nuclear Energy Agency (NEA), “Beyond Electricity: The Economics of Nuclear Cogeneration”, published on 22 July says: “Nuclear energy is an important source of low-carbon electricity and plays a significant role in avoiding carbon emissions. It has the potential to contribute further to the decarbonisation of the world’s energy sector if it is also used to provide heat for industrial applications, which today mainly run on fossil fuels.”
The 216- page report notes: “The feasibility of non-electrical applications of nuclear energy has already been demonstrated through decades of experience with approximately 67 reactors around the world (representing about 15% of the world’s reactors) providing either district heating, desalination or some other form of process heat. However, to date, cogeneration applications have used only a small fraction of nuclear energy.”
NEA adds that, while existing reactors can supply thermal energy for industrial applications at less than 300ºC, advanced reactors now being developed now would reach outlet temperatures many times higher, “making them suitable for cogeneration applications over a wider temperature range”. Furthermore, “Nuclear cogeneration can also enhance the flexibility of electricity supply in combination with high levels of renewables.”
An NEA ad hoc “Expert Group on the Role and Economics of Nuclear Cogeneration in a Low-Carbon Energy Future” investigated the challenges and opportunities for nuclear cogeneration. “The group recognised that cogeneration applications of nuclear energy are more likely to develop if they are more economical than the technical solutions they replace, namely gas-fired production of steam and electricity.”
NEA says understanding the economics of nuclear cogeneration, including associated system costs, is essential. “However, there is no clear methodology to assess the economic case for developing non-electrical applications of nuclear energy, even though there are proven examples of developing such applications on an industrial scale, especially for district heating.”
While the report focuses principally on cogeneration, “it also highlights the significant potential of nuclear power, when coupled with thermal storage, to support the integration of variable renewable energy sources”. Integrating this type of with cogeneration applications, “can further improve its economics and climate mitigation potential”.
The purpose of the study is to fill a methodology gap by reviewing existing research and proposing an approach that can help assess the costs and benefits of developing other products besides electricity. The expert group contributed detailed case studies demonstrating the feasibility and economics of nuclear cogeneration in various member countries, which comprised a major part of the report. The case studies “illustrate potential applications of nuclear cogeneration” and “provide practical examples of the diversification of nuclear energy use tailored to meet multiple urban and industrial heat and power demands without GHG emissions during operations”
The first example of the diversification of nuclear energy use is district heating. Case studies on district heating included both the existing systems as well as the proposed projects. In Switzerland, the Beznau Nuclear Power Plant has continuously provided up to 20 000 people with thermal power for more than three decades. The Paks Nuclear Power Plant in Hungary provides a small fraction of thermal energy to about 2 600 households. Other case studies explored connecting the existing or new heating networks to existing nuclear plants in Finland, France and Slovenia.
Another example of nuclear heat application is desalination.There have been 250 reactor-years of cumulative experience of nuclear desalination with 17 reactors around the world mostly based on heat supplied from water-cooled reactors. The cases explored in this study are based on advanced reactor concepts. The GTHTR300C is a multi-stage flash (MSF) desalination process specially configured and optimised to efficiently recover the sensible waste heat from the power conversion cycle of Japanese high-temperature gas-cooled reactors. Another case study showed economical desalination of sea water using hybrid of reverse osmosis and multi-effect distillation (MED) units coupled with SMART, a Korean-designed 330 MWth integral pressurised water reactor.
Case studies of hydrogen production were based on high-temperature, water-splitting processes using high-temperature heat and electricity from advanced generation IV type reactors. Large-scale hydrogen production using a sulphur-iodine thermochemical process coupled with a very high-temperature reactor (VHTR) with outlet temperature up to 950ºC was found to be economically feasible in Korea and Japan. A case study also explored the use of nuclear energy for bitumen and synthetic crude production from Canada’s oil sands.
The goal of the nuclear-renewable hybrid energy systems (NRHES), which are being developed under a US Department of Energy (DOE) programme, is to identify technologically feasible solutions capable of mitigating the impact of variable renewables in decreasing the baseload fraction while maintaining low electricity costs and a high standard of reliability.
To realise the potential of nuclear cogeneration for decarbonisation, the group of experts made a set of recommendations.Governments should consider developing national/regional roadmaps for decarbonising the heat sector: in most countries, only roadmaps for the electricity sector are developed. These roadmaps should recognise nuclear energy’s potential for replacing fossil fuel used for heating in industrial and commercial sectors.Governments should recognise that nuclear cogeneration can be an integral part of low carbon energy systems. Government policies promote nuclear thermal energy and discourage fossil fuel use through carbon taxes and other incentives Nuclear cogeneration helps increase penetration of renewables on the grid while ensuring grid reliability and the economic viability of the integrated system.Governments should co-ordinate energy and water policies to advance nuclear desalination projects. Energy and water planning communities should work together on innovative financing and business models for water desalination projects.There is a need for demonstration projects to advance nuclear cogeneration, and these should be funded by public/private partnerships with a strong participation by industrial actors.Awareness and information regarding the potential of nuclear cogeneration should be further developed and studies on the integration of nuclear and renewables using nuclear cogeneration as an energy storage/buffer should be carried out, including full life cycle assessments.
NEA also looks at the opportunities and challenges for nuclear cogeneration, namely:The experience of nuclear district heating (DH) in some countries has been a remarkable success. Nuclear DH may be a mature technology, and NPP designs can be made to incorporate cogeneration readiness, but it should also be recognised that DH operators have alternative choices. Thus, proponents of nuclear DH should work with DH operators to build a more convincing case.The cost of the heat transport line is a major factor affecting the competitiveness of nuclear DH, especially in countries where NPPs are typically located several tens of kilometres from large urban centres. If the cost of the transport line is not allocated to the nuclear cogeneration project, nuclear DH is the most competitive solution.For desalination projects, there is a need to address energy policies and water policies in a co-ordinated manner.Small modular reactors (SMRs) could be more suited for desalination without emitting GHGs, as the demand for desalinated water is growing rapidly.Advanced nuclear reactors under development as generation IV reactors and several types of SMRs will have higher outlet temperatures and could therefore be more suited for supplying heat to industrial processes.The problem of the difference in time frames of NPPs (40-60 years) and industrial plants that could use process steam (up to 20 years) needs to be addressed. For district heating, the time frames of nuclear and district heating systems are similar.The concept of nuclear-renewable hybrid energy systems shows that cogeneration can play an important role to better integrate variable renewables and nuclear plants in decarbonised energy systems.Coupling NPPs with an industrial facility and related safety issues are important points to consider in licensing. There is not enough information regarding the licensability of cogeneration applications in existing and new NPPs.
Image: NEA ad hoc group for the 'Role and Economics of Nuclear Cogeneration in a Low-Carbon Energy Future' discuss the challenges and opportunities for nuclear cogeneration (photo courtesy of NEA)