Harvesting waste heat as electrical power: Theory-led control of heat transport in thermoelectrics

Switching to cleaner sources of energy to alleviate global warming is the most important scientific and technological challenge of our time. More than 60 % of the energy used worldwide is wasted as heat from sectors including transportation and industry, representing vast quantities of unnecessary greenhouse gas emissions. Thermoelectric generators improve the efficiency of energy-intensive processes by recovering waste heat as electricity, and viable thermoelectric power is therefore an important part of a secure, sustainable energy strategy. Despite a projected global market of $1bn by 2024, however, large-scale thermoelectric power is currently not feasible due to limited efficiency and the scarcity and toxicity of the materials used.

High-performance thermoelectric materials need to be good conductors of electricity and poor conductors of heat. Decades of advances in electronics have enabled materials scientists to reliably optimise the electrical properties of thermoelectrics to improve their performance, but developments are being held back by our poor understanding of heat transport and how to control it. This is an area where materials modelling - calculating and analysing material properties using theory and high-performance computing - has proven to be very successful.

The research programme pioneered by this fellowship will cross the boundaries between physics, materials science and chemistry to develop the modelling tools needed for more complete understanding and control of heat transport in materials in general and thermoelectrics in particular. This will be achieved through three complementary aims:

(1) Improving our understanding of how doping and alloying - both engineering strategies widely used to optimise thermoelectric performance - affect heat transport. This will allow a set of design rules to be established for choosing the best material modifications to optimise heat transport in tandem with electrical properties, allowing for targeted improvement of new and existing flagship thermoelectric materials.

(2) Explaining how the complex ("anharmonic") structural dynamics found in some of the highest-performing thermoelectric materials leads to their desirable ultra-low heat transport, and developing strategies to "design in" this behaviour as a new route to improve thermoelectric performance alongside existing strategies.

(3) Developing a novel class of high-performance thermoelectrics based on traditional inorganic materials incorporating small molecules. These "hybrid" materials made headlines for their potential use in high-performance solar cells, and have very recently been shown to have unusually low thermal conductivity, indicating that similar materials may be good candidate thermoelectrics. This last aim will therefore build on the tools and insight developed within the first two to identify and develop these materials into the next generation of high-performance thermoelectrics.

This research will establish new routes to improve the performance of current and future thermoelectric materials and will demonstrate the theory-led design of a new class of efficient, cost-effective and sustainable thermoelectric materials suitable for widespread commercialisation. It will put the UK at the forefront of thermoelectric research to provide timely solutions to a critical worldwide challenge and benefit from a growing global market. An improved ability to control heat transport enabled by this programme will also be of immediate benefit to other technologies, yielding more efficient solar cells, better thermal management in batteries and improved power electronics and silicon chips, among others.

This research programme will deliver fundamental developments that enable scientists to understand and control the heat transport in materials. It will then apply them to develop new materials for low-cost, efficient thermoelectric power and to improve materials for solar power and batteries - all of these are vital parts of the low-carbon ecosystem needed to meet stringent emissions targets. This research will accelerate the UK's switch to clean energy, contribute towards achieving net zero greenhouse gas emissions by 2050, and help position it as a global leader in low-carbon technologies.

To achieve this, the programme will:

(1) Provide an improved understanding of heat transport in materials and establish strategies to optimise it for technological applications by materials engineering;
(2) Deliver the high-performance, low-cost thermoelectric materials needed for large-scale thermoelectric power, leading to improvements in the efficiency of energy-intensive processes such as transportation and industry;
(3) Provide new opportunities to balance economic growth against meeting strict emissions targets by driving UK leadership and innovation in thermoelectric power and other low-carbon technologies; and
(4) Demonstrate the central role of effective science policy in addressing global challenges such as climate change.

The UK's 2017 Clean Growth strategy highlighted the potential of low-carbon technology to bring two million jobs and £170 bn to the UK economy over the next decade. As initiatives such as the Supergen Programme and the Faraday Institute have shown, strategic investment in research and strong links between academia and industry are critical for the UK to grow and maintain an international leadership in this emerging area. The body of knowledge and targeted improvements to thermoelectric power delivered by this research programme will enhance the competitiveness of UK science and industry and create new opportunities for future growth.

The UK has a strong global presence in the automotive industry that stands to benefit from the accelerated development of thermoelectric power through this project, including the global brands Jaguar Land Rover and Alexander Dennis. Technologies to improve the efficiency of automobile engines are extremely important - electric vehicle technology is in relative infancy, and until it matures emissions from combustion engines will become an increasingly large fraction of overall carbon emissions.

This research will also combine with other research programmes to benefit the UK's portfolio of low-carbon companies including, for example, UKSOL (solar energy), Thermoelectric Conversion Systems Ltd. (thermoelectric power) and Hyperdrive (batteries). As some of these have shown, developing and manufacturing new technologies in the UK can have the added benefit of bringing jobs and investment to parts of the country where investment and economic growth have traditionally fallen behind.

In broader terms, this research programme will work alongside other flagship UK science projects to address the global challenge of mitigating climate change. This is arguably the most important scientific and technological challenge of our time, and rising to the challenge requires science, industry and policy makers to work together to meet tough emissions targets. By pushing forward the development and commercialisation of the core technologies needed to meet these targets, this research programme will join others in establishing the UK as a leader in effective policy making by showing how countries can reap the benefits of fundamental science through economic growth.