From the Indian Copper Belts to Chulhas: Affordable Thermoelectric Materials for Rural India

An estimated 840 million people in India use a solid-fuel cookstove (chulha) powered off wood or biomass. These are very inefficient and produce emissions harmful to health and the environment. Chulhas emit harmful pollutants and particulates that contribute to respiratory diseases, including chronic obstructive pulmonary disease and lung cancer. India has the largest number of people exposed to high levels of indoor air pollution (IAP), which is primarily caused by solid-fuel cookstoves. IAP was responsible for 482,000 deaths in India in 2017 alone, the largest number of deaths attributable to IAP worldwide. The cooking stoves operate at temperatures up to 600 deg. C, providing a ready supply of waste heat. A thermoelectric (TE) device is capable of converting this waste heat into useful electricity, providing a localised power source to power an auxiliary fan to improve combustion in the stove, making them cleaner, safer and more efficient and mitigating the effects of IAP.

Approximately 100 million people in rural areas of India have no access to electricity. The areas which electrification has not reached are among the more remote, where off-grid electricity generation is essential. A TE device would also provide sufficient electrical power to fulfill basic needs in lighting, communication and mobile device charging. Addition of a TE device to a chulha would therefore provide a cleaner cooking environment whilst simultaneously delivering a localised electricity supply delivering a major impact on the health and well-being of rural communities.

Central to the creation of a TE generator for use with a cooking stove is the development of materials that are affordable, sustainable and optimised to the working temperature (< 600 deg. C) of the stove. Proof of principle has been demonstrated with commercially-available bismuth telluride modules. However tellurium is scarce and bismuth telluride and the corresponding modules expensive. In this project we seek to develop materials that meet the criteria of performance and cost that are optimised for use in the traditional cooking stoves. In particular, we will create new sulphide TE materials for electricity generation that are derived from minerals such as chalcopyrite, bornite and chalcocite, to which India has access to potentially cheap and abundant reserves in the Indian copper belts, including the Khetri, Singhbuhum, and Malanjkhand copper belts. In this way the project seeks to apply the natural resources of India to the solution of a problem affecting a substantial number of the most disadvantaged sector of the population.

The project will benefit from the combined computational and experimental expertise of three leading TE laboratories in the UK and India. By applying a variety of materials design strategies and synthetic approaches, we seek to create new high performance n- and p-type semiconductors that can be incorporated into a TE device for electrical power generation in the temperature range 200 < T/deg. C < 400, using the waste heat from a cooking stove.

The use of a thermoelectric-powered fan to provide more complete combustion in the cookstove will have a positive impact on the health of the rural population through reductions in the emission of harmful pollutants and particulates. This is a particularly acute problem in India, where in 2017 60% of the population (846 million people) still cooked using traditional solid-fuel stoves. In 2017 alone, there were 1.2 million deaths in India attributable to air pollution, which causes a variety of chronic non-communicable diseases including chronic obstructive pulmonary disease and lung cancer; of these ca. 0.5 million deaths were attributed to indoor air pollution. Exposure to indoor air pollution arising from solid-fuel combustion is particularly high among women and young children under the age of five, who spend more time near the stove. Two thirds of the illnesses caused by indoor air pollution occur in women and children. Therefore the project would have a disproportionately positive impact on the female population.

The 100 million people in rural India who do not have access to a distributed electricity supply will benefit from the novel thermoelectric materials developed in this project for use in the temperature range 200 < T/deg. C < 400. These materials will provide the capability to generate electricity from heat produced by burning solid fuels in cooking stoves, providing an off-grid source of electrical power to supply basic needs.

We also foresee an impact through the training element of the project, which will support research capacity building by increasing the skills and knowledge base in the area of advanced materials that supports economic development. There will also be an impact on the researchers themselves, employed through the project, as they will acquire new high-level scientific and technical skills that will have a major impact on their future careers. This in turn will have an impact on wider society as these trained individuals will contribute to the further development of knowledge-led societies in India and the UK.

Although the project is fundamental in scope, there is also the opportunity for a longer term economic impact as the materials to be developed are derived from copper sulphide minerals, of which the Khetri, Singhbuhum, and Malanjkhand copper belts in India have a rich supply. Successful development of routes to make the most effective and direct use of the raw minerals would therefore have an impact on Hindustan Copper Ltd, the principal operator of mines in this region.

Although focused on the needs of the rural population of India, there would be secondary impact on the wider global community of TE researchers in academia and industry. In particular, demonstration of the effectiveness of compositing with two-dimensional inorganic nanosheets and advances in understanding the relationship between microstructure and transport across interfaces, have the potential to lead to new design paradigms and underpin future developments across a wide range of TE materials and devices.