Turning 'waste' into power

UNIVERSITY OF WOLLONGONG

Waste heat is a byproduct of nearly all electrical devices and industrial processes. Image: MichaelUtech/iStockphoto Thermoelectric power generation is expected to play an increasingly important role in meeting the energy challenges of the future. And helping to meet that energy challenge is PhD student, Priyanka Jood, from the Institute for Superconducting and Electronic Materials (ISEM) whose groundbreaking research has just been published in the American Chemical Society journal, Nano Letters. Priyanka, the first author of the paper, supervised by Dr Germanas Peleckis and Professor Xiaolin Wang, is working on thermoelectric materials which can generate electricity directly from waste heat. Dr Peleckis, Professor Wang, and the Director of the ISEM, Professor Shi Dou, are co-authors of the Nano Letters paper. The UOW team along with researchers from Rensselaer Polytechnic Institute (RPI) in New York have created large marble-size pellets of thermoelectric nanomaterials. Priyanka spent about a year working alongside the US team. The RPI team are also co-authors in the paper. The team was led by Professor Ganpati Ramanath and the other team members who contributed were Rutvik J. Mehta, Yanliang Zhang, Richard W. Siegel and Theo Borca-Tasciuc. Waste heat is sometimes referred to as secondary heat or low-grade heat which is heat produced by machines, electrical equipment and industrial processes. It is a byproduct of nearly all electrical devices and industrial processes from driving a car to flying an aircraft or operating a power plant. Now the UOW team based at the Innovation Campus along with engineering researchers at Rensselaer Polytechnic Institute have developed new nanomaterials that could lead to techniques for better capturing and putting this waste heat to work. The key ingredients for making marble-sized pellets of the new material are aluminium and a common everyday microwave oven. Harvesting electricity from waste heat requires a material that is good at conducting electricity but poor at conducting heat. One of the most promising candidates for this job is zinc oxide (ZnO) -- a non-toxic, inexpensive material with a high melting point. While nanoengineering techniques exist for boosting the electrical conductivity of zinc oxide, the material’s high thermal conductivity is a roadblock to its effectiveness in collecting and converting waste heat. Because thermal and electrical conductivity are related properties, it’s very difficult to decrease one without also diminishing the other. Now the UOW and US-based teams have demonstrated a new way to decrease zinc oxide’s thermal conductivity without reducing its electrical conductivity. The innovation involves adding minute amounts of aluminium to zinc oxide, and processing the materials in a microwave oven. The research could lead to new technologies for harvesting waste heat and creating highly energy efficient cars, aircraft, power plants, and other systems. Researchers say harvesting waste heat is a very attractive proposition, since the heat can be converted into electricity and used to power devices such as a car that is creating the heat in the first place. This would reduce the world’s dependence on fossil fuels. Priyanka said it was possible that even further power factor enhancements using nano-structured zinc oxide might be possible making this material highly valuable for thermoelectrical industrial applications. She said that researchers at ISEM are continuing to explore new and novel methods for producing high performance thermoelectric materials as a part of their research program in energy storage and energy conversion materials. Results of the Australian Research Council funded study entitled “Al-Doped Zinc Oxide Nanocomposites with Enhanced Thermoelectric Properties,” can be seen online at Nano Letters at this site. Editor's Note: Original news release can be found here.