Thermoelectric devices play an important role in energy management and the recovery of wasted heat. National Physical Laboratory (NPL) is a partner in the NexTec project, which aims to create better thermoelectric modules for the automotive, refrigeration and IT industries.
Two key factors for improving thermoelectric performance are investigated in parallel: (1) the development of better thermoelectric materials and (2) the development of new system geometry and methods to integrate the module more efficiently; both of these approaches are required to ensure optimal performance.
One of the key outputs of the consortium involving NPL, research centres and end-users, such as Seat, Siemens and Electrolux, is to have demonstrated a working prototype able to recover thermal energy up to 1000 K; existing commercial products are limited to 500 K.
NPL's role is to improve the accuracy of materials and module performance measurements, and to provide support for the integration of modules in real world conditions. NPL is measuring the module performance curve at high-temperature and developing new metrology for nanostructured materials and thin-films.
Thermoelectric materials work best at different temperature ranges, for example bismuth telluride is optimised to work between room temperature and 500 K. At higher temperatures, new materials such as skutterudite are needed to efficiently recover the heat wasted from car exhausts, for example - this can reach temperatures of up to 1000 K.
"Our new materials and device geometry not only perform better at high temperatures, but also solve a lot of the problems related to thermal expansion," explains Alexandre Cuenat, who leads work on thermoelectric energy conversion at NPL. "The NexTec project will result in more efficient thermoelectric materials. Because these can be optimised for different temperature ranges and nanostructured to reduce thermal conductivity, they could help deliver more electrical power to your car. The same goes for applications in other transport sectors (trains or shipping) or in industry where there is often wasted heat."
Although the project focused essentially on the automotive industry and industrial sectors, other applications in low-grade heat recovery such as energy harvesting for wireless sensors can also be considered.
"The device we are proposing aims to save costs by making fabrication more practical, faster and easier to automate. We are also exploring applications in refrigeration because nanostructured materials have the potential to extract more heat from the environment with the same electrical power," says Cuenat.
NexTec is the acronym for the project, 'Next Generation Nano-engineered Thermoelectric Converters - from concept to industrial validation'. It is funded by the European Commission under the Seventh Framework Programme (FP7) and began in July 2011. The NexTec consortium brings together 12 world class institutions, from five EU member states, to open new avenues of joint research in complementary areas.
Source and top image of a thermoelectric convertor: National Physical Laboratory
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