Concentrated solar thermalProject Thermoelectric Generator for Concentrated Solar Thermal Systems
This report details how to better understand the applicability of thermoelectric power generation within a useful concentrated solar thermal (CST) technology.
The project aims to investigate the combination of a medium temperature thermoelectric generator with an absorption chiller in a concentrated solar thermal system. Thermoelectrics are materials which can generate electrical power when exposed to a thermal gradient, and absorption chillers produce chilled air from a thermal source, in this case water superheated to 180°C. The two technologies have been combined so that the thermoelectric generator (TEG) is heated on once face to greater than 400 °C by solar radiation concentrated at 200x with a parabolic mirror, and cooled on the opposite face by flowing superheated water which is fed to the absorption chiller. This configuration is envisaged to be useful in a variety of applications including remote communities without grid power operating as a Stand-alone Solar Cooling System (SASCS). A complete test bed was constructed and operated at the CSIRO Energy Centre. The system consists of two 15 m2 solar concentrating dishes with cavity receivers and a 10 kW absorption chiller.
The technologies required for this system were developed under three tasks: (1) The development and process scale up of improved ceramic oxide thermoelectric materials, (2) The design and construction of cavity receivers which incorporated medium temperature TEGs, and (3) Design, construction and operation of the SASCS test bed.
The development of improved thermoelectric materials focused on ceramic oxides due to their stability in air. The research lead to some improvements in the performance of both CaMnO3 and Ca3Co4O9. However, the overall thermal-to-electrical efficiency is seen as limited to around 3.5% which may limit the applicability of these materials, such that higher-performing and more expensive materials which would also require a protective atmosphere may be required to provide the necessary efficiency.