Analysis of a wooden pellet-fueled domestic thermoelectric cogeneration system

Abstract

A domestic thermoelectric cogeneration system (DTCS) is a noiseless and maintenance-free method of on-site micro-cogeneration, with no moving parts. This paper contributes to the research by characterizing, modeling and assessing the performance of a DTCS, where thermoelectric modules are integrated directly in the combustion chamber of a wooden-pellet fueled boiler (nominal thermal output 20 kWth), to keep structural changes minimal and the temperature difference large. The results suggest that temperature differences up to 660 °C can be achieved with the proposed configuration, the hot side temperature reaching the level of 750 °C (1023 K). The electrical output is 1.9 kWe at most, and the electrical plant efficiency of 8.9% (LHV) can be obtained, when the figure of merit of the thermoelectric material is unity. Maximum 47% of the on-site electricity consumption can be met in a single-family house located in Finland. In comparison with a standard pellet-fueled boiler, the integrated DTCS is able to cut the annual non-renewable primary energy by 11% and CO2 emissions by 21%. At present, the annual cost savings of 160 €/y at maximum can be achieved. To make the DTCS economically viable, further development of thermoelectric materials and better investment support is required.