Thermoelectric cogeneration of heat and electricity from agricultural residues

A thermoelectric cogeneration unit consisting of a honeycomb-structured steel heat collector, twelve oxide thermoelectric modules, and three water jackets was installed in the flue of a portable biomass burner and tested using dried wheat residue. Heat-transfer performance was evaluated by comparing configurations with ninety-one and sixty-five open through holes. Under the tested conditions, the sixty-five-hole configuration showed higher flue-gas temperature, cooling-water heat recovery, and electrical output than the ninety-one-hole configuration. The sixty-five-hole configuration achieved a total cooling-water heat-recovery rate of 5.42 kW and a summed maximum power output of 63 W from the three subunits measured sequentially. The maximum apparent thermoelectric conversion ratio based on the recovered cooling-water heat was 0.78%. However, independent replicate combustion tests were not performed; therefore, the observed differences should be regarded as preliminary. These results demonstrate the potential of high-temperature oxide thermoelectric modules for small-scale biomass cogeneration while highlighting the need for controlled replicate tests and further optimization of heat transfer.