Techno-economic analysis of different plant configuration for thermoelectric cogeneration from biomass boiler

Thermoelectric modules integration within biomass boiler for the direct conversion of heat into electricity is a possibility to increase efficiency and to realize a stand-alone biomass boiler. Due to the low conversion efficiency (up to 5%) of commercial thermoelectric modules, the aim of the integration shall not be the electricity production for external power supply, but the energy self-consumption of biomass boiler electric auxiliaries. The paper describes and analyses four different options for the integration of thermoelectric modules within a biomass boiler: in the combustion chamber, in the convective tubes, in the chimney and with a condensing fluid circuit to be realized outside the biomass boiler. Five quantitative and qualitative key performance indicators have been defined to assess how the integration strategy can influence the electric yield of thermoelectric modules, the ease of maintenance, the operation continuity, the need of auxiliaries systems to be added as well as the impact on biomass boiler redesign or retrofit. The analysis shows that the realization of a circuit with a condensing fluid allows reaching the best combination of key performance indicators. On the basis of this result, the paper also shows the preliminary design of a new test facility to test Glycerol Triacetate as condensing fluid to produce electricity by thermoelectric modules.