Microchp, thermoelectric, thermophotovoltaic
MicroCHP involves the coproduction of both heat and electric power in (typically) residential heating systems. A range of different energy conversion technologies are currently receiving attention for this application including Stirling engines, internal combustion engines, fuel cells, and Rankine cycles with steam or organic compounds as working fluids. In this work the use of ThermoPhotoVoltaic (TPV) and ThermoElectric (TE) conversion devices either alone or in combination for power production in an oil-fired heating system have been explored. The focus of this work to date has been on sufficient electric power output to achieve self-powering of the appliance with the consideration that reliability of the heating system during power outages may provide the greatest value to the consumer. Also explored is the potential for producing larger power output levels, to 1 kW. Low cost, currently available TE devices, based on bismuth telluride, have very low thermal to electric power conversion efficiencies. The use of these in self-powered heating appliances for other applications is established art. Further for simply self-powering, a low conversion efficiency is all that is required to produce the 100 watts needed to power the system. Advanced TE materials under development offer strong potential for increased efficiency in the future. TPV, while currently at an earlier state of development offers the potential for higher conversion efficiencies. This work will report the production of power with both TE and TPV integrated with a residential boiler. A hydronic system was selected relative to a forced air system because of the lower electric power requirements. Using a novel pressure atomized oil burner in combination with very low power circulating pumps, the total running power demand has been reduced to 72 watts. In consideration of cycling, it is estimated that a minimum steady state power output level of 120 watts is required. Experimental results on power production with both TE and TPV in this system are presented. The potential for integration of both TE and TPV devices in a hybrid system are discussed.