Waste Heat Recovery in a Transcritical Carbon Dioxide Vapor Compression Cycle with Thermoelectric Generators

Thermoelectric generators are a great alternative for waste heat energy harvesting in several technological fields. Vapor compression refrigeration systems present great potential for waste heat energy harvesting as they dissipate heat in a condenser/gas cooler from the refrigerant to the ambient. This heat can be harvested by utilizing a thermoelectric generator. The objective of this study is to evaluate the energy harvesting potential of thermoelectric generators in transcritical vapor compression cycles and their effect on cycle performance. A computational model is used to simulate a transcritical carbon dioxide refrigeration cycle with the inclusion of a thermoelectric generator between the compressor and the gas cooler. The energy harvested by the generator is calculated, and the effect on the vapor compression system is quantified. The results show that by including the thermoelectric generator, two positive effects are obtained: the electrical energy generated by the thermoelectric system positively enhances the efficiency of the cycle, and the heat extracted in the generator leaves room for further cooling in the gas cooler, producing an increase in cooling capacity that also enhances efficiency. The results show an increase in the coefficient of performance that ranges between 3.74 and 12.14% for different working conditions.