Abstract:

Geothermal energy, widely recognized as a green, clean, stable and reliable resource, exhibits significant potential to replace traditional fossil energy. Geothermal resources are abundant and widely distributed in China, but geothermal power generation technology in China remains far behind global advancements. Thermovoltaic power generation technology shows great application potential in the low- and medium-temperature range, however, its large-scale application remains challenging. Modulization is a promising method to scale up the installed capacity of a thermovoltaic generator (TEG). This paper proposes a modular TEG with symmetrical arrangement of the heat sinks, which can be installed with different number of thermoelectric modules depending on the heat source types. The heat sinks employe a compact design to increase the volumetric power density of the system. A modular TEG was developed and tested at Shenzhen University on the test platform for low- and medium-temperature geothermal thermovoltaic power generation system. The TEG yielded a maximum output power of 136.5 W and volumetric power density of 26.9 kW/m³, under the conditions of cooling water flow rate of 3.3 m³/h, temperature of 20 ℃ and heat input power of 9 kW. The relative thermoelectric conversion efficiency reached 82.5% of the maximum theoretical value, which was achieved with a figure of merit (ZT) of 0.5 for the current module. If the equivalent ZT value can be improved to 1—2, under the same operating conditions the maximum output power of the TEG can be as high as 1.69—2.63 kW, and the volumetric power density can reach 338.3—518.8 kW/m³. Accordingly, the thermoelectric conversion efficiency would increase to 10.5%, or 92.8% of the theoretical maximum value. Under this scenario, the modular design of the thermovoltaic generator proposed in this paper can achieve higher application value.

Key words: thermovoltaic generator, modularization, low-medium temperature, geothermal resource, volumetric power density