Field test of a geothermal thermoelectric generator without moving parts on the Hot Dry Rock field of Timanfaya National Park

Abstract

Although in the last years thermoelectric generators have arisen as a solution to boost geothermal power generation, tests on field are still scarce. The vast majority of the available studies focus on computational simulations or laboratory experiments, mainly with active heat exchangers that require pumps or fans, and, consequently, present moving parts and auxiliary consumption. The present paper demonstrates for the first time the suitability of a geothermal thermoelectric generator (GTEG) with passive phase change heat exchangers, and therefore, without moving parts nor auxiliary consumption, on the shallow Hot Dry Rock (HDR) field of Timanfaya National Park (Canary Islands, Spain), where 173 °C air anomalies can be found. The device has been in operation without maintenance for 2 years now, producing more than 520 kWh of energy. In terms of power generation, since the installed device is in turn composed of two prototypes with 10 and 6 thermoelectric modules, it has been confirmed that installing more modules leads to a lower generation per module, although total generation can be higher. In fact, the prototype with 10 thermoelectric modules generated a maximum of 20.9 W (2.09 W per module) with a temperature difference between sources of 158 °C, while the prototype with 6 thermoelectric modules obtained 16.67 W (2.78 W per module) under the same conditions. These results open the door for a large-scale exploitation thanks to the intrinsic advantages of modularity, reliability, robustness, and minimal environmental impact of the developed device.