Thermoelectric generator for high temperature geothermal anomalies: Experimental development and field operation

Design and Optimization of Thermoelectric Generators for Harnessing Geothermal Anomalies: A Computational Model and Validation with Experimental Field Results

“…For this reason, as the number of thermoelectric modules increases, the heat absorbed from the borehole is greater, which decreases the temperature on the hot side of the TEMs, and thus decreases their efficiency. This effect was also demonstrated in laboratory for the HT-GTEG in [23].…”

“…The second GTEG (HT-GTEG), installed in June 2021 in the zone with the highest temperatures, Islote Hilario, is operating in a borehole with gases emerging at 465 °C, and it contains the same type of heat exchangers but only 8 thermoelectric modules in one only thermosyphon, as can be seen in Fig. 3 [23]. Moreover, the thermosyphon is made of steel due to its poper mechanical properties at such high temperature and does not include fins.…”

“…Then, to join the three parts together, it is necessary to consider the thermal contacts due to the tiny air gaps that remain between the surface when two parts are assembled as a consequence of their roughness. In the GTEGs considered here, graphite sheets have been added between the surfaces in the hot and the cold sides of the modules in order to reduce these thermal contact resistances (𝑅 𝐻 𝑐𝑜 and 𝑅 𝐶 𝑐𝑜 ) [12,22,23]. Their value depend on the roughness of the materials and the pressure distribution in the assembly process.…”

“…Alegría et al [12] characterized in laboratory a GTEG for medium temperature geothermal anomalies (MT) without moving parts, and were able to install it in Timanfaya National Park, demonstrating the feasibility of the technology for the first time in real conditions, working for more than 2 years in perfect operation without the need for maintenance and generating between 2.09 and 2.78 W per module [22]. Thank to this development, they could finally install a thermoelectric generator in the area with the highest temperature (HT) geothermal anomalies recorded in Lanzarote, reaching a generation of 4.5 W per module, 36 W total, working also without maintenance and generating more than 280 kWh of energy per year [23]. These include thermosyphons as heat exchangers, which makes them totally passive, with no auxiliary consumption, and are the only geothermal thermoelectric generators installed an operating in a real geothermal field.…”

“…Hence, although the geothermal thermoelectric generators taken as reference were analysed in the aforementioned studies [22,23], for a better understanding of this work, the GTEGs are deeply described in Section 2. Then, Section 3 details the developed computational model, which is subsequently validated by means of the experimental results.…”