Enhanced energy extraction from low-grade geothermal sources for clean hydrogen generation using thermoelectric generators and Kalina cycle integration

This study proposes an integrated energy conversion system that combines the Kalina cycle, thermoelectric generators, and a proton exchange membrane electrolyzer to enhance green hydrogen production from low-grade geothermal heat at the Wayang Windu power plant in Indonesia. The Kalina cycle employs an ammonia-water mixture (88.58% NH 3 and 11.42% H 2 O) as the working fluid to recover waste heat, while electricity from the turbine and thermoelectric generator modules jointly powers the proton exchange membrane electrolyzer for hydrogen generation. The hybrid Kalina-thermoelectric generator configuration achieved a hydrogen production rate of up to 0.03722 kg/h (0.89342 kg/day). To assess the contribution of thermoelectric generators as a secondary power source, the relationship between thermoelectric generator performance and thermal contact resistance was analyzed. The result shows that lower thermal resistance leads to higher initial open-circuit voltage, heat flow, and power output. However, lower thermal resistance would also increase degradation of open-circuit voltage, efficiency, power output, and heat flow. Thermoelectric generator efficiency is also determined by the internal electrical resistance of the module. Higher internal resistance would cause higher initial efficiency. The Kalina cycle used in this study generated 1510 kW of electricity and produced 0.035 kg/h of hydrogen. TG12–4-01LS is observed to be the thermoelectric generator module that exhibits the highest power output of 8199 W with an installed number of 20,408 across the condenser surface area of 20.816 m 2 . This study demonstrates, for the first time, the feasibility and performance benefits of integrating Kalina and thermoelectric technologies to efficiently produce hydrogen from low-grade geothermal resources.