Integration of hydrogen production with geothermal power plants: Utilizing H2 as a spinning reserve unit

The targeted integration of a Hydrogen-Oxygen direct combustor followed by a high-pressure turbine within an existing geothermal power plant (GPP) is investigated. Hydrogen and Oxygen are produced by an electrolyser when electricity production from PV is relevant; extra power is produced at night when the demand is high and the cost of electricity higher. This solution uses largely existing equipment in the GPP and represents an alternative for daily energy storage and load shifting with respect to the adoption of dedicated units like batteries. The system can be an alternative to using the electrolyser coupled to a dedicated fuel cell unit. Thermodynamic and exergy models for each operating mode (accumulation and peak load operation), complemented by economic analyses, provide a multifaceted evaluation. Referring to a standard 20 MWe GPP unit, the peak load capacity is extended 1.4 MWe. The first law efficiency of the integrated system improves to 23.0 % with the direct combustor and 23.5 % with the fuel cell, compared to the base plant efficiency of 22.8 %. The exergy efficiency shows a slight reduction to 54.4 % for the direct combustor mode and 57.1 % for the fuel cell mode, from the plant's 58.0 %. Economic analysis suggests that the proposed system can potentially offer a cost-effective solution with competitive operational costs. These findings unveil promising prospects, indicating the potential contribution to a more sustainable economic framework.