Integrated Techno-Economic and Life-Cycle Assessment of Subsurface Energy-Storage Technologies for Renewable Energy

Abstract The reliance on renewable energy in the modern energy mix is expanding due to two primary factors: the need to decrease dependence on fossil fuels and the imperative to lower carbon emissions. Integrating renewable energy sources into the grid is crucial for mitigating greenhouse gas emissions. However, a significant challenge associated with increasing reliance on renewables is the inadequate methods for effective storage of this energy, which is essential for minimizing curtailment and maintaining grid stability by balancing supply and demand. This study identifies the technical and economic feasibility of two potential storage technologies: subsurface heat storage and subsurface hydrogen storage. As a first step this study used the average energy curtailment data from the Energy Reliability Council of Texas (ERCOT) to demonstrate the applicability of these energy storage technologies. This study also quantifies the technical and economic feasibility of each technology using reservoir simulation by determining the subsurface withdrawal efficiency. It also determines the optimal storing option in terms of estimated efficiency, levelized cost of storage, and GHG emissions. Results showed that around 29-57% of the curtailed energy can be recovered through subsurface H2 storage, whereas around 6-17% can be recovered through synthetic geothermal storage. The levelized cost is between $102-115/MWh for H2 storage and $19-73/MWh for geothermal heat storage. The conclusion is that subsurface H2 storage can be a more promising technology for mitigating renewable energy curtailments from both technical and economic standpoint.