Green hydrogen-based energy storage in Texas for decarbonization of the electric grid

Increasing the penetration of renewables-based power generation such as from wind and solar is key to curbing greenhouse emissions resulting from the use of fossil fuels. As the capacity of solar and wind installations increase, the highly dynamic nature of renewable generation leads to frequent energy curtailment in instances when the total generation exceeds the load Presently, we analyze data from ERGOT (which manages the primary electric grid in Texas), to study potential storage of excess wind and solar energy via electrolysis-driven conversion to hydrogen (green hydrogen). This stored hydrogen could be converted back to electricity and fed into the grid whenever there is an energy deficit. In this study, we characterize a long-duration storage system (based on estimated capacity increases by 2025) in terms of storage size, rated power and the costs involved in generating H-2 via electrolysis. Our analysis reveals the need for long-duration storage in two periods: i) mid-March to June, and ii) mid-October to December. During these periods, the surplus energy generated and stored in the form of green hydrogen would be self-sufficient to provide the deficit energy for instances when generation from renewables cannot meet load requirements. Minimum storage capacities of 10,000 & 3500 GWh would be required for these periods to avoid curtailment. Preliminary techno-economic analysis suggests that total electrolyzer capacity of similar to 40 GW would be required to avoid significant curtailment. Any added capital cost beyond this rating would not yield significant returns on investment as hydrogen production would have reached its peak capacity. Furthermore, the cost for producing hydrogen via electrolysis ($2-4) for electrolyzers at such capacity would be competitive with existing steam reforming technologies. Overall, the proposed long-duration storage system can increase the contribution of renewables to the Texas grid by 16%. The analysis and insights obtained from this study can serve as a benchmark and seed future studies in planning and designing long-duration storage systems based on the estimated capacity increase in renewables.