Geothermal modeling shifts to address seasonal output reductions in the Southwest

Geothermal energy's potential in California faces critical challenges, as highlighted in a recent workshop by the California Public Utilities Commission. Experts discussed the need for improved modeling of geothermal power plants, particularly regarding how varying heat engine cycles and cooling technologies impact energy output throughout the year.

Key concerns were raised about the influence of seasonal and diurnal temperature shifts on geothermal plant performance, especially for air-cooled systems. During warmer months, these plants may experience significant reductions in output—up to 40% during peak afternoon hours—due to high ambient temperatures. This is particularly alarming as these periods coincide with heightened reliability risks for the state's energy supply.

To address these challenges, the commission is considering three modeling options to better capture geothermal output fluctuations. These include a monthly derate model, a month-hour profile for maximum output, and a temperature-dependent derate model. Each option aims to incorporate historical data to accurately reflect the performance of new geothermal resources.

Stakeholder input is crucial as the commission seeks guidance on whether to implement additional derates during hot periods and how to determine their size. The call for data and insights from stakeholders underscores the collaborative effort needed to enhance the reliability of geothermal energy in California's evolving energy landscape.