This concept addresses the need for large-scale energy storage to help manage the intermittent nature of solar and wind electricity generation.
The large variation in solar produced electricity daily must be met by non-solar (and non-renewable) resources. There is a massive amount of dispatchable capacity that must be brought on line in a short time of several hours. The hours of dispatchable electricity needed when the sun is not shinning is huge (see attached Figure 1). No present storage for this large amount of energy is currently available. What is being addressed by our project concept is how to store large (10 megawatt hours) amounts of energy in order to manage the daily intermittent nature of renewable solar energy and, to a lesser extent, wind energy. Our concept is to use solar thermal energy to heat water on the surface and inject the hot water into a low-quality geothermal reservoir creating a ‘geothermal battery’. This solar thermal hot water would elevate the reservoir temperature making the non-economical geothermal reservoir acceptable for conventional geothermal energy recovery. The concept effectively combines solar and geothermal into an economically and environmentally acceptable energy source. Alone, neither the low-quality geothermal reservoir nor the intermittent nature of solar offers an acceptable energy source. However, combined, energy can be stored and recovered from deep in the earth and from the sun.
This proposal is a continuation of a program that began considering sedimentary basins as geothermal energy sources. Unfortunately, sedimentary basin reservoirs tend to be too low a temperature for economic geothermal energy recovery. Additionally, the appreciation has emerged that renewable electricity production in the US has become limited by the intermittent nature of solar and wind energy. Some form of energy storage--large scale energy storage--is essential. The Geothermal Battery Energy Storage concept emerged as an opportunity to increase the temperature of a low-quality geothermal reservoir and by storing 'energy' in the earth to provide electricity when the sun is not shining.