Energy storage is a critical component of a low carbon energy infrastructure. For example, heat may not be needed at the time of generation (e.g. in summer), but if efficiently stored, it could be useful in times of high heat demand (e.g. in winter).
This project evaluates two geothermal energy storage systems based on geologic/thermal properties of a typical fractured reservoir in crystalline rock. Using a fully-coupled fracturing, wellbore, and reservoir numerical model, two scenarios were evaluated: one for thermal storage within a single, fracture-stimulated well, and the other for thermal storage in a well pair (connected with fractures with stimulated injectivity). The systems are operated in seasonal injection/production cycles, injecting waste heat in the summer when not needed, and producing warm fluid back in the winter.
The conductivity of the fractures was calibrated to have similar stimulated injectivity as observed in fractured crystalline basement, such as at the Bedretto Underground Laboratory in Switzerland. The dominant operational parameters such injection and rate, injection temperature, and bottomhole pressure were adjusted to obtain an efficient energy storage system. The results were evaluated based on power and energy input, power and energy output, and overall efficiency. A sensitivity analysis was performed on the well pair model to understand the impact from well spacing.
