ABSTRACT
Underground pumped hydroelectric energy storage (UPHES) is an adaptation of conventional surface-pumped hydroelectric that uses an underground cavern or water structure as a lower reservoir. Conceptually, this seems a logical and sound solution to energy storage. The practical design and actual construction of large UPHES systems represent challenging tasks. Smaller UPHES systems may be more easily built, especially if existing underground and surface structures can be used. To date, no UPHES system, commercial or otherwise, has ever been installed and used. This chapter will overview concepts and design considerations for UPHES systems, both large and small.
