ABSTRACT

Electric power systems today have limited storage capacity. Both in the United States and worldwide, storage makes up less than 3" of generation capacity. This lack of storage forces grid operators to continuously balance generation and load and prevents the electricity sector from operating as a conventional competitive market that relies on inventory. Pumped hydropower storage (PHS) is the predominant storage technology today, making up 99" of all deployed storage capacity. Renewables such as wind and solar are variable across a broad range of time scales. While technologies such as batteries and flywheels can balance the highest-frequency variability, their cost and technical aspects render them impractical for balancing renewable power output over the course of hours or days. The compressed air energy storage and PHS are well suited to balancing both the higher-frequency and lower-frequency fluctuations of renewable power.