Utilizing spinning reserves as energy storage for renewable energy integration

Energy Storage Systems (ESS) show much promise for mitigating the dynamics introduced by nondispatchable variable generation. By taking advantage of spinning reserves as a form of flywheel energy storage, the fossil fuel power plant becomes a form of ESS. The spare power capacity in the generator and prime mover represent the throughput of the ESS and the stockpile of fuel defines the energy capacity. The ESS discharging and charging behavior can be seen as increasing and decreasing the fuel pile usage. Similar forms of energy storage have been recently implemented using gas turbines with fast dynamic responses, which are necessary for renewable generation. Criticism of fossil fuel generation focuses on high operational costs of thermal power plants. However, the cost of operating a thermal power plant compares favorably to the cost of implementing other forms of ESS such as battery storage. Utilizing thermal plants in this way allows for reliable increase of renewable penetration, and reduces capital and operating cost. This paper presents analysis tools necessary to properly evaluate the economics of energy storage provided by thermal plants. These tools also balance the available energy storage against spinning reserve requirements for system reliability.