Energy storage capacity credit variation with system adequacy

This paper investigates the contribution of energy storage systems to resource adequacy under different power system reliability conditions. To this end, the capacity credit of storage is assessed, assuming different thermal capacity levels integrated in to the system. A reliability-oriented policy for the dispatch of storage is implemented to minimize load curtailments. Storage capacity credit is estimated via the equivalent firm capacity (EFC) metric. The paper demonstrates significant variability in storage capacity credit, contingent upon the level of system adequacy. A consistent trend is observed in the storage EFC as system thermal capacity changes. Specifically, the EFC exhibits low values in two cases: (a) when the system maintains exceedingly high adequacy levels and (b) when it encounters severe inadequacies. Between these extremes, the EFC appears to stabilize around a peak value, thus allowing the identification of the system thermal capacity level at which the storage contribution to adequacy is maximized. Eventually, the analysis suggests that this maximum EFC value can potentially serve as a definitive measure of storage capacity credit.