Evaluating existing water supply reservoirs as small-scale Pumped Hydroelectric Storage options – A case study in Connecticut

Abstract Considering the reduction of steep power ramps caused by renewable energy penetration, the present study evaluates the potential of utilizing existing water supply infrastructure as small-scale pumped-hydroelectric storage (PHS) units. A novel methodology is developed that estimates the total storage capacity via the available space in five water supply systems in Connecticut (United States), by solely employing water level measurements and considering a water release schedule that favors power-demand peak reduction. The study culminates in the estimation of optimal areal requirements for hypothesized solar farms neighboring the studied systems, based on deficit minimization between storage capacity and energy generation over the study period. Analysis reveals that, in most cases, the seasonal pattern of the storage capacity is in accordance with the behavior of the corresponding hydraulic head timeseries, showing higher values in winter/autumn. Given certain assumptions regarding the infrastructure, a yearly average of approximately 95 MWh/day can be stored as an intersystem aggregate, illustrating that the amalgamation of existing water supply reservoirs could provide significant energy storage capacity to complement substation variability. Finally, the area covered by PV arrays increases proportionally with the storage capacity, while the calculated solar energy output demonstrates significant variability relative to the PHS storage potential.