An Evaluation of Seawater Pumped Hydro Storage for Regulating the Export of Renewable Energy to the National Grid

A seawater inlet with a surface area of 6 km(2) was assessed for the potential to be used as a 100 MW, low head, high flow, sea water pumped hydro energy storage system. The capital cost was estimated to be recouped after a number of years and the plant has a predicted energy storage capacity of 320 MWh. National and international policies are driving the increased penetration of solar and wind energy onto the electricity networks, in an effort to reduce carbon emissions. Transmissions System Operators depend on ancillary services such as spinning reserve from thermal generators or pumped hydro systems to enhance grid stability. The increased penetration of renewable energy onto the electricity grid is driving a demand for greater capacity in the area of energy storage. This research presents a case study, which is a technical and economical appraisal of using an inland sea water reservoir to store energy. This project involves building a seawater dam around an existing natural inlet, and placing turbines at the mouth of the inlet. As part of the study an evaluation of current pumped hydro, seawater storage, and tidal barrages was carried out. The optimum design of the low head, high flow rate seawater energy storage facility was determined for the seawater inlet and different scenarios for the optimum head and flow rates are presented for analysis. Using low-head, high-flow seawater storage near the coast, greatly reduces the danger of contamination of inland freshwater supplies, thus reducing the environmental impact of pumped seawater energy storage. This research indicates that sea water pumped hydro energy storage with a high flow rate and low head is technically and economically feasible for increasing the ability of national grids to allow high penetration of intermittent renewable energy. (C) 2014 The Authors. Published by Elsevier Ltd.