Toufani, ParinazNadar, EmreKocaman, Ayse Selin2023-02-242023-02-242022-072352-152Xhttp://hdl.handle.net/11693/111672This study evaluates the potential benefit of retrofitting existing conventional cascade hydropower stations (CCHSs) with reversible turbines so as to operate them as pumped hydro energy storage (PHES) systems. We examine the energy generation and storage problem for a CCHS with two connected reservoirs that can be transformed into a PHES system in a market setting where the electricity price can be negative. We formulate this problem as a stochastic dynamic program (SDP) under uncertainty in the streamflow rate and electricity price. We analytically derive an upper bound on the profit improvement that can be obtained from the PHES transformation. We conduct numerical experiments with data-calibrated time series models and observe that the PHES system provides a greater benefit under more limited streamflow conditions or more frequently observed negative prices.EnglishCascade hydropower stationsNegative electricity pricesPumped hydro energy storageStochastic dynamic programStreamflow rateArticle10.1016/j.est.2022.1044442352-1538