Comparison of pumping station and electrochemical energy storage enhancement mode for hydro-wind-photovoltaic hybrid systems

Utilizing hydropower to mitigate the variability of wind power and photovoltaic has been proven to be an effective strategy for enhancing their utilization. However, the integration scale depends largely on hydropower regulation capacity. This paper compares the technical and economic differences between pumped storage and electrochemical energy storage enhancement modes for hydro-wind-photovoltaic systems. Pumped storage retrofits involve adding pumping stations between adjacent reservoirs. Two detailed coupling models are developed, and a fine-grained simulation optimization approach is used to capture operational details. Moreover, economic indicators are established from an engineering project perspective to evaluate their profitability. Taking a cascaded hydropower in China as a case study. The results show that: (1) Pumping station mode has 2.58 times more annual incremental revenue than battery storage mode. The differences can be attributed to energy storage and transmission capacity occupations variances. (2) Considering the high replacement cost of batteries, the net revenue of the battery storage mode over the project's life is negative and economically infeasible. In contrast, the net revenue from the pumping station mode amounts to 251 million CNY. (3) Initial battery cost must be reduced to at least 75 %, and transmission capacity needs to be increased to realize the economics.