Profitability of battery storage in hybrid hydropower-solar photovoltaic plants

Increased energy demand and rapid environmental changes triggered by global greenhouse gas emissions have forced numerous countries to consider renewable energy sources (RES) as possible alternatives to conventional fossil-fuel energy sources. Due to the inherent uncertainty, intermittency, and generally uncontrollable power generation by single-source renewable power plants, hybrid power plants (HPPs) incorporating several mutually complementary RES have lately gained much interest. Integrating battery storage systems with such HPPs has the potential to run them more similarly to conventional fossil-fueled power plants, providing controllable power generation, and reducing its variability. Given such a future scenario and the lack of existing detailed studies, this paper investigates the profitability potential for a viable business case for battery storage integration with utility-scale hybrid hydropower-solar photovoltaic (PV) plants. The study presented here is based on a hypothetical, two-reservoir cascaded hydropower plant in Sub-Saharan Africa. The role of the battery is assessed by considering the overall profitability of the HPP when participating in capacity markets, ancillary services, and energy arbitrage. The relationship between the value stacking of battery services and its impact on battery life has been critically examined. This study provides estimates on increased profitability, cost-optimal battery capacities, battery degradation estimates, and the HPP-battery interoperability aspects under various hydropower and electricity market operating scenarios. Batteries will likely increase cost-effectiveness by co-optimization with PV-system as well as power market contracts. In this case, adding a battery increased the profitability by about 2% when combining revenues from capacity markets and ancillary services.