Rationale for adding batteries to hydropower plants and tradeoffs in hybrid system operation: A review

There is increasing interest in hybridizing generation resources with batteries to improve the flexibility and value of the primary energy resource. The value propositions of hybridization are more acute with variable renewable energy (VRE) generation resources, such as wind and solar, and therefore these types of hybrids have been most studied and deployed in the real world. Here we review the state-of-the-art understanding on wind or solar plus batteries systems and compare these to value proposition opportunities for pairing hydropower with batteries. While less studied, there are also opportunities and value propositions associated with hybridizing hydropower resources. Comparing the state of hydro-hybrids research to wind and solar hybrids reveals the gaps in understanding for hydro-hybrids and provides the foundation for categorizing value propositions that are unique to hydropower. Many studies that focus on solar and wind can be adapted to inform hydro hybrids research, but wind studies were found to be the most applicable. The key lessons learned are that hydro-hybrids should take inspiration from the battery-health concerned controls and stochastic market bidding strategies, developed for solar and wind. Unlike solar and wind, modes of power generation at hydropower plants are directly linked to competing objectives around irrigation, flood control, and river ecosystem health. New studies and models that take these objectives into account are required to realize the full potential of hydropower-battery hybrids. We conclude that valuation of hydropower hybridization must go beyond an assessment of the energy arbitrage potential of the battery to include reduced cost of hydropower operations.