| Hybrid projects


because of grid-fee structures rather than physical necessity. In many markets, injecting or withdrawing power triggers grid charges linked to megawatt-hours or capacity. When batteries and hydropower operate behind the same meter, energy can be shifted and stored locally, which helps in avoiding those charges. For grid health, however, co-location is not


required, it is just a response to cost system setup. “If both are connected to the grid, it doesn’t really matter where they’re connected,” she says. Their impact on the system is the same. The real issue is that grid-cost systems were designed for an earlier era, with fewer, bigger producers, and no prosumers to speak of. As rooftop solar and distributed generation proliferate, the number of actors paying grid fees becomes smaller even as system costs are still calculated based on total injections and extractions. Goodenough believes that this trend will inevitably lead to future renegotiation of how grid costs are allocated between producers and consumers.


Hybridisation brings significant operational benefits for plants with limited flexibility. For run-of-river hydropower, pairing with batteries can introduce several hours of controllability, allowing operators to shift generation and participate more effectively in markets. This can also reduce grid fees when energy is stored rather than exported at moments of congestion.


How hydropower supports


batteries When asked how hydropower can support battery deployment, Goodenough reframes the issue. “I wouldn’t say that hydro directly helps batteries,” she explains. Instead, hydro and long-duration energy storage as a whole


supports the renewable transition. By balancing the increased share of intermittent renewables – wind and solar – hydropower improves the carbon footprint of the energy system and reduces dependence on imported fossil fuels. Energy autonomy, she adds, is the highest motivator behind green field hydro. She points to China, which is building more pumped storage hydropower “than the entire rest of the world combined.” This is not driven by environmental concern, she argues, but because China recognises the economic need for long-duration storage to stabilise the grid and support economic growth.


Operational complexity Managing hybrid assets raises significant


operational challenges. Goodenough explains that battery operation is simpler than hydropower because batteries are not constrained by environmental flows, meteorology, water rights or concession requirements. Hydropower optimisation must consider turbine capacity, efficiency curves, reservoir storage levels and mandated water releases. Batteries add their own set of constraints: maximum charge and discharge rates, temperature effects, cycle limits and degradation. Unlike hydropower turbines, which may run for decades, batteries reach end-of-life after 4,000 to 10,000 cycles. This introduces a fundamentally different optimisation problem. Every MWh dispatched from a battery has a wear cost. Every deep cycle shortens asset life. Over-cycling a BESS in pursuit of short-term market gains can destroy long-term project value. This complexity is amplified by changes in reserve markets. In many countries, secondary


HYDROGRID Insight dashboard


and tertiary reserves that were once auctioned weekly are now procured daily, with some places auctioning hourly delivery blocks. For operators, this means what was once a single weekly optimisation task has become 24 separate tasks per day. Manual processes are no longer viable. Forecasting, scheduling, trading and reserve bidding must all be automated. When batteries are added to portfolios, fast operational cycles become even more important. A battery with a few hours of storage must be managed in near real-time. “Unless you are operationally able to react optimally within minutes, that scenario is too slow,” Goodenough explains. Because of these differences, Goodenough


believes hydropower operators are better positioned to expand into batteries than battery operators are to expand into hydro. The former already manage complex, multi-constraint assets; the latter do not. Hybrid operation therefore must account for: Battery degradation costs. Market price volatility. Physical constraints. Tariff structures and grid costs. Environmental requirements.


Reserve markets and a growing design flaw


One of Goodenough’s concerns is the evolution of flexibility products. She describes three layers procured by grid operators: Primary reserve – ultra-fast response providing inertia. Secondary reserve – response within two to three minutes. Tertiary reserve – response within approximately fifteen minutes.


www.waterpowermagazine.com | December 2025 | 15


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