Hydro & renewables integration |
Above: Hydropower plant in Norway. Upgrading hydroelectric power plants at existing reservoirs in southern Norway could boost production capacity by 11-20GW and pumping capacity by 5GW
expansion analysis of a two-zone system – a
hydro-dominated region and a neighbouring region with aggressive decarbonisation targets, as represented by the Pacific Northwest and California regions in the US. Working to address several existing knowledge gaps they: Introduced a flexibility index as a proxy for the level of operational flexibility available to reservoir hydro resources.
Analysed how varying levels of hydropower flexibility, rather than simply an on-off dichotomy, influence the amount of new wind and natural gas generation capacity in the system least-cost generation portfolio.
Assessed how transmission congestion impacts the ability of hydropower flexibility to influence least-cost generation investment pathways in neighbouring regions. Applied a reliability assessment model to quantify the synergies between flexible hydro power and wind resources in meeting system resource adequacy objectives.
The authors say their research shows that system optimal investments in wind generation increase when reservoir hydropower is operated with greater operational flexibility and investments in natural gas and battery storage decreasing accordingly. As hydropower flexibility increases, total system emissions and costs decrease as well. More specifically, they add, when the flexibility index increases from 0 to 20%, wind generation
20 | April 2025 |
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increases by 297MWh per MW of installed reservoir hydropower and the combined value of reductions in system cost and emissions total US$38,587 per MW of installed reservoir hydropower. These metrics exhibit decreasing marginal returns as the flexibility index approaches 100%, reducing to 49MW of installed hydropower when the flexibility index increases from 80% to 100%.
Two major changes in the system dispatch profile
where also observed when hydropower operates with more flexibility. Wang et al found reservoir hydropower generation decreases when excess wind generation is available and subsequently increases to cost-effectively displace costly natural gas generation. As a result, the operating profits of reservoir hydropower resources also increase with increasing flexibility, as they can shift generation to periods with higher energy prices. Further demonstrating a substitution effect between the grid services provided by flexible hydropower operation, increased transmission capacity on a congested line, and energy storage resources, the authors believe these results suggest infrastructure investments or operational changes that increase the operational flexibility of hydropower should be considered in tandem with transmission upgrades and energy storage investments. It may also be prudent, they add, to revisit policies,
regulations or practices that inhibit the operational flexibility of hydropower due to non-power considerations. Many of the restrictions may have been established at a time when there was much less
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