Collaboration Could Be a Win-Win for Cascading Hydropower

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NLR Modeling Shows Coordinated Operation of Mid-Columbia Hydropower Plants Could Boost Efficiency Systemwide

By Karen Petersen, NLR

Collaboration is essential to any successful river expedition. Turns out, it is no different in a cascaded hydropower system—especially one where different operators run dams, each with their own goals and needs.

But how exactly does a coordinated approach to operations affect power system performance? Could increased synergy enhance efficiency systemwide, boosting the capacity to store and release energy the grid needs to respond to sudden peak demands and unpredictable market conditions while meeting all other water use requirements?

The answer to these questions is of particular interest to Grant Public Utility District (PUD), which owns Wanapum and Priest Rapids, the last two dams in a cascade of seven in Washington state’s Mid-Columbia system. So, when Grant PUD’s owners saw an opportunity to team up with the National Laboratory of the Rockies (NLR) to model the impacts of coordinated operations, they were all in.

Along with identifying potential co-benefits of coordination among the Mid-Columbia generation plants, NLR and Grant PUD sought to clarify whether the value—to the utilities and the public they serve—would justify the expense and effort involved in coordinating operations.

A broader objective of the NLR technical assistance effort, funded by the U.S. Department of Energy (DOE) Hydropower and Hydrokinetic Office, was to identify the impacts of coordination across the entire Western Interconnection, which the Mid-Columbia hydropower plants operate within.

The tight coupling and variety of owners make the Mid-Columbia system a valuable model of the challenges and opportunities of coordination, according to an article published by the NLR research team in Energy.

Cascaded Systems Pose Unique Challenges

“In a cascaded hydropower system like the Mid-Columbia, water flowing out of one dam greatly influences the operation of the one right below it,” said NLR researcher Wesley Cole, the article’s lead author. “When all the units in the system are run by the same owner-operator, there is a natural incentive to coordinate operations.”

While no such incentive exists across the Mid-Columbia system, Grant PUD’s end-of-line positioning creates unique challenges that make coordination an attractive prospect.

“Their water is driven by what happens upstream, so they’ve got to be able to manage that,” Cole said.

What happens downstream places an additional onus on Grant PUD as one of the key stewards of the Mid-Columbia hydropower resource.

Below Priest Rapids is the longest free-flowing stretch of the Columbia River. This area is a salmon spawning ground, which creates operational constraints that add another layer of complexity to Grant PUD’s mission to provide affordable, reliable electricity to its customers while safeguarding natural resources.

Tapping into NLR’s modeling capabilities enabled the utility to investigate whether coordinated operations would allow them to not only do more with the resources they manage but also improve efficiency across the system.

Enhanced Grid Model Explores Impacts

Although several previous studies on the Mid-Columbia hydropower system explored the potential for increased system efficiency, none had specifically considered the impact of coordinated operations.

To examine the value of coordinated efforts relative to those performed without coordination and understand exactly where the benefits would accrue, NLR’s team developed a model that combined river flow and production cost models and ran it in two ways.

In the fully coordinated scenario, the seven dams were operated as if they were centrally dispatched, with the objective of minimizing production costs throughout the Western Interconnection. In the uncoordinated scenario, the dams were segmented into four groups according to their owner or power marketer.

Benefits Flow Both Ways

The results revealed that a fully coordinated Mid-Columbia hydropower system produces more energy.

All seven dams see an increase in annual generation in the coordinated scenario, according to the article published in Energy. Because the coordinated scenario can see the impact on all the dams simultaneously, it optimizes storage levels and releases across the dams, allowing more water to be used rather than spilled.

Furthermore, the research team found that each of the seven dams experiences an annual revenue increase due to coordination, ranging from 2.8% to 4.3%: “The coordinated case results in 3.3% higher revenue [across the seven dams] than the uncoordinated case, both because of the greater amount of generation and because the full Mid-Columbia resource is better able to generate during hours that are more advantageous for the system.”

In practice, this means when an upstream plant holds water back in anticipation of shifting grid conditions, less water is available to the downstream units when prices are high, Cole explained. But if, in a coordinated scenario, the upstream plant were to release more in advance, “there would be more water for all of the plants to be able to produce during the highest-price hours.”

In turn, coordination allows operators to better anticipate and respond to high-stress events in advance, leading to increased revenues for all operators—which, because they are all public utilities, would likely be passed along to consumers, Cole said.

The Cascading Impact of Data-Driven Insights

“One of our motivations for doing this is the development of day-ahead markets in the West,” Cole said. “All of the dam owners are evaluating whether they might want to join these markets.”

For Grant PUD, that was a hard problem to solve.

“The collaboration with NLR presented an opportunity for Grant PUD to pair their deep experience in Mid-Columbia operations with the laboratory’s grid modeling capabilities to gain targeted insight as they navigate critical strategic decisions,” Cole said.

Through its work with NLR, Grant PUD was able to address a challenge specific to its operations while also supporting informed decision-making on multiple fronts, highlighting the compounding value of technical assistance.

“Together, we delved into a complex question of particular interest to a relatively small group of utilities,” Cole said. “And in supplementing Grant PUD’s nuanced in-house expertise with NLR’s large-scale modeling tools and capabilities, we arrived at answers with potential to address Grant PUD’s problem while also informing a broader set of hydropower operators and utility energy planners and capturing impacts across the broader Western Interconnection.”

Interested in working with NLR on solving energy challenges? Learn how NLR’s hydropower modeling capabilities and technical assistance could help strengthen grid planning and optimize operations.