NREL Develops FLASH Hydropower Framework for a Greener Grid

Aug. 24, 2021

As the weather heats up this summer, electric grid operators are planning for increased energy demand as millions of Americans turn on their air conditioners. And in many parts of the country, the energy from rushing rivers will be a critical resource in making sure their houses stay cool and the lights stay on.

Electric grid operators continuously anticipate fluctuations in power demand on the order of hours, days, months, and years. Hydropower is a key factor in that planning, much of which is based on forecasts from computer models. Supplying 37% of the nation’s renewable electric power in 2020, hydropower is a leading contributor to clean energy, helping to meet our energy needs while reducing greenhouse gas emissions.

Hydropower’s contributions are expected to become even more important as we move toward higher-renewable, lower-carbon grids. It is one of the few renewable energy technologies that is fully dispatchable, a capability that will become increasingly important as fossil fuel powered generation retires. However, maximizing hydropower's utility on the grid requires insight into how much hydropower is available and when.

With support from the U.S. Department of Energy’s Water Power Technologies Office, researchers at the National Renewable Energy Laboratory (NREL) are developing a systems-engineering-based approach that will address this problem, improving hydropower's representation within grid operations models.

The underlying basis for this effort is known as the Framework for Linked Analysis of Streamflow and Hydropower, or FLASH. FLASH leverages NREL's expertise in grid integration as well as the river-basin-scale modeling and water forecasting knowledge of RTI International, a North Carolina-based nonprofit research organization and NREL’s partner on this project.

FLASH will help users better understand the linkages between river-basin operations and hydropower’s availability, opening new opportunities for renewable energy to support the grid. FLASH will also provide an example that the research team hopes will be helpful for those developing the next generation of market simulation and grid operations models.

wide-angle view of a dam
About 2,500 dams across the United States produce electricity. Pictured here is Gross Reservoir Dam in Colorado. Photo from Brent Olson, U.S. Department of Energy

A New Chapter for Hydropower

Americans have been harnessing the energy from rivers for over a century, and some hydroelectric facilities are among the oldest power plants in the United States. Yet hydropower is more relevant than ever, not only because it is a source of renewable power, but also because it is able to help integrate other, variable renewable energy sources onto the nation’s power grids.

In a recent joint agreement, stakeholders ranging from industry leaders to conservationists called U.S. hydropower both a "climate solution and a conservation challenge," highlighting the dual responsibilities in managing this resource for decades to come. The statement, published by Stanford University’s Stanford Woods Institute for the Environment and developed through its Uncommon Dialogue process, calls out seven areas for collaboration. The areas range from working to accelerate hydropower technology development to advocating for increased funding for dam rehabilitation, retrofits, and removals.

Parallel Work in Process

While the Uncommon Dialogue process was moving forward, so was work on FLASH. The framework is being developed as part of NREL’s holistic approach to hydropower, and it provides tools that can help stakeholders achieve two of the seven goals that the Stanford work suggests for collaboration:

  • Increasing basin-scale decision-making and access to river-related data
  • Improving the measurement, valuation of, and compensation for hydropower flexibility and reliability services and support for enhanced environmental performance.

FLASH couples NREL’s open-source Scalable Integrated Infrastructure Planning (SIIP) model with Colorado State University’s freely available river basin operations decision support tool, MODSIM-DSS. This combination enables users to investigate how renovations, retrofits, or dam removals at hydropower facilities could affect basin-scale operations in terms of both watershed flows and grid performance.

In addition, FLASH can attach an economic value to proposed changes. Its grid market simulation capabilities allow users to estimate costs and revenues at timescales ranging from immediate needs to seasonal storage, directly capturing the value that hydropower provides to a system. In the longer term, the research team hopes to add water market capabilities, too, which will enable FLASH to co-optimize river basin operations across electric power and water power sectors. These combined capabilities should provide a strong foundation for energyshed work, an emerging science that explores a community’s energy usage in terms of its geographic footprint.

Mapping Hydropower to the Flow of Time

Hydropower differs from many renewable resources in that its power output can be adjusted dynamically without discarding energy. Unlike wind or solar power, hydropower that is not used today can be stored for later use and has the additional advantage that it does not have to be converted into another form of energy. That makes hydropower ideal for helping the grid accommodate variable renewable energy sources.

But this capability brings with it a complex task for operators: maximizing utility while satisfying all the reservoir operation rules. With its ability to represent reservoir operations, FLASH unlocks new opportunities for hydropower flexibility, lowering costs and increasing the amount of wind and solar power that can be integrated into the grid.

"If you were to ask a hydropower operator how much flexibility they have on a given day, many would say almost none," said NREL Hydropower Platform Lead Greg Stark. "While that may be true at the daily timescale, within those 24 hours, they often have quite a bit of room to adjust water flows. Ultimately, that flexibility could go a long way in helping us to put more renewables on the grid."

FLASH can help simplify this task by providing situational awareness, helping users understand how natural events affect how a hydroelectric plant operates. For example, rainstorms change how much water—and thus power—can (and sometimes must) be released from a dam to manage flooding concerns. At the same time, errors in wind, solar, hydrologic, and load forecasts can shift how much hydropower is needed across a given period. FLASH uses this information to provide stakeholders with insight on how to maximize hydropower operations while fully respecting safety, water rights, and environmental commitments.

FLASH accomplishes this by exchanging information between the river basin and power system models at daily, weekly, and seasonal intervals. Accounting for such uncertainties and constraints is expected to give hydropower operators an exceptional level of insight into the overall system.

Additionally, the FLASH team is developing new computational methods to help users make scheduling decisions across an entire year with unprecedented levels of modeling detail. These advancements will give hydropower operators better tools to understand the times of the year when the water stored in their reservoirs can provide the most value to the grid.

"We need better methods to be able to understand when hydropower is likely to be most critical so we can make sure water is available," said NREL Senior Research Engineer Clayton Barrows. "It's not clear that anybody is co-simulating the river networks and the power networks with this level of detail and over the time periods that we are with FLASH."

FLASH's capabilities are expected to confer several benefits for both hydropower plants and the grid. Making better use of hydropower’s available flexibility can boost grid resilience and will likely lead to improved valuation and compensation for hydropower, a goal mentioned in the Uncommon Dialogue agreement.

“FLASH brings the best of two worlds together, letting each do what they do best,” Stark said. “We’ve only begun to imagine what’s possible for hydropower and its role on a clean, reliable power grid.”

Learn more about NREL's FLASH initiative.