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Winds of Change Blowing for Wind Farm Research with NREL’s SOWFA Tool

April 1, 2016

Before the Energy Department's National Renewable Energy Laboratory (NREL) released its Simulator fOr Wind Farm Applications (SOWFA) simulation tool in August 2013, there had not been an open-source, freely available tool of this capability that researchers all over the world could embrace.

Now, the winds of change are blowing.

SOWFA is a software framework allowing users-ranging from academia to industry-to investigate effects of weather patterns, turbulence, and complex terrain on the performance of wind farms and individual wind turbines. The overarching goal is to gain better knowledge of wind farm physics. That increased understanding will ultimately enable reduced cost of wind energy through more informed turbine and wind farm designs that capture more energy and incur less damaging structural loads.

The tool is being used to research ideas ranging from multi-turbine control schemes to wind turbine wake dynamics that cause wind farm underperformance, all in a limitless range of atmospheric conditions.

In 2016, SOWFA will be a key part of an upcoming collaborative test of wind farm control systems by researchers from the National Wind Technology Center at NREL and Sandia National Laboratories at the Scaled Wind Farm Technology (SWiFT) facility in Lubbock, Texas. In preparation for the tests at SWiFT, researchers used SOWFA "to simulate the experiment first, so we know what to expect," said Senior Engineer Matt Churchfield, who along with Senior Engineer Pat Moriarty and a team including Paul Fleming, Sang Lee, Avi Purkayathsa, and John Mikalakes, developed SOWFA.

SOWFA is beneficial for streamlining experimental tests and controlling costs. "The simulation goes hand-in-hand with the experiment, and can help researchers plan an experiment," Churchfield said. "If issues arise during an experiment, they can go back to simulations to help figure them out." Once researchers have data, they can also validate the model further, creating a reinforcing cycle.

The team began working on the SOWFA concept about a decade ago, following the idea of analyzing wind farms as a group of interacting systems rather than focusing on individual wind turbines. "SOWFA is a tool that enables us to do wind farm aerodynamics," Moriarty said.

New wind farm control ideas tested in SOWFA promise impressive results, with possible energy capture increases on the order of 5%, which could potentially translate into millions of dollars of revenue annually for a medium-sized wind farm.

Since its release, SOWFA has been adopted by industry and is used for wind farm physics research by some of the major wind industry companies. SOWFA's arrival was timely. Scott Haynes of Iberdrola Renewables, a major international developer of wind farms, said "the SOWFA code is a tool desperately needed by industrial wind farm developers and would be out of reach if not for the efforts of Pat Moriarty and Matt Churchfield." In recognition of its impact on industry, Churchfield and Moriarty were given the Outstanding Public Information Award 2015 at the NREL Tech Transfer Award ceremonies.

SOWFA continues to reflect new applications. As an open-source community model, SOWFA's source code is freely available and can be modified by users to fit their own needs and to build SOWFA's overall capabilities. SOWFA's modular framework allows users to swap out the components that model different scales or phenomena to create custom-tailored applications, including applications for developing marine and hydrokinetic systems.

Now the Energy Department is embarking on a project to create a newer version of the code that will efficiently run on its largest computers, utilizing 100,000 computer cores instead of a few thousand as it currently does. "Then we could do entire large wind plants. We're at that ceiling now, and can't quite simulate the largest farms at fine resolution," Moriarty said.

The NREL team is eager to take the tool to the next level, and see further impacts on the next generation of wind farms. Said Moriarty, "it has the ability to simulate what's going on, including new technologies being applied to wind that haven't been field tested as of yet."

Expect the winds of change to keep blowing thanks to tools such as SOWFA.

—Kelly Yaker