Coordinating traditional and renewable energy sources

With the advent of renewable energy technology, such as wind turbines and solar photovoltaics, the public and quasi-public agencies that operate the U.S. interconnected power grid look for optimal ways to integrate traditional energy sources with new renewable energy sources. Power grid operators must decide how and when to switch on coal or gas back-up systems when wind or solar energy production drops in local areas. These decisions are made to provide continuity in the supply of electricity at lower costs.

Two UC Davis professors were recently awarded grant funding from the U.S. Department of Energy to research this coordination problem. Mathematicians refer to this coordination issue as the “electric power dispatch problem,” explained Roger J-B Wets, a professor in the UC Davis department of mathematics, and one of the researchers working on the project.

Wets is widely recognized as a pioneer in a branch of mathematics known as “variational analysis,” and has worked on mathematical techniques which are being applied to the current problem for many years. When applied to real situations involving significant levels of uncertainty, the application becomes extremely complex.

Since weather patterns cannot be predicted with certainty, mathematicians use models to find optimal solutions in applications involving weather. David Woodruff, a professor in the UC Davis Graduate School of Management, refers to this process as “optimization under uncertainty.”

“The future is always uncertain, but unfortunately we haven’t been able to deal with that as well as we do now,” Woodruff said.

This particular branch of mathematics, which is known as stochastic variational analysis, involves finding a way to create one special function that approximates the information provided by the hundreds of possible equations involved, Woodruff explained.

“[Stochastic variational analysis] essentially provides the mathematical justification to approximate these ultra-difficult problems and obtain guarantees that you get excellent approximate solutions,”  Wets said.

The project, funded by the U.S. Department of Energy sub-agency called “Advanced Research Projects Agency—Energy” (ARPA-e), is a response to concerns that the U.S. is falling behind in its economic security.The purpose of ARPA-e is to fund projects with cost-to-performance ratios that are too high to be attractive to private industry. After the projects are partially developed and costs are brought down, other funders can adapt the results for use in specific applications.

The creation of ARPA-e in 2007 was meant to mirror the creation of the original Advanced Research Projects Agency (ARPA) that was created in 1958 in response to concerns that the U.S. was falling behind the Soviet Union in technological research and development. One well-known successful ARPA project was the ARPANET, which evolved into today’s internet.

The specific ARPA-e program which is providing funding for electrical grid coordination project is called “GENI,” which stands for Green Electricity Network Integration.

According to Sarah Ryan, professor in the Department of Industrial and Manufacturing Systems Engineering at Iowa State University, the GENI-sponsored project involves “bridging the gap in green energy integration between basic research and implementation.”

BRIAN RILEY can be reached at science@theaggie.org.

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