Colo. research center partners with utility to better manage wind resources

Source: Scott Streater, E&E reporter • Posted: Wednesday, May 8, 2013

The National Center for Atmospheric Research (NCAR) is expanding ongoing efforts to design and implement wind-energy forecasting systems that should allow utilities to better integrate wind-generated electricity onto the power grid.

NCAR today announced it is expanding an existing partnership with Minneapolis-based Xcel Energy to add sophisticated weather forecasting systems aimed at calculating times of peak wind energy and, perhaps as important, providing utilities advance notice of when winds are expected to be low.

Xcel Energy Inc. is already using a wind-energy forecasting system designed by NCAR. But Xcel — the largest utility provider of wind energy in the nation — continues to add more wind-driven electricity to its portfolio, necessitating the need for even more sophisticated weather forecasts.

The forecast systems are designed to help integrate the volatile energy source onto the power grid, which must have a consistent source of electricity to handle the peaks and valleys of customer demand.

Scientists and engineers with Boulder, Colo.-based NCAR will over the next two years develop custom forecasting systems to predict sudden changes in wind that could allow grid operators to power down natural gas and coal-fired power plants or even shut down turbines ahead of potentially damaging icing events. The systems would be used at Xcel Energy control centers at the company’s home base in Minneapolis, as well as Denver and Amarillo, Texas.

“This is pushing the state of the art still further, using the latest science to enable Xcel Energy to generate energy from the atmosphere more effectively,” said Sue Ellen Haupt, an NCAR program director overseeing the new project. “Every improvement to the forecasts results in additional savings.”

The latest agreement builds upon a 2009 partnership between NCAR and Xcel in which the research center first developed a wind-energy forecast system that helped save Xcel Energy customers $6 million in 2010. The specialized system relies on a suite of tools, including highly detailed observations of atmospheric conditions, an ensemble of powerful computer models and artificial intelligence techniques to issue high-resolution forecasts for wind farm sites, according to NCAR.

Gabriel Romero, an Xcel Energy spokesman in Denver, said the current system has proved so reliable that several times last year the utility felt comfortable enough to allow wind power to provide more than half the electricity for customers utilitywide.

“The wind forecasting has allowed us to be very aggressive in using energy from renewable sources,” he said.

Xcel Energy has 2,167 megawatts of wind-generated electricity in its portfolio.

Wind-generated electricity, as well as solar or any other source, must be promptly consumed because large amounts of electricity cannot be stored in a cost-effective manner, according to NCAR, a federally funded research and development center. But if an electric utility powers down a coal or natural gas facility in anticipation of wind-driven energy that does not come, those plants may not be able to power up fast enough should the winds fail to blow.

If those fossil-fuel generating plants cannot be quickly powered up, then the utility must buy electricity on the open market, which can be very expensive. The expense, of course, is passed on to the ratepayers. Xcel Energy serves 3.4 million customers in Colorado, Michigan, Minnesota, New Mexico, North Dakota, South Dakota, Texas and Wisconsin.

“The importance and value of accurate renewable energy generation forecasts increases with the size of our renewable energy generation portfolio,” Ben Fowke, Xcel Energy’s chairman, president and CEO, said today in a statement. “Xcel Energy has been the largest utility provider of wind energy for the last nine years and we are continuing to grow our renewable energy portfolio.”

Ongoing effort

The latest two-year agreement between NCAR and Xcel Energy announced today will focus on several areas, most notably forecasting so-called ramp events, which are sudden changes in wind energy due to atmospheric conditions as common as a passing cold front or other weather system.

The system NCAR is developing is known as VDRAS — the Variational Doppler Radar Analysis System — and it relies on techniques that combine observations from radars and other tools with computer simulations to create more accurate forecasts for particular wind farms.

Another area of focus is developing systems that forecast ice and extreme temperatures. The new ice-forecasting systems for Xcel will be similar to systems NCAR has developed to help protect aircraft from potentially lethal icing conditions, and it includes the use of computer models and specialized algorithms.

Applying similar technology, researchers at NCAR and Pennsylvania State University will develop a 48-hour forecasting system at designated wind farms to predict the impacts of freezing rain and fog on wind turbines, which cannot operate when coated in ice. The team also will forecast extreme low and high temperatures, which can cause wind farms to temporarily shut down, according to NCAR.

“We’re taking our expertise in critical areas, such as keeping airplanes safe from icing, and applying it to obtaining as much energy as possible from the atmosphere,” said Marcia Politovich, an NCAR program manager who is overseeing the development of icing and extreme temperature forecasts.

NCAR researchers will also attempt to develop solar-energy forecasts, which are becoming necessary as more and more Xcel Energy customers install roof-mounted solar panels.

Once the systems are finalized, they will be turned over to Xcel Energy or a utility contractor for ongoing operation. NCAR researchers will publish the results in peer-reviewed journals, according to the research and development center.

“Xcel Energy is recognized by the energy industry as a national leader in proactively moving forward with the utilization of renewable energy,” said William Mahoney, deputy director of NCAR’s Research Applications Laboratory. “This new project is an example of how improved understanding of the atmosphere can provide significant benefits to society.”