Forecasting breakthrough aims to put more solar on grid

Source: Scott Streater, E&E reporter • Posted: Wednesday, August 24, 2016

A team of researchers has developed a groundbreaking forecast system that could save utilities hundreds of millions of dollars by more efficiently integrating solar-generated electricity into the grid, a Boulder, Colo.-based research institution announced today.

The National Center for Atmospheric Research has been working for three years with researchers from government laboratories, universities and six public utilities to develop the Sun4Cast system, which NCAR says “uses a combination of advanced computer models, atmospheric observations and artificial intelligence techniques.”

NCAR says the Sun4Cast system will allow utilities to deploy solar energy more reliably and inexpensively by significantly improving daily forecasts of clouds and other atmospheric conditions such as atmospheric pollution that influence the amount of energy generated by solar arrays.

The system is designed to help ease solar-generated electricity onto the power grid, which must have a consistent source of electricity to handle the peaks and valleys of customer demand. With better forecasting, utilities would save an estimated $455 million through 2040 as they use more solar energy, according to an analysis by NCAR economist Jeffrey Lazo.

“This type of research and development is important because it contributes to the reduction in costs for solar and wind energy and makes it easier for utilities to integrate renewables into the electrical grid,” said William Mahoney, deputy director of NCAR’s Research Applications Laboratory.

NCAR will make the technology available to utilities, which will customize the system to individual solar power units.

The Sun4Cast system, which has been tested at numerous sites, should “help enable the nation’s expanding use of solar energy,” said Sue Ellen Haupt, who directs NCAR’s Weather Systems and Assessment Program. “More accurate predictions are vital for making solar energy more reliable and cost-effective.”

The system’s development, which was funded by the Energy Department as part of DOE’s SunShot Initiative, builds on work NCAR has led in recent years to develop forecasting systems for the wind power industry.

Wind-generated electricity is especially vulnerable to so-called ramp events — sudden drops or spikes in wind energy caused by rapidly changing atmospheric conditions as common as a passing cold front.

NCAR, in a formal agreement with Minneapolis-based Xcel Energy Inc., the nation’s largest utility provider of wind energy, developed the Variational Doppler Radar Analysis System several years ago to forecast such events.

“Our previous experience with the National Center for Atmospheric Research in developing a wind forecasting system has saved millions of dollars and has been highly beneficial for our customers,” Drake Bartlett, senior trading analyst for Xcel Energy in Colorado, said in a statement.

Xcel Energy is already using the new Sun4Cast system “at several of its main solar facilities,” NCAR said.

“It is our sincere hope and belief that we will see positive atmospheric forecasting results for predicting solar generation, as well, again to the benefit of our Xcel Energy customers,” Bartlett said.

Knowledge is power

Precise forecast information can benefit utilities in a number of ways.

Electricity must be promptly consumed because large amounts of it cannot be stored in a cost-effective manner. But if an electric utility powers down a coal or natural gas facility in anticipation of increased solar-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 spot market, which can be very expensive. The cost is passed on to the ratepayers.

The Sun4Cast system, among other things, should allow utilities to better handle increases in solar power from distributed rooftop panels feeding back into the grid.

Sun4Cast provides six-hour “nowcasts” of solar irradiance and the resulting power production for specific solar power plants at 15-minute intervals, NCAR said, enabling utilities to continuously anticipate the amount of available solar energy.

In addition, forecasts can extend out to 72 hours, allowing utility officials to make decisions in advance for balancing solar with other sources of electricity, such as natural gas, NCAR said.

The research team tested the system “in geographically diverse areas,” including Long Island, N.Y.,; the Colorado mountains; and sites along the California coastline.

“We have to provide utilities with confidence that the system maintains a high degree of accuracy year-round in very different types of terrain,” said Branko Kosovic, NCAR’s program manager for renewable energy.