Batteries replacing windmills

Although the windmills at the Green Mountain Wind Energy Center near Garrett are coming down, one of the first battery storage facilities in Pennsylvania has been built at that location.

Bryan Garner, spokesman for NextEra Energy Resources, said the 10.4 megawatts of power that the eight turbines had generated is being provided to the power grid by the Green Mountain Energy Storage facility, which opened in June.

"Our Green Mountain storage facility helps feed power to the grid to help meet the area's energy needs when the wind isn't blowing — modulating the voltage of existing wind farms and providing even greater reliability to customers," he said. "This is exciting new technology that is changing the way power is delivered to customers. Wind energy continues to be a valuable resource in Pennsylvania, and the storage technology complements it well."

The site has about 1,500 batteries that receive power from the grid and store it. They then return power to the grid when it is needed.

"The batteries can offset fluctuations between peak and low demand times," he said. "Energy storage fills in the gaps resulting from intermittent resources like wind and solar generation."

A battery management system monitors the individual cells and controls the voltage, temperature and current for safe, reliable transfer of energy, according to the NextEra website. Energy from the power grid or from renewable energy sources is delivered via a bidirectional inverter, which converts the energy from alternating current into direct current. Today's batteries can store only direct current.

This energy goes into an array of batteries housed within a battery container or a building structure. When the energy is needed, the inverters are used again, but this time to convert the direct current from the batteries into alternating current. It is then stepped up in voltage and sent to an on-site substation or directly to a distribution or transmission line.

Garner said it is not true that the turbines were not maintained. The reason the wind farm was decommissioned was there was no longer a customer for the electricity. The contract with the energy cooperative expired in 2012.

"This technology is older," he said. "There are more cost-effective ways of producing energy. The battery storage facility is new and will continue to operate."

The Green Mountain Wind Energy Center was the first wind farm in Pennsylvania. It opened in 2000, and NextEra Energy Resources purchased it in 2003. It was decommissioned in December. The wind turbines will be removed and the land restored to the original state. Mid-December is the target date for the completion, but that is weather-dependent. Some wind farms last 20 years and others last 30 years, he said.

NextEra Energy Resources is primarily a wholesale power generator and is the world's largest generator of renewable energy from the wind and sun. It is a subsidiary of NextEra Energy Inc. and has headquarters in Juno Beach, Florida.

In addition to the Green Mountain site, in this region, NextEra owns the Meyersdale and Somerset wind farms in Somerset County, Mill Run in Fayette County and Waymart in Wayne County.