On May 17, General Motors unveiled one of the largest rooftop photovoltaic arrays in Maryland, a 1.23 megawatt photovoltaic array at their White Marsh, Md., plant where they will soon manufacture electric motors for future hybrid-electric cars. It’s also the second new solar installation they announced in less than a week.

Last Wednesday the company announced that it was installing an array at its Detroit-Hamtramck Volt manufacturing plant. At the Maryland facility the company produces transmissions for heavy-duty vehicles and two-mode hybrids (not the Volt) at the location. The Michigan facility’s photovoltaic array is being developed by DTE Energy (NYSE: DTE). It will supply on-site electricity to GM. Under the agreement, GM will continue to pay DTE for the electricity used, but GM will receive a $15,000 easement payment from DTE for 20 years.

While the photovoltaic array at the Volt plant is a ground-mounted array, the Maryland facility’s array is a rooftop array. “The solar array on the plant is a 1.23 megawatt array and it provides about 9 percent of annual energy consumption at the existing facility,” said GM spokesperson Sharon Basel.

The array was installed under a 20 year power-purchase agreement with Constellation Energy, a Maryland utility. The array consists of SolarWorld photovoltaic modules, said Constellation spokesperson Kelly Diemer. It is projected to save GM a total of $330,000 over the term of the contract.

The company actually made a couple of announcements that day. “Today we broke ground on the new building on the site of our existing operations in Baltimore,” Basel said. That, “And that the solar system on the roof of the existing facility is now operational.”

The new facility is expected to be complete in 2013. “There we’ll produce motors for future hybrid vehicles that we haven’t yet announced,” Basel said. It’s too early to tell if GM will include solar on the new facility, she said. Currently transmissions for GM’s two-mode hybrid vehicles are produced at the facility. These include vehicles like Chevy Silverado pick-up hybrid and the Cadillac Escalade hybrid.

The facility also is a zero-landfill waste facility, which the achieved in 2007 by recycling, reusing or converting to energy all wastes from daily operations, according to a press release.

Image courtesy of GM