A Michigan company, Energy Conversion Devices, plans to announce Tuesday that it is providing the solar electric system for what it says will be the world’s largest rooftop array, on a General Motors assembly plant in Zaragoza, Spain. The project will be 12 megawatts, a huge number in a field where most arrays are measured in kilowatts, units 1,000 times smaller.
The project will use solar devices manufactured in rolls, like carpet runners. Installation will be completed this fall, according to the company, which is based in Rochester Hills, Mich. Energy Conversion will supply the equipment to Veolia Environment and Clairvoyant Energy, which will lease the rooftop space from G.M. and own and operate the installation, which will be two million square feet.
Spain has become a center of solar installations because it offers generous subsidies, 0.42 euro a kilowatt-hour (66 cents). That is about five times the average cost of a kilowatt hour to residential customers in the United States. The Spanish government is considering a reduction in the subsidy for installations after September.
Energy Conversion plans to produce about 150 megawatts of cells this year. Last month, the company raised $400 million in new capital and announced plans to raise its annual production to 1 gigawatt, or 1,000 megawatts, by 2012. The company did not say what the Zaragoza installation would cost.
Solar cell arrays on houses are commonly a handful of kilowatts, or thousandths of a megawatt. On big commercial buildings, installations of one or two megawatts have become common. A one-megawatt installation will run about 1,000 window air-conditioners simultaneously, at least as long as the sun is shining.
According to the Solar Energy Industries Association, a trade group based in Washington, the largest installation planned in the United States, announced in June, was in Atlantic City, where the convention center will have 2.36 megawatts, about one-fifth the size of the installation to be completed in Spain.
Southern California Edison announced in March that it would install 250 megawatts of rooftop solar arrays, spread over 100 or more roofs.