The mayor of Pittsburgh says he'd like to put a solar farm on the site of a former coal mine.

Pittsburgh Mayor Luke Ravenstahl thinks putting ground-mounted solar photovoltaic panels on a 15-acre abandoned mine site in the Glen Hazel suburb of Pittsburgh will not only restore the land to useful function, but provide electricity for area residents within two miles of the array.

The sloped 15-acre site, owned by the Pittsburgh Housing Authority, or PHA, overlooks the Monongahela River. At one time, the PHA planned to build public housing, but mine subsidence has since put paid to that idea.

Mine subsidence is the (sometimes serious) sinking or shifting of ground under former mines – in this case, coal – where miners following veins of coal created a grid or checkerboard pattern of ‘rooms’ beneath the earth’s surface, leaving pillars of rock to support the roof of the mine.

The subsidence is particularly evident in areas of high rainfall, like Pennsylvania, North and South Carolina, Virginia and most other states along the Appalachian Range, which in the early years of the Industrial Revolution saw the greatest amount of coal mining in the nation. Nowadays, Wyoming’s Powder River Basin is the major U.S. coal-producing region.

Ravenstahl foresees enough solar panels to power perhaps 2,000 homes, and is soliciting bids from area consultants to study the site for solar feasibility. If the site has enough solar radiance (and, presumably, enough stability to support the weight of solar panels), the PHA would then lease it to a solar developer.

Ravenstahl and city fathers are aiming at a Feb. 19 deadline to find a consultant from the solicitation for bids posted on the city’s website (hopefully for less than $20,000), and the study – begun in early April – should be able to identify by late summer how many acres are stable enough to support solar panels, which can weigh between 2 and 40 pounds.

Costs will be funded through Ravenstahl's Green Initiatives Trust Fund and possibly the Department of Energy's Solar American Cities Initiative as well. All the funding together represents about $300,000, according to Jim Sloss, city energy and utilities manager.

If the entire 15-acre site were used, the solar panel array might be as much as 2 megawatts, which could produce up to 3.5 million kilowatt hours of electricity per year. At least, this is the output of the solar array at the University of Colorado at Fort Collins (also known as “the Foothills campus”).

Of course, the same number of kilowatt hours of electricity are also produced by the solar photovoltaic system at Denver International Airport (DIA), where 7.5 acres of land support 9,200 solar panels, providing enough energy to power about 1,500 homes and power the “People Mover” (DIA’s underground transportation system).