The Air Force is moving ahead with plans to build a 14.5-megawatt photovoltaic solar array at Davis-Monthan Air Force Base.

The D-M installation would be the Air Force's largest in terms of generating capacity, eclipsing a 14-megawatt array that went online at Nellis Air Force Base in Nevada in 2007.

Construction on the D-M project, initially announced in September 2010, will begin soon with completion planned for no later than December, the Air Force said.

The base has entered into an agreement with California-based solar developer SunEdison LLC to design, finance, build, operate and maintain the array on 170 acres of underutilized base property.

D-M is already home to the largest residential photovoltaic installations in the nation, 6 megawatts worth of solar at D-M's Soaring Heights Communities base housing complex.

The new array must be built and generating electricity by the end of the year to qualify through renewable-energy credits from Tucson Electric Power Co., said Ken Gray of the Air Force Civil Engineer Support Agency at Tyndall Air Force Base, Fla.

D-M officials could not immediately explain the delay in getting the project going.

The $38.4 million power purchase agreement provides electricity to Davis-Monthan at a reduced rate for a period of 25 years, saving the base from $400,000 to $500,000 a year in utility costs, the Air Force said. The project will provide 35 percent of the energy needed to power the base.

The Davis-Monthan solar array required the first Pentagon approval for an Air Force project of that type.

Gray said complying with the National Environmental Policy Act process is challenging in Arizona, home to many sensitive Native American historical areas.

A 14-megawatt solar array also is planned for Luke Air Force Base in Glendale in partnership with Arizona Public Service Co.

The Luke project was announced in 2010 and was planned to go online last year, but the discovery of historical artifacts led to a preservation effort that delayed the solar project. A full archaeological dig conducted last spring yielded Native American artifacts dating back as far as 3000 B.C.

The project is still on hold for now, APS spokesman Alan Bunnell said.

Gray said dealing with such development issues at D-M highlighted areas where the Air Force needs to improve its renewable-energy development process.

"We think lessons learned during the development of this (D-M) project will allow us to shorten execution time to six months," said Gray, who is chief of the Rates and Renewables Branch of the Civil Engineer Support Agency at Tyndall.

The Air Force now operates 131 solar, wind, waste-to-energy and landfill gas projects, which help meet goals established by the Energy Policy Act and an executive order. The service says it has plans to build 30 new projects by the end of 2013.

Besides Nellis, the Air Force has built smaller solar projects at bases including Edwards Air Force Base in Southern California and Buckley Air Force Base in Colorado.

Among the Air Force's next solar projects are a 6-megawatt array at Otis Air National Guard Base, Mass., and a 10-megawatt solar array at Joint Base McGuire-Dix in Lakehurst, N.J.

Contact Assistant Business Editor David Wichner at or 573-4181.