A trio of companies — CarbonFree Technology, Integrys Energy Services, Inc., and SunPower Corp. — today announced the completion of Harvard University’s first large rooftop solar energy system. Installed atop one of the historic buildings that make up the Arsenal on the Charles complex in Watertown, MA, the 500-kilowatt (kW) system is expected to generate the equivalent amount of electricity annually consumed by 83 average Massachusetts homes.

“The multi-story building was erected during World War I and is an ideal site for solar, with a flat, unshaded roof,” said Joseph Gregory, assistant director of sustainability at Harvard Real Estate Services. “Despite the age of the building, the roof has been upgraded and has a long expected life, making it perfect for this system.”

In March 2009, Harvard issued a request for proposal, seeking bidders interested in installing, owning and operating a solar energy system. CarbonFree Technology — a solar power project developer with offices in Arizona, Maryland and Ontario — headed up the winning bid, working with SunPower to design and install the system, and provide operations and maintenance (O&M) services.

The system is owned by Crimson Solar, LLC, a wholly owned subsidiary of Integrys, a Chicago-based firm specializing in the development, acquisition and operation of renewable energy projects throughout the U.S. Harvard will buy from Crimson Solar the system’s output, along with the associated renewable energy certificates (RECs), at a fixed rate for a term of 25 years. Such an arrangement is called a power purchase agreement (PPA). The project was made possible by a $1.1 million rebate provided by the Massachusetts Technology Collaborative, which promotes the installation of grid-connected solar photovoltaic (PV) systems.

“It is clear to us that Harvard has a serious commitment to environmental sustainability, and is looking for ways to creatively reduce operating costs on campus,” said Tom Leyden, managing director at SunPower. “We feel this project serves both objectives.”

In sum: Harvard’s new 500-kW system is a wicked smart idea.