Urban Renewability through Solar Power

Dunbar High School Online Statics-single screen
An online dashboard allows users to track energy generation at Dunbar High School.

The District of Columbia Department of General Services, Sustainability and Energy Management Division recently ramped up a renewable energy program for public buildings. The jurisdiction and Constellation signed a power purchase agreement, a first for the city, for a solar panel project at Dunbar High School. When it was completed in 2013, the 463 kilowatt array was the largest rooftop installation in the city.

KCI provided structural engineering analyses for the installation, which consists of 1,940 photovoltaic panels using ballast, trestle and film installations. These kinds of public-private partnerships are helping to advance clean energy initiatives throughout the country. In this case, the array helped the school meet its U.S. Green Building Council LEED certification by providing roughly 20 percent of the building’s estimated energy needs. Constellation financed and now owns and operates the array, and the District of Columbia Department of General Services purchases the energy generated under a 20-year agreement.

Ballasted racking systems are not permanently affixed, but simply sit on the roof using concrete or sand-based weights to keep the panels in place.
Trestle systems are installed on an elevated platform.
Film-based panels don’t require additional structural capacity. Weighing little, they are attached directly to the roof surface but are less efficient in generating energy.