Rockville, Md.-based Standard Solar has installed a 930 kW photovoltaic power system with rooftop and carport arrays at the Upper Marlboro, Md., headquarters of Melwood, a nonprofit organization that creates jobs and opportunities to improve the lives of people with disabilities.
The system features a 1,335-panel rooftop array and six carport arrays, with the latter having a combined capacity of 517 kW. The entire PV system is expected to produce over 1.2 GWh of electricity per year – enough to offset nearly all of the annual load at the Melwood campus.
It is increasingly common to see solar shading canopies incorporated into photovoltaic power projects, either as an element of a larger project or as a stand-alone array. Scott Wiater, president of Standard Solar, says the growing popularity of solar shading structures and carports is due, in part, to the improving economics of the segment. However, he says customers are finding value in the carports themselves over and above their value as electricity generators.
According to Wiater, Melwood had been interested in a PV project for some time but didn't have enough roof area to make a power purchase agreement (PPA) worthwhile. In order to develop a project large enough to attract a financier for a PPA agreement, Standard Solar determined that it was necessary to make use of the parking lot space to build solar shade structures. However, solar canopies typically are more expensive than rooftop and ground-mount alternatives due to the extra material involved in their construction.
One of the keys to the project was the Parking Lot Solar PV Canopy with Electric Vehicle Charger Grant Program from the Maryland Energy Administration (MEA).
‘When Maryland came out with its carport grant program, that brought everything together,’ Wiater says. ‘It made it inexpensive enough to make the whole deal pencil out.’
According to Wiater, the MEA's program came from an understanding in the administration that there were a number of good opportunities to develop solar in the state based on carports that were hanging on the economics. ‘I think the MEA did a really good job in calculating the grant,’ he says. ‘The economics are still tight, but just enough to make it feasible. It's not a big lucrative grant that just makes a lot of people money.’
Another regulatory policy in play that made the project possible was Maryland's net-metering law that permits nonprofits to aggregate their solar arrays. The design for the Melwood project called for seven distinct arrays – six carports and the rooftop – each with its own meter. The ability to aggregate these under a single PPA was important for attracting financing for the project from WGL Energy.
By comparison, solar carport projects in nominally sunnier and hotter locations, such as New Mexico, don't always make financial sense because of the economics. At the same time, Wiater says, solar carports are extremely popular for schools in California because of the seismic load requirements for getting permits for roof-mount arrays. ‘If you're doing a school that is governed by an architectural committee at the state level, they've got very strict guidelines,’ he says. ‘So for a school in California, it's just easier to do a carport.’
Although the components and engineering for solar carports are coming down in price because of improved fabrication methods and increasing competition, Wiater says attitudes among organizations that host such arrays are broadening to encompass considerations other than strict cost. High among the other values to having a solar carport is the benefit of the shade it provides.
‘We did a carport several years ago that was about 700 kW at a community college,’ Wiater says. ‘The host wanted to use a section of the parking lot for the array that was farthest away from the buildings. What they found after we built the carport was that those were the favorite spots. Even though they were farther away, those spots filled up first. The shade made them premium.’