For NASA's Glenn Research Center, the installation of a grid-tied photovoltaic (PV) power system on the roof of its Visitor Center is a return to its roots. In the 1970s, Glenn pioneered the use of solar power at earth-based settings with no access to electricity. Today, Glenn's scientists continue to play an instrumental role in furthering photovoltaic research.
The Visitor Center's 12-kW DC, grid-tied power system doesn't demonstrate a new concept or use cutting-edge technology. Glenn just wanted to install a cost-effective, low maintenance, renewable energy source to reduce its carbon footprint, pave the way to turn its multiple flat-roofed buildings into mini energy plants, and educate northeastern Ohio in how to use solar energy.
"It's a huge benefit to spread the knowledge," explained Dennis Eichenberg, the electrical engineer in the Avionics Group who spearheaded the 2008 installation. The power system produced 13,593 kilowatts of energy in its first year, surpassing the estimate and reducing Glenn's carbon dioxide output by 37,152 pounds. It provides enough energy to power 596 homes for a day.
Commercial applications of solar power are common in warm regions. In the Midwest and Northeast, installations are less common and as much as one-third more costly to install than in states like Arizona and California, according to an October 2009 Department of Energy report, published by the department's Lawrence Berkeley National Laboratory.
Eichenberg set out not only to help Glenn lower its use of nonrenewable energy sources (federal law requires that government installations receive 7.5 percent of power from renewable sources by 2013), but also to show colder, snowier regions how to "green" their institutions. "PV generation has the highest power density of renewable energies. It's entirely pollution-free during use, and end wastes and emissions are manageable," Eichenberg said. "PV panels also last upwards of 25 years."
Instead of choosing a system that rotates the panels as the sun moves, Eichenberg calculated the best tilt for the Cleveland area and had the panels set at that tilt. Rotating panels sometimes use moving parts, which can break. Even panels with a passive rotation system (ones that use sun-generated power to turn towards the sun) are more prone to breaking down.
To save money, Eichenberg also wanted a system that didn't involve altering the roof's surface. The Visitor Center utilizes a unique ballast mount system for mounting its solar panels. This system dramatically reduced installation labor, lowering overall system costs, and improved system efficiencies. The system makes no roof penetrations, and it is quick and easy to install. The angled design increases annual system energy production by 11.5 percent compared to a flat-mount system. The angled design also reduces buildup of dirt and debris, sheds snow, and reduces heat buildup through front, side, and rear ventilation for improved system performance. The system is maintenance free, has no moving parts, and can be moved easily for any routine building maintenance.
The new power system has met all of the Center's goals. In its first full year of operation, it produced energy equal to 4.47 percent of the power needed to run the Visitor Center. Glenn's system cost slightly less than $10 per watt installed, about the same as 10-kW or smaller installations in Ohio typically cost. More importantly, it has helped pique interest in solar power in northeastern Ohio, spreading the word about the system. This power system produced only 3,000 kWh less than the same size system installed in sunny Tampa, Florida. "We've gotten calls from universities. Our electrician, who retired after installing the system, is now installing commercial systems in our area," said Eichenberg.
Glenn has played a large role in the evolution of solar power—for cutting-edge applications used in space and practical solutions here on Earth. In 1976, Glenn (then known as Lewis Research Center) began installing 83 photovoltaic power systems around the world—often in settings where no power grid existed to tap into. The systems helped refrigerate vaccines, brought power to a U.S. Indian reservation, and pioneered solar power water pumps used in developing nations.
In recent years, Glenn has studied the best ways to tie PV systems to the power grid. Eichenberg began working on the Hybrid Power Management Program a decade ago, with the goal of integrating diverse power devices in an optimal configuration for space and terrestrial applications. "PV can displace the highest cost electricity during peak demand times in most climatic regions, like on hot sunny days when the air conditioning is running, thus reducing grid load," Eichenberg said.
Eichenberg has proposals written to mount more rooftop PV systems at Glenn. He hopes some of these will use a PV panel featuring a type of concentrator that uses less silicon and drawing even more of the sun's energy into the panels. Just now becoming commercially available, these panels—like so much in the solar energy world—got their start at Glenn.
