US researchers envision community-based solar systems

Engineers at Oregon State University (OSU) in the U.S. Pacific Northwest believe small "community-based" systems is part of the future of solar energy, especially for residential use.

Such systems, in which neighbors join together in the construction and use of solar energy, could increase the total electricity produced by 5 to 10 percent and enable residents to optimize the energy produced in their neighborhood and share in the benefits.

In what the researchers called "an optimal development" approach, the use of various rooftops and land for solar energy production may vary from house to house, depending upon such issues as the home's orientation, roof slope and shading from trees or other structures.

This approach, with a significant gain by the standards of solar energy efficiency, said Mahmoud Shakouri, a doctoral candidate at the OSU College of Engineering, "makes the most sense in a neighborhood where there's a lot of variation in terms of sun and shadow, and the orientation of buildings."

It can reduce the variability and unpredictability of the solar resource.

In their papers published recently in the journals of Applied Energy and Data in Brief, the researchers included a case study of collaborative solar energy among 24 homes in a neighborhood in Corvallis, Oregon, which has sunny summers but often cloudy and rainy winters, not exactly the nation's best bet in terms of solar energy production.

Even there, the researchers found, the new approach increased the annual electricity output of the homes by 4.6 percent and reduced the volatility in electrical output by 4.3 percent.

"The conventional approach to residential solar energy is to look at each home as an individual package, building its own solar system whether or not that's a good location," Shakouri said. "But by grouping 10 or 20 houses in a neighborhood, all of whose owners are interested in solar energy, we can optimize the use and placement of solar panels and let everyone share in the savings."

The researchers have created a "decision support model" that homeowners could use to help consider the best options for their neighborhood. Free software to help implement such a strategy is also available from the U.S. Department of Energy.

Initial solar installations can be expensive, making it all the more important to maximize the long-term output of the systems. But such systems are durable and pollution free, usually with a performance guarantee of up to 25 years, using a technology that produces no greenhouse gases.

Residential energy use is a big-ticket item in the United States, and the building sector accounts for 40 percent of the country's total energy consumption, and residential buildings consume more than half of the energy in the building sector. By 2035, the U.S. government estimates that 74 percent of the energy consumed in residences will be in the form of electricity.

The new approach developed at OSU, Shakouri said, borrows formulas from economic theory. It has long been used in the stock market in the form of portfolio investment, to maximize profit while reducing risks. Given the high initial cost of some solar systems, about 20,000 U.S. dollars for a 4 kilowatt residential system, reducing risk is of considerable value to many people interested in the technology.