This article first appeared in the St. Louis Beacon, Aug. 8, 2011 - Those solar panels that are beginning to appear on the roofs of homes and offices in the St. Louis area may turn out to be a cool idea in more ways than one. A study published in this month's issue of Solar Energysays the panels can produce the unintended but welcome benefit of making buildings a little cooler during the summer. This is in addition to widely mentioned justifications of turning to solar energy to lower carbon emissions and cut heating costs.
The findings come from research by the University of California at San Diego's School of Engineering. Relying on thermal imaging, the researchers discovered a 38 percent reduction in the amount of heat reaching the roof of a commercial building with solar panels. They also found that temperatures on the ceiling were 5 degrees cooler under the panels than under roofs with direct exposure to the sun.
Jan Kleissl, the professor who coordinated the study, likened the effect to getting relief by standing under a shade tree on a hot day. In effect, he says, the panels provide shade for the roof. While noting that the research was limited and focused on a certain type of building, the environmental engineering team says it is convinced that this unintended cooling effect has valuable implications for use of solar panels.
The findings come as solar energy is getting an assist this summer through the federal stimulus program. St. Louis County, for example, has used funds to install solar panels to capture sunlight and for generating heat and hot water for a building in Tilles Park. Solar panels also are installed at some other public sites and buildings in the county.
Public Housing Benefits
But the biggest solar initiative, now nearing completion, involved a project between the St. Louis Housing Authority and McCormack Baron Salazar, a St. Louis-based builder. The $10.4 million project included installing 2,000 solar panels on nine affordable housing complexes. The work is being done by Sunwheel Energy Partners, an affiliate of McCormack Baron Salazar.
While team members say they welcome any additional and unexpected benefits, like those mentioned in the California study, they also say they are pleased that the city's project will reach its intended objectives of helping the housing authority make use of clean energy and lower its utility bills.
Dan Magni, vice president for project engineering at Sunwheel, says the project will generate energy that is the equivalent of operating 81 homes for a year or removing 170 vehicles from the highway. The switch to solar is expected to result in a 10 percent reduction in the use of electricity as well as a reduction in the carbon footprint and pollution.
"In other words, instead of receiving all their electricity from coal-fired power plants, they will be getting some of it from solar energy," Magni says. "They are trying to reduce their long-term cost and use what's called green energy from solar panels and less brown energy from coal-fired power plants."
The goal shows how much public housing has changed over the years. The authority has remade itself as an agency that develops mixed-income housing. That's a far cry from the days when its buildings were occupied exclusively by the poor and the agency struggled almost daily through one crisis after another involving problems ranging from crime to maintenance. During the old days and scorching summers like this one, heat used to be the enemy, knocking out poorly maintained air-conditioning systems and causing tempers to flare.
But the latest research suggests that even on sweltering summer days, the solar panels can be a silver lining by taking the heat off the buildings. The solar project also shows how the agency has stabilized to the point that it can team up with groups like McCormack Baron Salzar to think through ways to use new technology to benefit tenants and reduce some of its costs.
Stimulus money has been used for solar energy programs before. But the Housing Authority's project is thought to be unique in that the money was combined with energy tax credits to make the solar energy program feasible. Officials say they saw the opportunity to do this project almost as soon as HUD began to announce its stimulus funding grants. The Housing Authority got $5.1 million in stimulus grants for so-called green improvements, meaning it would rely less on non-renewable energy resources. The rest of the funding came from energy and redevelopment tax credits.
In addition to addressing energy needs, Magni says the federal housing grant offered training to encourage tenants to think green in household maintenance. This includes turning to sustainable, low-impact solutions, such as nontoxic chemicals when cleaning their homes.
The St. Louis project is the largest solar installation program in Missouri.
