Rooftop Solar Panels Double as Cooling Agents

PV systems keep rooftop temps down in the summer, keep heat inside in the winter.

2 min read
Rooftop Solar Panels Double as Cooling Agents

Energy Secretary Steven Chu has famously touted the energy-saving benefits to painting rooftops white. This works by reflecting the sun's energy away from a building, helping to keep it cool and requiring less energy to do so. It turns out, though, that it isn't just white paint that can cool your roof. Solar panels can do it too.

Research published recently in Solar Energy suggests that daytime ceiling temperatures under rooftop solar photovoltaic systems are lower than under exposed rooftops. In the buildings the researchers studied in San Diego, it was 2.5 degrees K cooler (about 4.5 degrees F). At night, this situation was reversed, with ceiling temperatures under the solar panels registering higher than under exposed rooftop, which the authors said suggests "insulating properties" of PV systems.

Though the study's measurements occurred over a few days in April, modeling suggested that the overall reduction in cooling load would be 38 percent. In the winter, there would be no advantage or disadvantage to the panels in terms of heating load.

This seems to be one of the rare occasions where ancillary effects of a positive technology are also positive. We install solar panels on rooftops to help lessen carbon emissions, and it appears that we actually reduce energy needs at the same time.

And if we start combining some of this knowledge, there is some amazing potential here. The white roof idea that Secretary Chu espouses would, in ideal circumstances, save enough energy to equal taking the world's cars off the roads for 18 years. Then, consider some recent work in New York: about two-thirds of city rooftops could accommodate solar panels, with potential to generate an incredible 5,847 MW of power. If you mix in the cooling potential given New York's well-known heat island effect, and rooftop solar starts to look better and better.

(Image via murphyz)

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Smokey the AI

Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires

7 min read
Smokey the AI

The 2021 Dixie Fire in northern California is suspected of being caused by Pacific Gas & Electric's equipment. The fire is the second-largest in California history.

Robyn Beck/AFP/Getty Images

The 2020 fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. These West Coast fires killed at least 37 people, destroyed hundreds of structures, caused nearly US $20 billion in damage, and filled the air with smoke that threatened the health of millions of people. And this was on top of a 2018 fire season that burned more than 700,000 hectares of land in California, and a 2019-to-2020 wildfire season in Australia that torched nearly 18 million hectares.

While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection (Cal Fire) calculates that nearly 100,000 burned hectares of those 2018 California fires were the fault of the electric power infrastructure, including the devastating Camp Fire, which wiped out most of the town of Paradise. And in July of this year, Pacific Gas & Electric indicated that blown fuses on one of its utility poles may have sparked the Dixie Fire, which burned nearly 400,000 hectares.

Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure. Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis.

However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires. In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a 40-year lifespan, are entering their final decade.

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