Solar power

Full-spectrum dominance

Electric power has been a key factor in creating a healthy and comfortable society. Unfortunately, conventional sources are plagued with unacceptable liabilities. Solar photovoltaic (PV) technology, which converts sunlight directly into clean and green electricity, is poised to replace those sources—and this is the goal of a team of undergraduates, graduate students and post-docs working with Joshua Pearce on every aspect of PV technology, including the fundamental materials science, device physics, solar electrical system design and energy policy.

The US solar industry is growing at a record-breaking pace, while becoming more affordable and accessible than ever before. In many parts of the country, solar electricity is already cost-competitive with traditional energy sources. The average price for a utility-scale PV project dropped from about $0.21 per kilowatt-hour in 2010 to $0.11 per kilowatt-hour at the end of 2013. According to the Energy Information Administration, the average US electricity price is about $0.12 per kilowatt-hour, and can run higher than $0.20 per kilowatt-hour in Michigan’s Upper Peninsula, New York, and elsewhere.

Although solar power costs have plummeted, most American families still simply do not have enough cash to purchase a PV system to meet their needs; they need a loan with reasonable terms. Securitization, or a pooling of solar assets for investors, provides a solution to this problem as shown in a study by Pearce’s research group that found billions of dollars of potential solar asset-backed securities in the US. “With the current cost of solar equipment and our financing model the home owners make money, the solar industry makes money and the firms setting up the financing make money. There is no question, the solar industry is ready for investors,” says Pearce.

His group is working to reduce costs on several other fronts. Last year, the group investigated spectral effects of albedo (reflection) from surfaces around PV systems and found that by using non-tracking planar concentrators (small mirrors) they could increase PV output by more than 30 percent. “Firms avoid using such mirrors now because of fear of voiding warranties,” says Pearce. “Our work is starting to provide the data needed to lessen these fears, and we are developing optical models for non-ideal surfaces to optimize PV systems for the real world.”

In addition, Pearce’s group found they could increase efficiency by using the PV module as a heat absorber for solar thermal applications. “The trick is to be careful about PV material choice and use the thermal system to anneal (bake) the PV to refresh it,” he adds. Their results pumped up the electrical output by another 10 percent.

“Our work enables PV systems to be optimized for a specific location, which drives the cost of solar even lower,” Pearce concludes. “Soon most roof tops will sport a solar power system for economic reasons alone.”