Effort underway to make solar electricity more affordable without government subsidies

Those who invest in solar energy facilities currently receive tax credits or other government subsidies, and the U.S. Department of Energy (DOE) is funding research into improved photovoltaic technology to make solar energy cost-competitive without government subsidies.

The SunShot Initiative was launched in 2011 to make solar electricity cost-competitive with conventional energy sources by 2020 in the absence of any subsidies. The Aug. 9-13 annual meeting of SPIE, the international scientific society which furthers knowledge of optical science, included an Aug. 10 plenary session with a presentation titled "The Importance of Reliability to the SunShot Initiative" and given by DOE program manager Becca Jones-Albertus.

"Our overall mission is to lower the cost of solar electricity," Jones-Albertus said. "Where we're trying to go is to make solar cost-competitive without subsidies."

Jones-Albertus is the photovoltaic program manager for photovoltaics research and development in DOE's Solar Energy Technologies Office. She oversees $200 million of funding to reduce photovoltaic material and process costs, including improved module efficiency and reliability. The SunShot Initiative plans to award $40 million of grants for reliability research in 2015.

"What we want to do is to decrease the cost of solar energy more significantly, well below grid parity," Jones-Albertus said. "Reliability is a critical cost lever."

Research in reliability plays a major role in achieving that goal, including improving the photovoltaic module lifetime and reducing degradation rates. That reliability increases the lifetime energy output, which also increases confidence in system prediction and thus lowers perceived investment risk and the cost of capital.

"We need significant further innovation," Jones-Albertus said.

When the SunShot Initiative was launched, solar energy was approximately four times as expensive as conventional generation. The cost of solar energy has decreased by approximately 64 percent since that time. "Costs are coming down dramatically," Jones-Albertus said.

The United States currently generates approximately 20 gigawatts of solar energy, or enough to power four million homes for a year. This is approximately 10 times the output generated in 2010. The DOE SunShot goal is to generate 300 gigawatts of solar energy annually by 2030, which would equate to 14 percent of all United States energy produced.

"Reliability is an important factor," Jones-Albertus said.

Reliability tends to be defined in terms of degradation rates, but a system with a higher degradation rate may be less expensive while a technology with a lower degradation rate may cost more. "There's always the risk of reverse progress," Jones-Albertus said. "Choices might be made to cut costs that negatively impact reliability."

Currently the median annual degradation rate is 0.5 percent while the average is 0.7 percent. "Work is under way to look at what is the true shape of performance," Jones-Albertus said while showing charts whose efficiency figures reflect degradation.

The DOE's photovoltaics program has three goals: improving reliability and durability, improving conversion efficiency, and lowering material and processing costs. "These things are often tradeoffs," Jones-Albertus said.

The National Renewable Energy Laboratory and Sandia National Laboratories have test laboratories in Las Vegas, Albuquerque, Denver, Orlando, and Williston, Vermont. That combination covers different climates, latitudes, and altitudes. "Our goal is to have systems that can power for decades," Jones-Albertus said. "We want to think about performance more broadly than efficiency."

Greater penetration of solar onto the grid will include additional costs for factors such as storage and enhanced power electronics, which will require the cost of photovoltaic electricity to be even lower. "There are going to be additional costs," Jones-Albertus said.

One pathway to make solar electricity cost-competitive with other forms of energy involves lowering the annual degradation rate from 0.75 to 0.2 percent and increasing system life expectancy from 30 to 50 years, increasing module efficiency from 16 to 25 percent, reducing the module price from $0.65 to $0.30 per unit, decreasing labor and hardware costs from $0.60 to $0.30 per unit, and lowering the finance costs from 7.0 to 6.0 percent. "There are many pathways to get here," Jones-Albertus said.

The solar energy markets include rooftop residential, commercial, and utility generation. "Most of what we've done would apply equally well to all markets," Jones-Albertus said.

That doesn't preclude the DOE from recognizing the different traits of those markets. "We have funding in our department-based programs that look separately at each of the markets," she said.

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