Solar power study inspired by field of medicine

Funded by a $1.35 million U.S. Department of Energy (DOE) SunShot Initiative award, the study's goal is to drive designs that make modules last longer and have more predictable power output, which can help reduce the cost of clean power and add certainty for renewable energy investors.

The DOE seeks to predict precisely, and thereby extend, the performance lifetime of solar panels, which are expected to generate power for 30 years or more. But, to create a predictably longer lifetime, manufacturers need better information about what factors contribute to the end of a module's usefulness.

Rather than study portions of photovoltaic modules in the lab, "We take a bioinformatics and data analysis approach," said Roger French, the F. Alex Nason Professor of Materials Science and Engineering and director of the Solar Durability and Lifetime Extension (SDLE) Center. "Like doctors who study 30,000 nurses over 20 years, looking at how many smoke, how many are overweight, and how many exercise…We're using this same approach to analyze solar PV modules."

"In that kind of study, you can ask sophisticated questions and get answers," French said.

The researchers will collect and analyze data from various brands of modules, in varying climates at various ages and installations, on four continents. They will also develop new tests at the SDLE Center to understand the physical processes taking place in the field. The center will accelerate aging, exposing modules to the equivalent of decades of solar radiation and weather in just a few years.

"We will determine, and rank in the importance of prediction accuracy, the variables that change modules' predicted lifetime performance using our statistical/epidemiological, degradation science approach," said Jiayang Sun, professor of epidemiology and biostatistics in CWRU's School of Medicine and director of the Center for Statistical Research, Computing and Collaboration.

By combining that information with the degradation mechanisms found in the lab tests, the researchers will identify the factors that most contribute to a module's decline. Those factors will be the targets of improvements in the technology.

"We will be able to more accurately estimate how much energy and money modules will produce over their lifetime -- information that's useful to manufacturers, users and investors," said Timothy Peshek, a Case Western Reserve materials science and engineering research professor and one of the project leaders.

Partners in the effort include Underwriter's Laboratories; SunEdison, maker of solar systems for homes, businesses and power plants; Terraform Power, a renewable energy company that will provide data from nearly 400 solar power plants it owns and operates in North and South America; Sandia National Laboratory; and Fraunhofer-ISE, the largest solar energy research institute in Europe.

The research group at the Case Western Reserve SDLE Center will also be a sub recipient of another SunShot Initiative award focusing on the study of backsheets of more than 200 modules. A backsheet is a thin, multilayer sheet that covers the back of a module, protecting workers from high voltages and the other panel materials from damaging ultraviolet light and the elements.

Underwriter's Laboratories will lead the backsheet study. Partners in that project include Arkema, an international chemical and advanced materials company; 3M, an advanced materials manufacturer; the National Institute of Standards and Technology, the National Renewable Energy Laboratory and Northeastern University.

The SDLE will perform epidemiological analysis of backsheet data provided by the rest of the group and will test for weaknesses in the lab.

The backsheet, like insulation on an electrical wire, protects installers and maintenance workers from electric shock. The covering also protects the insides from humidity, rain and snow, dust and chemical pollution.

"Degradation leads to safety failures and failures of the module itself," said Laura Bruckman, a CWRU research professor in materials science and engineering who will lead the analysis. "Our goal is to understand how the backsheets fail in the real world in different climate zones."

The studies begin in October and may continue through 2018.