A new system for long-term measurement of solar power in scalable photovoltaic systems, developed by researchers at Arizona State University, represents a breakthrough in the cost and longevity of interconnected power supplies.
When solar cells are developed, they are “current-voltage” tested in the laboratory before being used in panels and systems outdoors. Once installed outdoors, they are usually not retested unless the system exhibits major problems. The new Suns-Voc test system measures the voltage of the system as a function of the light intensity outdoors, enabling real-time measurements of performance and detailed diagnostics.
“However, everything is checked in the laboratory,” explained Alexander Killam, doctoral student and research assistant at the ASU for electrical engineering. “Our research has developed a way to use Suns-Voc to measure the degradation of solar panels when they are outdoors in the real world and affected by weather, temperature and humidity,” he said.
Current photovoltaic modules have a service life of 25 years with an efficiency of 80 percent. The aim is to extend this period to 50 years or more.
“This monitoring system will give photovoltaic manufacturers and large utility companies the kind of data they need to adjust designs to increase efficiency and lifespan,” said Killam, lead author of “Monitoring Photovoltaic System Performance Using Outdoor Suns-Voc” for Joule.
For example, most of the techniques used to measure solar efficiency outdoors require you to be disconnected from the power supply mechanism. The new approach can automatically measure sunrise and sunset every day without affecting the power supply.
“When we developed photovoltaics 20 years ago, modules were expensive,” said Stuart Bowden, an associate research professor who heads the silicon division of ASU’s Solar Power Laboratory. “Now they’re so cheap that we don’t have to worry about the cost of the panels. We’re more interested in how they keep performing in different environments.
“A Miami banker who is drawing a photovoltaic system wants to know in dollars and cents how the facility will perform in Miami rather than Phoenix, Arizona.”
“The effects of weather on photovoltaic systems in Arizona will be very different from those in Wisconsin or Louisiana,” said Joseph Karas, co-author and graduate student in materials science, now a PhD student at the National Renewable Energy Lab. “The ability to collect data from different climate zones and locations will support the development of universally effective solar cells and systems.”
The research team was able to test its approach in the ASU research park, where the Solar Lab is primarily solar powered. For the next step, the laboratory is negotiating with a power plant in California that wants to expand its performance profile to include a megawatt of silicon photovoltaics.
The system, which can remotely monitor the reliability and lifespan of larger, interconnected systems, will be a major breakthrough for the energy industry.
“Most residential solar roof systems do not belong to the homeowner, but rather to a utility or broker who has a vested interest in monitoring photovoltaic efficiency,” said Andre ‘Augusto, director of Silicon Heterojunction Research at ASU’s Solar Power Laboratory and a co-author of the paper.
“Likewise, interest in large-scale surveillance will grow as developers of shopping centers or even planned residential communities start incorporating solar energy into their construction projects,” said Augusto.
According to Bowden, it’s all about the data, especially when it can be monitored automatically and remotely – data for the bankers, data for developers, and data for the utilities.
If Bill Gates’ smart city, slated about 30 miles from Phoenix in Buckeye, Arizona, uses the team’s measurement technology, “it could become the IoT of photovoltaics,” Bowden said.
This material is based on work mainly supported by the National Science Foundation (NSF) and the Department of Energy (DOE) under NSF CA No. EEC-1041895.