NREL develops open source tool to monitor PV plant performance & degradation


New software developed by NREL and industry partners takes a different approach to evaluating field performance data in PV, aiming to increase energy production, decrease costs and raise investor confidence.

The software, Rd Tools, is open source and available to the public via GitHub. The package aims to solve issues with the number of variables potentially affecting performance, giving a more accurate picture of system performance degradation over time.

“The RdTools method was used to analyze energy generation from 264 PV systems at locations across the globe, revealing that degradation rates were slower than expected,” said Greg Kimball, a senior performance engineer at U.S. module manufacturer, SunPower, which co-developed the tool with NREL. “The result prompted improvements to and extension of our warranty coverage to customers.”

One of the system’s innovations is the ability to switch between ‘sensor based’, which calculates system performance based on site-measured parameters, and ‘clear sky’, which uses modeled data.

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The system also utilizes a year-on-year method to calculate degradation, which NREL says reduces potential bias from seasonal effects, such as shading, soiling and temperature, as well as missing or partial data sets.

“There's a high level of interest in this software because it provides user-friendly, accurate, and objective assessments that can help owners make sense of their data,” said Dirk Jordan, engineer and solar PV researcher at NREL. “We spent years building consensus in the industry around a common set of analytical rules. Now PV stakeholders can learn much more about the performance of their technology and improve decision-making on multiple fronts.”

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