The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) is the United States’ primary laboratory for testing the performance of solar photovoltaic (PV) cells and modules. Its goal is to offer measurements with the lowest possible measurement uncertainty. This capability allows PV module manufacturers to measure and sell their modules against the real power and not less, while at the same time enabling PV module buyers to measure and buy modules against the real power and not more. In other words, it improves confidence throughout the whole industry, thereby decreasing transaction costs and thus speeding up solar installations worldwide.
In its goal to offer the lowest possible measurement uncertainty, in 2018 NREL has introduced a multi- testbed method termed “module self-reference” (MSR) to achieve 1.1% measurement uncertainty for Pmax calibrations of Silicon PV modules.
An essential testbed for achieving NREL’s goal of highly accurate PV module calibrations is a high quality large area continuous solar simulator. In the past, the group relied on a solar simulator which, after 25 years of use, was showing clear signs of decline in its performance. In addition, new emerging module technologies such as perovskites require much longer measurement times under continuous illumination which makes controlling the temperature of the device a formidable challenge.
To address these needs, NREL recently installed a new Eternalsun Spire High Performance Light Soaker, an AAA+ rated simulator which includes an environmental chamber. The system includes a uniformity calibration robot to perform fast and high-resolution non-uniformity measurements.
Nikos Kopidakis, the principal investigator of the group at NREL, says that the AAA+ steady-state illumination with stable and uniform temperature control “enables us to continue improving PV module calibration quality not only for existing technologies but to extend it to emerging PV modules. This is an important task for us, that is to help emerging technologies on their way to market, and accurate evaluation of their performance is essential for this.”
Pepijn Veling, Sales director of Eternalsun Spire, adds: “We are very happy that NREL has been using Spire long pulse flashers for years and has now added the Eternalsun Spire High Performance Light Soaker, enabling them to maintain their leadership in offering high precision PV module measurements worldwide with a system that is reliable, accurate and innovative.”