Hearing of a current-voltage (IV) sweep (or tracing) product made by a small start-up company, Sandia contacted Stratasense to discuss its compact product that had three features for studying photovoltaic (PV) performance: (1) it was rated for mounting outdoors at the PV module, (2) it was self-powered, and (3) it wirelessly reported the IV sweep data. Sandia and Stratasense subsequently entered into a collaborative partnership to develop the additional capability of in situ module IV tracing, something that no other industry products offered. Stratasense developed additional product capabilities, tested a module-level prototype, and delivered all units after removing each module from a functioning string, performing an IV sweep, and returning the module to the functioning string, until 16 modules had been IV swept. Sandia Labs funded the design development and provided expert testing and feedback to refine the initial design, and published its collaborative research, In-Situ Module-Level I-V Tracers for Novel PV Monitoring.
More recently, Sandia was contacted by the National Institute of Standards and Technology (NIST) about commercial off-the-shelf wireless PV string monitoring options for their previously installed PV arrays. Sandia introduced NIST to the new in-situ capability which would meet the need for NIST to easily retro-fit its PV with an increased level of monitoring. NIST ordered 96 Stratasense units for their 271kW monocrystalline silicon array. The first 24 units were installed in January 2016; the Stratasense system is now fully deployed and functioning.
Sandia also contracted with Pordis, LLC, to develop a string level, in-situ, IV sweep system in late 2014. A functioning 8-string unit is currently in operation. Sandia researchers have recently published work that used this Pordis system in Automatic Fault Classification of Photovoltaic Strings Based on an In Situ IV Characterization System and a Gaussian Process Algorithm. No other industry products offer in situ string IV tracing; existing IV string level sweep instruments are far more costly than those developed by Stratasense and Pordis.
Achieving a “pennies per watt” string monitoring system will encourage utility and commercial scale PV installations to increase PV monitoring, thereby improving their operations and maintenance (O&M) activities. Sandia-developed automated analysis of in situ string level data may be the final piece for improved and affordable utility and commercial scale PV O&M. This work is national laboratory/industry partnership at its best.