Preliminary Results from SolarWorld’s University of Richmond Test Bed

In April 2016, Virginia-based project developer Secure Futures commissioned a 205 kW PV system on the roof of the Weinstein Center for Recreation and Wellness at the University of Richmond. The project is unique for several reasons. It marks not only the first power purchase agreement within the Dominion Power Virginia service territory, but also the first commercial project deployed in the US using SolarWorld’s mono-PERC bifacial modules. In addition to providing the university with clean energy, the project also offers its students and faculty—as well as SolarWorld—an educational opportunity.

SolarWorld’s projects and solutions team, which provides in-house project development and EPC services, designed the University of Richmond system as a test facility to study the side-by-side performance of bifacial and monofacial PV modules in real-world conditions. The project features SolarWorld’s 265 W and 270 W Bisun PV modules, which are 60-cell bifacial models. To provide a basis of comparison, the project also uses SolarWorld’s 295 W 60-cell monofacial modules. All the modules are deployed at a 10° tilt atop two different low-slope roof materials—a white TPO membrane and a tar-and-gravel surface—using Unirac’s RM10 ballasted roof mount, which places the lowest point of the modules about 6 inches off the roof surface. Enphase microinverters provide module-level power processing as well as granular performance and monitoring data for about 80% of the array. SMA string inverters provide power inversion for the remainder of the array and string-level performance data.

The goal of the project was not to optimize the performance of the bifacial modules, but rather to field bifacial modules using standard commercial system-installation methodologies. Based on extensive testing, we know that bifacial gains due to the albedo effect increase in proportion to module height off the roof and module tilt angle. The ideal environment to significantly boost back-side performance would have the Bisun modules installed at least a foot off the roof using a mounting system that minimizes back-side shading. We also understand that installation methodologies optimized for bifacial performance can be cost prohibitive. Therefore, we designed this test bed with commercially available products to discover how bifacial modules perform in mainstream applications.

The data collected and analyzed to date show that it is possible to significantly increase yield without incurring substantially higher design, installation or component costs. The average daily bifacial energy boost over the white roof membrane exceeds 8%, with daily boosts as high as 15%. As expected, the bifacial boost over the tar-and-gravel roof is lower, averaging about 2.5%. Interestingly, the bifacial boost for the Bisun modules is greater on days with lower insulation, a finding that our colleagues in Germany have confirmed. The key takeaway, however, is that bifacial modules provide a considerable performance boost even in less than ideal circumstances.

SolarWorld is using data from the University of Richmond project in several ways. We have used these field-test results to fine-tune our third-party–validated Sunmodule Bisun Boost Calculator, an online tool for estimating the additional energy yield our bifacial technology offers in different applications. We can employ these data when supporting project developers who are contemplating using Bisun