Go back

Schatz Solar Hydrogen Project Photovoltaic Array

This 9.2 kWp photovoltaic (PV) array is located at Humboldt State University’s Telonicher Marine Laboratory in Trinidad, CA. The array was installed in 1990 and is situated approximately 150 meters from the ocean in a cool, marine environment. It is an integral part of the Schatz Solar Hydrogen Project, a renewable hydrogen demonstration project. The primary function of the SERC array is to power an air compressor for the marine laboratory. Excess power produced by the array is shunted to a Teledyne Energy Systems ALTUS™ 20 electrolyzer to produce hydrogen fuel for a proton exchange membrane (PEM) fuel cell. Together, the PV array and the PEM fuel cell power the air compressor 24 hours a day using renewable solar energy.

The PV array consists of 192 ARCO M75 PV modules, a single-crystal silicon module with a rated power of 48 W. The individual PV cells are laminated to tempered glass with ethylene vinyl acetate (EVA). The modules are configured in 6 independent subarrays consisting of 32 modules wired in 4 sets of parallel strings of 8 modules in series pairs for 48 Volt DC operation. The array is tilted permanently at an angle of 30 degrees to the horizontal. One module was damaged in 1996 and replaced with a module with similar size and performance characteristics, a Siemens SM50-H.

Pre-Service Analysis
Prior to initial installation in 1990, SERC research engineer Jim Zoellick generated current-voltage (I-V) curves to describe the performance characteristics of each of the 192 modules. The purpose of Zoellick’s study was to investigate the effect of mismatch losses on power output from the array. The data indicated that mismatch losses were very small, averaging 0.1%, and that the actual field performance of the modules was lower than the nameplate rating. The pre-service data provided a valuable baseline for future analysis of the array. Click here to read Effects of Mismatch Losses in Photovoltaic Arrays.

In-Service Analysis
Between September 2000 and June 2001, research engineers Antonio Reis and Nate Coleman generated I-V curves and performance parameters for the 191 original ARCO M75 PV modules to evaluate the changes in their performance after 11 years in the field. Each module was removed from the array and cleaned prior to testing. These new data were compared to the original 1990 data to determine the extent to which each module’s power production had degraded over time. Reis and Coleman found that maximum power output for the modules decreased by an average of 4.39%. This power loss was due mainly to reduced current output, which is believed to be caused in part by the following visually observable physical defects:

1. mild discoloration or browning of the EVA encapsulant over every cell in the module, as shown in Figure 1
2. delamination of the EVA encapsulant at the silicon cell-EVA interface, as shown in Figure 2
3. intense browning of the EVA above individual cells, presumably caused by localized hot spots, as shown in Figure 3

Reis and Coleman presented the results of this study at the 29th IEEE Photovoltaics Specialists Conference held in New Orleans in May 2002. Click here to read Comparison of PV Module Performance Before and After 11 Years of Field Exposure.