NREL's Photovoltaic (PV) Engineering group supports the development of national and international standards for PV engineering.
Current standards lack specifics on how to precondition cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) modules so that when tested for reporting conditions, the results are well coordinated with subsequent field performance. This work examines existing and proposed methods and uses capacitance-voltage measurements, which is a useful indicator of stability.
Stabilization Procedures for Testing Thin-Film PV Modules
Using available CdTe and CIGS modules, NREL is evaluating different stabilization techniques and under what conditions they should be used, how to determine if they are adequate, and the required duration of the stabilization procedure. NREL will draft the procedures and test methods and initiate round-robin validation activities with participating organizations to transfer this test method and capability to industry.
Procedure for Determining Nominal Operating Cell Temperature
Nominal operating cell temperature (NOCT) is an indication of the anticipated operating temperature of a PV module. It can be used with PV models to predict energy performance or to compare the thermal aspects of one PV module to another. Procedures for determining NOCT are presented in ASTM E 1036. Shortcomings of the procedure have been identified as not being appropriate for building-integrated PV (BIPV) and that PV modules of similar construction, but different models, from the same manufacturer may be assigned significantly different NOCTs, perhaps indicating that the results are not repeatable. NREL is examining the repeatability of the procedure over the range of environmental test conditions allowed and evaluating methods to accommodate BIPV products.