Simulated Module Current Versus Voltage (I-V)

The National Renewable Energy Laboratory Device Performance group uses two I-V measurement systems to assess the performance parameters for photovoltaic (PV) modules under simulated conditions: a Spire 240A pulsed solar simulator and a large-area continuous solar simulator.

The following table is a condensed list of characteristics for simulated module I-V measurements instrumentation.

Major Instrumentation for Outdoor Simulated Module I-V Measurements

System	Typical Applications	Special Features	Light Source	Test Bed	Voltage Resolution/Limit	Current Resolution/Limit
Standard outdoor measurement system	Flat-plate and concentrator I-V measurements under outdoor conditions	2-axis positioning; meteorological parameters; spectral irradiance measured; user-controlled bias	Sunlight	200 cm × 300 cm	5 µV to ±300 V	± 1 µA to ±60 A
Daystar DS-10/125 portable I-V curve tracer	I-V measurements under outdoor conditions	Portable; may be powered either with a 120Vac line or with a 12Vdc battery.	Sunlight	unlimited	12 mV to 600 V	5mA to 125A
Prototype concentrator evaluation test bed	Unattended periodic I-V measurements of prototype concentrator modules and cells mounted in a 2-axis tracker; translation equations, stability and performance of concentrator	Up to 10 samples at a time; spectral irradiance and meteorological parameters; multiple temperature channels	Sunlight	Bare cells under a Fresnel lens or modules less than 2 feet by 4 feet	mV to 100 V	20 nA to 20 A

Spire 240A Pulsed Solar Simulator

This simulator uses a long-arc pulsed xenon lamp, flashed at a maximum rate of 15 Hz, that is filtered to simulate the global reference spectrum (IEC60904-3, class A), and whose irradiance has a spatial nonuniformity of ±3% over an area of 61 cm × 122 cm. Temperature measurements are made with a spring-loaded thermocouple in contact with the back of the module. The original software has been modified to store data and update the directory in our standardized tab-delimited text format. Temperature coefficients can be measured using an adjustable heating blanket. The I-V characteristics as a function of lamp intensity in the range of 0.15 to 1.3 suns can be measured using screen filters.

Large-Area Continuous Solar Simulator (LACSS)

The LACSS is a custom-designed system that is used for measuring module performance. It uses a Spectrolab model X200 continuous 20-kW xenon short-arc lamp to provide a filtered light source to simulate the global spectrum (IEC 60904-3, class A). It is capable of measuring modules as large as 152 cm × 122 cm with spatial nonuniformity of ±3%. Sample temperature is measured with a spring-loaded, type T thermocouple at the back of the module.

For additional information contact Keith Emery, 303-384-6632.