Test Conditions & Equipment

Goal: To conduct field research and demonstrations involving off-grid LED systems.

• Mills, E. and A. Jacobson. 2007. "The Need for Independent Quality and Performance Testing for Emerging Off-grid White-LED Illumination Systems for Developing Countries." Lumina Project Technical Report #1. [PDF]

Individual LED performance

Test conditions

• LEDs powered at 20mA; LED serves as load to determine voltage

Photometry

• LEDs in 4" Photodyne integrating sphere

• LED voltage measured with HP 3456A DMM current with Fluke A90 shunts and HP 3455A DMM (+/- 0.25%)

• Light measured with Tektronix J16 photometer and Licor Photometer (210S)

• Sphere / J16 calibrated with a Sylvania 796 quartz halogen lamp calibrated by Labsphere

Spectral measurements

• LEDs in 4" Photodyne integrating sphere

• Ocean Optics SD2000 spectrometer. Software: OOIBase32, ver. 2.0.6.3

• SD2000 calibrated with Ocean Optics LS-1-CAL calibrated lamp to +/- 40K

Illuminance Measurements from Integrated LED Systems

Illuminance distribution on a 1m2 surface

• light mounted 1 meter from measurement surface

• illuminance measurements made every 10 cm on a 1 square meter grid

• illuminance: Extech Datalogging Light Meter (model 401036), (precision 0.01 Lux; accuracy +/-3% of reading)

Lamp discharge curve

• light mounted in a "dark box" at a distance of 1 meter from illuminated surface

• light begins test with a full battery; it is discharged completely during test

• illuminance, current from the battery to the light, battery voltage at 1 minute intervals during discharge

• illuminance at center of beam measured with an Extech Datalogging Light Meter
  (model 401036; see above for specifications)

• current measured with a CR Magnetics DC Current Transducer (model 5210-2)
  (accuracy +/-1.0%; output signal 0.5 VDC)

• voltage and output signal from current transducer measured with a Hobo H08-006-04 Datalogger (8 bit resolution, accuracy +/-3% of reading)

Tests of Batteries

Battery storage capacity

• measurement made by discharging the battery at a constant current

• discharge curves are collected using a Cadex C7200 series battery analyzer
  (programmable analyzer; records voltage and current information at 1-minute intervals; 100 - 4,000 mA current range; 1.2 - 16 volts voltage range; NiCd, NiMH, SLA, and Li chemistries supported; +/-1% accuracy)

Tests of Solar Cells

Solar module peak power at standard test conditions

• outdoor performance measurement of module output made on a clear, sunny day

• PV module oriented so that it is normal to sun's beam during test

• peak power estimated from a current-voltage (IV) curve normalized to std. test conditions:1000 W/m2 and 25°C

• IV measurement collected over 30-40 seconds using a custom data collection system (accuracy +/- 0.5% for current; +/- 0.5% for voltage)

• module temperature measured with Type-K thermocouple (accuracy +/-2%)

• solar insolation measurement made with Licor LI200-SA pyranometer (accuracy +/-5%; LI200-SA calibrated annually with Eppley PSP pyranometer)

• overall accuracy of peak power estimate: +/-10%

Experimental instrumentation and equipment

• Granderson, J., J Galvin, D. Bolotov, R. Clear, A. Jacobson, and E. Mills. 2008. "Measured Off-Grid LED Lighting System Performance." Lumina Project Technical Report #4. [PDF]