New generation of PV module rating by LED solar simulator - A novel approach and its capabilities

Authors have been proposing a novel approach by employing light emitting diodes (LED) as a light source with discrete-wavelength spectrum. LEDs have a number of practical advantages. Each of different color LED lights works as sampling wavelength for scanning the spectral sensitivity of PV module by modulating intensity of each spectral component in a sequential order. Even by a limited number of sampling wavelengths, full range spectral response can be estimated easily by newly developed fitting model. Then AM 1.5 spectrum of IEC 60904-3 is applied to obtained response curve to give STC rating. 3 types of experimental LED arrays have been developed since early 2003: i.e., Mk-1 to Mk-3. Under these experiments, spectral characteristic fitting model has been successfully developed. Nonuniformity of ±2% has been achieved by MK-2, satisfying Class A uniformity specification. The latest Mk-3 achieved 0.42 sun in October 2006. Its array consists of 2304 elements of high-brightness LEDs (HB-LED) in total provided with blue (473 nm), red (643 nm) and 2 elements of infrared (845 nm) for 1 unit. The following experimental results are presently attained for a one-cell module of 100 mm × 100 mm of single crystalline silicon with P max at STC of 1.553 W calibrated under Class A simulator: i.e., I SC =3.757 A (+0.080 %); V OC =0.601 V (−0.121 %); P max =1.660 W (+4.312 %); I pmax =3.454 A (+2.493 %); V pmax =0.469 V (+1.74 %); FF=71.74% (+4.73 %). Values in parentheses are corresponding to % errors for reference values. It is felt that present result has been already reaching practically usable level. If 6 LEDs allocation pattern is adopted, spectral response fitting formula will be very much improved.