Experimental Evaluation of a Spectral Index to Characterize Temporal Variations in the Direct Normal Irradiance Spectrum

A simple index is desirable to assess the effects on both flat-plate and concentrating photovoltaics of natural changes in the solar spectrum. Some studies have suggested that the relationship between the Average Photon Energy (APE) and the shape of individual global tilted irradiance, global horizontal irradiance, or direct normal irradiance (DNI) spectra is bijective and can therefore be used as a single number to unequivocally replace a complete spectral distribution. This paper reevaluates these studies with a modified methodology to assess whether a one-to-one relationship really exists between APE and spectral DNI. A 12-month dataset collected in Jaén (Spain) using a sun-tracking spectroradiometer provides the necessary spectral DNI data between 350 and 1050 nm. After quality control and filtering, 78,772 valid spectra were analyzed. The methodology is based on a statistical analysis of the spectral distributions binned in 0.02-eV APE intervals, from 1.74 to 1.90 eV. For each interval, both the standard deviation and coefficient of variation (CV) are determined across all 50-nm bands into which the 350–1050-nm waveband is divided. CV stays below 3.5% within the 450–900-nm interval but rises up to 13% outside of it. It is concluded that APE may be approximately assumed to uniquely characterize the DNI spectrum distribution for Jaén (and presumably for locations with similar climates) only over the limited 450–900-nm waveband.

Effect of Glasshouse Maintenance on the Quality of Irradiance Spectrum under Mediterranean Climates

Glasshouses in Mediterranean areas are mainly used for experimental or nursery purposes and the production of high value ornamental species. In addition, glasshouses may be covered by dust and other particles in these areas as rainfalls are relatively scarce. Consequently, the quality of photosynthetically active radiation (PAR) may be affected. In the present experiment we evaluated the effect of dirt on the PAR spectrum in glasshouses in Valencia (Spain), compared to glasshouses submitted to suitable maintenance and washing. Photosynthetic Photon Flux Density (PPFD) measurements were done in March 2017 at 13h, and visible, UV-C and near infrared regions were recorded with a portable spectrometer. PPFD maximum values differed depending on the spectral region and glass conditions, with higher values corresponding to the visible region. Thus, clean glass showed values of 609, 588 and 423 μmol/m2s for PPFDR, PPFDG and PPFDB, respectively and 436 and 34 μmol/m2s for PPFDIR and PPFDUV. In comparison to clean glass, dirty glass decreased PPFD in all regions, particularly UV and blue region.

Studying Light Soaking of Solar Cells by the Use of Solar Simulator

A review of light soaking of solar cells by the use of commercial IV-characterization instruments is presented. The paper addresses the challenges of studying light induced degradation (LID) using a high intensity light source. Issues related to heating of the cell, temporal intensity instability and the impact of the irradiance spectrum are discussed. The main focus of the paper is devoted to the degradation of boron-doped Czochralski silicon (Cz-Si) where boron-oxygen related complexes are responsible for a metastable defect formation. Some advantages and limitations concerning the use of IV characteristics to reveal the degradation properties of boron-doped Cz-Si compared to applying minority carrier lifetime techniques are also presented.

Hybrid(Luminescent and Fresnel ) Concentrators to Improve Solar Panel Conversion Efficiency

The spectral response of the Si solar cell does not coincidence with the sun irradiance spectrum, so the efficiency of the Si solar cell is not high. To improve the Si solar cell one try to make use of most region of the sun spectrum by using dyes which absorb un useful wavelengths and radiate at useful region of spectrum (by stock shift). Fluorescence's dye is used as luminescent concentrator to increase the efficiency of the solar cell. The results show that the performance efficiency and out power for crystalline silicon solar cells are improved.