Determination of spectral variations by means of component cells useful for CPV rating and design

Abstract

A methodology is presented to determine both the short‐term and the long‐term influence of the spectral variations on the performance of multi‐junction (MJ) solar cells and concentrator photovoltaic (CPV) modules. Component cells with the same optical behavior as MJ solar cells are used to characterize the spectrum. A set of parameters, namely spectral matching ratios (SMRs), is used to characterize spectrally a particular direct normal irradiance (DNI) by comparison to the reference spectrum (AM1.5D‐ASTM‐G173‐03). Furthermore, the spectrally corrected DNI for a given MJ solar cell technology is defined providing a way to estimate the losses associated to the spectral variations. The last section analyzes how the spectrum evolves throughout a year in a given place and the set of SMRs representative for that location are calculated. This information can be used to maximize the energy harvested by the MJ solar cell throughout the year. As an example, three years of data recorded in Madrid shows that losses lower than 5% are expected because of current mismatch for state‐of‐the‐art MJ solar cells. Copyright © 2015 John Wiley & Sons, Ltd.

Spectral study and classification of worldwide locations considering several multijunction solar cell technologies

“…The complete instrument is known as spectroheliometer and the one used in the experimental part of this work was developed at the Instituto de Energía Solar of the Universidad Politécnica de Madrid (IES‐UPM) in 2009. The instrument provides three photocurrent values (with an estimated uncertainty of the photocurrents of ±3% ) each one corresponding to one of the subcells, I L,top , I L,middle , and I L,bottom , which are the base for the calculation of spectral indexes (photocurrents are approximated by the short‐circuit currents). The SMR is an index that quantifies a particular irradiance spectrum by comparing it to the reference spectrum, i.e., AM1.5D given by the ASTM G173‐03 norm .…”

“…The results suggest that the CPV module optimization should increase top current for the four technologies and most of the sites, which can be made at the cell level or by means of the optics, as for example promoting short wavelength focusing or tuning the antireflective coating . The optimum top/mid current ratio under the reference spectrum must accomplish the following condition for a particular site. where stands for the top/mid current ratio at the reference spectrum AM1.5D‐G173.…”

Challenges in the design of concentrator photovoltaic (CPV) modules to achieve highest efficiencies

“…CPV characterization procedures address this effect with a deeper control of the spectral irradiance. 228,229 In the standard, the Spectral Matching Parameters (SMRs) 229 were introduced in the 62670-3 to determine spectral prevailing conditions similar to the reference spectrum. These SMRs can be determined with simple sensors based on component cells.…”

From component to multi-junction solar cells for spectral monitoring

“…Concentrator photovoltaic devices (CPV) employing multi-junction (MJ) solar cells exhibit strong spectral sensitivities due to their series-connected nature. The use of "isotype" or "component" cells for spectral monitoring is widely used in CPV [1][2][3] to fix the spectral conditions of the impinging irradiance. Component or isotype cells are spectrally-matched sensors to a particular MJ technology, i.e., devices whose spectral response is as similar as possible to a single sub-cell of the MJ cell to be characterized, and are made by epitaxially growing an identical MJ stack with only one electrically active p-n junction while the others act purely as optical filters.…”