Evaluation of misalignments within a concentrator photovoltaic module by the module optical analyzer: a case of study concerning temperature effects on the module performance

Instituto de Energía Solar, Universidad Politécnica de Madrid (IES-UPM) has developed a method [referred to as the luminescence inverse (LI) method] and equipment [called module optical analyzer (MOA)] to fast measure the optical-angular properties of a CPV module without illumination system nor module movement. This paper presents how the MOA can investigate the optical performance of concentrator photovoltaic (CPV) modules optical-angular performance (in particular, misalignments between the optical components comprising the module) at different temperature conditions

Methodology of quantifying curvature of Fresnel lenses and its effect on CPV module performance

Fresnel lenses used as primary optics in concentrating photovoltaic modules may show warping produced by lens manufacturing or module assembly (e.g., stress during molding or weight load) or due to stress during operation (e.g., mismatch of thermal expansion between different materials). To quantify this problem, a simple method called “checkerboard method” is presented. The proposed method identifies shape errors on the front surface of primary lenses by analyzing the Fresnel reflections. This paper also deals with the quantification of the effects these curvatures have on their optical performance and on the electrical performance of concentrating modules incorporating them. This method can be used to perform quality control of Fresnel lenses in scenarios of high volume production

Assessment of the optical efficiency of a primary lens to be used in a CPV system

This article summarizes experimental methods to evaluate the performance and to assess the efficiency of a lens that will be used as primary optics in a concentrating photovoltaic system comprising multijunction solar cells. The methods are classified into two groups: those intended to quantify the transmission losses and those that estimate the size and shape of the light spot. In addition, the optical efficiency definition is reviewed and a systematic procedure to evaluate it is proposed

Module optical analyzer: Identification of defects on the production line

The usefulness of the module optical analyzer when identifying module defects on production line is presented in this paper. Two different case studies performed with two different kind of CPV modules are presented to show the use of MOA both in IES-UPM and Daido Steel facilities

A novel scanning lens instrument for evaluating Fresnel lens performance: equipment development and initial results

A system dedicated to the optical transmittance characterization of Fresnel lenses has been developed at NREL, in collaboration with the UPM. The system quantifies the optical efficiency of the lens by generating a performance map. The shape of the focused spot may also be analyzed to understand change in the lens performance. The primary instrument components (lasers and CCD detector) have been characterized to confirm their capability for performing optical transmittance measurements. Measurements performed on SoG and PMMA lenses subject to a variety of indoor conditions (e.g., UV and damp heat) identified differences in the optical efficiency of the evaluated lenses, demonstrating the ability of the Scanning Lens Instrument (SLI) to distinguish between the aged lenses

Hybrid dome with total internal reflector as a secondary optical element for CPV

Secondary optical elements (SOEs) are used in Concentrator Photovoltaic (CPV) modules to allow the concentration ratio to exceed those typically achievable by Fresnel lenses, reducing cell costs, without sacrificing tolerance to tracking errors. One option is a “dome” SOE: a simple, single surface refractive optic that images the primary lens onto the cell while immersing it. In this article, we explore the limits of this type of SOE and propose an evolved version, which we dub the Hybrid Dome Reflector (HDR), which offers advantages especially for high concentration modules with large cells, where reflective secondaries do not offer sufficient acceptance angle, but other dielectric secondaries, such as the Dielectric Totally Internally Reflecting Concentrator DTIRC, may be too large for economical manufacture. We discuss aspects of HDR design and share selected ray-tracing simulations and experimental results. We show that the new HDR design improves acceptance angle and tolerances to manufacturing error and lens temperature as compared to a reflective SOE built while offering similar efficiencies

Characterization of the spatial distribution of irradiance and spectrum in concentrating photovoltaic systems and their effect on multi-junction solar cells

The irradiance and spectral distribution cast on the cell by a concentrating photovoltaic system, typically made up of a primary Fresnel lens and a secondary stage optical element, is dependent on many factors, and these distributions in turn influence the electrical performance of the cell. In this paper, the effect of spatial and spectral non-uniform irradiance distribution on multi-junction solar cell performance was analyzed using an integrated approach. Irradiance and spectral distributions were obtained by means of ray-tracing simulation and by direct imaging at a range of cell-to-lens distances. At the same positions, I¿V curves were measured and compared in order to evaluate non-uniformity effects on cell performance. The procedure was applied to three different optical systems comprised a Fresnel lens with a secondary optical element consisting of either a pyramid, a dome, or a bare cell

Understanding causes and effects of non-uniform light distributions on multi-junction solar cells: Procedures for estimating efficiency losses

This paper presents the mechanisms of efficiency losses that have to do with the non-uniformity of the irradiance over the multi-junction solar cells and different measurement techniques used to investigate them. To show the capabilities of the presented techniques, three different concentrators (that consist of an acrylic Fresnel lens, different SOEs and a lattice matched multi-junction cell) are evaluated. By employing these techniques is possible to answer some critical questions when designing concentrators as for example which degree of non-uniformity the cell can withstand, how critical the influence of series resistance is, or what kind of non-uniformity (spatial or spectral) causes more losses

Concentration photovoltaic optical system irradiance distribution measurements and its effect on multi-junction solar cells

This paper proposes an indoor procedure based on charge-coupled device camera measurements to characterize the non-uniform light patterns produced by optical systems used in concentration photovoltaic (CPV) systems. These irradiance patterns are reproduced on CPV solar cells for their characterization at concentrated irradiances by using a concentrator cell tester and placing high-resolution masks over the cells. Measured losses based on the masks method are compared with losses in concentrator optical systems measured by using the Helios 3198 solar simulator for CPV module

Power rating based on two different spectroheliometers with lattice-matched (LM) and upright metamorphic (UMM) component solar cells

Synthetic and empirical data have been used to explore the influence of spectral mismatch between MJ cell technologies on outdoor CPV module rating uncertainty. Calibration biases are attenuated by tightly filtering spectral conditions to a spectral matching ratio (SMR) of 1 ± 2.5%. The sensitivity of calibrated current to spectral deviations greatly depends on the direction and distribution of the deviations on the SMR space