Eduardo F. Fernández

High Concentrator Photovoltaics

The chapter addresses building integration (BI) issues from the basic concepts to the most specific concerns related to high concentration photovoltaic (HCPV) systems. The reader is introduced into the topic by learning the main aspects of the true building integration of photovoltaic systems. While concentrating PV were developed to generate electricity at reduced price compared to non-concentrating systems, their BI can provide additional advantages related to a range of building energy needs and functions. Characteristic case studies of building integrated concentrating systems are presented and discussed to demonstrate how different types of optical arrangements are designed to be architecturally integrated. BI HCPV systems require two-axis tracking arrangements which poses a range of challenges in addition to those general for low-concentration or non-concentrating BI solar systems. Two examples of truly BI HCPV, from the very few that can be found at present, are presented.

Temperature coefficients of monolithic III-V triple-junction solar cells under different spectra and irradiance levels

A complete set of temperature coefficients determined under controlled laboratory conditions is reported for a lattice-matched Ga0.50In0.50P/Ga0.99In0.01As/Ge and metamorphic (MM) Ga0.35In0.65P/Ga0.83In0.17As/Ge triple-junction solar cell. The cells have been investigated at one sun condition at different temperatures and spectra in order to identify a possible influence of the spectrum on the temperature coefficients. At the same time, the cells have been investigated at different temperatures and concentration levels to study the behaviour of the temperature coefficients under concentration.

Quantifying the effect of air temperature in CPV modules under outdoor conditions

CPV modules are influenced by incident irradiance, air temperature and incident spectrum. However, the study of these effects and the ability to quantify them individually is not easy and it is still under study. The aim of this paper is describe a procedure to study the influence of air temperature in the maximum power point independently of the incident irradiance and spectrum. Two different CPV modules have been studied during one year, the main conclusions and the differences in the behaviour of CPV modules under study will be given.

Multijunction Concentrator Solar Cells: Analysis and Fundamentals

Multijunction (MJ) concentrator solar cells are primarily constructed of III-V semiconductor materials. The high solar-conversion efficiencies of these devices are dependent on precise control of growth conditions using one of several techniques such as molecular beam epitaxy, metal organic chemical vapour, or metal organic vapour-phase epitaxy deposition. The use of several junctions in an MJ tandem stack allows these devices to achieve efficiencies that are not possible for single-junction devices. Their behaviour is consequently complex, but it can be understood through an examination of the external quantum efficiency and the temperature dependence of each cell in the stack. This chapter lays out a systematic approach for understanding the spectral and temperature dependence of the overall MJ device by way of consideration of its component subcells. The efficiency of the cell as a function of temperature and concentration is described for both lattice-matched and metamorphic triple-junction (TJ) solar cells. The electrical characteristics and current–voltage curves are described from these considerations, and the performance of MJ solar cells under real operating conditions are then presented by considering a term describing the overall thermal factor and another term for the spectral factor. These terms can be understood from the background presented in the previous sections. Finally, the power output for the complete cell incorporated into a Fresnel lens‒based high-concentration photovoltaic system is presented for a particular geographic location using meteorological data.

Monolithic III-V triple-junction solar cells under different temperatures and spectra

This paper concentrates on the performance of lattice-matched and metamorphic triple junction solar cells under different temperatures and spectral conditions. This information is essential for a better understanding of concentrator photovoltaic systems. It is well known that, compared to single-junction cells, the performance of multi-junction solar cells shows a stronger dependence on the incident spectrum. The influence of temperature can in first approximation be described with linear coefficients, that themselves do no depend on the incident spectrum, which will be shown in the paper.

Analysis of high concentrator photovoltaic modules in outdoor conditions: Influence of direct normal irradiance, air temperature, and air mass

The study of high concentrator photovoltaic (HCPV) technology under real conditions is essential to understand its real behavior. The influence of direct normal irradiance (DNI), air temperature (Tair), and air mass (AM) on the maximum power of two HCPV modules was studied for more than three years. Results found are presented in this paper. As expected, the main influence on the maximum power is DNI. Also, Tair has been found to have small influence on the maximum power. Regarding AM, two different behaviors have been found. The maximum power could be considered independent of AM for AM ≤ 2, while it decreases with an approximate linear behavior for AM > 2. Also, the maximum power of a HCPV module could be estimated with a linear mathematical fitting based on DNI, Tair, and AM.

Analytical Modelling of High Concentrator Photovoltaic Modules Based on Atmospheric Parameters

The goal of this paper is to introduce a model to predict the maximum power of a high concentrator photovoltaic module. The model is based on simple mathematical expressions and atmospheric parameters. The maximum power of a HCPV module is estimated as a function of direct normal irradiance, cell temperature, and two spectral corrections based on air mass and aerosol optical depth. In order to check the quality of the model, a HCPV module was measured during one year at a wide range of operating conditions. The new proposed model shows an adequate match between actual and estimated data with a root mean square error (RMSE) of 2.67%, a mean absolute error (MAE) of 4.23 W, a mean bias error (MBE) of around 0%, and a determination coefficient () of 0.99.

Performance Analysis of Models for Calculating the Maximum Power of High Concentrator Photovoltaic Modules

Due to its special features, one of the problems of high concentrator photovoltaic (HCPV) technology is the estimation of the electrical output of an HCPV module. Although there are several methods for doing this, only some of them can be applied using easily obtainable atmospheric parameters. In this paper, four models to estimate the maximum power of an HCPV module are studied and compared. The models that have been taken into account are the standard ASTM E2527, the linear coefficient model, the Sandia National Laboratories model, and an artificial neural network-based model. Results demonstrate that the four methods show adequate behavior in the estimation of the maximum power of several HCPV modules from different manufacturers.

Scalable solar thermoelectrics and photovoltaics (SUNTRAP)

This paper presents the design, manufacture and electrical test of a novel integrated III:V low concentrator photovoltaic and thermoelectric device for enhanced solar energy harvesting efficiency. The PCB-based platform is a highly reliable means of controlling CPV cell operational temperature under a range of irradiance conditions. The design enables reproducible data acquisition from CPV solar cells whilst minimizing transient time for solid state cooling capability.

Effect of Spectral Irradiance Variations on the Performance of Highly Efficient Environment-Friendly Solar Cells

The increasing environmental concerns on photovoltaic (PV) materials have attracted much attention to environment-friendly materials for solar energy conversion. In this paper, the environment-friendly materials based on dye-sensitized solar cells (DSSC), CuZnSnSSe2 (CZTS), and CH3NH3SnI3 based on perovskite solar cells have been studied for their spectral dependence at selected different locations with varying parameters such as air mass, aerosol optical depth, and precipitable water. The spectral dependences of the materials have been obtained by the use of the spectral factor, and ground-based long-term climatologies in conjunction with the Simple Model of the Atmospheric Radiative Transfer of Sunshine have been used. Results show that the perovskite and DSSC solar cells show an important spectral dependence with annual spectral gains up to 3% and spectral losses up to -15%. On the other hand, CZTS solar cells show a low spectral dependence with annual spectral gains up to 2% and spectral losses up to -4%.