P. Pérez-Higueras

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.

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.

Performance analysis of the lineal model for estimating the maximum power of a HCPV module in different climate conditions

A model based on easily obtained atmospheric parameters and on a simple lineal mathematical expression has been developed at the Centre of Advanced Studies in Energy and Environment in southern Spain. The model predicts the maximum power of a HCPV module as a function of direct normal irradiance, air temperature and air mass. Presently, the proposed model has only been validated in southern Spain and its performance in locations with different atmospheric conditions still remains unknown. In order to address this issue, several HCPV modules have been measured in two different locations with different climate conditions than the south of Spain: the Environment and Sustainability Institute in southern UK and the National Renewable Energy Center in northern Spain. Results show that the model has an adequate match between actual and estimated data with a RMSE lower than 3.9% at locations with different climate conditions.

High-Concentrator Photovoltaic Power Plants: Energy Balance and Case Studies

High-concentrator photovoltaic (HCPV) power plants are inherently different from conventional photovoltaic (PV) power sources due to the use of concentrator modules and two-axis solar trackers. HCPV technology is a relatively new energy source; therefore, there is limited experience in its application in power plants. Bearing this in mind, this chapter aims to provide information about the special features and performance of HCPV power plants under real operating conditions. The analysis of current concentrator modules and solar trackers is addressed to achieve a better understanding of the main characteristics of this kind of systems. In addition, different methods for estimating the energy yield of an HCPV system or power plant are discussed. This is a crucial task to analyse the potential of such emerging technology. Finally, several HCPV power plants and relevant data concerning their energy yield and performance ratio (PR) are described and commented.

Optical design of a 4-off-axis-unit Cassegrain ultra-high concentrator photovoltaics module with a central receiver.

Ultra-high concentrator photovoltaics (UHCPV), with concentrations higher than 1000 suns, have been pointed out by different authors as having great potential for being a cost-effective PV technology. This Letter presents a UHCPV Cassegrain-based optical design in which the sunrays are concentrated and sent from four different and independent paraboloid-hyperboloid pairs optical units onto a single central receiver. The optical design proposed has the main advantage of the achievement of ultra-high concentration ratios using relative small mirrors with similar performance values of efficiency, acceptance angle, and irradiance uniformity to other designs.

High-Concentrator Photovoltaic Systems Configuration and Inverters

A high-concentrator photovoltaic (HCPV) system is the result of the electrical interconnection of several CPV modules with additional components denominated “balance of system.” The wide variety of elements that compose a module makes possible different types of HCPV systems, although the most widespread is the point-focus pedestal type. Among the elements that compose an HCPV system, the inverter, which has been studied deeply for flat-PV systems, should be adapted to the particularities of HCPV technology. A different definition of weighted efficiency is proposed that has been adapted to an HCPV system located in southern Spain. This definition is compared with other ones proposed by some authors within this technology and also with the most used conventional PV systems definitions, which are the European and Californian efficiencies. It is highlighted that the differences are minimal. Beyond that, a novel classification of the most common interconnection configurations is proposed and some experiments were performed to show that the maximum power point tracker methods traditionally used for standard PV systems are somehow also valid for HCPV systems.