F. Almonacid

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 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.

Calculation of cell temperature in a HCPV module using V oc

Knowledge of solar cell operating temperature is critical to evaluate the energy performance of a HCPV module. However, the measurement of the cell temperature in HCPV modules is a very complex task due to the special features of these types of modules, so it is useful to find indirect methods to calculate this. DNI, cell temperature and I-V curves have been measured for one year in the Centre of Advanced Studies in Energy and Environment of the University of Jaen located in the south of Spain. Thanks to these measurements, cell temperature can be determinate as a function of Voc with a mean relative error of -0.38 %.

Efficiencies and Energy Balance in High-Concentrator Photovoltaic Devices

Actual and forecast high-concentrator photovoltaic (HCPV) systems efficiencies may provide a scenario where HCPV represents a potential alternative to flat PV technology. The present status of HCPV efficiencies will be studied, and, on this basis, future trends regarding HCPV cells, modules, and systems efficiencies will be forecast. It will be shown that HCPV technology represents a real alternative to the current PV systems. Guidelines and normalized documents are needed to assess the overall performance of HCPV systems and to provide a general assessment of the potential of HCPV technology. The International Standard IEC 61724 publication, Photovoltaic System Performance Monitoring—Guidelines for Measurement Data Exchange and Analysis, will be highlighted. Because these guidelines are specially addressed to flat-PV technology, some suggestions, especially those adapted to the particularities of HCPV systems on both monitored and derived parameters, will be covered. Moreover, different indices of performance and losses that intend to provide comparisons between different HCPV installations will be offered adapted to the HCPV idiosyncrasy. These comparisons may be extremely useful when it comes to optimizing HCPV installation technology.

Enhancing ultra-high CPV passive cooling using least-material finned heat sinks

Ultra-high concentrating photovoltaic (CPV) systems aim to increase the cost-competiveness of CPV by increasing the concentrations over 2000 suns. In this work, the design of a heat sink for ultra-high concentrating photovoltaic (CPV) applications is presented. For the first time, the least-material approach, widely used in electronics to maximize the thermal dissipation while minimizing the weight of the heat sink, has been applied in CPV. This method has the potential to further decrease the cost of this technology and to keep the multijunction cell within the operative temperature range. The designing procedure is described in the paper and the results of a thermal simulation are shown to prove the reliability of the solution. A prediction of the costs is also reported: a cost of 0.151

Comparison of methods for estimating the solar cell temperature and their influence in the calculation of the electrical parameters in a HCPV module

/Wp is expected for a passive least-material heat sink developed for 4000x applications.

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

The electrical parameters of a multi-junction solar cell are influenced by its operating temperature. Hence, the estimation of the cell temperature of a HCPV module is critical for its electrical characterization. However, measuring the cell temperature of a HCPV module is a complex task due to its unique features. This paper calculates the cell temperature in a HCPV module by using a number of methods to address this important issue. We conducted a comparative study of three methods used to estimate the cell temperature of a HCPV module: the Voc-Isc method, the thermal resistance method and the lineal method. The results show that all of the studied methods can be used to estimate cell temperatures with an acceptable margin of error.

Two New Applications of Artificial Neural Networks: Estimation of Instantaneous Performance Ratio and of the Energy Produced by PV Generators

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.