Low-concentration Photovoltaic System Research Articles

Photovoltaic Energy Production in Greenhouses With Spectral Splitting Solar Trackers

The spectral filtering low concentration photovoltaic system developed by Voltiris is an innovative solution for energy production in greenhouses without affecting food production. A first prototype was installed in the greenhouse of the agricultural research center Agroscope in Conthey, Switzerland. During an eight-month agronomic study from March to October, the yield of tomato, pepper bell and basil under this system was on a par with a control group. I-V curves were recorded to evaluate the photovoltaic system performance, and the impact of concentration and filtering. The curves showed that the prototype achieved a direct normal irradiation efficiency of 10.1 %. The specific power output of the Voltiris system inside the greenhouse was comparable to the one of a conventional solar panel placed outside. Filters with two different transmission spectra were used, both of which were matched to the absorption spectra of chlorophyll and reflected 50 % and 60 % of the incident global radiation respectively. To transfer the performance of the system to other greenhouses, the transmittance of the test greenhouse and its glass cover were measured for global and diffuse radiation. This allowed to determine the transmittance of the greenhouse specific metal structure. In the test greenhouse, the overall transmission coefficient for direct solar radiation was 0.28, hence limiting the system yield.

Experimental Investigation of the Influence of Longitudinal Tilt Angles on the Thermal Performance of a Small-Scale Linear Fresnel Reflector

This paper analyses the influence of the longitudinal tilt angle of the secondary system of a low-concentration photovoltaic system based on a small-scale linear Fresnel reflector. Several evaluation indicators, such as useful heat gain, thermal efficiency, incident solar irradiance gain on the photovoltaic cells, and total useful energy gain, were evaluated for five wind speed conditions and six locations in the Northern Hemisphere. The tests were performed with two small-scale linear Fresnel reflector configurations: the classical large-scale linear Fresnel reflector configuration (base configuration) and the optimal longitudinal tilt angle configuration (longitudinal tilt configuration). An experimental platform based on an open-loop wind tunnel was designed and built for this purpose. As far as useful heat production, the longitudinal tilt configuration performs worse as the longitudinal tilt angle and wind speed increase. A useful heat gain 33.91% lower than the base configuration is obtained with a wind speed of 10.03 (m/s) at the 36.86 (°) latitude location. Thermal efficiency decreases with increasing wind speed and longitudinal tilt angle. The thermal efficiency is between 0.3 and 0.2 with wind speeds of 4.99 (m/s) and 10.03 (m/s). The longitudinal tilt configuration shows the best increase in total useful energy gain in the absence of wind (up to 53% at a latitude of 36.86 (°)). This increase is 25% at this same location with a wind speed of 10.03 (m/s). It can be concluded that the effect of the longitudinal tilt of the secondary system has a positive effect. To highlight the importance of this work, the results obtained in the configuration comparison were used to compare a nonconcentrating photovoltaic system and a low-concentration photovoltaic system. The incident solar irradiance on the photovoltaic cells is much higher with nonconcentrating photovoltaic technology. This solar irradiance gain is over 60% for the base configuration and 45% for the longitudinal tilt configuration. The total useful energy gain is 70% in the absence of wind and at the 36.86 (°) latitude location in favour of the low-concentration photovoltaic system. The nonconcentrating photovoltaic system performs better with a wind speed of 10.03 (m/s).

Influence of an Anti-Reflective Coating (ARC) with a pyramidal texture on a Building Integrated low-Concentration Photovoltaic (BICPV) system

Photovoltaic solar energy brings a new opportunity to reduce electricity generation costs and the emission of greenhouse gases. This generation has positioned itself as the most important for renewable energies, mainly because of its impact on generation at an industrial scale. However, in the residential sector, different strategies are proposed within the framework of the best use of the available area to reduce costs, as is the case of low-concentration photovoltaic systems. This document presents an Anti-Reflective Coating (ARC) with a pyramidal texture in two dimensions, for a V-Trough type photovoltaic concentrator, specifically for a Building Integrated low-Concentration Photovoltaic (BICPV) system to increase the light capture avoiding the energy loss caused by the rays coming from incidence angles different from the normal surface. For this, the authors propose a design methodology for the concentrator, determining the material and the geometry of the texture for the ARC and ray tracing simulations and experimentation validate the whole assembly. Finally, electrical generation data is taken in real-time, and it is observed how this texture's application positively affects the photovoltaic system's generation, increasing the normalized efficiency by more than 3 %.

Effect of Increasing Solar Radiation Reflected with Mirrors Perpendicularly on the Power Output of Photovoltaic System with Cooling

Solar energy is one of the most popular renewable energies in the world as solar energy can be easily accessed throughout most places of the world. However, converting solar energy into other sources of energy is not very cheap and numerous efficiency improvements methods are under investigation by researchers around the world. The current study proposes a low concentration photovoltaic system (LCPVS) with 4 mirrors and cooling. The aim of this project was to examine how using mirrors to concentrate solar radiation affects the amount of power generated by solar panels. The mirrors (ranging from 1 to 4) radiated the sun reflection onto the panel with a cooling system. The results obtained from the proposed project were compared to the results collected from the normal panel without concentration to measure the differences which revealed that the proposed system output power was almost three times more than conventional photovoltaic (PV) panel without concentration.

Supervisory control using fuzzy logic for fault ride-through capability of a hybrid system in grid supporting mode

This paper demonstrates a novel fuzzy-supervisory control algorithm for power extraction and management in a grid-tied low concentration photovoltaic (LCPV) system with battery energy storage system (BESS). The novelty of this paper lies in avoiding dump load (DL) at the dc link, to regulate dc link voltage (Vdc) under all conditions, with an increase in power dispatch. This increases system efficiency and lessen power extraction from BESS. The supervisory controller directs all converters and maintains power balance at the dc link. Enhanced reactive power (Q) support of the grid inverter during a grid fault is controlled by using the magnitude of grid voltage sag. This control prevents islanding of the dc micro-grid as per the Indian grid code. Variation in duty cycle of the converter for optimum power extraction from LCPV generator is done by using fuzzy logic. Power references of converters depend on different operational modes and grid condition.

Supervisory control using fuzzy logic for fault ride-through capability of a hybrid system in grid supporting mode

This paper demonstrates a novel fuzzy-supervisory control algorithm for power extraction and management in a grid-tied low concentration photovoltaic (LCPV) system with battery energy storage system (BESS). The novelty of this paper lies in avoiding dump load (DL) at the dc link, to regulate dc link voltage (Vdc) under all conditions, with an increase in power dispatch. This increases system efficiency and lessen power extraction from BESS. The supervisory controller directs all converters and maintains power balance at the dc link. Enhanced reactive power (Q) support of the grid inverter during a grid fault is controlled by using the magnitude of grid voltage sag. This control prevents islanding of the dc micro-grid as per the Indian grid code. Variation in duty cycle of the converter for optimum power extraction from LCPV generator is done by using fuzzy logic. Power references of converters depend on different operational modes and grid condition.

Performance investigation of low – Concentration photovoltaic systems under hot and arid conditions: Experimental and numerical results

In this study, a comparative performance analysis was performed between a conventional photovoltaic system and a low-concentration photovoltaic system. Two typical photovoltaic modules and two compound parabolic concentrating photovoltaicsystems were examined. A Cooling system was employed to lower the temperature of the solar cells in each of the two configurations. Experimental and numerical investigations of the performance of the two arrangements with and without cooling were presented. Experiments were conducted outdoors at the Egypt-Japan University of Science and Technology, subjected to the hot climate conditions of New Borg El-Arab City, Alexandria, Egypt (Longitude/Latitude: E 029°42′/N 30°55′). A comprehensive system model was established, which comprises an optical model, coupled with thermal and electrical models. The coupled model was developed analytically and solved numerically, using MATLAB software, to assess the overall performance of the two configurations, considering the concentration ratio of the concentrated photovoltaic system to be 2.4X. The results indicated that cooling the solar panels considerably improved the electrical power yield of the photovoltaic systems. By employing cooling, the temperatures of the conventional photovoltaic system and the concentrated photovoltaic system were effectively lowered by approximately 25% and 30%, respectively, resulting in a significant enhancement in the electrical power output of the photovoltaic system by 11% and that of the concentrated photovoltaic system by 15%. Furthermore, the results revealed that the concentrated photovoltaic system outperformed the non-concentrated photovoltaic system, for both non-cooling and cooling cases, by 33% and 52%, respectively. Finally, experimental verification of the numerical results revealed a good agreement for both configurations, with an average error of 4% and 5% for the photovoltaic systems and the concentrated photovoltaic systems, respectively.

Analysis and simulation of concentrating photovoltaic systems with a microchannel heat sink

A new cooling technique for low concentration photovoltaic (LCPV) system is presented using a microchannel heat sink. This study investigates the influence of operating conditions such as concentration ratio, cooling mass flow rate, wind speed, ambient temperature, and cooling liquid inlet temperature on the performance of the low concentration photovoltaic thermal system. A comprehensive thermal model is developed which includes a thermal model for the photovoltaic, coupled with a thermo-fluid model for the microchannel heat sink. The numerical results are validated using different sets of the available experimental and computational data. The variation of solar cell temperature and electrical and thermal efficiency with operating conditions is investigated using the energy budget approach to interpreting the influence of operating conditions. The predicted results indicate that the use of a microchannel heat sink is a very effective cooling technique. This is especially true for concentrated photovoltaic systems in which a significant reduction in solar cell temperature is attained, along with uniform temperature distribution. At a microchannel flow Reynolds number of 100, it is found that at a concentration ratio of 20, the local solar cell temperature varies between 33.5 and 35.6°C, while at a concentration ratio of 40 the local solar cell temperature ranges from 37 and 41°C. Furthermore, at a concentration ratio of 40, the electrical efficiency reaches 18.5%, and the thermal efficiency achieves the maximum of 62.5%, whereas the power loss in microchannel friction is estimated to be about 0.4% of the electrical power output. Finally, a comparison between the previous solar cell temperatures using different cooling systems and the current results using microchannel is conducted using the dimensional analysis approach to finding the common groups for the various cooling methodologies used. Comparisons indicate that using a microchannel cooling technique achieves the utmost possible reduction of solar cell temperature.

Performance Comparison between Low Concentration Photovoltaic and Fixed Angle PV Systems

This paper focuses on the comparison between two different Photovoltaic systems. Both of them are located in the same place in the south part of Italy - Sicily. The first system is a photovoltaic system (PV) with a fixed tilt angle of 30° and an azimuth orientation of 0° South; its peak power is about 1.63 kWp and its 10 modules are made up of polycrystalline silicon for a total area of 13.13 m2. The second system is a low concentration photovoltaic system (LCPV) with a biaxial suntracker and a concentration of 25 suns; its peak power is about 4.65 kWp and its modules are made up of monocrystalline Silicon for a total area of 44.6 m2. In order to analyse the behaviour of these two different systems the most common Performance Indexes (YR, Yf, PR and η) has been used for the comparison, starting from the measured radiation data for both systems. The experimental data were treated for almost one year. Moreover it was analysed the thread of these indexes for two typical days in different seasons. Analysis results showed that LCPV has better performances (according the PR index) during the summer months thanks to a greater percentage of direct irradiation, while the efficiency of the fixed angle PV system is higher during the other months.

Performance analysis of a novel rotationally asymmetrical compound parabolic concentrator

Abstract The low-concentration photovoltaic (LCPV) system has been identified as one of the potential solutions in lowering the overall installation cost of a building integrated photovoltaic (BIPV) system. This paper evaluates the performance of a novel type of LCPV concentrator known as the rotationally asymmetrical compound parabolic concentrator (RACPC). A specific RACPC design with a geometrical concentration ratio of 3.6675× was fabricated and integrated with a 1 cm by 1 cm monocrystalline laser grooved buried contact silicon solar cell. This design was tested indoors to evaluate its current–voltage ( I – V ), angular response and thermal characteristics. Under standard test conditions, it was found that the RACPC increases the short circuit current by 3.01× and the maximum power by 3.33× when compared with a bare solar cell. The opto-electronic gain from the experiment showed good agreement when compared with the simulation results, with a deviation of 11%.

Effect of varying concentration and temperature on steady and dynamic parameters of low concentration photovoltaic energy system

Low-concentration photovoltaic (LCPV) system has huge potential for further cost reduction of solar photovoltaic (PV) power as compared to flat panel PV. The dependence of steady state and dynamic parameters on concentration and temperature is crucial to extract maximum power from solar photovoltaic system. This article aims to present the effect of varying concentration and temperature on steady state and dynamic parameters of LCPV system under actual test conditions (ATC). The rate of change in ISC with solar irradiation i.e., dISC/dG is found as 0.25A/W assuming ≈±1°C change in module temperature. The effect of temperature on inherent material properties responsible for photo-conversion efficiency is studied using impedance spectroscopy technique. A linear response of series resistance of LCPV module is observed with respect to change in module temperature, i.e. dRS/dT from 297 to 333K is in the range of 1.15–1.20Ω with a rate of 1mΩ/K. From real-time analysis of LCPV system open-circuit voltage found decreasing from 21 to 20.6V with temperature coefficient of voltage ≈−0.061V/K. The dynamic resistance has a positive coefficient of module temperature i.e., drd/dT given by 0.49Ω/K.

Estimation of steady state and dynamic parameters of low concentration photovoltaic system

The estimation of steady state and dynamic parameters is indispensable to extract maximum power from solar photovoltaic system. This article aims to extract steady state and dynamic parameters for a low-concentration photovoltaic system under actual test conditions. A theoretical model is reported to estimate dynamic resistance under varying concentration and temperature for low-concentration photovoltaic system. When the concentration ratio is changed from 1 sun to 5.17 suns the maximum power delivered by low-concentration photovoltaic system increased by threefold. The results show that the higher solar PV module temperature has negative impact on the open circuit voltage for a given concentration with negative temperature coefficient of ≈−0.021V/K. The observed dynamic resistance was in the range of 17.99 to 24.84Ω for the low-concentration photovoltaic system under actual test conditions.

Effect of temperature and concentration on commercial silicon module based low-concentration photovoltaic system

A low-concentration photovoltaic (LCPV) system has immense potential for further cost reduction of solar photovoltaic (PV) power as compared to flat panel PV. This paper explains the performance of commercially available solar PV module mounted on parabolic trough collector experimentally and theoretically. A piecewise linear parabolic trough collector is modeled and designed to focus the solar radiation with uniform intensity on solar PV module. Silicon solar PV module based LCPV system is also modeled and simulated to study the variation of output power, open-circuit voltage, and short-circuit current with respect to module temperature and irradiance. The developed theoretical model is able to predict the performance of a LCPV system under the actual test conditions (ATCs). It was observed that the open-circuit voltage decreases from 9.86 to 8.24 V with temperature coefficient of voltage ≈−0.021 V/K under ATC. The short-circuit current of LCPV system shows increasing trend with light concentration with a rate of ≈0.285 Am2/kW. The results confirm that the commercially available silicon solar PV module performs satisfactorily up to ∼8 Sun concentration.

Exergy, Energy, and Dynamic Parameter Analysis of Indigenously Developed Low-Concentration Photovoltaic System

Piecewise linear parabolic trough collector (PLPTC) is designed and developed to concentrate solar radiation on monocrystalline silicon based photovoltaic module. A theoretical model is used to perform electrical energy and exergy analysis of low-concentration photovoltaic (LCPV) system working under actual test conditions (ATC). The exergy efficiency of LCPV system is in the range from 5.1% to 4.82% with increasing rate of input exergy rate from 30.81 W to 96.12 W, when concentration ratio changes from 1.85 to 5.17 Sun. Short-circuit current shows increasing trend with increasing input exergy rate of≈0.011 A/W. Power conversion efficiency decreases from 7.07 to 5.66%, and open-circuit voltage decreases from 9.86 to 8.24 V with temperature coefficient of voltage≈-0.021 V/K under ATC. The results confirm that the commercially available silicon solar PV module performs satisfactorily under low concentration.

Characterizing FluidReflex Optical Transfer Function

FluidReflex is a novel concentrator concept that has been designed to achieve a low cost concentration photovoltaic (CPV) system over 1000× by using reflective optics and a fluid dielectric. In this paper, results regarding the characterization of the concentrator Optical Transfer Function (OTF) are presented. The reflectance and transmittance of the different materials that the concentrator is composed of have been measured using a spectrometer. In addition, a method using component cells (isotypes) has been used to experimentally determine which of the subcells within the multijunction (MJ) solar cell is limiting the current when it is illuminated by the concentrator.

Design and Construction of a ∼7× Low-Concentration Photovoltaic System Based on Compound Parabolic Concentrators

We report on the design, construction, and initial performance measurements of a low-concentration photovoltaic system based on compound parabolic concentrators (CPCs). The system is approximately a 7× concentration system and uses commercially available laser groove buried contact monocrystalline silicon photovoltaic cells. The CPCs are fabricated using a second-surface aluminized acrylic mirror with proven weather durability. The asymmetric CPC optical design was driven by a balance between concentration factor, thermal issues, and optical angle of acceptance and was thoroughly evaluated by optical ray tracing. The design was targeted for a single-axis tracking system, with extruded aluminum heat sinks doubling as structural components. We fabricated a 120-cell (10 × 12) prototype array, and over three months of operation, we estimated an approximate peak total system power efficiency of 7.9%, limited mostly by the CPC optical efficiency (∼55%) and the cell conversion efficiency. We discuss several issues regarding system performance, reliability, and cost.

Low-Concentration Linear-Array Photovoltaic System with Two-axis Sun Tracking

In a concentrator photovoltaic (PV) system, high concentration causes a decrease of electrical output, since the temperature of the PV cell increases. A linear-array photovoltaic system (LAPS) with a relatively low concentration using a cylindrical mirror was developed. In this system, the sunlight was concentrated on a linearly-arrayed PV system with 7 mono-crystalline silicon PV modules. The LAPS was mounted on a two-axis sun-tracker system. The electrical efficiency was approximately 11% under typical operating conditions.