Low Concentration Photovoltaic Research Articles

Low Concentrating Photovoltaic Geometry for Retrofitting Onto European Building Stock

Abstract The most appropriate low concentrating photovoltaic (LCPV) technology suitable for European buildings located in mid-high latitudes under both maritime and continental climatic conditions has been identified as the asymmetric compound parabolic concentrator (ACPC). To date, there is no published experimental data at different latitudes on the long-term performance of these systems at these latitudes nor how location would modify the optical characteristics of deployed systems. Previous theoretical research by the authors has demonstrated the superiority of the ACPC with this additional work experimentally confirming the robustness of the design. To investigate how seasonal and locational variations affect their measured technical performance two identical ACPC-LCPVs were installed, instrumented, and monitored at two different climatic locations (Uxbridge, UK, and Vevey, Switzerland) from May 2020 to September 2020. A valid comparative performance investigation characterizing two geometrically equivalent ACPC-based LCPV systems using real-life experimental data collected is presented in this paper. Locations at higher latitudes experience greater transverse angles more frequently compared to locations nearer the equator making ACPC geometries more appropriate than symmetrical concentrator configurations for building retrofit. This is shown in this paper over a latitudinal expanse of 31.35 deg for four separate locations; Tessalit (20.19 deg N, 1.00 deg E; Mali), Timimoun (28.03 deg N, 1.65 deg E; Algeria), Uxbridge (51.54 deg N, 0.48 deg E, UK), and Vevey (46.6 deg N, 6.84 deg E, Switzerland).

Sawtooth V-Trough Cavity for Low-Concentration Photovoltaic Systems Based on Small-Scale Linear Fresnel Reflectors: Optimal Design, Verification, and Construction

Ensuring the uniformity of solar irradiance distribution on photovoltaic cells is a major challenge in low-concentrating photovoltaic systems based on a small-scale linear Fresnel reflector. A novel sawtooth V-cavity design method based on an optimization algorithm to achieve uniform irradiance distribution on photovoltaic cells is presented. The reliability of the design was verified using the Monte Carlo ray-tracing method and a laser experiment. A prototype was built using 3D printing technology with a biodegradable green polymer material known as polylactic acid. The new cavity was compared to the standard V-trough cavity, keeping the cavity aperture, reflective surface area, and photovoltaic cell width constant. In addition, the focal height, number of mirrors, mirror width, and mirror spacing were also kept constant; so, the cost of the two configurations was the same from the point of view of the primary reflector system. The new design ensured the uniform distribution of solar irradiation and significantly reduced the height of the cavity. The significant decrease in the height of the proposed cavity has the following advantages: (i) a decrease in the dimensions of the fixed structure of the small-scale linear Fresnel reflector, thus reducing its cost, (ii) a significant decrease in the surface area exposed to wind loads, thus reducing the cost of the fixed structure and secondary system structures, (iii) a reduction in the difficulty of the manufacture, maintenance, and transportation of the cavity’s reflecting walls, and (iv) an increase in the cooling surface area, which increases the electrical efficiency of the photovoltaic cells.

Long term performance analysis of low concentrating photovoltaic (LCPV) systems for building retrofit

Low concentrating photovoltaic (LCPV) systems offer viable solution for generating higher energy output per unit cell area compared to a typical flat PV panel, making them potential candidates for building retrofit. However, the best LCPV geometry for a given location is yet to be identified. The current study investigates the technical, economic and environmental feasibility of three geometrically equivalent LCPV designs installed at a building within Brunel University London (UK). The studied LCPV systems comprised of Asymmetric Compound Parabolic Concentrating (ACPC), Compound Parabolic Concentrating (CPC) and V-Trough optical concentrators with the post-truncation geometric concentration ratios of 1.53, 1.46, 1.40 respectively. The performances of the prototypes have been monitored every 15 min over 10 months and analyzed on hourly, daily, and monthly basis. Performance parameters such as reference yield, array yield, performance ratio, electrical conversion efficiency and the generated energy output per unit area have been derived and presented. Payback periods have been estimated in two separate scenarios. Measurements have showed that the ACPC integrated LCPV achieved the highest annual optical efficiency generating the highest amount of electrical energy per unit cell area of 246.2 kWh/m2 compared to CPC-LCPV, V-Trough-LCPV and conventional flat modules which produced 224.6 kWh/m2, 196.1 kWh/m2 and 185.4 kWh/m2 respectively. One particular conclusion of the study is that the ACPC based LCPVs perform better in locations where diffuse component of solar radiation is predominant as in the case of the UK. Consequently, ACPC based LCPV modules are recommended for the building retrofit in such locations.

Application of LCA to Determine Environmental Impact of Concentrated Photovoltaic Solar Panels—State-of-the-Art

Photovoltaic systems represent a leading part of the market in the renewable energies sector. Contemporary technology offers possibilities to improve systems converting sun energy, especially for the efficiency of modules. The paper focuses on current concentrated photovoltaic (CPV) technologies, presenting data for solar cells and modules working under lab conditions as well as in a real environment. In this paper, we consider up-to-date solutions for two types of concentrating photovoltaic systems: high-concentration photovoltaics (HCPV) and low-concentration photovoltaics (LCPV). The current status of CPV solar modules was complemented by the preliminary results of new hybrid photovoltaic technology achieving records in efficiency. Compared to traditional Si-PV panels, CPV modules achieve greater conversion efficiency as a result of the concentrator optics applied. Specific CPV technologies were described in terms of efficiency, new approaches of a multijunction solar cell, a tracking system, and durability. The results of the analysis prove intensive development in the field of CPV modules and the potential of achieving record system efficiency. The paper also presents methods for the determination of the environmental impact of CPV during the entire life cycle by life cycle assessment (LCA) analysis and possible waste management scenarios. Environmental performance is generally assessed based on standard indicators, such as energy payback time, CO2 footprint, or GHG emission.

A Combined Thermal and Electrical Performance Evaluation of Low Concentration Photovoltaic Systems

A Combined Thermal and Electrical Performance Evaluation of Low Concentration Photovoltaic Systems

Temperature regulation of concentrating photovoltaic window using argon gas and polymer dispersed liquid crystal films

Low concentrating photovoltaic (LCPV) system has been studied extensively, which showed excellent potential for the building integration application. However, such a system suffers from higher operating temperatures due to the concentrated light exposed into the solar cell. In this work, two different methods have been used to regulate the operating temperature of the solar cell without the interference of any other external mechanism. Two concepts were used to study the operating temperature of the solar cells are: i) use of Argon gas within the concentrator element, ii) incorporation of polymer-dispersed liquid crystal films (PDLC) on top of the module. In both cases, the power was improved by 37 mW–47 mW when temperature was reduced by 10 °C and 4 °C for the Argon gas-filled module and PDLC integrated module, respectively. In addition, the temperature effect of the PDLC integrated module showed a unique nature of reduction of the short circuit current due to the orientation of the liquid crystal particle, which increased at a higher temperature. The current study, therefore, shows the greater potential of improving the operating efficiency and reduction of solar cell temperature, without the need for additional pumping power such as needed for photovoltaic thermal application.

Low Concentrating Photovoltaics (LCPV) for buildings and their performance analyses

Low concentrating photovoltaic technologies (LCPV) for building application offer viable solutions in improving the conversion efficiency of solar cells leading to an improved electrical output per unit cell area required when compared to conventional solar photovoltaic modules. The current study explores the feasibility of different geometrically equivalent LCPVs designed for building application through indoor experimental characterisation and analytical investigations. LCPV concentrator geometries were designed and simulated to predict optical efficiency at various truncation levels and range of angles of incidence using ray trace module in COMSOL Multiphysics version 5.3. The geometric concentration ratios of LCPVs investigated Compound Parabolic Concentrator (CPC), V-Trough and Asymmetric Compound Parabolic Concentrator (ACPC) with geometric concentration ratios of 1.46, 1.40, and 1.53 respectively. These prototypes were manufactured and their electrical conversion efficiency in conjunction with crystalline silicon (c-Si) solar photovoltaic cells were measured using OAI Trisol Class AAA solar simulator. Analytical model developed in the present study predicts the annual energy output generated and payback period for the LCPVs compared to an equivalent area of conventional flat module. Theoretical modeling results have showed that Asymmetric Compound Parabolic Concentrator (ACPC) with mono-crystalline silicon cells (m-Si) have generated highest energy output per unit area of 177 kWh/m2 as compared to the other configurations which make it economically viable for building retrofit with a predicted payback period of 9.7 years.

Design, Modeling, and Experimental Investigation of Active Water Cooling Concentrating Photovoltaic System

This work presents performance study of a concentrating photovoltaic/thermal (CPV/T) collector and its efficiency to produce electric and thermal power under different operating conditions. The study covers a detailed description of flat photovoltaic/thermal (PV/T) and CPV/T systems using water as a cooling working fluid, numerical model analysis, and qualitative evaluation of thermal and electrical output. The aim of this study was to achieve higher efficiency of the photovoltaic (PV) system while reducing the cost of generating power. Concentrating photovoltaic (CPV) cells with low-cost reflectors were used to enhance the efficiency of the PV system and simultaneously reduce the cost of electricity generation. For this purpose, a linear Fresnel flat mirror (LFFM) integrated with a PV system was used for low-concentration PV cells (LCPV). To achieve the maximum benefit, water as a coolant fluid was used to study the ability of actively cooling PV cells, since the electrical power of the CPV system is significantly affected by the temperature of the PV cells. This system was characterized over the traditional PV systems via producing more electrical energy due to concentrating the solar radiation as well as cooling the PV modules and at the same time producing thermal energy that can be used in domestic applications. During the analysis of the results of the proposed system, it was found that the maximum electrical and thermal energy obtained were 170 W and 580 W, respectively, under solar concentration ratio 3 and the flow rate of the cooling water 1 kg/min. A good agreement between the theoretical and experimental results was confirmed.

An experimental analysis of the optical, thermal and power to weight performance of plastic and glass optics with AR coatings for embedded CPV windows

A low concentrator photovoltaic is presented and the optical losses within a double glazed window assembly are described. The use of plastic instead of glass is analyzed for its reduced weight and hence greater power to weight ratios. Although the transmittance of glass is higher, the power to weight ratio of the plastic devices was almost double that of the glass counterparts and even higher than the original non concentrating silicon cell. The plastic Topas material was found to be the best performing material overall. Crystal Clear, a plastic resin, had a higher average transmittance but had a lower optical efficiency due to the cold cast manufacturing process in comparison to injection moulding of the other materials. This proves the importance of considering both the materials and their associated manufacturing quality.External quantum efficiencies, optical properties, silicon cell temperatures and performance is analyzed for concentrating photovoltaic devices made of varying optical materials. The measurement methods for optical analysis are given in an attempt to separate the optical losses experimentally. The Silicon cells were found to gain higher temperatures due to the insulating plastic optics in comparison to glass but these effects are eliminated during vertical window orientation where instead the encapsulate dominates the insulation of the cell. The results presented here prove plastic optics to be a worthwhile alternative to glass for use in low concentration photovoltaic systems and have the significant effect of reversing the weight disadvantage concentrator photovoltaic technology has compared to standard flat plate solar panels.

Using Static Concentrator Technology to Achieve Global Energy Goal

Solar energy has demonstrated promising prospects in satisfying energy requirements, specifically through solar photovoltaic (PV) technology. Despite that, the cost of installation is deemed as the main hurdle to the widespread uptake of solar PV systems due to the use of expensive PV material in the module. At this point, we argue that a reduction in PV cost could be achieved through the usage of concentrator. A solar concentrator is a type of lens that is capable of increasing the collection of sun rays and focusing them onto a lesser PV area. The cost of the solar module could then be reduced on the assumption that the cost of introducing the solar concentrator in the solar module design is much lower than the cost of the removed PV material. Static concentrators, in particular, have great promise due to their ability to be integrated at any place of the building, usually on the building facade, windows and roof, due to their low geometrical concentration. This paper provides a historic context on the development of solar concentrators and showcases the latest technological development in static PV concentrators including non-imaging compound parabolic concentrator, V-trough, luminescent solar concentrator and quantum dot concentrator. We anticipated that the static low concentrating PV (LCPV) system could serve to enhance the penetration of PV technology in the long run to achieve the Sustainable Development Goal (SDG) 7—to open an avenue to affordable, reliable, sustainable, and modern energy for all by 2030.

Practical approaches to assess thermal performance of a finned heat sink prototype for low concentration photovoltaics (LCPV) systems: Analytical correlations vs CFD modelling

The performance of a low-cost extruded heat sink prototype for a Low Concentration Photovoltaics system is studied using various analytical correlations and CFD simulations. An experimental test, with temperature measurements at different monitoring points of heat sink surface, was carried out in order to select the most appropriate approach. Large deviations (of up to 20 °C) in the estimation of base plate temperature from correlations were found when compared to experimental results, probably due to the specific geometry characteristics of the heat sink, with variable fin thickness and high fin length. Furthermore, discrepancies of up to 48% have been found among the different correlations. The numerical CFD results of temperature at monitoring points and at the base plate showed relative errors of about 1%, which were at least 15 times smaller than the results given by analytical correlations. Also, numerical simulations allowed the identification of stagnation zones due to the great length of the heat sink and characteristic air flow patterns, which help to explain its performance under different operating conditions. Thus, results showed that multiple chimney flow pattern and air stagnation zones seem to disappear for inclination angles greater than 30°.

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.

Effect of Reflector Geometry in the Annual Received Radiation of Low Concentration Photovoltaic Systems

Solar concentrator photovoltaic collectors are able to deliver energy at higher temperatures for the same irradiances, since they are related to smaller areas for which heat losses occur. However, to ensure the system reliability, adequate collector geometry and appropriate choice of the materials used in these systems will be crucial. The present work focuses on the re-design of the Concentrating Photovoltaic system (C-PV) collector reflector presently manufactured by the company Solarus, together with an analysis based on the annual assessment of the solar irradiance in the collector. An open-source ray tracing code (Soltrace) is used to accomplish the modelling of optical systems in concentrating solar power applications. Symmetric parabolic reflector configurations are seen to improve the PV system performance when compared to the conventional structures currently used by Solarus. The parabolic geometries, using either symmetrically or asymmetrically placed receivers inside the collector, accomplished both the performance and cost-effectiveness goals: for almost the same area or costs, the new proposals for the PV system may be in some cases 70% more effective as far as energy output is concerned.

Life-cycle assessment of a low-concentration PV module for building south wall integration in China

Low-concentration PV (CPV, concentrating photovoltaic) technology is a promising concept because it can work with the fixed installation. However, besides the economic consideration, the environmental impacts of the CPV module throughout its life cycle should be addressed as compared with the flat PV technology. Thus, in this paper, a novel high optical performance low-concentration concentrator namely asymmetric compound parabolic concentrator (aCPC) for building south wall integration is proposed. And based on the proposed aCPC-PV module, a life cycle assessment (LCA) has been performed for the low-concentration PV in China to make a scientific comparison with the PV module with the same output level environmentally. Several environmental indicators are calculated for Beijing, Hefei, Lhasa, Lanzhou, Harbin. The primary energy demand, energy payback time and environmental impacts are considered over the entire life cycle of the aCPC-PV module. The results show that the primary energy demand, energy payback time and environmental impacts of the aCPC-PV module are all relatively lower than that of the PV module with the same output. It is confirmed by the LCA study that the aCPC-PV module on behalf of the low-concentration PV technology is still a feasible and effective way for actual engineering because it’s more economic and more environmental friendly than the PV technology although the PV is experiencing continuous decrease in price and increase in efficiency.

Multi-physics analysis: The coupling effects of nanostructures on the low concentrated black silicon photovoltaic system performances

Black silicon (nanostructured front surface) can significantly improve the efficiency of the silicon solar cell by absorbing more solar irradiance. However, due to the band gap of the semiconductor material, most part of the absorbed solar irradiance is converted into heat to increase the temperature of solar cell. Especially under the concentrating condition, the waste heat is more. Besides, multi-physics coupling problem makes it difficult to study the effects of nanostructures on the performances of the low concentrated black silicon photovoltaic system. In this study, a multi-physics model of a low concentration photovoltaics (LCPV) that employs an all-back-contact black silicon solar cell is built. As for the multi-physics problem in LCPV, a multi-physics coupling mathematical model is developed. Its advantage is to couple near-flied optics, photoelectric conversion, and heat transfer. Furthermore, through parameter sensitivity analysis, it is proved that the coupling mathematical model is more accurate, because it takes full account of the nonlinear correlation between the output power and the temperature, and the effects of series resistance under concentrating condition. Hence, the mathematical model is used to investigate the coupling effects of nanostructures, and it is found that the nanostructure with lower reflectance may not be beneficial for the low concentrated black silicon photovoltaic due to the increased temperature. According to different circumstances, the maximum output power with the lower cost could be achieved by choosing the nanostructure with appropriate reflectance. At last, the dynamic analysis proves that the coupling effects of nanostructure lead to the result that the nanostructure with lower reflectance reduces the annual power generation per square meter of the low concentrated black silicon photovoltaic system by about 116 kW h/m2 when the concentration ratio is 10.

Potential of Implementing the Low Concentration Photovoltaic Systems in the United Kingdom

This paper discusses the prospect of integrating a novel type of low concentration photovoltaic (LCPV) design known as the rotationally asymmetrical compound parabolic concentrator (RACPC) in a building in the United Kingdom. This is done by proposing a number of building integration designs to create a zero carbon building. A cost reduction analysis of installing the LCPV systems in the country is also presented. It was found that an RACPC design could reduce the LCPV module’s manufacturing cost by 31.75% and the LCPV module’s cost per unit power output by 33.87% when compared with the conventional PV module.

Low-concentration photovoltaic module with reflective compound parabolic concentrator fabricated by roll-to-roll slot-die coating and 3D printing.

We fabricate a low-concentration photovoltaic (LCPV) module with a reflective compound parabolic concentrator (CPC) using roll-to-roll (R2R) slot-die coating and 3D printing technologies. A highly reflective silver thin-film is coated on a flexible plastic substrate, and the CPC frame is manufactured via 3D printing. The slot-die-coated silver film with thickness of more than 100 nm stably exhibits 95% reflectivity at 550 nm. Further, CPC concentrators with concentration ratios of 4X and 3X are assembled into silicon solar cells and characterized. Although the fill factor and maximum voltage slightly decrease, power and efficiency increase by factors of 3.51 and 2.63 with respect to the no-CPC-module case. Our approach can be used to optimize the design of various engineering products.

A comparative study on the effect of glazing and cooling for compound parabolic concentrator PV systems – Experimental and analytical investigations

A key barrier to achieving the economic viability and widespread adoption of photovoltaic (PV) technology for the direct conversion of solar radiation to electricity is the losses related to the high operating temperatures of typical flat-type PV modules. This technical and economic study addresses the cost reduction of PV systems by proposing a methodology for the improvement of solar cell efficiency using low-concentration PV technology and compound parabolic concentrators (CPCs). A theoretical model was developed to evaluate the performance of PV-CPC systems considering their optical, thermal and electrical properties. The model was implemented to investigate glazed and unglazed PV-CPC systems with and without active cooling and it was validated against experimental data. A laboratory-scale bench-top PV string was designed and built with symmetrically truncated CPC modules in these four configurations. The constructed glazed and unglazed PV-CPC systems were used for measurements at the geographic location of Dhahran and showed a very good agreement of 3.8–6.5% between the calculated and experimental results. The effect of glazing was studied and from the electrical point of view, glazing was found to reduce the power output. From the thermal point of view, glazing increased the thermal gain of the PV-CPC system. An unglazed PV-CPC system is recommended for greater electric power output, and glazed system is recommended for higher thermal gain. For economic feasibility, levelized cost of energy (LCE) analysis was performed using annual power output simulations and cost parameters incurred in the installation and operations phase of four systems considered. Annual power output was found to increase by 53.45% for unglazed CPC and 37.1% for glazed CPC systems. The minimum LCE of 0.84 (€/kWh) was found for unglazed CPC with cooling whereas the maximum LCE of 1.67(€/kWh) was obtained for glazed uncooled system due to high cell temperatures.

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.