Concentrator Photovoltaic Systems Research Articles

Finding optimal operating point for advection-cooled concentrated photovoltaic system

Concentrated photovoltaic is a promising route to achieve high efficiency solar conversion. Concentration of sunlight increases the irradiation on panel along with its temperature. At higher temperature, the efficiency of the cells drops necessitating active cooling. However, flow of a coolant consumes pumping-power leading to reduction in net power output. These two counter-acting factors lead to a two-stage optimization for designing an advection cooled concentrated photovoltaic (ACCPV) system. Here, we attempt developing a design methodology where standard numerical scheme for solving a multi-level conjugate heat problem is utilized to obtain optimal operating conditions in terms of the coolant flow rate, and the sunlight concentration ratio for a series of widely used photovoltaic materials: a-Si, m-Si, p-Si, CIGS, CdTe. For the chosen ACCPV geometry, the estimated concentration ratios are computed to be 7, 9, 9, 16 and 20 for m-Si, p-Si, CIGS, p-Si and CdTe cells, respectively. Even though the estimated values of optimal parameters depend on the choice of PV material, coolant and the geometry of the system, the methodology presented here is universally applicable for any such ACCPV system. The general intuition - higher the irradiation, better the performance - is demonstrated to be false through the present analysis.

Performance investigation of inclined CPV system with composites of PCM, metal foam and nanoparticles

Three passive cooling configurations of a concentrator photovoltaic (CPV) system have been proposed to dissipate the heat via pure phase change material (PCM), Nano-PCM, and metal Foam-PCM as heat absorbers. A computational fluid dynamic model has been developed to compare the cooling capacity, thermal performance, and electrical efficiency of these configurations at three inclination angles. Evaluation of metal Foam-PCM performance, comparison between Foam- and Nano-PCM at different inclination angles, and exploring the effects on the output efficiencies are the most significant innovations of this study, which is not presented extensively before. In this regard, an experimental setup has been provided to validate the numerical simulations. The results revealed that the Foam-PCM sink could accelerate the melting process so that it mitigates the complete melting time and average PV temperature by 13.6% and 10.7%, respectively, at 150° inclination angle compared to the pure PCM. While the Nano-PCM sink does not make significant improvements. The results also indicate that the amount of absorbed heat and produced electricity till the complete melting time in Foam-PCM are increased by 7.5% and 4.8%, respectively. The superiority of the metal Foam-PCM sink could be improved by increasing the mass of metal through reducing the foam porosity.

Improvement of BIPV Efficiency by Application of Highly Reflective Surfaces at the Building Envelope

The use of concentrated solar irradiation for the improvement of electric generation improvement has been implemented on different scales, mainly in photovoltaic systems. High-concentration Fresnel lenses are widely chosen for this approach in large installations, while low-concentration systems are rather applied in medium-low scales. For the latter, the improvement on electric performance was revealed, even when no solar tracking was implemented. The presented work aims to analyse a low-concentration photovoltaic installation by a numerical approach. First, the reflective surfaces were designed geometrically considering the optimal slope determined for each month. Subsequently, different simulation techniques were used separately for prediction of solar irradiation and energy production. Three criteria were selected to analyze power generation: the highest increase in total annual solar irradiance on panels with reflective surfaces, the highest total annual solar irradiance collected, and the optimal slope of panels for the entire year. The increase in energy was found to not exceed 10% in the winter months. Whereas in the spring and summer months the energy improvement is about 15–20%. Moreover, it was observed that the temperature of the proposed concentration photovoltaic system increased significantly, reaching more than 90 °C, while for traditional PV panels it did not exceed 75 °C.

Energy and exergy analyses of new cooling schemes based on a serpentine configuration for a high concentrator photovoltaic system

High concentrator photovoltaic is expected to play an increasingly important role in electrical energy production. Controlling multijunction solar cell temperature within the recommended conditions is a key challenge that limits the functionality of this growing technology making the identification of an efficient cooling method an essential requirement. Hence, in this research, new heat sink configurations based on a serpentine design are studied and compared with the straight channel arrangement. To assess the performance of the high concentrator photovoltaic, a 3D model is built for the multijunction cell and heat sink and impact of the heat sink configuration, mass flow rate, and concentration ratio are investigated. The results include solar cell temperature distribution, thermal resistance, pumping power, thermal and electrical energy and exergy efficiencies. The study shows that the straight channel is not recommended for concentration above 1000×, whereas the centre inlet serpentine design can maintain a uniform temperature distribution for the system for concentration up to 2000×. Temperature non-uniformity varies between 18 °C and 5 °C. The highest overall energy and exergy efficiencies reached 78% and 35.2% respectively at concentration of 2000×. The results prove the effectiveness of implementing a serpentine design as a new cooling scheme for the system.

Evaluation of the Performance of Silicon Solar Cell with Fresnel Lens as Photovoltaic Solar Concentrator

In this paper, the performance of a silicon cell with a Fresnel lens (FL) for building a solar photovoltaic concentrator system was evaluated; the solar concentrator is a Fresnel lens, which is a point concentrator made of polymethyl-methacrylate (PMMA) as a thin lens for the optics system.
 As the radiation from the sun on the solar cell is concentrated to the levels of solar radiation of 750, 1300, 1930, 2600, 4250, 7250, and 10500) W/m2, the work was conducted at the midday in summer weather conditions, with ambient temperatures ranging 40-45 °C. The evaluation was performed in three cases; each case was conducted in succession. The performance of the cell was evaluated first without a cooling system, and then it was evaluated using the heat-sink (phenolic (pcb) printed circuit boards type). Finally, the fan with the heat-sink was used as a cooling system, which was more effective in dissipating the heat generated in the solar cell. The evaluation, based on the current and voltage (I-V) results with cell temperature, showed the following efficiency values for the abovementioned three cases, respectively:(6.91 ,7.76 ,6.65 ,7.77 ,6.27 ,4.74 ,3.37 ) %, (7.41 , 9.21 , 7.5 , 8.31 , 9.71 ,7.53 ,4.72 ) %, and (7.63 ,9.34 , 7.57, 8.37 , 10.2 ,7.75, 4.7) %.

Performance analysis of a concentrated photovoltaic cell-elastocaloric cooler hybrid system for power and cooling cogeneration

A new hybrid system model comprised of a concentrated photovoltaic cell (CPC) and an elastocaloric cooler (ECC) is proposed, where the ECC is driven by the thermal energy from CPC that cannot be converted into electrical energy. Mathematical expression between the exhaust heat of CPC and the operating electric current as well as the time required for one cycle are derived. Mathematical formulas for the power output and efficiency of CPC and proposed system and the cooling rate and efficiency of ECC are specified. Calculations show that maximum energy efficiency (MEE) and maximum power density (MPD) of hybrid system are, respectively, 20.20 % and 767.47 W m−2 larger than that of the CPC alone. A variety of design parameters and operating conditions affecting the hybrid system performance are studied. Numerical calculation results show that the environmental temperature, solar irradiation, concentration ratio and cross-sectional area ratio of CPC as well as length ratio are helpful to improve the hybrid system performance. The results obtained are helpful to optimally design and run such a real CPC/ECC hybrid system.

Performance evaluation of concentrator photovoltaic systems integrated with combined passive cooling techniques

Enhancing the performance of concentrator photovoltaic cells integrated with passive heat sinks is essential. The objective of the present work is to boost the performance of combined fins and phase change materials (PCMs) as passive cooling for low concentrator photovoltaic systems during phase transition and after complete melting. Thus, a new passive heat sink is presented, including extended aluminum fins outside the PCM containeras a viable solution to elongate the PCM melting time and prevent temperature rise after the PCM completely melted.The developed design is compared with other different heat sinks such as fins, aluminum heat sink with PCM, andaluminum heat sink withfour parallel cavitiesfilled with PCM. A comprehensive two-dimension model for photovoltaic layers with integrated phase change material and extended fins is developed to predict the average solar cell temperature, conversion efficiency, and energy budget for each design at different concentration ratios. The model is numerically simulated and validated with the available experimental and numerical data. Results indicate thatthe use of PCM for passive cooling enhances solar cell thermal regulation during solid–liquid phase transition process due to latent heat absorption and maintains the solar cell temperature around 60 °C at concentration ratio of 5 suns. However, the PCM cooling capability is significantly reduced after the dissipation of its latent heat. At concentration ratio of 5, by using an aluminum heat sink with PCM, andwithfour parallel cavitiesfilled with PCM, the steady state solar cell temperature rises to 120 °C and 125 °C, respectively. However, the developed heat sink with extended aluminum fins outside the PCM container elongates the melting timeand prevents temperature rise after the PCM fully melted, sustaining a steady state temperature of around 82 °C. Accordingly, the new design of heat sink is able to maintain the steady state solar cell temperature below the maximum permissible temperature with the capability of storing thermal energy.

Non-uniform illumination in low concentration photovoltaic systems based on small-scale linear Fresnel reflectors

Low concentration photovoltaic systems improve performance by absorbing and concentrating more sunlight than non-concentration ones. However, they require uniform illumination of the PV cells, as their electrical performance can decrease dramatically otherwise. A thorough analysis of the design causes of non-uniform illumination in small-scale linear Fresnel reflectors (SSLFR) is carried out, yielding the main parameters to be optimized. Then, such an optimized SSLFR guaranteeing uniform illumination is designed, and an optimum operation interval is estimated during which, furthermore, neither shading nor blocking on the mirrors happens. The study requires computing the maximum optimal transverse incidence angle, θt0, whose influence on the time-span of optimum operation, width of the SSLFR, annual solar irradiation, width of the mirrors, and position of the mirrors is also studied. We include a detailed example showing the accuracy of our calculations, using Monte Carlo Ray Tracing.

Математическое моделирование производства электроэнергии солнечной энергоустановкой для условий Республики Марий Эл

The authors built a mathematical model of the production of electricity by a PV installation with a grid inverter, intended for power supply of a rural residential building, for the conditions of the central part of the Republic of Mari El. Authors considered several options for the PV system: fixed-tilt PV panels, PV panels with a solar tracking system and a concentrator PV system. The most effective in terms of the electricity sold is the concentrator PV system. Compared to the version of the system with fixed-tilt PV panels, the use of concentrators provides a more than threefold increase (with a solar radiation concentration factor of 2) in the annual volume of electricity sold. For the variant of the system with PV panels with the solar tracking system (without concentrators), the analogous figure is 18.4%. The cost of electricity sold per year (at a price of 3.2 rubles / kWh) for three variants of the system will be: the system with fixed-tilt PV panels – 9140 rubles, the system with PV panels with the solar tracking system - 10820 rubles, the concentrator PV system - 30250 rubles. Keywords: PV INSTALLATION, MATHEMATICAL MODELING, VOLUME OF SOLD ELECTRICITY

Design and optimization study of a densely packed ultrahigh concentration photovoltaic thermal array for desalination usability

The cogenerated energy from the densely packed ultrahigh concentration photovoltaic thermal systems (UHCPV/T) can not only promote higher exergetic efficiency but also enable the usability of the collected thermal energy for potential desalination purposes. In the present study, three finned heat sink designs of UHCPV/T have been proposed toward maximum collected thermal power and minimum required pumping power. A conjugate heat transfer model has been developed and validated to simulate the different designs under various operating conditions. The cooling setups are based on copper millimeter-scale finned heat sinks immersed in fully developed laminar flow in a rectangular microchannel. It was found that the configuration from the more efficient heat sink design to the poorest thermal one is the rectangular fins (RFs), elliptical fins (EFs), diamond pin-fins (DPFs), and then traditional round pin-fins (TRPFs) heat sink. The RF heat sink has demonstrated the best thermal performance with a maximum multi-junction solar cell (MJSC) temperature of 81.4°C and water temperature increase of 14.21°C under ×1200 and water inlet velocity of 0.02 m/s. Despite the RF heat sink has recorded the highest values of pressure drop and required pumping power equal to 78.74 Pa and 570.7 mW, respectively, it was selected as the optimal heat sink design, ensuring the highest net electrical output power and thermal collected power.

Microstructured antireflective encapsulant on concentrator solar cells

AbstractMicrostructured antireflective coatings (ARCs) can reduce reflection losses over a wide range of incidence angles when applied to the surface of a high‐efficiency III‐V photovoltaic cell in a concentrator photovoltaic (CPV) system. In this article, we present a microstructured ARC consisting of a monolayer of close‐packed silica microbeads partially submerged within a polydimethylsiloxane (PDMS) cell encapsulant for use within a reference 500× CPV submodule. Comparing a commercialized SiOx encapsulant to this microstructured coating with 25% submerged 1,000 nm‐diameter beads, angle‐dependent external quantum efficiency measurements yield a 2.6% current gain for the microstructured coating. Simulations demonstrate good agreement with measurements, predicting a 2.4% current gain for the same configuration. Extrapolating with our validated model, we estimate a maximum and achievable (within a large manufacturing tolerance) current gain of 3.4% and 2.9 ± 0.4% using 60% submerged and 10%–32% submerged 760 nm‐diameter beads, respectively.

Optical component analysis for ultrahigh concentrated photovoltaic system (UHCPV)

This article investigates the discrepancy between the theoretical and the experimental optical characterisation results of a Fresnel Lens - silicon on glass (SOG), as a primary optical component toward UHCPV of >3000 suns design (Shanks et al., 2018). All the equations were elaborated for single- and multi-junction solar cells, emphasising the performance when the focal spot area is larger or lesser than the solar cell area. This simple prediction approach of optical characterisation has shown a strong agreement between the theoretical and experimental results of the multi-junction solar cell with a discrepancy of 2% at 7.7 W (77 suns) and 6% on the average cross a solar irradiance on the cell from 3.1 W to 7.7 W corresponding to 31 suns – 77 suns in concentration ratio. A theoretical analysis of the optical performance for a 1/4 of the system grouping three optical interfaces is performed to estimate the optical loss and its influence on the optical efficiency and optical concentration ratio.

Optical design of centered-receiver trough-based CPV system

Concentrating photovoltaic (CPV) systems require less area of the solar cell while achieving a high efficiency. One of the development factors in the CPV includes the irradiance uniformity over the solar cell. To overcome this issue, a parabolic trough-based optical design is proposed using two nonimaging secondary reflectors: reflective grooves and compound parabolic concentrator (CPC). The reflective grooves convert the line focus to a square shape irradiance distribution, and the CPC is used for redirecting the rays to the receiver. The proposed system delivers the concentrated light over the solar cell having a size of 30 × 30 mm2 at the center of the trough. The CPV system reduces the number of cells compared with conventional trough-based CPV systems by attaining the concentration ratio of 285. The results indicate that the system has achieved an optical efficiency of 60% at an acceptance angle of ±2 deg. The detailed optical design and raytracing simulation are presented showing that the proposed concentrator can achieve significantly higher overall concentration while maintaining irradiance uniformity.

A concentrated solar spectrum splitting photovoltaic cell-thermoelectric refrigerators combined system: Definition, combined system properties and performance evaluation

Currently, a concentrated solar spectrum splitting photovoltaic cell driven semiconductor thermoelectric refrigerator has no relevant report. In this work, a new style model of the concentrated solar spectrum splitting photovoltaic cell-thermoelectric refrigerators (CSSPV-TERs) combined system is established. On the basis of numerical calculation and theoretical study in detail, the influences of the critical parameters on the property of the CSSPV-TERs combined system are analyzed and evaluated. The total efficiency of the CSSPV-TERs combined system is 23.4%. Meanwhile, the current density J, structural factor c and numbers of thermoelectric devices N has been optimally selected to obtain the best COP. The three critical optimal parameters, N = 7, J = 11.7 A/cm2, and c = 0.000125 cm−1, of the CSSPV-TERs combined system can be obtained, which cause the maximum COP, i.e., COPmax = 0.078. The maximum COP and total efficiency of the CSSPV-TERs combined system are superior to other thermoelectric refrigeration combined systems. The research results and new model not only can provide a valuable reference and theoretical support for the optimal design of the novel solar cell driven thermoelectric refrigeration system, but also improve the conversion efficiency of the combined system by efficiently utilizing full-spectrum solar energy.

Synthesis of graphene oxide nanofluid based micro-nano scale surfaces for high-performance nucleate boiling thermal management systems

The objective of this study is to explore the exceptional thermal management ability of Graphene Oxide (GO) nanofluid and microporous surfaces (M) for nucleate pool boiling based thermal management systems. The performance of the designed system has been analyzed for thermal management of concentrated photovoltaics (CPV) system. A detailed analysis has been performed for GO nanofluid, with concentrations; 0.0001%, 0.001%, and 0.01%, and deionized (DI) water-based working fluid over the plane unmodified surface (P) and microporous (M) surfaces. GO nanofluid enhanced critical heat flux (CHF) and the heat transfer coefficient (HTC) over the plane surface. However, over M surface, GO nanofluid resulted in thick layer formation and significantly affected the NBHT performance. The highest CHF of 1850 kW/m2 has been observed for GO over the plane surface, increasing 2.31 times. M surface with deionized water resulted in the highest average HTC of 64.36 kW/m2.K, increasing 3.47 times. GO over the plane surface (Np) based NBHT thermal management system resulted in the highest concentration ratio of 3102 and can be used for CPV system. In comparison, M surface-based thermal management system resulted in the highest efficiency.

Thermal and electrical performances of actively cooled concentrator photovoltaic system

• Reliable thermal management for CPV is mandatory for efficient/safe operation. • 3D heat transfer/thermal model for DL-MCHS coupled with CPV layers are developed. • Including and ignoring the header of DL-MCHS is considered in the simulation work. • Without headers, CPV/T system attained a lower average and local cell temperature. • With headers, electrical efficiency is improved while pumping power is augmented. The double-layer microchannel heat sink (DL-MCHS) is commonly applied for thermal management of high heat flux surfaces, including electronic chips and concentrator photovoltaic (CPV). However, most of the recent studies neglected the header effect in the simulation of the DL-MCHS. The current study compressively investigated the impact of considering the inlet and outlet headers on the CPV systems' performance. A three-dimensional conjugate heat transfer model of the fluid flow in the DL-MCHS coupled with the CPV layers' thermal model was employed. The thermal performances of DL-MCHS with and without considering the headers were evaluated. Parallel flow (PF) and counter flow (CF) conditions at a solar concentration ratio ( CR ) of 20 suns were studied. The results showed that the header section should be considered in the numerical model for obtaining a more realistic average and local silicon layer temperature profile, especially in the CF operation. For instance, the difference in solar cell temperature between including and ignoring the header section is about 13.86 K for CF operation at CR of 20 and 200 ml/hr coolant flowrate. The predicted pumping power and net gained electric power were also significantly affected by neglecting the headers in the numerical modelling. The electrical efficiency deviation reached about 23.5% at CF, while PF reported almost 4.0%.

High-performance 4096× ultra-high CPV module based on multiple concentrator units and optical guides.

Ultra-high concentrator photovoltaic systems aim to enhance the conversion efficiency of sunlight and to reduce the cost of electricity. However, it is still necessary to develop optical systems with higher efficiencies and angular tolerances for them to become a reality. This Letter proposes a novel design that is able to achieve a geometric concentration of 4096×. The system consists of four concentrator units based on parabolic mirrors and optical guides that concentrate the sunlight onto a single cell. Additionally, a preliminary proof-of-concept module has been assembled for validation purposes. The novel design exceeds the optical efficiency of the existing systems, ≈84%, and offers almost double acceptance angles, ≈0.6∘.

Experimental and Economic Analysis of a Concentrating Photovoltaic System Applied to Users of Increasing Size

The costs of concentrating photovoltaic (CPV) and concentrating photovoltaic and thermal (CPV/T) systems are highly reduced in the last years because of their increasing diffusion. The unit power cost also depends on the plant size. Hence, the main aim of this paper is to analyze the feasibility of a CPV/T system adopted for users with increasing sizes located in Salerno (Italy): the house, the hotel, and the food industry. An experimental model was developed for an accurate evaluation of the electrical and thermal powers supplied by the CPV/T system when direct normal irradiation (DNI) and environmental temperature vary. A modular configuration of a line-focus CPV/T system was sized to match the electrical and thermal loads of each user. The current economic results, together with a forecast till the year 2025, were discussed. In 2025, for the same CPV system adopted for the domestic user, the net present value (NPVs) are expected to increase by 6.7% and 13% in pessimistic and optimistic scenarios, respectively, with reductions of its discounted payback period (DPBP) of 16% and 30%. For the same CPV systems adopted for the other two users, the NPVs are expected to increase by about 4.2% and 8.4% in pessimistic and optimistic scenarios, respectively, with decreases of its DPBP of 14% and 27%.

Experimental Comparison between Spherical and Refractive Optics in a Concentrating Photovoltaic System

Since there are not standard configurations of the Concentrating Photovoltaic (CPV) systems, several types of optics are designed and analyzed. In this paper, the optical performances of a spherical mirror and a commonly used Fresnel lens of the same diameter are compared, highlighting their impact on the CPV system energy performance. First, the absolute and percentual variation trends of optical concentration factor and optical efficiency as function of the distance between each optical system and receiver are analyzed. The concentration levels obtained by means of the spherical mirror are much higher than the Fresnel lens, with maximum values of optical efficiency equal to 72.8% and 24.1%, respectively. The analysis of the concentration reduction due to a solar-tracking failure has also allowed the estimation of the acceptance angle, thus observing that the spherical mirror requires a less accurate solar tracker with respect to the Fresnel lens, especially if a secondary optics is adopted. As for the energy comparison, the spherical mirror allows increase of the Triple-Junction (TJ) cell temperature up to about 65 °C higher than the environmental temperature and to reach an electrical power of about 15 W in correspondence of a concentrated solar radiation of 470 kW/m2. Finally, the deviation between the cumulative electric energy produced by the TJ cell in the cases of correct and incorrect solar tracking and for the configurations with and without secondary optics has been also evaluated for both the optics. The equations experimentally obtained in this paper represent a more accurate tool to describe the physical phenomenon in comparison with the equations theoretically obtained for similar CPV systems. The results can be used to design a real CPV system that adopts a Fresnel lens or a spherical mirror. The equations experimentally obtained in this paper represent a more accurate tool to describe the physical phenomenon in comparison with the equations theoretically obtained for similar CPV systems. The results can be used to design a real CPV system that adopts a Fresnel lens or a spherical mirror.

Optical Performance of Single Point-Focus Fresnel Lens Concentrator System for Multiple Multi-Junction Solar Cells—A Numerical Study

This paper investigates the potential of a new integrated solar concentrated photovoltaic (CPV) system that uses a solo point focus Fresnel lens for multiple multi-junction solar cells (MJSCs). The proposed system comprises of an FL concentrator as the primary optical element, a multi-leg homogeniser as the secondary optical element (SOE), a plano-concave lens, and four MJSCs. A three-dimensional model of this system was developed using the ray tracing method to predict the influence of aperture width, height, and position with respect to MJSCs of different reflective and refractive SOE on the overall optical efficiency of the system and the irradiance uniformity achieved on the MJSCs’ surfaces. The results show that the refractive homogeniser using N-BK7 glass can achieve higher optical efficiency (79%) compared to the reflective homogeniser (57.5%). In addition, the peak to average ratio of illumination at MJSCs for the reflective homogeniser ranges from 1.07 to 1.14, while for the refractive homogeniser, it ranges from 1.06 to 1.34, causing minimum effects on the electrical performance of the MJSCs. The novelty of this paper is the development of a high concentration CPV system that integrates multiple MJSCs with a uniform distribution of rays, unlike the conventional CPV systems that utilise a single concentrator onto a single MJSC. The optical efficiency of the CPV system was also examined using both the types of homogeniser (reflective and refractive).