High Concentration Photovoltaic System Research Articles

Novel design of centralized square array of pin-fins in microchannels heat sink for thermal management of high concentrator photovoltaic system

Novel design of centralized square array of pin-fins in microchannels heat sink for thermal management of high concentrator photovoltaic system

Experimental evaluation of passive and active cooling methods for high-concentration photovoltaic systems using nanofluids

Experimental evaluation of passive and active cooling methods for high-concentration photovoltaic systems using nanofluids

Performance of new hybrid heat sink with trimmed fins and microchannels for thermal control of a triple-junction concentrator photovoltaic cell

An efficient and low-cost cooling method for high concentrator photovoltaic systems is essential to improve the overall performance and prolong their lifetime. Therefore, a new cost-effective hybrid heat sink with trimmed fins and microchannels was developed to harvest the benefits of active and passive cooling techniques. Unlike the traditional heat sink designs, adopting trimmed fins saves the heat sink weight and cost without affecting its cooling performance. Thus, three different heat sink configurations, including (A) heat sink with trimmed fins, (B) microchannel heat sink, and (C) hybrid heat sink with trimmed fins and microchannels, were compared. A comprehensive three-dimensional model for the proposed heat sink designs coupled with the triple-junction cell was numerically simulated and solved using ANSYS FLUENT software to predict the cell temperature distribution, temperature uniformity, electrical efficiency, and net output power. Compared to the other trimming angles, the fin trimming angle (α) achieves a 20 % reduction in the heat sink weight and cost with no noticeable effect on its cooling performance. The new hybrid heat sink efficiently controls the cell temperature below 110 ˚C up to a high concentration ratio of 3600 suns, compared to 1220 suns and 3010 suns for configurations A and B, respectively. Furthermore, using the hybrid heat sink improves the electrical efficiency by 3 % and 3.2 % compared to configurations A and B, respectively. Generally, the hybrid heat sink achieves the maximum generated power of 123.7 W compared to 41.9 W and 103.4 W for configurations A and B, respectively.

Enhancement of concentrator photovoltaic system through convergent-divergent microchannels

Concentrated photovoltaic technology is one of the evolving technologies that converts solar to electrical energy with a high efficiency percentage. Increasing concentrated photovoltaic cell’s temperature significantly reduces the performance of the system. Thus, in order to properly functioning of system, thermal management will be a rudimentary issue. This article focuses on the cooling performance of high-concentration photovoltaic system using microchannels attached to the bottom plate of solar cell. To this end, the effect of convergent-divergent microchannels at three amplitudes and three wave lengths at different Reynolds numbers is investigated, and results are compared with simple microchannels. The output results are presented via temperature, pressure, velocity contours as well as Nusselt number, friction factor, and effectiveness ratio. Compared to the simple microchannels, convergent-divergent microchannel lowers the wall temperature about 0.4–2 Kelvin by making velocity gradients along the channel. This leads to boosting the heat transfer capability up to 3 times in the best case and up to 1.5 times in the worst case. Increasing the wave length enhances the performance of system, while the opposite trend has been seen for greater wave amplitudes. For case A with lowest wave length, Nu increases 1.92 and 2.4 times at lowest and highest Re numbers while friction factor increases due to the higher contact surface area along the fluid stream. Moreover, increasing the wave amplitude leads to higher Nu number, higher friction factor and consequently lower effectiveness ratio. Finally, effectiveness ratio as a criterion to choose best case has shown that a higher wave length alongside with lower wave amplitude offers better heat transfer enhancement and lower pressure drop compared to simple channel. Case C-1 as a best case offers 0.8K lower wall temperature, 1.6 times better Nu number with only 1.3-time higher friction factor.

Indoor experimental analysis of Serpentine-Based cooling scheme for high concentration photovoltaic thermal systems

High concentration photovoltaic thermal hybrids are expected to play an important role in meeting growing energy demands. When approaching concentrations over 1000 suns, a cooling system is needed to maximise both the thermal and electrical performance of the multi-junction solar cell without producing excessive parasitic losses.This study develops a novel simulation model to provide an in-depth understanding of the functionality of a concentrated photovoltaic thermal hybrid system with serpentine-based cooling systems. An ultra-high concentrator photovoltaic optic irradiance profile (peak effective concentration ratio: ∼1500 suns) is considered within the simulation model, which has been validated through indoor experimentation. The effectiveness of cooling is also evaluated through maximum thermal stresses generated in the multi-junction solar cell. The double serpentine design was deemed the highest performing, primarily because of the single serpentine’s excessive pressure drop. Copper as the heat sink material yielded superior performance because of its higher thermal conductivity. The maximum total exergetic efficiency achieved by the receiver was ∼ 10.9% with this configuration. Compared to some examples in the literature this value may seem low, however, it is more accurate due to the inclusion of a specific irradiance profile. All serpentine-based cooling systems could maintain the recommended operating temperature.

Hybrid high-concentration photovoltaic system designed for different weather conditions

In this study, we propose a novel high-concentration photovoltaic (HCPV) cell by considering both the light leakage characteristics of the Fresnel-lens-based solar cell modules and the performance issues arising from cloud shading in practical use. We use our self-constructed systems to conduct field measurements for up to half a year under various environmental conditions. According to the acquired results, it was surprising to know that in the area other than the focusing area, the so-called light leakage region, there always bears illuminance of about 20,000–40,000 lx whether it is a sunny day or a cloudy day with different cloud conditions. Such an interesting result is caused by the light scattering of the clouds and the inherent leakage characteristic of a Fresnel lens. To prove this important finding, we simulated the illuminance of the Fresnel lens structure used in the measurement with apertures of different sizes to determine the detected area. In the laboratory, the diffuse plates were used to mimic the situation of varying cloud layer thicknesses. The trend of calculated and measured results fitted well with the field measurements. Also, the experimental and simulation results show that the round angle and draft facet of the Fresnel lens were responsible for light leakage. This finding prompted us to propose a hybrid high-concentration solar module in which more cost-effective polycrystalline silicon solar cells are placed around the high-efficiency wafer of HCPV to capture the dissipated light leakage and convert it into usable electricity.

Thermal management of high concentrator photovoltaic system using a novel double-layer tree-shaped fractal microchannel heat sink

With the aim to overcome the excessive temperature and uneven temperature distribution on cells in high concentrator photovoltaic (HCPV) system, a novel cooling method based on double-layer tree-shaped fractal microchannel heat sink (FMCHS) is proposed. A three-dimensional heat transfer and flow model is established. The effects of four different flow modes and inlet velocity on thermal-hydraulic performance, cell surface temperature and electrical efficiency are investigated. The results show that compared with single-layer FMCHS, under unilateral, bilateral, inner and cross flow modes, the average temperature of cell surface (Tcell) are decreased by 2.14%, 1.65%, 1.61% and 1.41%, respectively; while the temperature difference of cell surface (ΔT) are decreased by 84.9%, 82.6%, 70.9% and 72.8%, respectively. For double-layer FMCHS, ΔT under four flow modes are all less than 3 K; the inner flow has the best cooling effect, which can minimize Tcell and ΔT to 339.2 and 2.1 K respectively, and maximize electrical efficiency (ηcell) to 41.68%. With increasing inlet velocity from 0.5 to 2 m s−1, for double-layer FMCHS under inner flow, Tcell is decreased by 11.7 K. The designed double-layer FMCHS has higher cooling performance than single-layer FMCHS, and can ensure the efficient and safe operation of HCPV system.

Numerical analysis in thermal management of high concentrated photovoltaic systems with spray cooling approach: A comprehensive parametric study

High concentrator photovoltaic (HCPV) systems receive concentrated solar irradiation and operate at higher temperatures. It is challenging to control the cell temperature in a permittable range preventing overall performance destruction. In the present study, a comprehensive 3D numerical solution is performed to simulate spray cooling on a multijunction HCPV. The effective parameters are categorized as the distance from the nozzle to the surface, the thickness of the thermal paste, and the spray mass flow rate. The results indicate that the spray cooling method reduces the cell temperature below the allowable operating range (353 K). Increasing the distance from the nozzle to the surface raises the maximum cell temperature by 2–14 % in different concentration ratios, causing the cell temperature to exceed the permittable temperature range. Also, the temperature non-uniformity is within an acceptable range between 1.4 and 7.1 K for the minimum distance from the nozzle to the surface. Increasing the thermal paste thickness negatively affects the cell efficiency by increasing the cell temperature and non-uniformity. The cell temperature is reduced by spray mass flow rate, but the net cell output power is also reduced by 1–7 % as the required pumping power increases. At a fixed distance from the nozzle to the surface, the liquid film temperature increases with the concentration ratio, while the thermal efficiency remains almost constant. The best cooling performance was achieved at the minimum distance from the nozzle to the surface (5 mm) and minimum thermal paste thickness (0.5 mm), improving the solar cell's electrical efficiency by increment rate of 0.2 to 1.4 % (corresponding to concentrations of 250 to 1500 suns).

Hybridized high concentration photovoltaic unit with enhanced performance air gap membrane distillation unit via depositing reduced graphene oxide layer upon the condensation plate using electrophoretic deposition technique

Amongst the membrane distillation techniques, the air gap configurations showed an outstanding thermal efficiency, while a decline in productivity was recorded due to the additional thermal and mass resistances. The current study proposes minimizing the additional thermal and mass resistances by altering the condensation process to dropwise condensation. Depositing a layer of reduced graphene oxide using the electrophoretic deposition technique on the copper condensation plate was investigated to obtain a hydrophobic nature and attain dropwise condensation. Moreover, different operating conditions were examined for the optimum conditions, which were 45 V, 30 s, 1 cm, and 0.5 mg/ml, for the applied voltage, deposition time, distance between electrodes, and concentration, respectively. This modified condensation plate was investigated experimentally on the lab-scale test rig and showed an improvement in the productivity of 12.5% and 28.5% at the minimum and maximum feed temperatures, respectively. On the other hand, solar energy was utilized to eliminate the heating source required for the membrane distillation unit. A high concentration photovoltaic (HCPV) unit was introduced numerically in the current work with 36 multijunction cells. Furthermore, a microchannel heat sink was successfully designed to keep the cells from thermal degradation. The numerical results showed that the HCPV system could supply hot water up to 55 °C and produce electric power up to 230 W.

Investigation of the feasibility and potential use of sun tracking solutions for concentrated photovoltaic Case study Fez Morocco

This paper investigates the requirements, the feasibility and reliability of concentrator photovoltaic (CPV) with trackers in Fez city (Morocco) climate. In a first step, an appropriate sun tracker for a CPV prototype is design-simulated and then, based on finite element analysis, the effect of wind velocity distribution induced charge on the global structure (tracker and CPV module) is investigated for several elevation angle of the CPV unit. For all the investigated configurations, the maximum simulated misalignment still negligible, and is estimated to 4.6 × 10−6°, for a wind speed of 3.3 m/s. As a result, it is anticipated that the examined high CPV system (HCPV) will works safely under these effects. In a second step, using a home-developed Python code, and geometrical solar equations, calculations have been performed to estimate the diffuse, the direct and the global irradiations in this location. Ultimately, the energy performance of the system using System Advisor Model (SAM) software is carried out and compared to some on site real measurements. This simulation process led to a rigorous evaluation of the potential energy production with a tracked CPV panel, proving its viability in Fez Morocco. It also shows the level of accuracy of at least 0.5° that sun-tracking photovoltaic systems are necessary to maintain the least amount of power yield loss, especially for CPV facilities. This research will also serve as a valuable guide for the future sun-tracking CPV system.

Research of the design of a solar radiation concentrator for autonomous photoenergy installation

Significant increase in power due to the use of concentrators of solar radiation confirms the feasibility of using concentrated radiation, and the development of concentrators makes a separate task of optical physics. Hubs deserve special attention to obtain a high degree of radiation concentration, their development requires a number of innovative technical solutions. The complex researches on optimization of concentrators of solar radiation for use as a part of high-concentration photovoltaic systems by research of optical properties and features of degradation of facet, vacuum and segment concentrators are carried out in the work. According to the results of field testing of the experimental sample of the facet concentrator, it was found that the procedure of adjusting the concentrator is associated with individual adjustment of the position of each of the 400 mirrors, which is extremely difficult. And due to the insufficient rigidity of the structure, the concentrator needs to be adjusted in the settings after the operations of moving or assembling-disassembling the experimental sample of the concentrator. As the concentrator needs regular cleaning due to natural pollution from dust, rain and other natural factors, this operation is associated with mechanical impact on the mirrors, which leads to a violation of their settings. According to the results of testing the vacuum type concentrator, it was found that such concentrators are very sensitive to the quality of the base because due to design features cannot be adjusted after manufacture and they had too large a focal spot larger than the heat sink. According to the results of field testing, it is established that the design of a segment-type concentrator is promising for use in the high-concentration photovoltaic systems, which is a circular array of segments made of mirror material, the integrated reflection coefficient of which reaches 95% and made an experimental sample with an area of 3.6 m2, which allows to obtain a focal spot with a diameter of 120 mm with a trapezoidal light distribution with a radiation concentration factor of 360 units.

Solar Concentrator Bio-Inspired by the Superposition Compound Eye for High-Concentration Photovoltaic System up to Thousands Fold Factor

We have proposed a fruitful design principle targeting a concentration ratio (CR) >1000× for a typical high concentrating photovoltaics (HCPV) system, on account of a two-concentrator system + homogenizer. The principle of a primary dual-lens concentrator unit, completely analogous basic optics seen in the superposition compound eyes, is a trend not hitherto reported for solar concentrators to our knowledge. Such a concentrator unit, consisting of two aspherical lenses, can be applied to minify the sunlight and reveal useful effects. We underline that, at this stage, the CR can be attained by two orders of magnitude simply by varying the radius ratio of such two lenses known from the optics side. The output beam is spatially minimized and nearly parallel, exactly as occurs in the superposition compound eye. In our scheme, thanks to such an array of dual-lens design, a sequence of equidistant focal points is formed. The secondary concentrator consists of a multi-reflective channel, which can collect all concentrated beams from the primary concentrator to a small area where a solar cell is placed. The secondary concentrator is located right underneath the primary concentrator. The optical characteristics are substantiated by optical simulations that confirm the applicability of thousands-fold gain in CR value, ~1100×. This, however, also reduced the uniformity of the illumination area. To regain the uniformity, we devise a fully new homogenizer, hinging on the scattering principle. A calculated optical efficiency for the entire system is ~75%. Experimentally, a prototype of such a dual-lens concentrator is implemented to evaluate the converging features. As a final note, we mention that the approach may be extended to implement an even higher CR, be it simply by taking an extra concentrator unit. With simple design of the concentrator part, which may allow the fabrication process by modeling method and large acceptant angle (0.6°), we assess its large potential as part of a general strategy to implement a highly efficient CPV system, with minimal critical elaboration steps and large flexibility.

Numerical Study of Single-Layer and Stacked Minichannel-Based Heat Sinks Using Different Truncating Ratios for Cooling High Concentration Photovoltaic Systems

The present research aims to discuss and analyze the performance of truncated single-layer and stacked mini-channel-based heat sinks employed for the cooling of a single-cell high concentrating photovoltaic systems. The truncating technique of the fins at the entrance and exit regions from the internal fluid mini channels is opted to reduce the energy, raw material costs and time of the manufacturing process of the mini channels. This proposed solution is constrained by several metrics such as the thermal management and the overall performance of the high concentrating photovoltaic system. In the current research, the use of a truncating ratio of 31% has yielded minimum cell temperature and maximum electrical efficiencies for both single-layer and stacked mini-channel-based heat sinks, while a truncating ratio of 65% has enabled more uniform cell temperature distribution. Moreover, a truncating ratio of 65% has qualified the highest water outlet temperature and the lowest pressure drops relatively compared to the conventional mini-channel-based heat sink configurations. The highest water temperature has reached up to 52.7 ∘C by the stacked mini-channel-based heat sink with a truncating ratio of 65% under a geometrical concentration ratio of 2000× and a mass flow rate of 0.001kgs−1. For both the single-layer and stacked mini-channel-based heat sinks, the use of a truncating ratio of 65% has driven the upper hands to achieve higher ratio of the thermal power to the pumping power (RTP). The maximum RTP values have been recorded by the single-layer mini-channel-based heat sink with a truncating ratio of 65% equal to 23.61 ×106 and 233.06 ×103 at a mass flow rate of 0.008kgs−1 and 0.001kgs−1, respectively, under 2000×.

Enhanced Net Channel Based-Heat Sink Designs for Cooling of High Concentration Photovoltaic (HCPV) Systems in Dammam City

In this study, enhanced net channel based heat sink designs for cooling HCPV systems at geometrical concentration ratios ranging from 500× to 3000× are presented. The effect of increasing the number of layers in the parallel flow net channel, as well as the fraction of the coolant mass flow rate in the counter flow net channel, on the overall performance of the HCPV systems, are investigated. The various configurations of each proposed net channel based-heat sink design are examined, and a comparative analysis between the different proposed designs is performed under the climate weather conditions of Dammam city, Saudi Arabia. On one hand, the double-layered counter flow net channel heat sink outperformed the other designs in terms of electrical efficiency and in keeping the solar cell operating well below the safe operating limits, achieving a reduction in maximum cell temperature relatively compared to the parallel flow net channel with five layers and conventional mini channel of 11.72% and 12.01%, respectively. On the other hand, for effective usability of the heat recovery rate by the cooling mechanism, the parallel flow net channel is the most appropriate design since it has recorded 27.55% higher outlet water temperature than the double-layered counter flow net channel.

Theoretical and experimental evaluation on the electrical properties of multi-junction solar cells in a reflective concentration photovoltaic system

Solar photovoltaic systems represent an important technology for renewable energy utilization and have broad potential for application and development. However, the further development of solar photovoltaic systems is hindered by their higher generation costs. A high-concentration photovoltaic system (HCPVs) can use an inexpensive concentrator to replace solar cells; this, in turn, reduces the cost of electricity generation, because the solar cell requirement decreases for a given power. This study developed a mathematical model for multi-junction solar cell (MJSC) based on single-diode equivalent circuit, furthermore, an HCPVs with hyperboloid mirrors was established. The electrical properties for an MJSC module, including the short-circuit current (Isc), peak power (Pm), open-circuit voltage (Voc), fill factor (FF), and efficiency (η) were investigated at concentration ratios between 650 X and 800 X and direct solar radiation intensities between approximately 400 W/m2 and 730 W/m2. Furthermore, the experimental results and theoretical values were comparatively analyzed. The results demonstrated that Isc, Voc, and Pm of MJSC module increased as the direct solar radiation raised. In contrast, the FF and η of an MJSC module decreased as the direct solar radiation raised. As the direct solar radiation intensity was 700 W/m2 and concentration ratio increased from 650 X to 800 X, Isc, Voc, and Pm increased from 1.002 A to 1.243 A, 11.095 V to 11.158 V, and 9.466 W to 11.358 W, respectively. Conversely, the FF and η of the MJSC module decreased from 32.51 % to 31.33 % and 0.851 to 0.819, respectively. The tallied between the numerical and experimental results was evaluated, which indicated that root-mean-square error between the experimental and calculated values increased as the direct solar radiation increased.

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.

A novel designed manifold ultrathin micro pin-fin channel for thermal management of high-concentrator photovoltaic system

To meet the requirements of cooling challenges of high concentrator photovoltaic (HCPV), a novel manifold ultrathin micro pin-fin heat sink (MUMPFHS) cooling technique is developed in this study. A comprehensive three-dimensional simulation model is established to investigate the thermal, energy and exergy performance of 10 × 10 mm2 HCPV cells cooling with MUMPFHS, using Star CCM+ with the help of user defined field functions. Compared with the previously proposed designs of the HCPV cooling schemes using jet impingement, hybrid jet impingement/microchannel and stepwise varying width microchannel, the present one shows great advantages of both uniform solar cell temperature and high cooling performance under a high solar concentration of 1000 suns. At inlet flow rate of 3 kg/h and temperature of 25 °C, the solar cell temperature can be reduced to 51 °C, with a small temperature non-uniformity of 3.4 °C. As the inlet flow rate increases, the average cell temperature and its non-uniformity further decrease, resulting in a higher electrical efficiency. However, the inlet coolant temperature has little impact on the cell temperature uniformity, allowing maximizing the inlet temperature to improve the thermal exergy efficiency under the recommended temperature range. In addition, five different designs of inlet/outlet plenums are proposed and integrated on the MUMPFHS, which could achieve a uniform flow distribution in each manifold channel. Thermal and exergy analysis confirms that taking the plenums into consideration increases the friction power which can be compensated by the improvement of electrical power due to the decrease of solar cell temperature. The present simulation results indicate that our designed MUMPFHS could increase the feasibility of using HCPV under higher solar concentration with safe operation.

Numerical Analysis on the Performance of High Concentration Photovoltaic Systems Under the Nonuniform Energy Flow Density

Photovoltaic panels can directly convert solar energy into electricity, but temperature will have a certain impact on the efficiency of photovoltaic cells. Especially under the condition of nonuniform energy flow density of high-power concentration, it is of great significance to maintain the temperature uniformity of cells. Therefore, based on the radiation under nonuniform heat flux density, four heat exchangers were proposed: single-channel serpentine flow, multi-channel flat plate, full jet, and single-jet nozzle. Taking into account the uniformity of the cell temperature, the single-jet nozzle and single-channel serpentine flow can better maintain the uniformity of the temperature field compared with other heat exchangers. Especially under high-concentration energy flow density, considering the quality of heat and electricity, the performance of the four-jet nozzles is the best from the perspective of exergy efficiency. Under the condition of four-jet nozzles, the electrical efficiency and thermal efficiency of the cell can be maintained at about 29 and 62.5%, respectively, and the exergy efficiency of the system can reach 31%.

Exergy analysis of a high concentration photovoltaic and thermal system for comprehensive use of heat and electricity

By analyzing the temperature distribution cloud image of the solar cell, it was found that the temperature distribution was uneven and there was a large temperature gradient, resulting in reduced effective cell size requiring a dual inlet model. At the same time, simulations and experiments were established, and it was found that the simulation results were consistent with the experimental results. This paper offers the first law of thermodynamics efficiency and exergy analysis of a simple optimized model at different inlet flow, concentration ratios and inlet temperatures. The result shows that while the inlet flow is 0.02–0.06 kg/s, the system runs efficiently, which can provide considerable heat output, and has greater protection for the cell. When the concentration ratio increases, thermodynamic efficiency and exergy efficiency will decrease, but the total output exergy is in an increasing trend and the trend will decrease as the concentration ratio increases. As the temperature of cooling water increases, the thermal and overall exergetic efficiencies will also increase, and when the inlet temperature is 60 °C, the electrical efficiency is still greater than 20%. In practical applications, the quality of thermal energy can be improved by increasing cooling water temperature, broadening the field of application.

Analytical model for the prediction of solar cell temperature for a high-concentration photovoltaic system

This study presents a simple analytical model for the prediction of solar cell temperature for a high concentration photovoltaic system. The model is based on a heat transfer approach through the system's backplate. The results show that the solar cell temperature is governed by the incident light, material characteristics, ambient conditions, and cell size. The parameters that have a crucial impact on reducing the solar cell temperature were the backplate emissivity, wind velocity, backplate thickness, and backplate length. The backplate coating was found to be of paramount importance due to the considerable reduction of the solar cell temperature with emissivity. Higher wind speeds ventilated the HCPV system and helped lower the cell temperature through convective heat transfer. The thicker the backplate, the lower the cell temperature is due to thermal diffusion on the plate. But this finding prevailed only up to a certain thickness, after which its feasibility is neither maintained nor guaranteed. The study recommends using smaller cell sizes in harsh environments of ambient temperature higher than 40 °C to help manage the reduction of the cell temperature below a critical value of 80 °C.