High Concentration Photovoltaic Research Articles

Effects of partial shading on thermal stress and exergetic efficiency for a high concentrator photovoltaic

Highly concentrated photovoltaic systems can produce higher energy yields than conventional photovoltaic panels but have yet to reach widespread deployment, partly because of lower lifetime and hence cost effectiveness. One limiting factor in the lifetime is the excessive generation of thermal stress. This study takes a multi-objective approach to the calibration of a highly concentrated photovoltaic thermal hybrid system. Novelty is found by exploring the relationship and trade-off between thermal stress and exergetic efficiency. A variety of optical configurations are compared by partially shading the input aperture of the primary optics. Similarly, adjustments to the receiver are made by changing the angle of the solar cell by 45°. To minimise light spillage. The primary and secondary optic positions stay the same throughout all calibrations.By experimentally validating a COMSOL model of the concentrator photovoltaic system (including irradiance distribution) a thorough analysis is conducted. It was found that the maximum thermal stress within the solar cell in this study could drop by almost 10 % with small losses (<3.5 %) to total exergetic efficiency after only small changes to receiver position. Further investigations into other specialised concentrator photovoltaics are required to understand the range of impact on thermal stress.

Numerical study of combined phase change material and water cooling in hybrid wavy microchannels for HCPV cell

HCPV cells are known for their high efficiency in converting sunlight into electricity. However, this increased efficiency also generates higher levels of heat, posing a risk of cell damage. Therefore, the study proposes the combination of a phase change material (CPCM) and liquid flow in hybrid wavy microchannels to ensure stable temperature within the high-concentration photovoltaic (HCPV) cells. A three-dimensional numerical model has been developed to capture the thermal behavior of PCM integrated with water cooling in a microchannel heat sink. The comparison and analysis involved contrasting cases with phase change material (PCM) and cases without PCM. The PCM cases were studied at Reynolds number (Re) 100, while the cases without PCM were investigated at Reynolds numbers of 100 and 200. Three distinct types of PCM were employed, specifically OM 32, Rt 35, and PA - SA/EG. The various microchannel geometries under consideration included Raccoon, wavy, and hybrid wavy microchannels. The results showed that using both PCM and water cooling in a microchannel is preferable over using only water cooling. The outcomes reveal that employing PCM 3 (CPCM) in conjunction with the raccoon wavy microchannel design, there is an 11.61% reduction in the maximum pressure drop, along with a decrease of 6.58% in the maximum solid substrate temperature. Moreover, this configuration attains the highest electrical efficiency, reaching 39.32%.

Maximizing energy output of a vapor chamber-based high concentrated PV-thermoelectric generator hybrid system

Thermal management of triple-junction solar cell is crucial for enhancing electrical efficiency of a high concentrated photovoltaic (HCPV) system. In this paper, a HCPV system integrated with vapor chamber (VC) cooling and thermoelectric generator (TEG) is proposed to maximize the energy output. The VC as a passive cooling device can effectively extract the excessive heat from the triple-junction cell and the TEG module are used to convert the waste heat into electrical power thereby harvesting more energy. A detailed unsteady-state modeling of the VC based HCPV/TEG system is established in MATLAB. The effects of new VC structure, TEG type and concentration ratio on the dynamic performance of the system are discussed and a comparison with the CPV-TEG system without VC cooling is provided. Results reveal that effective cooling of the new VCs can maintain the sophisticated cell under 1000 suns at below 329 K and the average exergy efficiency of the system is 31.20%. It is observed that the appropriate selection of TEG module can improve the system performance. Using TEG5, the proportion of CPV power in total power for the proposed system reaches 99.02%, which increases by 2.81% compared with that of the reported CPV-TEG system without VC cooling.

A numerical modeling of thermal management of high CPV arrays using spray cooling

Liquid cooling is an efficient way of thermal management for high CPV cells, increasing the system performance by reducing cell's temperature. Thermal management complexity rises upon using an array of cells while the system becomes sizeable. The present numerical simulations follow a single cell study to investigate spray cooling for high CPV arrays with minimum number of injecting nozzles. The idea is to cool the cells by the liquid film formed on the thermal paste surface. Cooling the whole surface by the help of the liquid film decreases the number of nozzles to less than the number of cells. Both mass flow rate and pumping power are reduced, improving the system efficiency and lowering the liquid demands. To find cooling patterns, one-dimensional arrays with two and three cells and two-dimensional square arrays of order two and three are investigated at three solar concentrations; 500, 750, and 1000 Suns. The non-spraying cells' performance is assessed by consideration of two criteria; the damaging temperature and the increment rate of the difference between the cell power operating with and without injection. It is indicated that the patterns from smaller arrays can be applied to design the injection arrangement for the larger ones. Results from the cooling injection on a square array of order three demonstrate that decreasing the number of nozzles can reduce the mass flow rate by 55–89 % and increase the net power by 0.5–2.2 %, depending on the concentration ratio.

Effect of Recycling on the Environmental Impact of a High-Efficiency Photovoltaic Module Combining Space-Grade Solar Cells and Optical Micro-Tracking

This paper presents a life cycle assessment (LCA) analysis of a new, high-concentration photovoltaic (HCPV) technology developed as part of the HIPERION project of hybrid photovoltaics for efficiency record using an integrated optical technology. In the LCA calculations, the production stage of a full module was adopted as a functional unit. SimaPro version 9.00.49, the recent Ecoinvent database (3.8), and the IPCC 2021 GWP 100a environmental model were applied to perform the calculations. The environmental impact of the HCPV panel was determined for constructional data and for recycling of the main elements of the module. The results of the calculations show that recycling of PMMA, rubber, and electronic elements reduced the total carbon footprint by 17%, from 240 to 201 kg CO2-eq. The biggest environmental load was generated by the PV cells: 99.9 kg CO2eq., which corresponds to 49.8% (41.7% without recycling) of the total environmental load due to the large number of solar cells used in the construction. The emission of CO2 over a 25-year lifespan was determined from 17.1 to 23.4 g CO2-eq/kWh (20.4 to 27.9 without recycling), depending on the location. The energy payback time (EPBT) for the analyzed module is 0.87 and 1.19 years, depending on the location and the related insolation factors (Madrid: 470 kWh/m2, Lyon: 344 kWh/m2). The results of the calculations proved that the application of recycling and recovery methods for solar cells can improve the sustainability of the photovoltaic industry.

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).

Thermal and exergy analysis of Pin-finned heatsinks for nanofluid cooled high concentrated photovoltaic thermal (HCPV/T) hybrid systems

• Cooling performance of HCPV/T is systematically investigated. • Different shaped pin-finned heat sinks (inline and staggered) are examined. • Thermal performance is determined for MWCNT nanofluids. • Exergy efficiencies of pin-fin heat sinks in HCPV/T are evaluated. • 2% MWCNT nanoparticle concentration is found to be the optimum. Cooling of High Concentrated Photovoltaic (HCPV) cells is a major concern among researchers due to higher heat generation in the cells from highly concentrated solar radiation. In the present investigation, a numerical study of the High Concentrated Photovoltaic Thermal (HCPV/T) system is conducted for the combined effect of nanofluids and pin-finned heatsinks on the cooling performance. The investigation is carried out for AZUR SPACE solar cell (Model: 3C44C) for 1000 Concentration Ratio (CR) and the Reynolds number ( Re ) varies within the laminar range (600 ≤ R e ≤ 2200). Different shapes of pin-fins and their orientations are systematically investigated for the effect of Multi-walled Carbon Nanotube (MWCNT) nanoparticles in a base fluid. The results show a significant reduction in the temperature (up to 18K) of the solar cells for the MWCNT nanofluid compared to its base fluid counterpart. A higher heat transfer characteristics (Nusselt numbers) and lower average temperature of top surface of HCPV cells are found to occur for the staggered arrangements of pin-fins. It is also noticed that the volume concentration of MWCNT in water affects heat transfer characteristics and reduction in temperature takes place up to the volume concentration of 2%. About 1.3% reduction in temperature is predicted for adding MWCNT nanoparticle concentration from 0.5% to 2%. However, in terms of exergy efficiency, maximum overall exergy (about 67% for water flow rate of 0.00167 kg/s) is found for square pin-fins with inline arrangements. The average increase in Nusselt number from inline to staggered arrangement are around 11%, 74%, and 22% respectively for circular, square and triangular fins. The maximum electrical efficiency reaches to 42.2% for both 2% and 4% MWCNT with staggered circular pin-fins for a mass flow rate of 0.0058kg/s. Finally, it appears that a combination of nanofluids and pin-finned heatsinks gives a better cooling rate in the HCPV/T system and could be a promising alternative along with other cooling techniques.

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.

Numerical investigation of high concentrated photovoltaic (HCPV) plants in MENA region: Techno-Economic assessment, parametric study and sensitivity analysis

The Middle East and North Africa (MENA) region, enjoys one of the highest solar irradiations in the world. In this context, the objective of this paper is to carry out a techno-economic assessment of High Concentrated Photovoltaic (HCPV) Power plants with multijunction cells in six locations throughout the MENA region namely: Errachidia (Morocco), Tripoli (Lybia), Aswan (Egypt), Beyrouth (Lebanon), Doha (Qatar), and Tabuk (Saudi Arabia), carrying out parametric analysis of numerous design factors in order to optimize this technology. The System Advisor Model (SAM) tool was used to model a High Concentrated Photovoltaic plant to evaluate its technical and economic performances. The study takes into account, cell temperature, energy generation, capacity factor, and levelized cost of electricity (LCOE). The findings demonstrated that the highest yearly energy production is attained at the Aswan (Egypt) site, which achieved a value of 41.72 GWh for a total installed capacity of 20 MWdc. The annual capacity factor and Energy yield were estimated to be 23.8 % and 2086.47 kWh/kW, respectively. The economic analysis reveals that the levelized cost of electricity of the investigated system can be around 6.99 ¢/kWh if installed in MENA region. Concerning the parametric and sensitivity analysis, the results demonstrate that the increasing of the surface cell area, a 0.4 %/°C temperature coefficient, and a nearly non-existent temperature differential between the heatsink and the cells (1 °C in our case) can lead to an increase in the energy output and capacity factor. Based on the sensitivity analysis, an optimization of the inflation, discount rates, and internal rate of return can lead to a better bankability of the project.

Effect of Optical–Electrical–Thermal Coupling on the Performance of High-Concentration Multijunction Solar Cells

In the process of high-concentration photovoltaic (HCPV) power generation, multijunction cells work in the conditions of high radiation and high current. Non-uniformity of focusing, the mismatch between the focusing spectrum caused by the dispersion effect and the spectrum of multijunction solar cell design and the increase in cell temperature are the key factors affecting the photoelectric performance of the multijunction solar cell. The coupling effect of three factors on the performance of multijunction solar cell intensifies its negative impact. Based on the previous research, the light intensity and spectral characteristics under Fresnel lens focusing are calculated through the optical model, and the optical–electrical–thermal coupling model under non-uniform illumination is established. The results show that obvious changes exist in the concentration spectrum distribution, energy and non-uniformity along different optical axis positions. These changes lead to serious current mismatch and transverse current in the multijunction solar cell placed near the focal plane which decreases the output power. The lost energy makes the cell temperature highest near the focal plane. In the condition of passive heat dissipation with 500 times geometric concentration ratio, the output power of the solar cell near the focal plane decreases by 35% and the temperature increases by 15%. Therefore, optimizing the placement position of the multijunction cell in the optical axis direction can alleviate the negative effects of optical–electrical–thermal coupling caused by focusing non-uniformity, spectral mismatch and rising cell temperature, and improve the output performance of the cell. This conclusion is verified by the experimental result.

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) &gt;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.

Performance evaluation of high concentration photovoltaic cells cooled by microchannels heat sink with serpentine reentrant microchannels

Efficient cooling is critical to reduce cell temperatures of high concentration photovoltaic (HCPV) cells to avoid the output electrical performance degradation and lifetime reduction. In this study, we develop a novel type of microchannel heat sink (MHS) with serpentine reentrant microchannels (SRM) for efficient cooling of HCPV cells. They feature serpentine flow passages with Ω-shaped cross-sectional configurations, which contribute to promote fluid mixing and disrupt the normal development of thermal boundary layers. Thus they are able to provide excellent heat transfer characteristics and highly efficient cooling performance. By the comparison of a fin heat sink, both numerical and outdoor experimental studies were comprehensively conducted to explore the enhancement feasibility of thermal and electrical performance of HCPV cells. Results showed that the SRM reduced the cell temperatures and enhanced the temperature uniformity of HCPV cell module considerably, i.e., it presented cell temperatures of 25-31℃, much smaller than that of 45-63℃ of the fin heat sink. The temperature differences of HCPV cell modules were reduced to be less than 4.4℃. Besides, the output power increased by as high as 115%, and the electrical efficiency increased to 15–20% for the HCPV cell module with serpentine reentrant microchannels. Besides, the HCPV cell module with SRM was also found to induce smaller average cell temperatures and better electrical performance than a module with parallel reentrant microchannels (PRM). Moreover, the effects of flow rate and concentration ratio on the performance of HCPV cells with SRM were also assessed.

Hybrid membrane distillation/high concentrator photovoltaic system for freshwater production

Pure water shortage is a crucial issue that needs very rapid, applicable, and economical solutions. Membrane distillation is a promising technique, primarily when supplied with a sustainable heating source. The current work introduces the hybridization of high concentrating photovoltaic (HCPV) with membrane distillation (MD) to gain the maximum benefits from available solar energy. The challenge regarding the HCPV unit is to incorporate an efficient cooling system that could maintain the cells within the manufacturer’s recommended range. On the other hand, the challenge regarding the MD unit is the high energy required for water heating. The current work introduces an effective microchannel cooling system that could maintain the cells within the safe range and utilize this removed thermal load to be the heating source for the MD unit. The HCPV has been solved numerically using Ansys 2020 software, while the MD unit has been investigated numerically and experimentally. It was found that to keep the maximum cell temperature within a safe range, the coolant flow rate should be at least 370 ml/min, with a corresponding coolant outlet temperature of 68 ºC. Moreover, the MD distillation unit has been proved experimentally to produce approximately 46 kg/m2 per day. Electric power of about 685 W is available with the system.

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.