High-concentration Photovoltaic Cell Research Articles

Performance of high-concentration photovoltaic cells cooled by a hybrid microchannel heat sink

The electrical performance and equipment lifetime of high-concentration photovoltaic cells depends heavily on efficient cooling. In this paper, we applied a hybrid configuration to the cooling of a high-concentration photovoltaic cell, an innovative pattern derived from a comprehensive study on the combination of oblique microchannel and micro pin fin. Results from this study found that an elliptical pin fin pattern conforming with streamlines most effectively removed heat flux with a Nusselt number of 65.44 at a Reynolds number 1250. Then, the performance evaluation of a photovoltaic cell with a concentration ratio of 1000 was carried out on the hottest day of each season in Shiraz under actual boundary conditions. With an average flow rate of 30 ml/min in the spring, the implementation of this hybrid design resulted in the photovoltaic cell achieving an electrical efficiency of 40.16 while still maintaining a constant surface temperature of 301 K. Unlike a straight microchannel, which failed to maintain a constant cell temperature throughout summer’s hottest hours, this hybrid configuration succeeded in sustaining cooling with an average flow rate of 90 ml/min. In the winter and autumn, the pump’s average power consumption required for cooling was about 25 and 38 mW, respectively. Moreover, the maximum output electrical power in the summer was 2.8 W, with pumping power contributing to 1500 mW.

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%.

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.

Leveraging the entropy generation minimization and designed porous media for the optimization of heat sinks employed in low-grade waste heat harvesting

• A porous media model and optimization procedure to design heat sinks is presented • Different geometries of the heat sinks are treated within the same framework • Which geometry should be employed depends on operational conditions and size • Entropy generation is a reliable metric for low-grade waste heat recovery systems A comprehensive optimization procedure for the design of heat sinks used to harvest low-grade waste heat for secondary processes is proposed. A designed porous medium approach is used, providing modelling versatility and allowing for the treatment of several internal geometries within the same framework. Two applications, taken from the cooling of high concentration photovoltaic cells and membrane distillation, are used to illustrate the proposed procedure. Three internal heat sink geometries, namely plate fins, pin fins, and metal foams, are analyzed, and the selection as to which one is the more advantageous is shown to be dependent on size and operational conditions. Possible pitfalls of a traditional design procedure are pointed out, for heat transfer capability, under high heat load condition, should be emphasized over fluid friction avoidance. The entropy generation rate is then shown to be a reliable metric when designing for low-grade waste heat recovery, automatically focusing on either viscous dissipation or thermal resistance minimization without introducing any artificial figure of merit for that purpose.

Development of one-section microchannels cooling system for high-concentration photovoltaic cells

This paper presents the development of simple, effective and economic microchannel systems for cooling high-concentration multi-junction photovoltaic (HCMJPV) cells. The developed cooling system uses a short cooling fluid path concept with one microchannel section per the fluid path. The work is conducted using a 3D numerical model that is based on the finite volume method. The effects of design parameters on the thermal characteristics of one-section microchannels and output power of the HCMJPV cells are comprehensively investigated. Cooling systems that attained the largest net output power of HCMJPV cells are identified. The developed cooling system achieved superior characteristics compared to the existing state of the art system. The proposed constant-width one-section cooling system achieves comparable standard deviation and lower surface temperature (35.65°C), pressure drop (68.41%) and microchannel thermal resistance (49.57%) along with higher generated power (8.27%), net output power (8.44%) and overall heat transfer coefficient (175.8%) than the existed cooling system in literature. The developed cooling system allows the cells to produce an extra 820.5MWh/m2 of cells, during their lifetime.

Analytical, experimental, and numerical analysis of a microchannel cooling system for high-concentration photovoltaic cells

In this work, we present the results of an analytical, numerical, and experimental analysis on the performance of a heat sink system designed as a parallel arrangement of microchannels for cooling a high-concentration photovoltaic (HCPV) cell. The analysis considered the worst-case scenario where no electricity is generated, and the solar incidence is maximum on the northwest region of the Sao Paulo State in Brazil. For the experimental, analytical, and numerical analysis, the considered HCPV cell has a geometrical concentration ratio of 500×, a maximum efficiency of 40% at cell’s operating temperature of 41.0 °C, and a cell base area of 100 mm2. The numerical analysis adopts the finite volume method implemented in ANSYS Fluent v15 to solve flow and energy equations with second-order upwind schemes, and the steady-state, incompressible, and laminar flow. In the experimental apparatus, the copper microchannel heat sink consists of 33 parallel rectangular channels of 10 mm in length, 200 μm in width, and 500 μm in height for each microchannel. A cartridge heater was used to simulate the on-sun test, i.e., it simulates the total heat rate supplied to the microchannel heat sink. The microchannel heat sink is capable of keeping the operating temperature of the cell below the maximum cell’s operating temperature (41.0 °C). In addition, the pressure drops are slightly higher than the predicted models, but not exceeding 34%. Moreover, the energy spent in the pumping in the microchannel represents < 1% of the energy generated by the photovoltaic cell.

A novel approach of accelerated ageing tests for high concentration III–V multijunction solar cells through rapid irradiation/thermal cycles

Today, investigations on degradation and failure mechanisms in solar cells are often based on accelerated ageing tests (AAT), where failure effects are reproduced and quantified within a much shorter time period than the actual lifetime. This paper presents a study upon a novel approach of AAT for high concentration photovoltaic (HCPV) cells. The intended approach aims to overcome several limitations encountered in most of the AAT adopted up today, proposing the use of an alternative experimental set-up for performing nearly 400 times faster and more realistic thermal cycles, under real sun conditions (irradiation cycling), without the involvement of any environmental chamber. The cumulative impact of such very rapid irradiation/thermal cycles on the ageing of HCPV assemblies can be determined, both quantitatively and qualitatively, by evaluating specific pre-ageing and post-ageing diagnostic measurements by means of I–V characterization and scanning acoustic microscopy (SAM). The proposed irradiation/thermal cycling arrangement was successfully employed for performing accelerated ageing of both HCPV assemblies (cell receiver and heat sink) and bare HCPV cell receivers. Ultimate goal of this AAT approach is to provide the basis for a future work on the reliability analysis of the main degradation mechanisms and failure propagation in HCPV cell assemblies.

Review of methods for the calculation of cell temperature in high concentration photovoltaic modules for electrical characterization

The solar cell operation temperature is an important input in models for the electrical characterization of high concentration photovoltaic cells and modules. However, the direct measurement of this temperature is difficult in these kinds of devices. Because of this, in recent years, the scientific community has proposed different methods for indirectly calculating the cell temperature in high concentration photovoltaic modules from atmospheric parameters and/or easily measurable parameters on the module. In this paper, a comprehensive review of existing methods for cell temperature calculation in high concentration photovoltaic modules for electrical characterization is presented. The different methods are summarized and a comparative analysis is done. Required inputs, advantages and technical difficulties of each method are highlighted. Also, an experimental campaign has been carried out at Jaén, south of Spain, in order to quantify the accuracy of the methods. Results show that methods based on direct measurements on the module are somewhat more accurate than methods only based on atmospheric parameters. The choice of the most suitable method for a specific application will depend on the availability of module information, on the required accuracy and on technical issues.

Computational Analysis of Nanofluid Cooling of High Concentration Photovoltaic Cells

High concentration photovoltaic devices require effective heat rejection to keep the solar cells within a suitable temperature range and to achieve acceptable system efficiencies. Various techniques have been developed to achieve these goals. For example, nanofluids as coolants have remarkable heat transfer characteristics with broad applications; but, little is known of its performance for concentration photovoltaic cooling. Generally, a cooling system should be designed to keep the system within a tolerable temperature range, to minimize energy waste, and to maximize system efficiency. In this paper, the thermal performance of an Al2O3-water cooling system for densely packed photovoltaic cells under high concentration has been computationally investigated. The model features a representative 2D cooling channel with photovoltaic cells, subject to heat conduction and turbulent nanofluid convection. Considering a semi-empirical nanofluid model for the thermal conductivity, the influence of different system design and operational parameters, including required pumping power, on cooling performance and improved system efficiency has been evaluated. Specifically, the varied system parameters include the nanoparticle volume fraction, the inlet Reynolds number, the inlet nanofluid temperature, and different channel heights. Optimal parameter values were found based on minimizing the system's entropy generation. Considering a typical 200-sun concentration, the best performance can be achieved with a channel of 10 mm height and an inlet Reynolds number of around 30,000, yielding a modest system efficiency of 20%. However, higher nanoparticle volume fractions and lower nanofluid inlet temperatures further improve the cell efficiency. For a more complete solar energy use, a combined concentration photovoltaic and thermal heating system are suggested.

Numerical and experimental study on cooling high-concentration photovoltaic cells with oscillating heat pipe

Both numerical and experimental methods are used to investigate the cooling of concentration photovoltaic (CPV) cells. A numerical study presents the temperature distribution under different heat flux and some other outdoor conditions. The CPV (12 suns) system was experimentally studied, and the results show that the CPV could enhance electric power with a good cooling system. A heat pipe gives a uniform, reliable, simple and costless cooling method. The oscillating heat pipe, without an air fan or a pump, and no power consumption, is suitable for the higher CPV system.

Investigation of high-concentration photovoltaic cell packages after three years field service

Abstract As part of a controlled, step-wise development program, silicon cells from an early production run were assembled into packages and installed in a prototype electrical module. After three years field service, the module was disassembled and the cell packages were examined in detail. Although all 48 cell packages were still functional, significant cracking was discovered in the solder layers between ceramic stand-offs and copper heat-spreaders. A simplified analysis of thermal fatigue as a cyclic creep process predicts useful lives of about twelve years for cell packages of this configuration and solder joint thickness.