Photovoltaic Module Temperature Research Articles

Combined cooling of photovoltaic module integrated with thermoelectric generators, by using earthenware water tank and ultrasonic humidifier: An experimental study

The purpose of the present research is to reduce the temperature of photovoltaic (PV) module using a combined cooling method in order to improve electrical output, having better performance and simultaneous integration of thermoelectric generators (TEG) with it and to generate surplus electricity from the existing temperature difference in the proposed system. An L-shaped earthenware water tank as the passive cooling method and an ultrasonic humidifier inside the tank as the active cooling method formed the combined cooling sections of the proposed system. The ultrasonic humidifier converts the cooled water inside the earthenware tank to cold mist in the enclosed space backside of the PV module by a piezoelectric actuator based on the cavitation phenomenon (reduction of PV module temperature occurs by heat transfer and conductivity). Temperature difference between the surface of the PV module and cold mist on backside of the PV module converts to surplus electricity by TEG. In this study, three cold mist creation capacities of 250, 400 and 550 mL/h were investigated and the greatest improvement in the utilization of solar energy compared to the control PV module was for the cold mist creation capacity of 550 mL/h. Temperature reduction of PV section of about 5.2 °C, PV maximum power improvement of 5.1% and total efficiency improvement of 4.96% were obtained in the proposed system with cold mist creation capacity of 550 mL/h compared to control PV module. It was concluded that unlike cooled PV module, the share of TEG array is very negligible in the total efficiency improvement.

Temperature Field Measurement of Photovoltaic Module Based on Fiber Bragg Grating Sensor Array.

Studying the temperature field of photovoltaic modules is important for improving their power generation efficiency. To solve the problem of traditional sensors being unsuitable for measuring the spatial temperature field, we designed a real-time detection scheme of the photovoltaic module temperature field based on a fiber Bragg grating (FBG) sensor array. In this scheme, wavelength division multiplexing and space division multiplexing technologies were applied. The multi-channel FBG sensor strings were arranged on the surface and in the near field of the photovoltaic module. Different FBG strings were selected through optical switches, and the wavelength of the FBG string was addressed and demodulated using the tunable laser method and a peak-seeking algorithm. A measurement experiment of the photovoltaic module temperature field was carried out in an outdoor environment. The experimental results showed that the fluctuation law of the photovoltaic module surface and near-field temperature is basically consistent with that of solar radiation power. The temperature of the photovoltaic module decayed from the surface to space. Within 6 mm of the photovoltaic module surface, the temperature sharply dropped, and then the downward trend became flat. The lower the solar radiation power and the higher the wind speed, the faster the temperature decay. This method provides technical support for measuring the temperature field of a photovoltaic module and other heat source equipment.

Experimental study on simultaneous use of phase change material and reflector to enhance the performance of photovoltaic modules

Due to the increasing demand for energy in the world and the problems caused by fossil fuels, the use of renewable energy has become the focus of governments. Therefore, the study and use of renewable energy, especially solar energy, is an essential development program for all governments. There are massive efforts to increase the efficiency of photovoltaic (PV) technology which is rapidly developing, in order to decrease the capital cost of a solar power plant. In this paper, two methods for enhancing the efficiency of PV modules are considered: using phase change material (PCM) as coolant and integrating reflectors. The experiments were performed in Dezful, Iran, with very hot summers. The results show that, using reflector boosts the received irradiation by the PV panel, but at the same time, leads to increase the PV module temperature. Therefore, using PCM in order to decrease the temperature is justified. Among different tilt angles of the mirror, 30° presents the best outcomes. Then, this case was tested with one additional mirror on top of the PV module. So, the case of double mirrors was selected and bring about 4.1 % improvement in electrical output, in comparison with the conventional one. As the next stage, this optimum case was repeated by utilizing the PV module with PCM at its back side. 12.5 % enhancement of electrical output and 24 % reduction in entropy generation were calculated, in comparison with the conventional one.

Performance enhancement of photovoltaic module using finned phase change material panel: An experimental study under Iraq hot climate conditions

ABSTRACT The operational temperature highly influences the efficiency of the solar photovoltaic (PV) module, in which high temperature decreases the output power accordingly. In this work, a polycrystalline PV module is modified using a finned phase change material (PCM) panel attached to the rear as a thermal energy storage unit to decrease and regulate the operating temperature under hot weather conditions in southern Iraq. For this purpose, local Iraqi paraffin wax is used as a PCM loaded into a galvanized steel panel that has internal smooth wavy fins to improve the PCM poor thermal conductivity and accelerate its melting and solidification rates. Experimental results showed that the modified PV module temperature is decreased by up to 16°C compared with the reference PV module, resulting in maximum output power of up to 38.4% more than an identical reference PV module. Moreover, the electrical efficiency of the modified PV module is improved respectively by 34% and 37.2% on the first and second day of the experiment over the reference PV module, indicating remarkable electrical and thermal performance improvement.

Progressive cooling techniques for photovoltaic module efficiency and reliability: Comparative evaluation and optimization

The temperature of photovoltaic modules during operation is one of the most critical criteria for determining both efficiency and reliability. Alternative PV module cooling techniques have been offered as a means of lowering module temperature, lowering deterioration rates, and enhancing efficiency. In this work, progressive cooling methods including water jacket, phase change material (PCM), and heatsink are thoroughly analyzed using the finite element model. In addition, considerable improvements in the PV module efficiency and reliability are accomplished by introducing new designs for the water jacket. The results show that a water jacket with an aluminum container design performs best when the mass flow rate is 8 kg/min, resulting in a 6.8% power gain, whereas a water jacket with an aluminum pipe design performs best when the pipe diameter is 2.5 cm and the mass flow rate is 2 kg/min, resulting in a 5.2% power gain. In natural convection conditions, the PCM paraffin wax RT-42 and water jacket implementations can reach a 10 °C and 12 °C drop, respectively, whilst the heatsink can only achieve a 4 °C drop. An empirical model is also used to predict and quantify the impact of each cooling method on the durability of PV modules. Water jackets, PCM, and heatsinks all increase solder fatigue life by 154, 103, and 27%, respectively. The module lifetime owing to hydrolysis mitigation is increased by 68, 56, and 18%, respectively, with water jackets, PCM, and heatsink, while the module lifetime due to photodegradation mitigation is increased by 37, 31, and 11%, respectively.

Measurement of the Convective Heat Transfer Coefficient and Temperature of Vehicle-Integrated Photovoltaic Modules

To improve the thermal design of vehicle-integrated photovoltaic (VIPV) modules, this study clarifies the characteristics of the convective heat transfer coefficient h between the vehicle roof surface and the surrounding air with respect to vehicle speed. Experiments on two types of vehicles with different body shapes indicate that h is strongly affected by vehicle speed, and it is also affected by body shape depending on the position on the roof. Empirical equations for approximating h as a function of vehicle speed and position on the vehicle roof are derived from the experimental datasets, and the differences between the equations derived herein and traditional equations that have been used for the heat transfer analysis of conventional stationary photovoltaic (PV) modules are clarified. Furthermore, the temperature change characteristics of the VIPV module were measured experimentally, confirming that h is the dominant factor causing the high temperature change rate of the VIPV module under driving conditions. In sunny summer conditions, the measured temperature change rate reaches up to 16.5 °C/min, which is approximately 10 times greater than that in the standard temperature cycle test for conventional stationary PV modules.

Hot Spot Detection of Photovoltaic Module Based on Distributed Fiber Bragg Grating Sensor

The hot spot effect is an important factor that affects the power generation performance and service life in the power generation process. To solve the problems of low detection efficiency, low accuracy, and difficulty of distributed hot spot detection, a hot spot detection method using a photovoltaic module based on the distributed fiber Bragg grating (FBG) sensor is proposed. The FBG sensor array was pasted on the surface of the photovoltaic panel, and the drift of the FBG reflected wavelength was demodulated by the tunable laser method, wavelength division multiplexing technology, and peak seeking algorithm. The experimental results show that the proposed method can detect the temperature of the photovoltaic panel in real time and can identify and locate the hot spot effect of the photovoltaic cell. Under the condition of no wind or light wind, the wave number and variation rule of photovoltaic module temperature value, environmental temperature value, and solar radiation power value were basically consistent. When the solar radiation power fluctuated, the fluctuation of hot spot cell temperature was greater than that of the normal photovoltaic cell. As the solar radiation power decreased to a certain value, the temperatures of all photovoltaic cells tended to be similar.

Contactless phase change material based photovoltaic module cooling: A statistical approach by clustering and correlation algorithm

By maintaining the photovoltaic(PV) module at its nominal operating temperature (TPV) in a sustainable way, we can enhance the total efficiency of the PV system. This study focuses on the effect of phase change material (PCM) as coolant medium in controlling the raise of photovoltaic module temperature during operation. The numerical simulations were performed for a detailed establishing in a contactless PCM based cooling technology, by comparing different PCMs, their melting temperatures, their thicknesses, and effect of solar irradiance. The results show that photovoltaic module cooling can be achieved for all solar irradiance cases by using contactless PCM modes. But the Cooling effectiveness of PCM is found to reduce beyond thickness of 1 cm, which makes it an optimal range for radiation based PV module cooling technique. Subsequently, this optimized Rubitherm (RT25HC) PCM container shows the peak temperature difference (ΔTPV) of 6 K and 10 K under solar irradiance of 300 W m−2 and 500 W m−2 respectively. Following that using Rubitherm 55HC and Rubitherm 35HC, 16 K and 11.5 K temperature difference (ΔTPV) at 800 W/m2 respectively, and 19 K, 15 K and 12 K for 1000 W m−2 using Rubitherm 25HC, 35HC and 44HC respectively are observed. Our study proves that, the increase in solar irradiance influences on both melting temperature of PCM and the PV module temperature. Further in our study, thermal profiles of the photovoltaic modules are analysed in detail using statistical method to understand (i) the correlation between different PCM and thicknesses (ii) z-score normal distribution of PCM assisted PV module temperature across different thicknesses and (iii) clustering algorithms to find the average PV module temperature reduction across all the PCM at different irradiances.

Analysis of Immersion Depth in Cooling a Photovoltaic Module by Water Immersion: An Experimental Study

Photovoltaic systems are one of the important methods used to obtain electricity from solar energy. Photovoltaic module temperature and the angle of incidence of solar radiation are the most important factors affecting the electrical energy obtained from the photovoltaic module. There are many experimental and numerical studies in the literature on increasing electricity production by cooling photovoltaic modules. Cooling with air, liquid, phase change materials, thermoelectric effect, and immersion in water are the commonly used cooling methods. In this study, the cooling of the photovoltaic module by the water immersion method was experimentally investigated. In addition to the results of the related studies in the literature, analyzes were made for different immersion depths and the most appropriate immersion depth was tried to be determined. Three scenarios, 5 cm, 20 cm, and 30 cm immersion depth were investigated in the immersion of the PV module in liquid. As a result of immersion of the PV module in water, the PV module temperature decreased, and the voltage output increased for all parameter values. The highest voltage increase was obtained for 5 cm immersion depth (7.85%). Although PV module temperatures decreased with increasing immersion depth, the voltage output decreased after 5 cm immersion depth.

Reassessment of different flat TCO integrated reflectors for the crystalline silicon solar PV module in view of its longer operational life

AbstractIn the present simulation work with experimental validation, the performance of a transparent conductive oxide (TCO) film‐coated spectrally selective reflector in the low‐concentrated photovoltaic application has been analysed. The use of mirrors in solar photovoltaic (PV) applications is a well‐established thing. However, it increases the operating temperature and requires more thermally stable, expensive solar modules. In this regard, for the first time, commercially available TCO‐coated glasses such as fluorine‐doped tin oxide (FTO) and indium tin oxide (ITO) have been integrated with mirrors. The spectrally selective reflector is a promising technology to achieve a high‐power yield from the commercially available crystalline silicon photovoltaic (C‐Si PV) module during its lifetime. They have the property to absorb unwanted photons in the region of the AM1.5 spectrum (1200 to 2000 nm), which partially thermalises the solar module through plasmonic absorption. The present study found that the proposed approach helps to restrict the increase in PV module temperature caused by the reflected rays from a mirror. The electrical performance of a standalone C‐Si PV was compared with that of the same system after the addition of FTO, ITO and a conventional mirror system. Our analysis indicates that, with the mirror integration, the degradation rate can increase to 1.5% per year if the standalone PV module's ageing rate is 0.8% per year. Through FTO incorporation with the same, the ageing rate has been reduced by up to 1.18% per year due to a reduction in temperature. This result is quite interesting, considering that spectrally selective reflectors do not stop high‐energy photons from thermalizing the PV module. The entire work has been done on commercially available materials, which makes it easier and ready to be implemented in large PV plants.Highlights A spectrally selective mirror for PV power boosting. Transparent conductive oxide (TCO) glass integration with mirror reduces the IR concentration approximately 50%. The reduction in thermalisation of PV module from the mirror by 3–5°C. This integration increases the PV module operational life by at least 4 years compared with commercial mirror.

Joule heating estimation of photovoltaic module through cells temperature measurement

Module temperature has a role in determining a PV module's performance. The purpose of this paper is to estimate the Joule heating in a photovoltaic (PV) module by comparing during PV-On (electricity generation) and PV-Off (without electricity generation). Joule heating was less evaluated due to simplifying formulation, which is easier to implement in experimental observation as proposed in this work. The experiment collected the temperature distributions of the PV module during PV-On and PV-Off. PV module temperature distribution follows the normal distribution curve as the irradiation uniformity pattern of the solar simulator has a slight ≤0.3 oC difference between PV-On and PV-Off. Joule heating slightly increased the PV module temperature by 0.53 K/A, proportional to the irradiances. Joule heating has increased almost seven times from 2.65 W at 700 W/m2 to 18.07 W at 1000 W/m2. Joule heating might slightly increase the overall thermal conductivity and slightly decrease the thermal resistances. It might affect the heat transfer. This research may improve the procedures prediction of PV or photovoltaic-thermal (PVT) collector temperature by considering Joule heating.

Enhancing performance of PV module using water flow through porous media

To achieve a high level of photovoltaic (PV) panel performance, a cooling process have to be added to reduce temperature of PV module. In present study, a new design of cooling system is suggested and investigated numerically. Water is used as a working fluid through the back chamber of PV panel. The chamber is filled with porous media to increase convection heat transfer. The incompressible steady state flow of water is simulated using the ANSYS program utilizing Navier Stokes equations. The flow field of cooling fluid and temperature distribution of PV panel have been presented at different conditions to study the effects of mass flow rate, solar radiation and porosity, on the performance of the PV module. The result show that adding the porous media decreases the average temperature of the module by about 9–14 °C. Additionally, the heat transfer is greatly enhanced with the increase of flow rate. For validation of the presented work, an experimental work is implemented to compare the experimental results with numerical ones. These comparisons show a good agreement with a range of error between 4.5% and 8.5% for cooling without porous media and between 2.9% and 10.9% for cooling with porous media.

Efficiency improvement of PV module using a binary-organic eutectic phase change material in a finned container

Solar photovoltaic (PV) is a promising technology in solar energy conversion. There is plenty of solar energy available in tropical regions. However, increased PV module temperature during operation affects its performance in negative way. Thus, PV module cooling via passive cooling is of interest to overcome the problem and shows more attractive against active cooling techniques. In this work, phase change material (PCM) filled in a finned container is attached at the back surface of a PV module as for passive cooling. The PCM used is a novel organic eutectic PCM which is a mixture of Myristic acid and Stearic acid. Three proportions of these two acids, which are 60:40, 70:30 and 80:20 %wt, are investigated for PV module temperature reduction. Light intensity of 900–1000 W/m2 is generated by tungsten halogen bulbs as an irradiation onto the PV module. The PV module performances are examined and compared to those without PCM cooling. The results show that the organic eutectic PCM can reduce the PV module temperature and thus, enhance the PV module performance. Among three proportions, the 60:40 %wt mixture gives best results which are 7.06 °C reduction, 0.454 W power increase, and 4.226% module efficiency improvement.

Optimizing the performance of solar panel cooling apparatus by application of response surface methodology

The high temperature of the solar photovoltaic module reduced the power output and efficiency of the solar panel. Water cooling is one of the best options for reducing the temperature of solar panels. In this research paper, an experimental setup of solar panel with water cooling arrangements has been developed and optimized. The measured experimental data and data generated by model equations have been optimized by the Response Surface Methodology (RSM) tool in the Design of Experiment. The optimized responses are the efficiency of solar panels, module temperature (MT) of solar panel, and exergetic efficiency. The main input parameters solar flux, water inlet velocity, and atmospheric temperature varied from 600 W/m2 to 1000 W/m2, 0.5 to 0.9 m/s, and 25°C to 45°C, respectively. The best set of input parameters after optimization in RSM is 705 W/m2 solar flux, 0.7263 m/s water inlet velocity, and 32.87°C atmospheric temperature on which the values of responses MT, exergetic efficiency and solar panel efficiency are 48.98 °C, 19.18 %, and 18.88 % respectively. The experimental setup of solar panel cooling has been run on these input parameters setting and responses are validated with the predicted value of the RSM and the previous research. The calculated percentage error in MT is 2.41%, solar panel efficiency is 1.62%, and exergetic efficiency is 3.82%.

Solar collector tube as secondary concentrator for significantly enhanced optical performance of LCPV/T system

Improving efficiency, controlling cost and reducing the temperature of solar cells are great challenges for linear concentrated photovoltaic/thermal systems (LCPV/T). In this work, we report a new design with a linear Fresnel lens as the primary optical element and an additional multi-functioned solar collector tube as the secondary optical element. With such design, the low-cost solar collector tube acts multiple roles simultaneously, i.e., lens, spectral beam-splitting filter and heat collector. It was demonstrated that the addition of such multi-functional solar collector tube in LCPV/T system can significantly increase the irradiation uniformity and decrease the average temperature of photovoltaic (PV) module under the same thermal condition, which results in the improved electricity output performance of PV module. Under the solar irradiance and ambient temperature for a typical daytime, the average electrical, thermal and total energy efficiencies of the proposed system are 11.39%, 64.72% and 76.11%, respectively. Our work should be of guidance for the design of LCPV/T system with high efficiency, long-life and low cost.

Performance comparative study of a concentrating photovoltaic/thermal phase change system with different heatsinks

• Performance of concentrating PV/T-PCM system with different heatsinks was compared. • Non-uniformity of PV module temperature dropped by 47%∼82% when PCM melted. • Primary energy-saving efficiency of S-type system was 8% higher than H-type. • Concentrating PV/T-PCM owned superior performance than PV-CPC and PT-CPC system. In this study, a compound parabolic concentrating photovoltaic/thermal phase change system with different heatsinks (S-type and H-type) are constructed in an open-air environment to experimentally analyze the influence on photothermal, photovoltaic and heat-electricity cogeneration performance. The non-uniform irradiance distribution at different moments is simulated with the Monte Carlo rays tracing method, and it is demonstrated to be the main cause of non-uniform temperature distribution on photovoltaic module surface. The H-type heatsink system integrating phase change material (PCM) owns better temperature regulation performance, as its photovoltaic modules temperature and non-uniformity factor are about 0.8 ℃ and 0.05 lower than those of S-type respectively when PCM begins to melt. The instantaneous electrical and thermal efficiency with H-type heatsink are 0.6% higher and 10.0% lower than those with S-type, respectively. Considering that the pump power consumption of S-type heatsink is over 3 times of H-type, the instantaneous priamry energy-saving efficiency of S-type system is 8.0% higher. Simultaneously, the maximum primary energy-saving efficiency of concentrating photovoltaic/thermal phase change system with H-type/S-type heatsink is about 7.9%/14.6% and 10.7%/17.4% higher than that of concentrating photovoltaic and solar collector system respectively, showing great potential of photovoltaic/thermal phase change system in heat-electricity cogeneration performance especially utilizing S-type heatsink. Results present advantages of the system utilizing S-type heatsink and help promote the application of heatsinks in photovoltaic/thermal phase change system.

Accurate thermal prediction model for building-integrated photovoltaics systems using guided artificial intelligence algorithms

Progress in development of building-integrated photovoltaic systems is still hindered by the complexity of the physics and materials properties of the photovoltaic (PV) modules and its effect on the thermal behavior of the building. This affects not only the energy generation, as its active function and linked to economic feasibility, but also the thermal insulation of the building as part of the structure’s skin. Traditional modeling methods currently presents limitations, including the fact that they do not account for material thermal inertia and that the proposed semi-empirical coefficients do not define all types of technologies, mounting configuration, or climatic conditions. This article presents an artificial intelligence-based approach for predicting the temperature of a poly-crystalline silicon PV module based on local outdoor weather conditions (ambient temperature, solar irradiation, relative outdoor humidity and wind speed) and indoor comfort parameters (indoor temperature and indoor relative humidity) as inputs. A combination of two algorithms (Grammatical Evolution and Differential Evolution) guides to the creation of a customized expression based on the Sandia model. Different data-sets for a fully integrated PV system were tested to demonstrate its performance on three different types of days: sunny, cloudy and diffuse, showing relative errors of less than 4% in all cases and including night time. In comparison to Sandia model, this method reduces the error by up to 11% in conditions of variability of sky over short time intervals (cloudy days).

A novel procedure for identifying the parameters of the single-diode model and the operating conditions of a photovoltaic module from measured current–voltage curves

Photovoltaic (PV) module measured current–voltage curves together with the mathematical single-diode model are potential tools for PV system condition monitoring. Changes in model parameters can reveal module degradation and aging. However, all the parameter values change with varying operating irradiance and temperature, so they should also be identified. Unfortunately, useful operating condition measurements are rarely available in PV power plants. Thus, it is necessary to identify both operating conditions and model parameters directly from measured current–voltage curves. Only one such method has been reported in literature, however, using approximate explicit equations. The present work proposes a novel fitting procedure that identifies both single-diode model parameters and PV module temperature and irradiance utilizing an iterative method instead of approximate equations, which guarantees accurate results. The procedure enables degradation and aging analyses using only the internal electrical current–voltage curve measurements of the inverter. The results showed that the identified irradiance and temperature accurately reproduced the measured ones in all outdoor conditions. The stable identification of other single-diode model parameters, of which series resistance is especially suitable for detecting aging, confirmed the functionality of the procedure for condition monitoring.

Sensitivity of accuracy of various standard test condition correction procedures to the errors in temperature coefficients of c‐Si PV modules

AbstractThe Standard Test Condition (STC) correction procedures are algorithms used for transforming the Photovoltaic (PV) module current‐voltage (I‐V) data measured at arbitrary conditions back to STC. The PV module Temperature Coefficients are used as inputs by various STC correction procedures and can significantly influence their accuracy. This paper presents the sensitivity analysis of accuracy of six STC correction procedures (IEC 60891‐Procedure 1, Procedure 2, Modified IEC 60891‐Procedure 1, IEC 60891‐Procedure 4 (Voltage Dependent Temperature Coefficient (VDTC) Procedure), Anderson Procedure, and Standard Irradiance and Desired Temperature Procedure) to the errors in the temperature coefficients of Pmax, Voc, and Isc. Experimentally measured as well as simulated I‐V curves of six multi c‐Si PV modules were used in this study. IEC 60891‐Procedure 4 (Voltage Dependent Temperature Coefficient) that uses a Voltage Dependent Temperature Coefficient which can be calculated using a single measured I‐V curve was found to be most robust against errors in the temperature coefficients.

Design and experimental evaluation of a PV /T system cooled by advanced methods

Photovoltaic thermal (PV/T) systems combine a hybrid photovoltaic (PV) module and a flat-plate solar thermal collector. The hybrid design allows for simultaneou increase in thermal energy while providing cooling for the PV module. In doing so, the PV module temperature drops, and therefore the electrical efficiency increases. Another benefit of PV/T collectors is that they allow for the usage of thermal, and PV module in the same area and so that saved space for the consumer. This study presents a numerical (CFD) design and experimental evaluation of a PV/T system cooled by nano-PCM and nanofluid. The selected nanomaterial and PCM were nano-silicon carbide (SiC) and paraffin, respectively. Nano-silicon carbide particles were employed with the paraffin to ameliorate its thermal conductivity. The study examined various aspects of the system such as the SiC particles' optimal mass fraction suspended in both water (base fluid) and paraffin, the optimum mass flow rate of nanofluid, voltage and current of the PV module, thermal energy of solar thermal collector, and the combined PV/T efficiency. The numerical and practical results were very close, which proves the validity of the hypotheses used in building the program. The significance of this study is demonstrated by the result as this design led to maximum thermal and electrical efficiencies of 72% and 13.7%, respectively. The proposed PV/T system introduced better stability of the generated power and thermal efficiency at peak time than the other two studied systems.