CFD Analysis and Electrical Efficiency Improvement of a Hybrid PV/T Panel Cooled by Forced Air Circulation

Renewable energy sources are becoming more and more popular, regarding the pollution and nonsustainability of common energy sources. The study mainly focused on the improvement of the PV collector performance by using ANSYS fluent. The design of the fin will change according to the previous study. In the current study, we will increase the thermal contact area of the fin by changing the design of the fin. The change in the design of the fin will increase the total heat transfer and efficiency of the system. It concluded that with betterdesigned fin arrangements, the required fan speed could be lowered for any number of fins or similar results could be obtained with fewer fins. On the other hand, since the power required by the PV-powered fan will also decrease with fewer fins and at lower air velocities, the total efficiency obtained from the PV system will also increase.


INTRODUCTION
Renewable energy sources are becoming more and more popular, regarding the pollution and non-sustainability of common energy sources. With increasing human population, a question arises, what is going to be the next reliable energy source after the disappearance of fossil fuels? One of most abundant resources is solar energy, which manifests itself directly, as solar irradiance, or indirectly as wind energy and biomass energy. When it comes to the efficiency of energy transformation, a couple of things need to be distinguished. There are two distinct types of energy that can be produced: electrical energy and thermal energy. Electrical energy, mostly because of its ability to be easily transferred to work, is more valuable than thermal energy. The most efficient way to obtain electrical energy is from direct solar irradiance via photovoltaic cells (PV cell). Although the overall efficiency of PV cells ranges from about 5 % -20 %, it is still higher than the total indirect efficiency when it comes to wind and biomass efficiency. However, it has been shown that the overall efficiency of photovoltaic cells drops drastically with an increase in temperature. The rate of decrease ranges from 0.25 % to 0.5 % per degree Celsius, depending on the cell material used. Especially for concentrated PV cells, which use concentrated sunlight to produce larger amounts of power, and reduce the cost of generally expensive PV equipment, it has been observed that high temperatures greatly decrease the working life of the whole PV system. Cooling mechanisms have already been proposed [1][2][3][4] and the development of cooling techniques continues [5].
II. LITERATURE REVIEW Pushpendu Dwivedi et al. [1] in this paper presented are the efficiency of solar systems, in particular photovoltaic panels, is generally low. The output of the P.V. module is adversely affected by their surface rise in temperature. This increase is associated with the absorbed sunlight that is converted into heat, resulting in reduced power output, energy efficiency, performance and life of the panel. The use of cooling techniques can offer a potential solution to avoid excessive heating of P.V. panels and to reduce cell temperature. MuhammetKaan et al. [2] Demand for electricity generation from solar energy, which is a clean and renewable resource, is increasing day by day. It is desirable that the panel surface temperature is not excessively hot while generating electricity with PVT panels. High temperature causes thermal degradation and panel electric efficiency decrease. A. N. Özakın et al. [3] The phenomenon of photovoltaic systems is based on the principals of semiconductor physics and they operate with a semiconductor element, such as silicon.
Swapnil Dubey et al. [4] in this paper presented are the Solar cell performance decreases with increasing temperature, fundamentally owing to increased internal carrier recombination rates, caused by increased carrier concentrations. The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of a photovoltaic (PV) module depend linearly on the operating temperature. Mansour NasiriKhalaji et al. [5] Demand for electricity generation from solar energy, which is a clean and renewable resource, is increasing day by day. It is desirable that the panel surface temperature is not excessively hot while generating electricity with PVT panels. High temperature causes thermal degradation and panel electric efficiency decrease. Ziyad S Haidar et al. [6] this paper presents the results of an experimental study on the effect of cooling of solar photovoltaic (PV) panels by evaporative cooling. The evaporation latent heat was utilized to absorb the generated heat from the body of a PV module to reduce its temperature.
III. OBJECTIVE • The effect of fins installed at the rear of a photovoltaic panel can be studied by using two types of fin to compute the efficiency and study it's effects on the performance of photovoltaic cell, in addition to that evaluate the efficiency for both types under study. • Fin diameter, fin length, fin spacing and air velocity at the rear duct is taken into account in this investigation about the photovoltaic panel. • The study mainly focused on the improvement of the PV collector performance by using ANSYS fluent.
• The design of the fin will change according to the previous study. In the current study we will increase the thermal contact area of the fin by changing the design of the fin. Due to the change in the design of the fin, it will increase the total heat transfer and efficiency of the system. IV. METHODOLOGY In this study the mathematical model of the PVT collector was designed by catiaV5.and CFD analysis preformed on ANSYS fluent. ANSYS software was used for calculating the performance of the PVT Collector.  Step 1: Collecting information and data related to PV Collector Step 2: A fully parametric model of the PV collector for 3 cases.
Step 3: Model obtained in Step 2 is analyzed using ANSYS 18.2.
Step4: Finally, we compare the results obtained from ANSYS.

F. The k-epsilon Model
• One of the most prominent turbulence models, the k-epsilon model, has been implemented in most general purpose CFD codes and is considered the industry standard model. It has proven to be stable and numerically robust and has a well-established regime of predictive capability. For general purpose simulations, the k-epsilon model offers a good compromise in terms of accuracy and robustness. • Within CFD, the k-epsilon turbulence model uses the scalable wall-function approach to improve robustness and accuracy when the near-wall mesh is very fine. The scalable wall functions enable solutions on arbitrarily fine near-wall grids, which is a significant improvement over standard wall functions. • While standard two-equation models, such as the k-epsilon model, provide good predictions for many flows of engineering interest, there are applications for which these models may not be suitable. Among these are: • Flows with boundary layer separation.
• Flows with sudden changes in the mean strain rate.
• Flows in rotating fluids.
• Flows over curved surfaces.
• A Reynolds stress model may be more appropriate for flows with sudden changes in strain rate or rotating flows, while the SST model may be more appropriate for separated flows. The exact k-ε equations contain many unknown and unmeasurable terms. For a much more practical approach, the standard k-ε turbulence model (Launder and Spalding, 1974 [3]) is used which is based on our best understanding of the relevant processes, thus minimizing unknowns and presenting a set of equations which can be applied to a large number of turbulent applications. For turbulent kinetic energy-k.
Where µi represented velocity component in corresponding direction Eij represents component of rate of deeformation µt represented eddy viscosity µt = ρCµ 2 ∈ Case-1:-simple fin In case first base model was created by using Catia software after modeling the cad model import into ansys.in first case the simple fin model was used for the validations study. Figure 6 shows the simple fin model with whole model.     Meshing is an integral part of the engineering simulation process where complex geometries are divided into simple elements that can be used as discrete local approximations of the larger domain. The mesh influences the accuracy, convergence and speed of the simulation. Furthermore, since meshing typically consumes a significant portion of the time it takes to get simulation results, the better and more automated the meshing tools, the faster and more accurate the solution.
Ansys provides general purpose, high-performance, automated, intelligent meshing software which produces the most appropriate mesh for accurate, efficient multiphysics solutionsfrom easy, automatic meshing to highly crafted mesh. Methods available cover the meshing spectrum of high-order to linear elements and fast tetrahedral and polyhedral to high-quality hexahedral and Mosaic. Smart defaults are built into the software to make meshing a painless and intuitive task delivering the required resolution to capture solution gradients properly for dependable results. Case-1: In case-1 total number of elements 4944832 and total number of nodes 933507.the elements and nodes are shown in fig4.12.     Specific heat(j/kg-k) 381 Thermal conductivity(w/m-k) 387.6

.5 Boundary Condition
A fan with 10W of power has been employed to feed more air through the control volume in order to create forced convection, and ambient air, used as the working fluid, was sucked through the air duct of the test setup, as shown in  Table 4:-boundary conditions for CFD analysis [1] Case-1 Result Velocity contours: -This simulation was run using the k-ε turbulence model. The purpose of running this simulation was to determine the role that a turbulence model played in the results. The maximum velocity 5.04m/s in first case. The blue color shows minimum velocity area. And the yellow color show maximum velocity area.                       V. RESULTS Result shows, a cooling of up to 60-65 degrees at the surface temperature of 120 degrees has been achieved, so the decrease in the electrical current is prevented to a great extent and the efficiency could be maintained. Consequent turbulent air flows occurring within the control volume, especially in the vicinity of the fins, contributes to heat removal from the panel; therefore, with the CASE-2 arrangement, the highest thermal efficiency was achieved 81% as expected.
Outl VI. CONCLUSION • The efficiency of the PV panel without active cooling decreases in relation to increasing surface temperature when the panel is not cooled, the forced convection heat transfer zone is formed in the control volume in the back of the PV panel. • As a result, a cooling of up to 60-65 degrees at the surface temperature of 120 degrees has been achieved, so the decrease in the electrical current is prevented to a great extent and the efficiency could be maintained. • Consequent turbulent air flows occurring within the control volume, especially in the vicinity of the fins, contributes to heat removal from the panel; therefore, with the CASE-2 arrangement, the highest thermal efficiency was achieved 81% as expected. • The heat transfer rate in case-2 maximum and case-1 is minimum.
• The perforated fin increase the overall efficiency of the system also increase the heat transfer rate inside the PV collector. • Similar efficiency gains can be achieved by using fewer fin elements and by creating the correct turbulence model compared to the cost of the cooling unit. In addition to the heat transfer surface area and air velocity, it is seen that the fin arrangement is an important parameter in the heat transfer rate. • It can be concluded that with better designed fin arrangements, the required fan speed could be lowered for any number of fins or similar results could be obtained with fewer fins. On the other hand, since the power required by Comparative Pressure Graph pressrure the PV-powered fan will also decrease with fewer fins and at lower air velocities, the total efficiency obtained from the PV system will also increase.
VII. FUTURE SCOPE • The total efficiency of the PV collector dependent of the thermal contact of area of the fin.so the contact area of the fin increases the total efficiency of the PV collector increases. • And the performance of the PV collector improved by changing the design of the fin. The change in fin will also improve the performance and efficiency of the PV collector.