Fabrication and Computational Analysis of a Building Integrated Photovoltaic Thermal Roofing Panel

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1 Fabrication and Computational Analysis of a Building Integrated Photovoltaic Thermal Roofing Panel Viswath Satheesh, Devanand C N Dept. of Mechanical Engineering, Model Engineering College, Thrikkakkara viswathsatheesh@gmail.com, devanand@gmail.com Abstract- A building integrated photovoltaic-thermal (BIPVT) multifunctional roofing panel has been developed in this study to harvest solar energy in the form of PV electricity as well as heat energy through the collection of warm water. As a key component of the multifunctional building envelope, conventional solar panel is embedded with copper tubes has been fabricated. The heat in the PV cells can be easily transferred into the conductive side of the panel and then collected by the water flow in the embedded copper tubes. Therefore, the operational temperature of the PV cells can be significantly lowered down, which recovers the PV efficiency in hot weather. In this way, the developed BIPVT panel is able to efficiently harvest solar energy in the form of both PV electricity and heat. The performance of a prototype BIPVT panel has been evaluated in terms of its thermal efficiency via warm water collection and PV efficiency via the output electricity. The experimental test results demonstrate that significant energy conversion efficiency improvement can be achieved for both electricity generation and heat collection by the presented BIPVT roofing system. Overall, the performance indicates a very promising prospective of the new BIPVT multifunctional roofing panel. Keywords-Building integrated photovoltaic/thermal (BIPVT) system, Building envelope,roofing panel,solar energy,energy conversion I. INTRODUCTION To reduce building energy consumption and greenhouse gas emissions, new technologies of efficient and renewable energy supply systems are in high demand. Solar energy is the most abundant renewable clean energy source, and modern technology can harness solar energy for a variety of uses, including generating electricity, providing light for a comfortable interior environment, and heating water for residential, commercial, or industrial use. As solar energy technologies have advanced in recent years, integrated technologies for harvesting solar energy into building sectors, such as building-integrated photovoltaic (BIPV) systems, building-integrated solar thermal (BIST) systems, or building-integrated photovoltaic/thermal (BIPVT) systems, have evolved as viable technologies to improve building energy performance and to reduce environmental effects.those integrated systems replace parts of the conventional building materials and the components in the climate envelope of buildings, such as facades and roofs, and simultaneously serve as both a building envelope material and power generator. Photovoltaic is array of cells containing a solar photovoltaic material that converts solar radiation into direct current electricity. Building integrated photovoltaic (BIPV) is the PV system that being applied within building component. Typically, an array is incorporated onto the roof or walls of a building. Arrays can also be retrofitted into existing buildings; in this case they are usually fitted on top of the existing roof structure. Solar energy is the most abundant permanent source of energy in the world and has become an important environmental compatible source of renewable energy. Solar energy is radiant energy and heat from the Sun is harnessed using a range of ever evolving technologies such as building integrated photovoltaic, solar heating, solar architecture, solar thermal energy and artificial photosynthesis. Photovoltaic power generation employs solar PV module composed of a number of cells containing photovoltaic material. Materials presently used for solar PV cell include crystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide.due to the growing demand for renewable energy sources, the manufacturing of solar PV cells and photovoltaic module has advanced considerably in recent years. Building integrated photovoltaics are solar PV materials that replace conventional building materials in parts of the building envelopes, such as the rooftops or walls. Furthermore, BIPV are considered 292

2 as a functional part of the building structure, or they are integrated into the building s design. The BIPV system serves as building envelope material and power generator simultaneously. BIPVs have a great advantage compared to non-integrated PV systems because there is neither need for allocation of land nor facilitation of the photovoltaic system. Illustrating its importance, BIPVs are considered as one of four key factors essential for future success of photovoltaic s. The on-site electricity producing BIPV modules can reduce the total building material costs and achieve compelling savings in terms of the mounting costs, especially since BIPV System do not require additional assembly components such as brackets and rails.. II. COMPUTATIONAL ANALYSIS The guideline for the CFD simulation in the urban environment is followed here to create the computational domain and mesh. The domain dimensions are set with reference to the panel height, H. The domain has 5H of upstream length, 15H of downstream length, 5H between the top edge of the solar panel and the top of the domain and 9.9H clearance between the side edge of the panel and the side wall of the domain. Inlet velocity and solar irradiation intensity are employed as the inlet boundary conditions at the domain entrance. At the domain exit, a fixed uniform zero gauge pressure boundary is used. Side walls of the domain are treated as slip walls. Fixed values of velocity and turbulence properties at the top of the inlet boundary are employed throughout the top surface of the domain. Bottom of the domain is modeled as rough wall with no slip boundary condition. The panel surfaces are treated as no slip smooth walls. Boundary conditions Inlet velocity= m/s Heat transfer coefficient=632.2w/m2k 293

3 III. IV. FABRICATION In field application, a transparent protective waterproofing layer will be further mounted on the BIPVT panel to protect the power generating elements and underlying building materials from external environmental distress such as moisture migration, surface wear and impact from dust, wind and storm. A schematic illustration of the developed BIPVT panel, where the FGM layer gradually transits material phases from a well-conductive side (aluminum dominated) attached to a photovoltaic (PV) solar cell, to a highly insulated side (polymer materials) bonded to a structural substrate. The water tubes are embedded in the top part of the FGM layer, where the high aluminum concentration creates a high thermal conductivity so that heat can be immediately transferred to the water tubes from all directions, yet be insulated by the bottom part of FGM layer and the thermal insulation plywood. The substrate provides support for mechanical loading and functions as thermal insulation for the building envelope. The multilayered solar panel is designed in such a way that layers with potentially shorter life expectancies can be easily replaced or removed from the design based on the sustainability measurement criteria, which can be applicable toother sustainable building materials and systems for building construction. 294

4 V. EXPERIMENTAL ANALYSIS Though the Hottel-Whillier model is able to provide better estimation of the long-term performance of a PVT collector in a sense of statistical average, it involves many operating parameters of a PVT product, such as the emittance of the panel, wind heat transfer coefficient, sky temperature, convection heat transfer coefficients, and natural convection loss. Those parameters need to be statistically determined from massive field tests. At current stage, they are not available for this prototype BIPVT roofing panel. Thus the first method is applied in this study to calculate the thermal efficiency of the present BIPVT roofing panel. According to the definition of instantaneous thermal efficiency, the useful collected heat Qwater gain by the BIPVT panel at different water flowing rates can be calculated by Equation where m(water) is the mass flow rate of the water flowing in the water pipe and C(water) is the specific heat capacity of water. 295

5 The thermal efficiency of the BIPVT panel is a ratio of the collected thermal energy to the irradiance energy absorbed by the panel, which can be expressed as where EIN =IR * A is the absorbed irradiance by the BIPVT panel, which is the product of the irradiance intensity (IR) and the total area of the BIPVT panel and the frame. In obtaining the current voltage (I V) curve of the solar panel, by adjusting the resistance, the current in the circuit was measured by a digital multimeter. The current reaches its maximum (ISC) in a short-circuit when the resistance is zero, while the voltage reaches its maximum (VOC) in an open-circuit where the resistance can be considered as infinite through which no current flows. By setting different values of resistance in between, the I V curve can be traced and the panel can be characterized at different irradiance intensities with different water flowing rates. The electrical power produced by the cell can be easily determined along the I V sweep by the equation P = IV. The corresponding I V and power voltage (P V) curves for the BIPVT panel at an irradiance of 845 W/m2 are shown From the I V and P V curves, some basic parameters such as fill factor (FF) and electricity conversion efficiency can be determined for the BIPVT under different irradiances with different water flow rates by following some fundamental studies in the literature. The Fill Factor (FF) is essentially an index of the BIPVT panel quality. It is calculated by comparing the maximum output electricity (EMAX) to the theoretically calculated value (ET) that would be generated at both the open circuit voltage and short circuit current together. A larger fill factor is desirable, which corresponds to an I V sweep that is more square-like 296

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7 VI. CONCLUSION Developed to efficiently harvest solar energy in the form of PV electricity as well as heat energy through the collection of warm water. The proposed BIPVT panel can be integrated into building skin with relevant system components such as water circulation, flow control, and heat storage. Provides a viable solution to significantly increase the overall energy utilization. Overall, the test results demonstrate that significant energy conversion efficiency improvement can be achieved for both electricity generation and heat collection by the presented BIPVT roofing panel. From the comparisons of the present BIPVT with other relevant technologies, it was found that the BIPVT panel in this study is able to harvest solar irradiance more efficiently in form of electricity and heat than most PVT or BIPVT technologies currently available in the literature. Because of the ability to control temperatures through the water flow, the PV modules can work at lower temperatures in the summer time, leading to a higher efficiency for PV utilization. Furthermore, due to the temperature control on the roof, better thermal comfort in the building can be achieved and therefore the energy demand for cooling can be reduced in the summer time. Moreover, the warm water flow can be applied to remove frost or ice on the roof in winter time, thus further restore and enhance solar energy utilization. In addition, the present BIPVT provides customers with much flexibility to adjust the water flowing rate to meet their specific requirements. ACKNOWLEDGMENT 298

8 All glory and honours to God, the Almighty. Without his grace this project work wouldn t have seen the light of success. Motivation is the driving source behind every successful venture. With regard to the completion of this project, I wish to acknowledge the following people who the source of motivation behind it. I have great pleasure in expressing my deep sense of gratitude and indebtedness to my project guide,devanand, Dr. Shouri P.V, HOD, Department of Mechanical Engineering, Govt. Model Engineering College Ernakulam, for his invaluable guidance through every stage of my work and timely advice. I express my sincere thanks to all other staff of Department of Mechanical Engineering, Govt. Model Engineering College Ernakulam, for their valuable suggestion and cooperation. REFERENCES [1] Fangliang Chen and Huiming Yin, Fabrication and laboratory-based performance testing of a building-integrated photovoltaic-thermal roofing panel, Newyork,2016. [2] Ahmad Ridzwan Othman and Ahmad Tirmizi Rushdi, Potential of Building Integrated Photovoltaic Application on Roof Top of Residential Development in Shah Alam, malaysia [3] Tingting Yang n and AndreasK.Athienitis,A review of research and developments of building-integrated photovoltaic/thermal(bipv/t)systems, Canada, [4] D. Brandl and T. Mach, CFD assessment of a solar honeycomb (SHC) facade element with integrated PVcells, Austria, [5] Aste and Rajendra Singh Adhikari, Solar integrated roof: Electrical and thermal production for a building renovation, italy,