DESIGN AND FABRICATION OF A PASSIVE EVAPORATIVE COOLING SYSTEM FOR COOLING SOLAR PHOTO-VOLTAIC PANE

International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN(P): 2249–6890; ISSN(E): 2249–8001 Vol. 10, Issue 3, Jun 2020, 2707–2714 © TJPRC Pvt. Ltd.

DESIGN AND FABRICATION OF A PASSIVE EVAPORATIVE COOLING SYSTEM FOR COOLING SOLAR PHOTO-VOLTAIC PANEL COOLING USED IN DOMESTIC APPLICATIONS KARTHIKEYAN. S1*, R. RAJARAMAN2*, KHISHEN. R3 & GAGAN PRAKASH. K4 1*,3 ,4 2*

Department of Mechanical Engineering, Saveetha Engineering College, Thandalam, Tamilnadu, India

Department of Mechanical Engineering, Sri Venkateswara College of Engineering, Sriperumbudur, Tamilnadu, India

ABSTRACT The decrease in output power of solar photovoltaic modules as their temperature increases during the operation is a major concern for users. This project involves the reduction in the temperature of solar PV modules during its operation. A passive evaporative cooling technique is used to control the temperature rise of PV modules that occur due to solar irradiation. This method involves designing a heat exchanger entirely by the clay material and integrating the same with the PV module so that it tends to reduce the temperature of the solar panel by evaporating the thin film of water. Thus, using the clay material for the heat exchanger is effective, silent, and environmentally friendly.

Received: Jun 09, 2020; Accepted: Jun 29, 2020; Published: Jun 30, 2020; Paper Id.: IJMPERDJUN2020255

1. INTRODUCTION One of the most widespread technologies of renewable energy generation is the use of photovoltaic (PV) systems

Original Article

KEYWORDS: Evaporative Cooling, Photovoltaic Panel & Panel Efficiency

which convert sunlight into usable electrical energy. This type of renewable energy technology which is pollutantfree during operation diminishes global warming issues, lowers operational cost, and offers minimal maintenance and highest power density compared to the other renewable energy technologies and highlights the advantages of solar photovoltaic (PV) energy. Apart from the several advantages displayed by the PV technology, this conversion system does have some general problems, such as hail, dust, and surface operating temperature which can negatively affect the efficiency of the conversion system. Exogenous climatic parameters such as wind speed, ambient temperature, relative humidity, accumulated dust, and solar radiation are the most common natural factors which influence the surface temperature of a PV module. Every 1 °C rise in the surface temperature of the PV module causes a reduction in efficiency of 0.45%. Therefore, due to the temperature rise, not all of the solar energy absorbed by the photovoltaic cells is converted into electrical energy. To satisfy the law of conservation of energy, the remaining solar energy is converted into heat. The consequences of this wasted heat bring about a reduction in the overall conversion efficiency.

Efficiency improvements in solar energy conversion systems must be made for this renewable energy technology to be a viable solution. To make it a viable solution, there is a need to find different means of solving this temperature problem, which must increase the overall conversion efficiency.

HEAT TRANSFER MECHANISM Evaporative Cooling

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Evaporative cooling is a process that uses the effect of evaporation as a natural heat sink. Sensible heat from the air is absorbed to be used as latent heat necessary to evaporate water. The amount of sensible heat absorbed depends on the amount of water that can be evaporated by evaporative cooling.

Evaporative cooling can be direct or indirect; passive or hybrid. In Direct evaporative cooling, the water content of the cooled air increases because air is in contact with the evaporated water. In indirect evaporative cooling, evaporation occurs inside a heat exchanger and the water content of the cooled air remains unchanged. Since high evaporation rates might increase relative humidity and create discomfort, direct evaporative cooling can be applied only in places where the relative humidity is very low. Where evaporation occurs naturally it is called passive evaporation. Space can be cooled by passive evaporation where there are surfaces of still or flowing water, such as basins or fountains. Where evaporation has to be controlled through some mechanical device, the system is called a hybrid evaporative system.

TYPES OF EVAPORATIVE COOLING 1. Direct Evaporative Cooling Direct evaporative cooling is used to lower the temperature and increase the humidity of the air by using latent heat of evaporation, changing liquid water to water vapor. In this process, the energy in the air does not change. Warm dry air is changed to cool moist air. The heat of the outside air is used to evaporate water. The moist air has to be continually released to the outside or else the air becomes saturated and evaporation stops. Direct air evaporative cooling can be a very economical and achievable way to reduce the temperature. Spray humidifiers deliver moisture to an atmosphere using either high pressure or compressed air to ensure evaporation.

2.Indirect Evaporative Cooling Indirect evaporative cooling is a cooling process that uses direct evaporative cooling in addition to some type of heat exchanger to transfer the cool energy to the supply air. The cooled moist air from the direct evaporative cooling process never comes in direct contact with the conditioned supply air. The moist air stream is released outside or used to cool other external devices.

2. LAYOUT OF THE MODEL

Figure 1: 2D SIDE VIEW

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Design and Fabrication of a Passive Evaporative Cooling System for Cooling Solar Photo-Voltaic Panel Cooling used in Domestic Applications

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Figure 2: 3D Model of Experimental Set

Figure 3: Final Completed Setup Components Used: Solar Panel, Pot, Caspian Pipeline Consortium, Coupling, Pipe Nipple, Wood, Digital Thermocouple, and Multimeter.

3. FORMULAE AND AVAILABLE DATA • Heat absorbed in the panel = cooling required from the pot • Q panel (rad in J ) = Q pot(required cooling energy in J ) • Heat absorbed by the panel = heat flux rate × Area of the panel ×Solar panel operation time • Q ( in J ) = ( in J/sm² ) × A (in m² ) × t ( s ) → Q = q×A×t • Cooling required from the pot, Q pot(in J ) = m×Cp×( Tpanel – Tpot )

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• Density=Mass/Volume • Q( Energy )=Q×t (Unit: Joule) • Q(rad)=500W/m² for low temperature months.(November,December,January, Febraruary) • Q(rad)=1100W/m² for high temperature months.(March,April,May,June) • Q(rad)=800W/m² for moderate temperature months.(July,August,September,October)

4. WORKING PROCEDURE The components include a pot, solar panel, CPC pipe, etc. Initially, all components are arranged in their respective position. The upper clay pot acts as a reservoir that stores the water. Due to evaporative cooling, the water inside the pot becomes cold. The solar panel is placed at an angle of 13.13ᴼ towards south direction above the lower clay pot such that it attains the maximum radiation energy from the sun. Due to the solar radiation the surface of the solar panel rises which decreases the energy output. To overcome this, the cold water from the upper clay pot is allowed to flow on the upper surface of the solar panel which results in a temperature drop. Similar to this, the lower surface of the panel is cooled by direct evaporative cooling. This reduces the lower surface temperature. Finally, the process is repeated continuously in a cyclic manner for 6 hours a day.

5. EXPERIMENTAL PROCEDURE • ANALYSIS: Panel efficiency without any cooling system and dust removal system.

• ANALYSIS: Panel efficiency with cooling system.

• ANALYSIS: Panel efficiency with both cooling dust removal system • ANALYSIS: Efficiency comparison.

6. EXPERIMENTAL INVESTIGATION Table 1: Experimentally Observed Readings

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7. CALCULATION • Q=1100w/m2 (2352240 J)

Q=1100w/m2(2352240 Jo)

• For Q=m×Cp×(Tp-Tpot),

For Q= m×Cp×(Tp-Tpot),

• 2352240J=m×4186×(41-35.28)

2352240J=m×4186×(42.75-35.26)

• Volume=Mass/density

Volume = Mass/density

• Volume=98.23 litres

Volume= 75.02 litres

Panel area : 330×300=99000mm2 1. P= V×I without cooling 8.48×0.14=1.1872W 8.76×0.19=1.6644W 2. P=V×I with cooling 8.69×0.17=1.4773W 9.07×0.2=1.814W

8. RESULTS AND DICUSSIONS

Figure 4: Before Cooling vs After Cooling

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Figure 5: Overall Comparison From the graph it is clear that reduction in temperature of the solar panel increases the energy output.

At 9am, the average temperature of the panel without cooling is 41ᴼC for which the power yield is 1.1872W. On cooling the average temperature of the panel is 36.02ᴼC for which the power yield is 1.4773W. For this rise of efficiency is 24.4%.

Similarly the rises in efficiency of power yield for the operating hours are tabulated.

Table 2: Results for the Observed Reading

9. CONCLUSIONS An experimental investigation of the performance of the solar PV system integrated along with the passive cooling system is carried out. The experiment with the solar PV system and passive cooling system has been conducted during day time hours under outdoor conditions. It is well known that the PV panel efficiency decreases with an increase in temperature. If there is no cool water flow on the surface of the panel the stagnant air definitely will increase the panel temperature to as high as 60–70°C depending on the ambient conditions. Hence the circulation of water over the panel is essential to avoid

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the rise in temperature. However, it is understood from the discharge experiments that if the water is allowed to flow at a higher velocity through a duct the turbulence intensity inside the duct will cause the heating effect. It is concluded from the present experiment that better cooling could be achieved only through the cool water supply at a lower velocity.

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