18LITERATURE REVIEW

18LITERATURE REVIEW

Literature Review

Table of Contents

Table of Figures

Figure 1: Solar water Pumping system 5

Figure 2: Equivalent PV Cell Circuit 6

Figure 3: Photovoltaic Fed Boost SPWM Inverter 7

Figure 4: Block Diagram of the Proposed System 8

Figure 5: Schematic diagram of standalone SPV based SRM Drive System for Pumping Water 10

Study 13[5]Figure 6: A PV Pumping Scheme Suggested in

14[6]Figure 7: Schematic of the LDS Proposed by

Figure 8: Optimization procedure 15

Figure 9: Schematic of the Hydraulic RAM Pump 18

Figure 10: Overall efficiency of Conventional PV Panel and of Combined System 19

20[9]Figure 11: Set Up of the System proposed by

Figure 12: Variation of Module Temperature during the Day 21

Figure 13: Variation of Module Efficiency during the Day 22

Solar Powered Water Pump – Literature review

1.0 Solar Water Pumping System

Photovoltaic array according to [ HYPERLINK l «KBR13» 1 ] is more and more utilised in the water pumping system. In their study, 1] created a boost converter that steps up the photovoltaic array’s voltage to a value that can properly run a single-phase induction motor. Basically, the DC is converted into the AC by the inverter and is controlled by sinusoidal pulse width modulation (SPWM) method. The authors utilised the LC-filter to eliminate the harmonics so as to obtain pure sine wave that cab be utilised directly to drive a pump system as well as single-phase induction motor. The experimental analysis conducted by [ HYPERLINK l «KBR13» 1 ] offers a design of solar water pumping system that is powered by the PV panels and coupled with full bridge SPWM inverter, centrifugal pump, LC filter, induction motor and DC to DC Boost converter. The authors utilised a proportional–integral–derivative (PID) controller so as to be able to control the voltage. To implement the model, matrix laboratory (MATLAB)/Simulink was used together with the SPWM controlled inverter. Globally, Photovoltaic is utilised in scores of applications in remote areas as well as islands as the source of power for water pumping. Basically, photovoltaic water pumping systems normally include inverter, controller, PV array, water storage tank, pump as well as motor. The PV systems for pumping water are predominantly appropriate for supplying water in remote areas, especially those with no electrical power. Solar powered water pumps are advantageous because of reliability, ease of installation and low maintenance. Additionally, water tanks may be utilised rather than batteries in PV pumping systems. The figure below block diagram of Solar powered water pump:

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Figure 1, they experienced some significant challenges while optimising the system in order to suit the PV panel power characteristic as well as the application’s hydraulic requirements. Therefore, they devised an iterative process that combined the analytic expressions and the finite element analysis so that comparisons could be made between various electrical as well as geometrical configurations of the linear actuator. A close comparison was realised by the model predictions with results measured from the current existing water pump [ HYPERLINK l «NSW12» 5 ]. The authors used the electromagnetic actuator that acted on the piston so that water could be lifted up the rising main (see Figure 6). The piston is pushed up by the actuator on the driving stroke; therefore, water is ejected into the rising main from the piston chamber by means of the outlet valve. Towards the end of the stroke, the outlet valve closes since the piston starts to fall; thus, water is and drawn through a piston cavity using the inlet valve and then goes into the piston chamber5].

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Figure 2: A PV Pumping Scheme Suggested in [ HYPERLINK l «NSW12» 5 ] Study

Similarly, 6] studied the feasibility of utilising a solar-powered liquid desiccant system (LDS) so as to meet the needs of fresh water and building cooling in Beirut. In this case, they sourced their heat from the parabolic solar concentrators so as to generate the liquid desiccant. They developed an integrated model of solar-powered LDS that uses calcium chloride for humidification/dehumidification of air. Additionally, [ HYPERLINK l «NAu11» 6 ]
formulated an optimization problem for operation as well as selection of the LDS in order for the system to meet air conditioning load and fresh water requirement at a reduced energy cost. This is for an archetypal residential space in the coastal climate of Lebanon so as to generate fresh water for drinking and meeting the need for air conditioning at a reduced energy cost. The solar-powered LDS as well as a condensing unit is depicted in figure 7. The proposed system consists of a desiccant cooler, parabolic solar collectors, regenerator, dehumidifier and heat exchangers. The dehumidifier input variables includes the ratio of the humidity, the air flow rate and the desiccant calcium chloride solution flow rate and ambient air temperature. In this case, the desiccant absorbs the entering humid air moisture while the air that leaves the desiccant bed is utilised for air conditioning the household. Furthermore, the liquid desiccant that leaves the dehumidifier goes into the heat exchanger where it is heated and before it enters the regenerator it is heated by another exchanger positioned in the water storage tank that is indirectly heated by solar power conveyed from the closed fluid circuit of the concentrators. The low concentrated liquid desiccant that has been heated enters the regenerator wherein the desiccant’s accumulated water is absorbed by the ambient air. The humidified air at the exit of the regenerator is directed towards a cooling coil plunged in a cold water where distilled water is collected after the condensation takes place. After cooling down, the desiccant leaving the regenerator enters dehumidifier again after cooling down leading to the closure of the loop.

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Figure SEQ Figure * ARABIC 7: Schematic of the LDS Proposed by CITATION NAu11 l 1033 [ HYPERLINK l «NAu11» 6]

]. HYPERLINK l «NAu11» 6 CITATION NAu11 l 1033 [ had to calculate the peak load conditions of the space as well as identify the design values of the peak load for air flow rate, humidity ratio and air supply temperature. Imperatively, the maximum air flow rate of the dehumidifier must be equivalent to that of the design value. For this reason, they pursued an optimized design in order to minimise the overall cost of the system incremental capital as well as the cooling season operational cost over the life cycle of the system. Figure 8 shows a flow chart of the optimization procedure that was proposed by ] HYPERLINK l «NAu11» 6 CITATION NAu11 l 1033 [In order to design the LDS for the recognised water needs,

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Figure SEQ Figure * ARABIC 8: Optimization procedure CITATION NAu11 l 1033 [ HYPERLINK l «NAu11» 6]

The LDS cost optimization of the proposed solar-powered LDS needs the total cost to be reduced as defined by equation 6 below:

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IHST = Total cost for a certain heat sink temperature

Ii,HST = The initial cost of the capital related to the solar concentrators used

Iop,HST = The total cost of operation over the operational life of the equipment

n = Number of operation years

i = Interest rate

IE,HST = Hourly energy consumption by the both the pump for circulating liquid desiccant and two fans

According to CITATION NAu11 l 1033 [ HYPERLINK l «NAu11» 6], the optimal temperature of the regeneration for a certain heat sink temperature can be established after calculating the investment life cycle cost (LCC):

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The proposed system is without a doubt important because it produces water, saves energy, generates relaxed environment through renewable energy source and with no environmental damage given that water is extracted from the atmosphere.

4.0 Increasing Solar Panel Efficiency through Water Cooling

According to CITATION Mel141 l 1033 [ HYPERLINK l «Mel141» 7], the existing solar panels efficiency is generally low and it further goes down when the solar panels are heated up. The drop in the overall efficiency is approximately 0.38 per cent per degree Celsius, and given that in full sun during a warm day the solar panel can certainly reach higher temperatures of between 40C and 60C, then cooling is needed so as to significantly improve the efficiency. Presently, the majority of the solar panels depend on passive cooling because of air flow along bottom and top of the solar panels. However, passive cooling is less effective when the ambient temperature is higher while active cooling systems need energy to operate, and are suitable for large installations where their power consumption can easily be ignored. Using active cooling system on smaller installations normally lead to higher overheads that are larger as compared to the actual gains realised. For this reason, CITATION Mel141 l 1033 [ HYPERLINK l «Mel141» 7] propose a system that uses less energy to cool down and clean the solar panels. According to the authors, solar panel can be cooled down easily by making sure that there is enough water that runs over the panels, whereby water is sprinkled to the solar panel at the top and then recollected at the bottom. Basically, collecting water at the bottom facilitates the reuse of the water, but the water must be pumped to the top of the solar panel once more. Energy consumption in such a pumping mechanism can be reduced by using the water kinetic energy through the Hydraulic RAM pump. The schematic of the Hydraulic RAM Pump is shown in the figure 9. Even though this pumping mechanism guarantees free pumping, only approximately 20 per cent of the water reaches the higher tank while 80 per cent of the water going into the waste tank.

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Figure SEQ Figure * ARABIC 9: Schematic of the Hydraulic RAM Pump CITATION Mel141 l 1033 [ HYPERLINK l «Mel141» 7]

Because Hydraulic RAM pump results in large amount of waste water, CITATION Mel141 l 1033 [ HYPERLINK l «Mel141» 7] utilised a Tesla pump so that water could be pumped from the waste tank back to the bottom tank (see figure 9). Besides that, they designed a control system that protects the water that flows over the panel during the dry weather. Imperatively, the panel temperature is measured by the control system and then increases or reduces the frequency of water that runs over the panels depending on the solar panels’ temperature. Additionally, the system needs less power and generally improves the overall efficiency by almost 12 per cent.

PV systems efficiency as observed by CITATION Hos11 l 1033 [ HYPERLINK l «Hos11» 8] can be increased by cooling them they are operating. In in their study, the PV system was cooled by a thin film of water, wherein they observed that the electrical efficiency and the power of the system were higher as compared to the conventional systems. Additionally, given that the heat that the water film removes from the PV panel is not wasted, the combined system overall efficiency is higher as compared to the conventional systems. Photovoltaic module can be cooled by allowing a film of water to flow over the Photovoltaic module so as to reduce its temperature and normally results in improved electrical efficiency. When photovoltaic array is cooled by thin water that runs on top of the PV system, it results in improved electrical efficiency due to the reduced reflection loss and low array temperature. Figure 10 shows the overall efficiency of the conventional PV panel and that of the combined system. Eveidently, the combined system’s overall efficiency increases significantly as compared to that of the conventional system.

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Figure SEQ Figure * ARABIC 10: Overall efficiency of Conventional PV Panel and of Combined System CITATION Hos11 l 1033 [ HYPERLINK l «Hos11» 8]

5.0 Using Silicone Oil to Cool Solar panels

Reducing temperature according to CITATION Yip091 l 1033 [ HYPERLINK l «Yip091» 9] is one of the suitable ways of improving the solar module performance. A number of studies as cited by CITATION Yip091 l 1033 [ HYPERLINK l «Yip091» 9] have stressed that liquid properties play an important role in improving sunlight absorbance. In their study, CITATION Yip091 l 1033 [ HYPERLINK l «Yip091» 9]
used silicone oil as a coolant and the experiments were carried out in the outdoor conditions. The proposed system included a solar module that had a power capacity of 7Wp, and were enclosed by glass sheets in order that the liquid could be retained on the module surface. Figure 11 shows the system set up, whereby the silicone oil was spread over the surface of the PV module. The module’s fill factor (FF) was assumed to be unchanged at 0.7 considering that the maximum power that the PV module delivers changes when carrying out cooling operations.

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Figure SEQ Figure * ARABIC 11: Set Up of the System proposed by CITATION Yip091 l 1033 [ HYPERLINK l «Yip091» 9]

that could deliver maximum power, while cooling; therefore, at standard condition, the delivered maximum power by the solar panel is calculated as: ] HYPERLINK l «PGN12» 10[ CITATION PGN12 l 1033 A model was developed by

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Pmaxo = Maximum power

Voc =
Open circuit voltage

Isc = Short circuit current

According to [ HYPERLINK l «PGN12» 10 ] the photovoltaic cell is vulnerable to thermal degradation, and this is so when the temperature goes beyond a particular value. Because of the cooling, the operating temperatures of solar panel are reduced significantly as compared to the solar panels with no cooling. Figure 12 shows a comparative difference of various thicknesses, and the results exhibited an enormous reduction of between 8C and 20C when the thickness was changed. Silicone oil at 2mm, 3mm, 4mm, as well as 6mm led to a drop of temperature of 3.92, 24.34, 23.9 and 29.17 per cent in that order. 18LITERATURE REVIEW 11

Figure SEQ Figure * ARABIC 12: Variation of Module Temperature during the Day CITATION PGN12 l 1033 [ HYPERLINK l «PGN12» 10]

From their experiment, CITATION PGN12 l 1033 [ HYPERLINK l «PGN12» 10] established that the value of maximum rated efficiency only reached 2.98 per cent for a non-cooling solar panel during the normal working conditions and 3.5 per cent when cooling was used. As evidenced in figure 13, silicone oil at 2mm had a high efficiency as compared to other thicknesses. The 2mm thickness had an improved maximum efficiency of 23.30 per cent as compared 6mm thickness that had 13.03 per cent maximum efficiency.

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Figure SEQ Figure * ARABIC 13: Variation of Module Efficiency during the Day CITATION PGN12 l 1033 [ HYPERLINK l «PGN12» 10]

According to CITATION PGN12 l 1033 [ HYPERLINK l «PGN12» 10], 2mm and 3mm thickness are more inclined to increase efficiency, but there is a need for optimization. Furthermore, the experimental value as well as model value had an error of less than 5 per cent. When cooling was applied, the maximum power increased by 23.29 per cent; therefore, cooling using silicone oil was important because it reduces temperature to a particular limit, between 45C and 55 C. In consequence, the thermal degradation is avoided. The results from CITATION PGN12 l 1033 [ HYPERLINK l «PGN12» 10] suggested how solar modules performance can be improved by cooling using silicone oil. Evidently, they noted that the efficiency of the solar modules had increased by 23.30 per cent when silicone oil of 2mm thickness was used.

References

BIBLIOGRAPHY l 1033 x

K. B. Rohit, Prof. G. M. Karve, and Prof. Khatri, «Solar Water Pumping System,» International Journal of Emerging Technology and Advanced Engineering, vol. 3, no. 7, pp. 323- 337, 2013.

B. Kavitha, S. Karthikeyan, and B. Iswarya, «Design of solar PV water pumping system using BLDC drive using sensorless method,» The International Journal Of Engineering And Science, vol. 3, no. 3, pp. 41-46, 2014.

Bhim Singh, Anjanee Kumar Mishra, and Rajan Kumar, «Solar Powered Water Pumping System Employing Switched Reluctance Motor Drive,» in 2014 6th IEEE Power India International Conference (PIICON), New Delhi, 2014, pp. 1 — 6.

Kusumlata Agarwal, Prof. (Dr.) B. L. Mathur, and Prof. (Dr.) Avdhesh Sharma, «Maximum Power Transfer to Solar Powered Water Pumping System Using Differential Compound DC Motor,» in IEEE International Conference on Computer, Communication and Control, Jodhpur, India, 2015, pp. 1 — 5.

N.S. Wade and T.D. Short, «Optimization of a linear actuator for use in a solar powered water pump,» Solar Energy, vol. 86, pp. 867–876, 2012.

N. Audah, N. Ghaddar, and K. Ghali, «Optimized solar-powered liquid desiccant system to supply building fresh water and cooling needs,» Applied Energy, vol. 88, pp. 3726–3736, 2011.

Wim J.C. Melis, Sajib K. Mallick, and Phillip Relf, «Increasing Solar Panel Efficiency in a Sustainable Manner,» in IEEE International Energy Conference, Dubrovnik, Croatia, 2014, pp. 912-915.

R. Hosseini, N. Hosseini, and H. Khorasanizadeh, «An experimental study of combining a photovoltaic system with a heating system,» in World Renewable Energy Congress, Linkoping, Sweden, 2011, pp. 2993-3000.

Yiping Wang et al., «The performance of silicon solar cells operated in liquids,» Applied Energy, vol. 86, pp. 1037–1042, 2009.

P G Nikhil and M Premalatha, «Performance enhancement of solar module by cooling: An experimental investigation,» International Journal of Energy and Environment (IJEE), vol. 3, no. 1, pp. 73-82, 2012.