Experimental Study of Solar Energy Based Water Puri er (SEBWP) of Single Slope Type by Incorporating N Similar Evacuated Tubular Collectors (ETCs) having Series Connection

12 This research paper deals with the experimental investigation of solar energy based water 13 purifier (SEBWP) of single slope type by incorporating N similar evacuated tubular collectors 14 (ETCs) having series connection. Experimental investigation has been done for a year from 15 August 2018 to July 2019. MATLAB has been used for evaluating performance parameters of 16 the system followed by the validation of these results with their experimental values. A fair 17 agreement has been found between theoretical and experimental values. Values of correlation 18 coefficients for condensing glass temperature, water temperature and water yield have been 19 found to be 0.9932, 0.9928 and 0.9951 respectively. Further, energy metrics, productivity, cost 20 of producing one kg of fresh water, exergoeconomic and enviroeconomic parameters have been 21 evaluated. Values of energy payback time, per kg cost of producing fresh water and exergy loss 22 per unit Rs. have been evaluated to be 1.72 years, Rs. 0.95/kg and 0.128 kWh/Rs. respectively. 23

1. Introduction: 26 The design, analysis, installation and experimental study of solar energy based water purifier 27 (SEBWP) of single slope type by incorporating N alike evacuated tubular collectors (ETCs) is a 28 pressing need at a time when the world is grappling with the current problem of fresh water 29 scarcity. The purification of dirty water using solar energy is one of the best solutions for 30 providing the fresh water as it is environment friendly and does not need much technical 31 knowledge for its maintenance. The experimental study of solar energy based single slope water 32 purifier (SEBWP) by incorporating flat plate collector was presented by Rai and Tiwari (1983). 33 Since then, a lot of modifications in the design of SEBWP operating in active mode have been 34 reported. Tripathi and Tiwari (2006) have studied SEBWP in active mode for different water 35 depth using solar fraction and concluded that the internal convective heat transfer coefficient 36 decreases with rising water depth due to increases in the sensible heat content of water mass. 37 Dimri et al. (2008) investigated performance of SEBWP in active mode by incorporating 38 material of cover and it was concluded that the production of fresh water (yield) of reported 39 system was higher with copper due to higher thermal conductivity of copper as compared to 40 glass and plastic. 41 The main drawback of SEBWP in active mode reported by Rai and Tiwari (1983), Tripathi and 42 Tiwari (2006), Dimri et al. (2008) was that SEBWP systems were not self sustainable as the 43 pump was running using conventional source of energy i.e. electrical energy from grid. These 44 systems could be made self sustainable by integrating photovoltaic panel with collector. Based (2013) investigated SEBWP of single slope type integrated with evacuated tubes and it was 69 concluded that the yield of SEBWP was increased by 129% after integrating with evacuated 70 tubes due to additional heat addition by evacuated tubes to basin of SEBWP. 71 In another study, Hamadou and Abdellatif (2014)  concluded that the percentage increase in fresh water production decrease as the collector to 76 basin area ratio is increased because heated water is further heated. Taghvaei et al. (2015) 77 investigated SEBWP in active mode experimentally for five days continuously and concluded 78 that the overall fresh water production and efficiency decreased with the increases in brine depth 79 due to sensible heat absorbed by brine mass at increased brine depth. Sandeep et al. (2015) 80 studied SEBWP of single slope type in which extra condensing surface was provided and 81 concluded that the fresh water production in the improved design was 14.5% higher than the 82 conventional SEBWP of single slope type due to improvement in the condensation as the extra 83 condensation surface was provided. Singh et al (2016) investigated PVT integrated SEBWP of 84 single slope type and concluded that there was a fair conformity between values of theoretical 85 and experimental analyses with coefficient of correlation varying between 0.97 and 0.99. 86 Issa and Chang (2017) studied SEBWP by integrating with evacuated tube in mixed mode 87 condition and it was concluded that the yield was better than the conventional SEBWP because by 32% with CuO nanofluid over base fluid (water) due to increased absorptivity of nanofluid. production of fresh water was 46% higher with improved condenser due to the difference of 115 partial vapor pressure between the water surface and condenser surface. Bait  and input to the first collector has also been taken through insulated pipe from pump which takes  The glass was fixed with help of iron clamp and rubber placed in between iron frame and glass.

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The sealing was done using window-putty with an aim to avoid seepage of vapor. The short wavelength solar radiation reaches the water surface after passing through the 199 condensing cover where a part of energy is reflected by water and the remainder is transmitted to   The observation on the hourly basis has been presented as Table 2.  Where r = Radius of copper tube.

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Using equations (1) and (2), the water temperature at the first collector's outlet can be expressed Where, the value of is equal to .

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The temperature at the first collector's outlet will be the same as the temperature at the second 279 collector's inlet, the temperature at the second collector's outlet will be the same as the 280 temperature at the third collector's inlet, and so on. Using this condition, the fluid temperature at 281 the Nth collector's outlet can be calculated as follows: The heated fluid (water) available at the outlet of N th collectors allowed to basin of SEBWP of 284 single slope type and hence, = .After getting the fluid temperature at the outlet of Nth 285 collector, one can obtain the expression for useful heat gain as Here, ́= 1denotes the effective absorptivity of glass cover and ℎ = ℎ + 291 ℎ + ℎ represents the rate of net heat transfer coefficient between water surface and inner 292 surface of the glass cover.

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Outer surface of condensing glass cover: Water mass in basin: Where, ́= 1 -1 -(1 -) which denotes the effective absorptivity of water 299 mass and ̇ denotes useful heat gain per hour basis from N same evacuated tubular collectors 300 connected in series.

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Basin liner: Where, ́= 1 -1 - Appendix-A contains the expressions for for and ( ) used in equation (7). The solution 310 to differential equation (7) is written as Where, is the temperature of water at = 0 and during the time interval 0-t, the average After estimating parameters namely water temperature ( ) and glass temperature, the hourly 319 yield ( ̇ ) can be estimated as: The value of L can be estimated using the relationship provided by Fernandez and Chargoy 322 (1990) and Toyama (1972).

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The value of e can be estimated as:

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The coefficient of determination can be evaluated as the square of correlation coefficient ( ). It  Values of COPW have been estimated using equation (25) and they have been presented in Table   370 5.

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.6.2.3 Productivity analysis 372 Productivity gives the relation between output and input and it is different from efficiency in the 373 sense that the value of productivity should always be more than 100% whereas the value of efficiency should be less than 100%. Higher the pruductivity better will be the living standard of 375 persons because higher productivity means more products are available for use. It is also 376 expressed as the rtio of effectiveness and efficiency. Input provided to SEBWPof single slope type integrated with ETCs will be UEOYAC and it can 387 be estimated using equation (20). The productivity has been evaluated using equation (26) and 388 has been presnted in Table 5.  The value of hourly exergy rate can be estimated as follows: is the reciprocal of term that represents the overall performance of the system. The  Table 6.  Table 4 to Table 8.   , and hourly yield. Table 3 represents the evaluation of annual yield for SEBWP of single  The monthly exergy has been estimated by multiplying daily exergy with number of clear days 494 in that month. It has been found that monthly exergy is maximum for April because of better  Evacuated tube @500each 6500 4 Aluminum stand 3000 5 Iron stand for solar still 1000 6 Motor and pump 2000 7 Fabrication cost 5000 8 Salvage value of the system after 30 years taking inflation rate is 4% 13755.46 500 The investment in installing SEBWP of single slope type integrated with ETCs has been 504 presented in Table 4. The cost of different components is the price of products as per local 505 market. Also, the salvage value has been estimated as per the local market price. UEOYAC for presented in Table 5. The life span of SEBWP integrated with ETCs has been taken as 30 years 508 except motor and pump. The life of pump with motor has been taken as 10 years and it has been 509 assumed that the inflation after 10 years can be adjusted with its salvage value. interest rates under consideration. It means that the system is feasible.
519 Table 6 presents the calculation of embodied energy ( ), energy payback time ( ), energy 520 production factor ( )and for SEBWP of single slope type integrated with ETCs.       There is no funding received for the research work carried out  Variation of monthly exergy loss for SEBWP of single slope type integrated with evacuated tubular collectors