Energy, Exergy, Environmental Impact and Economic (4E) Analysis of ET-CPC-Powered Solar Domestic Water Heating System


 World energy demand is increasing continuously; consequently, the environmental impact forces towards utilizing renewable energy resources with efficient and optimized cost-performance conversion technologies. Therefore in this study, an analytical model is developed to propose the energy, exergy, environmental impact and economic (4E) analysis of the water heating system at Jaipur (India) with evacuated tube compound parabolic concentrator ET-CPC field of the total area of 81m2. The model results were validated with the experimental data, and a good agreement has prevailed. After that, the model is used to perform parametric studies on the effect of operating and meteorological parameters on the productivity and performance of the system. Moreover, the system’s performance, environmental impact and economic aspects have been investigated and compared under different meteorological conditions at four different locations in Rajasthan (India) using TMY2 weather data files. Results clarified that Jodhpur receives the highest solar radiation intensity from these four locations. Consequently, the results indicate the highest annual energy and exergy with the value of 79.72 MWh and 9.311 MWh followed by Jaisalmer, Barmer, and Jaipur. The economic analysis results clarified that the simple payback period ranged from 4.5 to 4.75 years and the discounted payback period ranged from 6.6 to 7 years based on a 6% discount rate. At the same time, the Levelized Cost of Heating (LCOH) ranges from 1.62 to 1.72 INR/kWh of heat compared to closest with CNG as fuel ranging from 4.39 to 4.41 INR/kWh for specified locations. The internal rate of return is reported to be 16.76, 16.82, 16.77, and 16.75% for Barmer, Jodhpur, Jaipur, and Jaisalmer respectively, and savings of 74400, 78125, 75371, and 73813 kg of CO2 emission to the environment.


Energy, Exergy, Environment impact and Economic Analysis
Practical heat gain for the n-tube connected in series is given as: Instantaneous thermal efficiency (ηInstantaneous) is given as  Table 3 describes reduced equations for desired energy analysis of ET-CPC solar field. In the 221 existing setup, each ET-CPC module involves 18 evacuated tubes and four modules linked in 222 series to create an array and equally 7 rows are arranged parallel. Hence, 12 tubes are linked in 223 series and hence mass flow rate is distributed in 7 rows and 6 subdivisions. Hence, a total mass 224 flow rate is 0.83 kg/s out of centrifugal pump rated discharge 1.5 kg/s because of pressure drop 225 due to ET-CPC solar collectors but only 0.0198 kg/s mass flow rate is observed inside any 226 particular evacuated tube for this setup as shown in Figure 3. 227 Since this system's thermal energy storage is 2.2 m 3 in volume and oriented horizontally, a 228 complete energy mix model is considered inside the TES tank. Further, energy gain is calculated 229 as the successive sum of the energy gains, and subsequent temperature rise at any given time is 230 treated as per equation (3) of Table 3.
Exergy inlet (Petela 2003(Petela , 2005 max , , rad solar T total c in Sun Exergy destruction due to absorption Exergy destruction due to thermal losses

Exergy destruction due to conduction
Exergy destruction due to pipe friction (Bejan et al. 1981) in f , for Re>2200

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Thermodynamic analysis of thermal energy storage has been performed under actual environmental 244 conditions during the charging, storing, and discharging phase. Equations for energy and exergy 245 parameters have been reduced as presented in Table 5, and these are analyzed in conjunction with the 246 performance of ET-CPC. 247 Exergy Destruction   With the ever-increasing concern about the environmental impact and specifically global 250 warming due to greenhouse gases, it has become essential to evaluate and analyze the newly 251 designed and developed system environmentally before heading forward. calculated using emission conversion factor as follows: Where, λ is the emission conversion factor having a value of 0.968 kg/kWh. It is essential to 264 mention that India's energy mix has been used to obtain the results. Here it is taken as 1 kWhe 265 leading to 0.968 kg of CO2 production. incentives that may attract investment when looking to these social benefits. However, any 271 system must sustain itself until its financial viability or beneficiary.

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The fossil-based system is relatively cheaper in terms of initial cost but they have a higher 273 recurring cost including regular energy billing, maintenance cost, etc. whereas the Solar-based   Table 6.
295 Table 6 Indicators of Economical Analysis      The heat removal factor is an important design parameter as it is a measure of thermal resistance 348 encountered by the absorbed solar radiation is reaching the collector fluid. Figure 9 shows the 349 effect of mass flow rate on the heat removal factor. This can be concluded that there is an 350 increasing trend for heat removal factor, however, this increase in heat removal factor is not 351 significant thus an average value of 0.5635 is taken for further evaluation.  353 The effect of solar radiation intensity is quite essential to assess as an operating parameter since  to the environment at higher inlet temperatures. However, these relative differences reduce at the 381 higher value of solar radiation intensity. Further, it can be observed that instantaneous efficiency 382 is still in the range of 40-50% which is significantly better than any other stationary STC.     There are five conventional fuels-based water heating systems for the economic comparison with 515 the existing solar water heating system. Table 7 shows the different fuels used for water heating 516 and their corresponding price, conversion efficiency and calorific value of fuels. easily identified that the first cost of a solar water heating system is significantly higher than 520 those of other systems. Table 9 reports the annual operation and maintenance cost of various 521 fuels while Table 10 shows the estimated life expectancy of the selected systems. Economic 522 evaluation is done based on equations reported in Table 6.   A comparison of operation and maintenance costs has been presented in Figure 20. The kerosene 537 fuel-operated water heating system shows the highest cost of operation and maintenance, 538 followed by Electricity and LPG. This can be seen that solar energy is having significantly less 539 operation and maintenance costs as compared to that of other conventional fuels reported.

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An SDWH powered by an 81 m 2 ET-CPC solar collector field is reported in presented here.

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Energy, exergy, environmental and economic analysis is carried out. The following points are 556 drawn as the conclusion of this work. to be 79.72 MWh and 9.311 MWh followed by Jaisalmer, Barmer and Jaipur.

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• The economic analysis reports the simple payback period ranging from 4.5 to 4.75 years 574 and discounted payback period ranging from 6.6 to 7 years based on a 6% discount rate.

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• Along with this, based on levelized cost of heating using solar energy as fuel is ranging Jodhpur, Jaipur and Jaisalmer respectively which proved that it is a very profitable 582 business model.

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• The environmental analysis also supports the previous trends and report 74400, 78125, 584 75371 and 73813 kg of CO2 saved which anyway got added to the environment if the 585 electricity was used for the same purpose.

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Hence it can be recommended that ET-CPC is a viable, economical and pollution-free alternative 587 to meet the medium temperature heat demand such as in solar water heating systems for 588 domestic and community use. ET-CPC operation is not possible during weak sunshine (<200 589 W/m 2 ) hours and technology advancement is needed in this direction. The use of nanofluids as a 590 working fluid is reported to be advantageous to improve the productivity and performance of the 591 ET-CPC further but insufficient data is there and that also reports operational issues. Research 592 could be made to find the optimal configuration of nanofluids to offer less/no operational issues 593 and optimal performance. Further, ET-CPC life cycle cost assessment could be worked out to 594 understand the overall impact on nature.

-Ethical Approval 596
We confirm that this work has not been published elsewhere, nor it is currently under 597 consideration for publication elsewhere. Calculations data and other relevant material would be made available to editor/reviewer as and 615 when required. 616