Performance and Techno-economic Analysis of a Hybrid Photovoltaic/thermal System for Building Application in Turkey

: Residential buildings need demand of energy for both heat and electricity. However, it’s not always possible to meet 13 this need by using individual panels due to the limited roof area. In addition, performing electrical and thermal energy 14 production by using separate panels causes loss of performance and efficiency. The hybrid photovoltaic thermal (PV/T) 15 collectors could be used in order to meet this necessity into the same collector. This paper investigates the performance and 16 economic analysis of a PV/T collector for a building application in Turkey climatic conditions. For this purpose, the 17 Matlab/Simulink model of the PV/T collector was prepared. The electrical and thermal performance of the PV/T collector has 18 been investigated by changing various parameters on this model. In addition, market survey was conducted for economic 19 analysis. 11 different input variables such as average daily irradiation, electrical and thermal efficiency, price of electricity and 20 heating, operation and management cost, capital cost, debt to equity ratio, interest rate, discount rate and inflation rate are used 21 to calculate the economic evaluation parameters such as net present value (NPV), levelized cost of energy (LCOE) and 22 payback period (PBP). The results show that, the mean v alue of LCOE, NPV and PBP are 0.0467 €/kWh, 7905.3 € and 6 years 23 respectively for the project size at 8.96 m2 which is consist of 7 panels in the 25 years life cycle. Also, the average electrical 24 and thermal efficiencies are defined as 13.4% and 69.3% respectively during.


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The sun is the largest energy source for the world. There are basically two ways to make available the energy provided by the 29 sun. The first is to convert the solar energy into thermal energy and the other is to convert it into electrical energy. Because of 30 their unique advantages, both technologies are increasingly used in residential and industry applications. Because of the heat 31 and electrical energy obtained from the sun often complement each other and in order to eliminate the disadvantages arising 32 from the use of these two technologies separately, it is thought that it is more convenient to produce heat and electrical energy 33 from the same panels. A PV/T collector is a module which combines the photovoltaic and thermal technologies into the same 34 panel. 35 increase in PV panels has a negative effect on the efficiency. Since the panel temperature absorbed by the liquid fluid in PV/T 66 collector, higher efficiency is obtained than similar PV panels. In (Saitoh et al. 2003), the authors analyzed the electrical and 67 thermal efficiency of water-based PV/T system experimentally. The results showed that the electrical efficiency varied from 10% 68 to 13%, and the thermal efficiency ranged from 40% to 50%. Minglu et al. (2016) was proposed a PV/T integrated dual-source 69 heat pump water heating system for Shanghai climate condition. They found that when the top temperature was 69.2 °C, the 70 electrical conversion efficiency was 12.18% and when the operating temperature decrease to 45 °C the electrical efficiency 71 increases to 13.4%. Another experimental study was carried out at Politecnico di Milano University. The experimental 72 calibration and validation of the model was performed in outdoor conditions on a commercial PV/T product and the model was 73 run supposing the application in three different locations. In that study, the electrical efficiency of water-based PV/T was found 74 as 13%, 13.6%, 13.4% and the overall efficiency was found as 32.7%, 36.

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The other study has indicated that the building integrated PV/T collector's thermal energy efficiency of about 55-62% and the 78 maximum achieved electrical efficiency was 11.4% (Ibrahim et al. 2014). Kiran and Devadiga (2014) reported that the 79 electrical efficiency of PV/T was 7.58% without cooling and 8.16% with cooling and the overall efficiency was 58.97%. The 80 other experimental study was conducted during the spring season in United Arab Emirates. The results showed that electrical 81 efficiency increased from 15% to 20% and the thermal efficiency was found as %60 (Alzaabi et al. 2014). Rosa-Clot et al.

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(2016) performed the efficiency analysis of PV and PV/T in Italy. They found the electrical efficiency of PV and PV/T as 8.77% 83 and 13.19%, respectively. Also, they found thermal efficiency of PV/T as 62%. In addition to experimental studies, simulation 84 studies were conducted in the literature for PV/T. The results obtained in these studies differ according to the results of 85 experimental studies. Because, many factors which are affect the efficiency can be easily changed as desired. For example, in 86 the simulation study by Yazdanifard et al (2016), several parameters changed such as solar radiation, the number of pipes, 87 Reynolds number, packing factor, pipes diameter, and collector length to investigate the glass covered flat plate PV/T system's 88 electrical and thermal efficiency. They found maximum electrical and thermal efficiency as 17% and 70% respectively. 89 Daghigh et al. (2011) conducted the simulation study for amorphous silicon and crystalline silicon water based PV/T systems 90 in Malaysia. The results showed that the electrical and thermal efficiency of amorphous silicon PV/T was 4.9% and 72%, 91 respectively and the electrical and thermal efficiency of crystalline silicon PV/T was 11.6% and 51% respectively. In the 92 literature, there are many studies examining the performance of PV/T collectors. As summarized above, the results obtained in 93 these studies are quite different from each other. The reasons for this are that the studies were carried out at different ambient 4 temperatures in different regions, different cooling water flow rates and it is due to overestimation of the input parameters in 95 some simulation studies.
It has been seen in the detailed literature review that although there are many studies about PV/T collector performance 97 analysis which are evaluated electrical and thermal efficiency using different design parameters, there are also some economic 98 analysis studies. Different metrics can be used for the economic analysis such as payback period (PBP) (

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They did not consider tax rebate or other cost reduction in order to find out the maximum time to overcome the initial cost and 107 maintenance cost in their economic analysis. They found estimated cost payback period for electricity saving and electricity 108 and gas saving between 10.3-28.2 year and 17.2-30.8 year according to the different temperature and tilt angel. In ref 109 (Kalogirou and Tripanagnostopoulos 2007), 300 m 2 of hybrid PV/T collectors with polycrystalline and amorphous types PV 110 cell and a 10 m 3 water storage tank was evaluated for Cyprus, Greece and Wisconsin. In the study, Typical Meteorological

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Year (TMY) data is used in TRNSYS program. TMY was defined as a year, which was including all the meteorological data a 112 period the mean life of the system. The results show that the electrical production of polycrystalline PV/T is more than the 113 amorphous PV/T but the solar thermal fraction is slightly lower. Also, payback period was calculated for Cyprus, Greece and 114 Wisconsin as 26, 26, 28 years respectively. The water cooled PV/T collector which has different PV cell such as c-Si, p-Si, a-115 Si (thin film), CdTe and CIGS evaluated and compared under New Delhi, India conditions. It was observer that the c-Si PV 116 cell produced maximum electricity energy, maximum annual overall thermal energy and exergy. Also, the results showed that 117 the maximum and minimum EPBT of 1.01 and 0.66 years on energy basis is obtained for c-Si and CIGS respectively, whereas 118 on exergy basis maximum EPBT of 5.72 years is obtained for a-Si and minimum of 3.44 in obtained for CIGS PV module 119 (Mishra and Tiwari 2013). Another economic analysis of water-cooled PV/T was carried out in UK. The authors introduced 120 that the annual energy savings was 10.3 MW and the NPV was calculated as 19456.14 Dollar for the 25-year life span of and 121 the cost of power generation was 0.0778 per kWh (Mahmut et al. 2014). Another water-cooled PV/T economic analysis study 122 conducted in a real office scale building to support its electricity and hot water demand via computer program simulations in London, UK. According to the results of the study, a higher coverage of total household energy demands, and higher CO2 126 emission savings can be achieved if the system is installed under low solar irradiance levels and low ambient temperatures. 127 Also, they introduced that an annual electricity generation of 2.3 MWh, or a 51% coverage of the household's electrical 128 demand (compared to an equivalent PV-only value of 49%), plus a significant annual water heating potential of to 1.0MWh, or 129 a 36% coverage of the hot-water demand. The techno-economic challenges of PV/T systems in the housing sector for different 130 Europe locations, with local weather profiles and energy demand data relating to homes with a total floor area of 100 m 2 were 131 studied by Alba et al (2017). In the study, TRNSYS simulation models were prepared for 4 different systems based on meeting 132 electricity and thermal energy demand and the economic viability of the solutions is then assessed based on their LCOE. The 133 results showed that the overall levelized cost of energy of these systems is found to be in the range of 0.06-0.12 €/kW h, which

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 The amount of energy to be produced from the PV/T collector is calculated using monthly meteorological data.

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Moreover, these data are often obtained from various simulation programs rather than being measured. However, performance 148 and economic analysis studies using monthly average data do not give clear technical and economic results.  The main goal of this paper is to analyze the thermal-electrical performance of a PV/T collector and to assess the economic 168 feasibility of water-based PV/T systems under real measured meteorological data. For this purpose, the meteorological data 169 such as irradiation and temperature were collected every 5 minutes for one year. The thermal and the electrical performance 170 analysis were performed using this real data for everyone hour. The economic analysis was performed by considering all 171 financial and technical parameters such as annual degradation rate, inflation rate, dept to equity ratio, interest rate based on the 172 yearly energy output. Therefore, this study will provide a critical view on design and the associated parameters that affect the 173 PV/T system performance and economic results.

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The novelty of this study is that the entire gap in the literature listed above has been examined separately. These are 175 summarized as follows.

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 Hourly performance and energy production were performed for one year using real meteorological data. Then the 177 annual performance degradation rate implemented for life cycle of the PV/T collector.  Hot water supply cost has been determined using the average unit price of some of the central hot water plants in 186 Turkey and it has been determined by considering the costs that will occur in case of using natural gas for heating.

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The paper is organized as follows: Firstly, a detailed literature review was conducted, and related papers were presented in the 188 introduction in accordance with the subject compliance and the date of presentation. The remaining parts of the paper are 189 organized in the following order. Section 2 gives a detailed description of the PV/T system such as location, data set, PV/T 190 collector, measurement sensors and reference house. In section 3, the market price  water. In this study, the PV/T system consists of the 7 panels, converter, inverter, solar absorbing tube, storage tank and 202 circulating pump. Figure 1 shows the block diagram of the analyzed system.

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In this study, Simple House SFH15, which is used by IEA in Task44

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Heating cost is determined as 0.08 Euro/kWh when using natural gas.

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Although the installation costs are decreasing day by day, the economic results will vary from country to country or from year 284 to year due to the policies of countries, feed-in tariff, interest rate and inflation. Therefore, it should be considered in financial 285 parameters and policies as well as installation costs.

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The key input variables required for economic analysis can be classified as geographical, technical and financial. The

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The project can be financed with equity, using an amount of bank loan or using bank loan entirely. In this study, it is assumed 293 that bank loans will be used. Therefore, credit interest rates should be determined.   conditions. Otherwise, if the system is off-grid, a storage device is needed. Although the electrical energy produced in PV 357 panels depends on a large amount of radiation, panel area and panel efficiency also affect the amount of energy to be produced.

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The hourly energy generated by the PV panel is calculated using equation 17.

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,ℎ = ,ℎ . . ƞ Where the ,ℎ is the hourly total in-plane irradiance (kWh/m 2 ), is the PV/T available area (m 2 ) and ƞ is the overall PV  Where 0 is the capital cost (€) and DE is the dept to equity ratio (%).

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The loan cost is equal to the sum of the annual invested capital with the interest rate on the invested capital.

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However, the effect of s and ταpv on the electrical and thermal efficiency is shown in figure 3. The increases of the means 432 that more collector areas are covered by PV cells. Therefore, the increase of the absorber block area has the effect of 433 decreasing the heat increase in PV cells. This means that more areas are heated under the same irradiation. Therefore, a 434 decrease in thermal efficiency will occur due to the .
should be determined. The wavelength of the light that a typical PV cell absorbs smaller than the wavelength of the light that 437 the thermal collector absorbs. Therefore, large wavelength lights are reflected from the PV cell and absorbed by the thermal 438 collector. Therefore, increasing the ταpv increases the thermal efficiency. Since ταpv has little effect on electrical efficiency, it is 439 preferred that ταpv is close to 1.  Mains water temperature is associated with soil temperature. As the temperature of the soil does not change as fast as the 475 ambient temperature, mains water temperature does not change very fast. Therefore, it has been found appropriate to use 476 monthly average mains water temperature.

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In this study, the electrical and thermal efficiency of the PV/T were calculated by using the temperature and irradiation data 478 taken at 15-minute intervals. Hourly average irradiation and the ambient temperature are shown in Figure 5. The lowest ambient temperature and PV cell temperature were measured in January at -9.7 °C and -8.  year. Figure 7 shows the amount of electricity and heat energy that the system will generate on an hourly basis.  It is seen that the economic performance is good and acceptable for the market, where LCOE is calculated at 0.0467 €/kWh

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• The LCOE was calculated at 0.0467 €/kWh while NPV and PP are respectively estimated at 7905.3 € and 6 years.

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It is expected that this study and its results will lead to the use of PV/T based systems in buildings. Also, it is clear that the 540 results will contribute to the literature.  The effect of the s and ταpv on the performance of the electrical and thermal e ciency Hourly average irradiation and ambient temperature Figure 6 Thermal and electrical e ciency of the PV/T collector Monthly Electricity and Heat Generation