T Collector for Different Climates in Iran

Available online at www.sciencedirect.com

ScienceDirect Energy Procedia 75 (2015) 444 – 456

The 7th International Conference on Applied Energy – ICAE2015

Exergy and economic evaluation of a commercially available PV/T collector for different climates in Iran S. Nemati Jahromia,b*, A. Vadieec, M. Yaghoubia a

Department of Heat & Fluid, School of Mechanical Engineering, Shiraz University, Mollasadra St., Shiraz, Iran b Utility Department, Phase 1, South Pars Gas Complex(SPGC), Asalouye, Bushehr, Iran c Department of Energy Conversion, School of Mechanical Engineering, Shiraz University of Technology,Modarres blvd.,Shiraz,Iran

Abstract

Thermal photovoltaic (PV/T) water based collectors are used to convert solar radiation to both thermal energy and electricity simultaneously. Along with energy analysis, exergy analysis is also useful for thermal systems such as PV/T to evaluate the “quality” of energy obtained from the system. Various types of PV/T collectors are available on the market. However, in this paper, a commercialized PV/T system is selected and exergy and economic analysis (exergoeconomics) is performed for a specific collector using known technical parameters and price for three cities in Iran with different insolation level. A MATLAB simulation program is prepared for this purpose, and it is cross validated using a former study on the same collector performed by TRNSYS and good agreement is observed. According to the results, exergy efficiency is obtained to be 9.7%, 9.6%, and 9.6% for the cities of Tabriz, Shiraz, and Esfahan respectively. An economic analysis is also performed using Net Present Value (NPV) method for the mentioned cities, and it concluded that with the specified economic parameters, the system is marginally economically feasible. This is found to be due to high capital investment costs as well as cheap available fossil fuel that is utilized widely in order to supply thermal and electrical energy demand in the studied cities. © 2015 Published by Elsevier Ltd. This © 2015The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Selection and/or peer-review under responsibility of ICAE Peer-review under responsibility of Applied Energy Innovation Institute

Keywords:Photovoltaic- thermal (PV/T); Exergy analysis; Net Present Value(NPV)

* Corresponding author. Tel.: +98-917-391-4092. E-mail address:[email protected]

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Applied Energy Innovation Institute doi:10.1016/j.egypro.2015.07.416

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

1. Introduction The renewable energy sources have obtained considerable attention in the last decades after the oil crisis in 1970s. Solar energy is one of the most available and abundant renewable energy sources in Iran and solar flat plate collector is a common method to harness solar energy which can be converted to thermal energy. Solar energy can also be used to produce grid-connected or stand-alone electricity generators by converting photon energies into electricity. There is another combined type of collector which is called photovoltaic-thermal (PV/T) collectors. In this type of solar systems, a working fluid such as water or air passes through the PV/T module in order to absorb heat from PV and reduce the photovoltaic cell operating temperature. Therefore, a PV/T converts solar radiation to both hot water and electricity simultaneously. Beside the energy analysis which is essential to evaluate performance of any energy system, exergy analysis is also required to measures the “quality” of transferred energy through the system. Moreover, by considering the economic aspect, the system cost effectiveness can be evaluated. This paper is an exergoeconomic assessment that considers both exergy and economic analysis for a thermal photovoltaic solar system for various meteorological conditions, and some other aspects. There are numerous studies regarding PV/T developments. Zondag et al. [1] have evaluated the yield of nine different PV/T collectors. According to their results, thermal efficiency of uncovered collectors is 52% and that of single cover sheet-and-tube design is 58%, while channel-above-PV design has 65% thermal efficiency. Although using transparent PVs resulted in more efficiency, but the sheet-and-tube design was introduced as the best design due to low manufacturing cost [1]. Chow et al. [2] have carried out a study on various glass covers for a thermosyphon-based water heating PV/T system and showed that energy efficiency of glazed collectors is always better than unglazed ones. However the exergy efficiency of unglazed collectors is better than glazed ones. Huang et al. [3] and Kalogirou et al. [4] assessed the performance of PV panels which were attached to an absorbing heat mechanism. It has been shown in the corresponding studies that the overall energy gain has great effect on the economic viability of the systems, especially in the applications where low temperature water, like hot water production for domestic use is required. Thereafter, huge advances have been achieved regarding PV/T collectors to which several studies have pointed in [5-9].Among the researches on economic analysis of PV/T collectors, a few of them considered commercially available PV/T collectors [10, 11]. Axaopoulos and Fylladitakis [12] evaluated the thermo-economic performance of a commercially available PV/T system for electricity and hot water production for three European countries with different climatic and economic conditions. Sarhaddi et al. [13] evaluated exergetic performance of a solar photovoltaic-thermal air collector. They concluded that the agent fluid has a great effect on the exergy efficiency and for an incompressible fluid the exergy efficiency is increased. Sobhnamayan et al. [14] carried out an optimization of a solar photovoltaic-thermal water collector based on exergy concept using genetic algorithm. They concluded that exergy efficiency behaviour of their study is the same as the one given by previous studies with respect to the changes of inlet water velocity, pipes diameter and wind speed. According to the performed literature survey, it can be concluded that there isn’t many exergoeconomic studies of PV/T by considering various climate conditions for a specific country like Iran. Thus in this paper a thorough evaluation is performed for three cities including Shiraz, Esfahan and Tabriz which have different types of climatic conditions and insolation level. In this paper, governing equations are modelled in a programming software, rather than a predefined model like those used in TRNSYS. This will help to make changes and designing the model more adaptively, the fact that is not obvious in the previous studies.

445

446

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

Nomenclature Ac CF d šሶ FR h i I Isc Kalt-dir Kalr-dif

collector aperture area (m2) cloud factor discount rate exergy (W) heat removal factor altitude in Km inflation rate solar radiation (W/m2) Short circuit current (A) direct beam altitude correction factor diffused altitude correction factor

ሶ୵ collector fluid mass flow rate (kg/s) NOCT Nominal operating cell temperature Q Q R S T UL V ȕ ș ȡg İ ȗ (IJĮ)

heat transfer (W) useful solar heat gain (W) Internal resistance of PV (ȍ) solar irradiation (W/m2) temperature collector total loss coefficient (W/m2ƕC) Voltage (V) collector tilt angle solar ray incident angle ground reflectance emittance packing factor transmittance-absorptance product

2. Methodology The main aim of this study is to assess the effect of meteorological data on the exergy and economic of a PV/T system. For the study, three cities located in Iran, with different types of meteorological conditions are selected which are Shiraz, Esfahan and Tabriz. In order to perform an exergoeconomic evaluation, a separate exergy, and economic analysis has been assessed for each PV/T collector system. 2.1. Exergy analysis An analytical model is developed using MATLAB based on the theoretical equations defined by Duffie and Beckman [15] for a PV/T system. A cross validation has been considered in this study in order to verify the developed model as well as extending the results. Therefore the designing parameters for the PV/T system is defined similar to a PV/T model which was studied by Axaopoulos and Fylladitakis. [12]. A schematic of the system being used is shown in Fig. 1.

447

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

Fig. 1.Schematic view of the system being considered [12].

In order to assess the effect of radiation level as well as climatic parameters such as ambient temperature on the performance of PV/T system, the cities of Shiraz, Esfahan and Tabriz in Iran, are considered. The hourly weather data of the three mentioned cities are obtained by the modified Daneshyar model explained in Ref. [16] and imported to the MATLAB program as input data. The working fluid in the collector closed loop is considered to be 30% solution of glycol and water except for Tabriz where due to low ambient temperature, 40% glycol-water solution is used to avoid freezing. More detailed information regarding to the system design condition and the corresponding defined parameters are given in Table 1. Table 1.Technical specification of the PV/T collector. Parameters Value

İp 0.9

İg 0.88

Vmpp,ref

Impp,ref

36.04V

4.693 A

Voc

Isc

44.53V

4.967 A

Rsh 370ȍ

Rs 0.923ȍ

NOCT

ȝVoc

ȝIsc

ȝp

37ƕC

-124.8 mV/ƕC

+0.5857 mA/ƕC

-0.6771 W/ƕC

In the above table, the subscripts mpp, ref, oc, sh and s represent maximum powerpoint, reference, open circuit, short circuit, shunt and series, respectively. ȝ is the temperature coefficient which determines deviation of operating parameters from the standard conditions. For all the selected cities, four collectors, each having 1.42 m2 area and packing factor of 0.93 is considered connected in parallel and mass flow rate of fluid in each collector is designed as 0.01759 kg/s that is recommended by the manufacturer. The following assumptions are made for simulation: x x x x x

The simulation is performed as steady-state condition. Heat loss from the edge and back of the collector is considered negligible as it generally constitutes 10% of the overall loss [15]. Thermal resistance between PV and absorber plate as well as thermal resistance regarding to the welding bond material is assumed to be negligible. Efficiency of the heat exchanger in the tank of Fig.1 is assumed to be 0.7 as typical heat exchangers in industry. Inlet domestic water temperature to tank is assumed to be equal to the ambient temperature.

448

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

The following equations have been considered in order to calculate the useful heat gain from the collector [15]: ܳ௨ ൌ ‫ܣ‬௖ ‫ܨ כ‬ோ ሺܵ െ ܷ௅ ሺܶ௜ െ ܶ௔ ሻሻ

(1)

Where Qu is the heat absorbed between inlet and outlet of the collector, FR is the collector heat removal factor which is a number between 0 and 1 and measures the proximity of absorber plate temperature to inlet water temperature. UL is the heat loss from the collector assuming that the plate is at inlet water temperature. In order to calculate the useful heat gain according to the above equation, solar irradiation incident on aperture of the collector “S” has to be calculated. Solar irradiation is the key parameter in both of energy and exergy analysis in any solar energy systems. Solar irradiation incident on the aperture of the collector is calculated as follows [15]: S

§ 1  cos E · § 1  cos E · I b Rb (WD )b  I d (WD ) d ¨ ¸  U g ( I b  I d )(WD ) g ¨ ¸ 2 2 ¹ ¹ © ©

(2)

Where the subscripts b, d and g refer to beam, diffused and ground respectively and Rb is the ratio of beam radiation on tilted surface with slope angle equal to ȕ to horizontal surface at anytime Rb

cosT cosT z

(3)

ș is the angle between solar beam ray and normal line to the plane of collector and șz is the angle between solar beam ray and normal line to the horizontal surface. For calculating ș and other solar parameters, readers can refer to Ref. [15]. Solar beam and diffused radiation can be obtained from several procedures; one way is to use the solar radiation estimator softwares like Meteonorm. This software doesn’t yield accurate results for some areas of Iran as its data conflicts with the previous studies like [16] and [17]. Therefore the modified Daneshyar model [16] was employed for calculating the solar radiation components. According to this model: ‫ܫ‬௕ ൌ ͺʹǤͷͷͷሺͳ െ ‫ܨܥ‬ሻሺ‫ܭ‬௔௟௧ିௗ௜௥ ሻሾͳ െ ‡š’ሺെǤͲ͹ͷሺͻͲ െ ߠሻሻሿ

(4)

‫ܫ‬ௗ ൌ ൫‫ܭ‬௔௟௧ିௗ௜௙ ൯ሾͲǤͳͳʹ ൅ ͲǤͳ͸ͷሺͻͲ െ ߠሻ ൅ ͻǤͶͺ ൅ ͻǤͶͺ‫ܨܥ‬ሿ

(5)

‫ܭ‬௔௟௧ିௗ௜௥ ൌ ሾͳ ൅ ͲǤͲ͹ሺ݄ െ ݄௥௘௙ ሻ]

(6)

‫ܭ‬௔௟௧ିௗ௜௙ ൌ ሾͳ െ ͲǤͳሺ݄ െ ݄௥௘௙ ሻ]

(7)

In the above equation CF is cloud factor which is explained in [16], ‫ܭ‬௔௟௧ିௗ௜௥ and ‫ܭ‬௔௟௧ିௗ௜௙ are altitude correction factor for beam and diffused radiation, respectively. h and href are site altitude in km and reference altitude which is considered for Tehran (1.19 km), respectively. The heat rate of the system which is transferred through heat exchanger in the tank is calculated as follows [15]: ܳ௣௩Ȁ௧ ൌ ߝ௘௫ ‫݉ כ‬ሶ௪ ‫ כ‬ሺܶ௢ െ ܶ௔ ሻ

(8)

449

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

Where ߝ௘௫ is efficiency of the heat exchanger in the tank which is assumed to be 0.7. QPV/T is the heat rate of the exchanger in the tank in Fig. 1. The role of this parameter becomes evident when calculating the net cash flows of the system in which this heat rate is assumed to be substituted by electrical energy or fossil fuel to cover part of the thermal energy demand.݉ሶ௪ is mass flow rate of collector loop fluid, To and Ta are outlet fluid temperature and ambient temperature equal to the inlet domestic water to the tank, respectively. Thus, thermal efficiency is calculated using [15]: ߟ௧ ൌ

(9)

ܳ௨ ‫ܣ‬௖ ‫ܵ כ‬

Thermal efficiency is defined as the ratio of heat that collector absorbs to the total solar energy received on the aperture. PV efficiency is that part of this energy received which is transformed into electricity, which is calculated using [15]: ߟ௣௩ ൌ ߟ௠௣௣ǡ௥௘௙ ൅ ߤ௣ ‫ כ‬ሺܶ௖௘௟௟ െ ʹͷሻ

(10)

Where ߟ௠௣௣ǡ௥௘௙ is nominal efficiency of PV in standard conditions, which has been considered as 11.9% and ߤ௣ is temperature correction coefficient which is used to calculate PV efficiency in temperatures other than 25°C[12]. The nominal efficiency of PV is the efficiency of PV when the surface temperature of its laminate is 25ƕC. Beside the energy efficiency, exergy efficiency is also assessed. Exergy efficiency, which is a ratio of the exergy gain through the system to the total insolation exergy, is calculated using the following relation [4]: ߝ௣௩௧ ൌ

ሺ‫ܣ‬௖ ‫ݔܧ‬ሶ௧ ൅ ߞ‫ܣ‬௖ ‫ݔܧ‬ሶ௣௩ ሻ ‫ܣ‬௖ ‫ݔܧ‬ሶ௦௨௡

(11)

Where ‫ݔܧ‬ሶ௧ , ‫ݔܧ‬ሶ௣௩ and ‫ݔܧ‬ሶ௦௨௡ are exergy output of thermal, PV system and incoming solar exergy, respectively. The thermal exergy can be obtained from Eq. (12) and the PV exergy output is considered to be exactly equal to the electricity produced. ȗ is the packing factor which is defined as ratio of the area of collector covered by PV laminates to the aperture area. ‫ݔܧ‬ሶ௧ ൌ ܳ௨ ൬ͳ െ

ܶ௔ ൰ ܶ௢

(12)

Where Qu is the useful heat calculated in Eq. (3), and To is temperature of outlet water from collector. The incoming solar exergy to the collector which appeared in the denominator of Eq. (11) is given by: ‫ݔܧ‬ሶ௦௨௡ =ቂͳ െ

்ೌ ்ೞೠ೙

ቃ‫ݏ‬

The sun’s temperature (ܶ௦௨௡ ) is assumed to be 6000K

(13)

450

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

2.2. Economic analysis The Net Present Value (NPV) method is used to evaluate the economic viability of the system. Using this method all costs and benefits are discounted to their present value according to a specified discount rate [10]. The economic data used for this analysis is presented in Table 2, in which the economic data of Athens is presented only for comparison, and those of Iran are used as input parameter for the NPV method. Table 2.Economic data Location

Iran

Athens

Capital cost(€)

3792

3792

MC(€)

50

50

MC inflation rate

4%

4%

Electricity price (€/kWh)

0.0206

0.150

Natural gas price (€/kWh)

0.0192

0.089

Electricity inflation rate

25%

4%

Natural gas inflation rate

25%

4%

Bank loan interest rate

15%

4.5%

Discount rate

25%

5%

FIT (€/kWh)

0.25

0.25

FIT annual growth rate

5%

2%

The net cash flow (CFT) of each year is calculated as follows [12]: ‫ ்ܨܥ‬ൌ ሾ‫ כ ܵܧ‬ሺ‫ כ ܶܫܨ‬ሺͳ െ ݅ிூ் ሻ்ିଵ ሻሿ ൅ ሾ‫ כ ܧܪ‬ሺ‫ כ ܲܧܣ‬ሺͳ ൅ ݅௔௫ ሻ்ିଵ ሻሿ െ ்ܲܲ െ‫ כ ܥܯ‬ሺͳ ൅ ݅ெ஼ ሻ்ିଵ

(14)

Where ES is electricity sold, FIT is feed-in-tariff the rate at which government buys electricity from consumer, HE is the heat supplied by PV/T, PPT is payment of bank loan per year and MC is the yearly maintenance cost [18]. ்ܲܲ ൌ ‫ כ ܵܥ‬൬

݅௕௟ ൰ ͳ െ ሺͳ ൅ ݅௕௟ ሻି௒

(15)

Where CS is capital cost, Y is payback period of bank loan in years and ibl is the annual bank loan interest rate. Then the NPV is calculated using the following equation [12]: ்ୀଶ଴

ܸܰܲ ൌ ෍ ்ୀଵ

‫்ܨܥ‬ ሺͳ ൅ ݀ሻ்

(16)

In the above equation T represents the year and d, discount rate or inflation rate. NPV is a good measurement of viability of the system as it converts future costs to present worth. For choosing between

451

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

two mutually exclusive economic projects the one with higher NPV is suitable. The economic analysis is performed for a period of 20 years and all of the capital cost is assumed to be granted as a bank loan having payback period of 10 years. 3. Results and discussion An annual energy and exergy analysis has been performed using the developed model in MATLAB. In order to validate the developed model, annual PV/T performance located in Athens has been compared with the given results by Axaopoulos and Fylladitakisusing TRNSYS [12], and good agreements are observed. The validating results are shown in Figs. 2 (a) and (b) and Table 3. As it is shown in Fig.2, the electricity generation by the PV/T system has been compared between both developed models and the model developed by Axaopoulos and Fylladitakis [12]. Maximum difference between the results is about 20% and the best agreement is obtained with less than 1% difference between the given results. Regarding to solar useful heat gain maximum and minimum differences between the results are also 20% and less than 1% respectively.

MATLAB

MATLAB

Ref.[12]

Ref.[12]

Fig 2. (a)Validation of electricity produced (b)Validation of solar useful heat gains Table 3.Annual results (validation). Parameters

Ref. [12]

MATLAB

Error %

1725

1593

-8

Useful heat gain (kWh/m )

305

281

-8

Useful thermal efficiency (%)

18%

18%

less than 1

Electricity generation(kWh)

940

954

1

PV efficiency (%)

10

11

10

2

Solar irradiation(kWh/m ) 2

Dec

Oct

Nov

Sep

Jul

Aug

Dec

Oct

Nov

Sep

Jul

Aug

Jun

Apr

May

Mar

Jan

0

Jun

20

Apr

40

May

60

Feb

80

Mar

100

35 30 25 20 15 10 5 0 Jan

Solarusefulheatgain (kWh/m^2)

120

Feb

Electricityproduced(kWh)

However, by comparing the annual results, shown in Table 3, a better degree of agreement has been obtained. As it is presented in Table 3, maximum difference between the two models is about 10% for efficiency of PV, whereas only 1% difference is observed for total electricity generation. The main reason for such differences in the results is due to minor differences in the model TRNSYS considers for the collector and the fact that in the Ref.[12] no clear information has been provided about thickness of glass cover and the goodness of glass type.

452

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

3.1. Exergy results

Shiraz

Esfahan

100 50

Tabriz

Tabriz

Fig. 3. Temperature variation of the selected cities

Shiraz

Dec

Oct

Nov

Sep

Jul

Aug

Jun

0 Apr

Dec

Oct

Nov

Sep

Jul

Aug

Jun

Apr

May

Mar

Jan

Ͳ10

Feb

0

150

May

10

200

Mar

20

250

Jan

30

300

Feb

Temperature(°C)

40

Solarradiationonhorizontal surface(kWh/m2)

Temperature and solar irradiation on horizontal surface for the selected cities are shown in Figs. 3 and 4 respectively. It is clear that Shiraz has higher average temperature and higher solar radiation than the other cities. In the months June and July solar radiation is nearly equal for all the cities, this is due to longer day light time in Tabriz located on the north-west of Iran. Total heat supplied by the system for domestic hot water is shown in Fig. 5. Also in this figure, it is clear that the model for Shiraz provides the highest heat supply, and Esfahan and Tabriz are in the next ranking. Total electricity generation is represented in Fig. 6. Accordingly total electricity yield of warm months is slightly higher for Tabriz because of lower ambient and therefore cell temperature. Three kinds of efficiencies including electrical, thermal and exergy efficiency are calculated in this study which is presented in Figs. 8-10. It can be concluded from these figures that the model in Tabriz has the highest annually PV efficiency and that in Shiraz has the lowest (Fig.8).

Esfahan

Fig. 4. Solar radiation variation on horizontal surface

Tabriz

Shiraz

Esfahan

Fig. 5. Total monthly heat supplied by the system.

40 20

Tabriz

Shiraz

Dec

Nov

Oct

Sep

Jul

Aug

Jun

0 Apr

Dec

Nov

Oct

Sep

Aug

Jul

Jun

May

Apr

Feb

Mar

Jan

0

60

May

200

80

Mar

400

100

Jan

600

120

Feb

Heat(kWh/m^2)

800

Generatedelectricity(kWh)

For cold months, thermal and exergy efficiency of the system in Tabriz is better than the other locations (Figs. 9 and 10.), although the supplying heat is lower (Fig. 5.), this is due to the lower temperature of ambient air in Tabriz for this period.

Esfahan

Fig. 6. Total monthly electricity production of the system.

453

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

Radiation(kWh/m^2)

300 250 200 150 100 50 0 Jan

Feb

Mar

Apr

May

Tabriz

Jun

Jul

Shiraz

Aug

Sep

Oct

Nov

Dec

Esfahan

PVefficiency%

Fig. 7. Variation of solar irradiation on collector aperture throughout the year.

9.40% 9.20% 9.00% 8.80% 8.60% 8.40% 8.20% 8.00% 7.80% 7.60% 7.40% Jan

Feb

Mar

Apr

May

Shiraz

Jun

Jul

Esfahan

Aug

Sep

Oct

Nov

Dec

Nov

Dec

Tabriz

Fig. 8.Variation of PV efficiency throughout the year. 55.00%

Thermalefficiency%

54.00% 53.00% 52.00% 51.00% 50.00% 49.00% 48.00% Jan

Feb

Mar

Apr

Shiraz

May

Jun Esfahan

Jul

Aug

Sep

Oct

Tabriz

Fig. 9.Variation of thermal efficiency throughout the year.

454

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

10.40%

Exergyefficiency%

10.20% 10.00% 9.80% 9.60% 9.40% 9.20% 9.00% 8.80% 8.60% Jan

Feb

Mar

Apr

Shiraz

May

Jun

Jul

Esfahan

Aug

Sep

Oct

Nov

Dec

Tabriz

Fig. 10.Variation of exergy efficiency throughout the year.

3.2. Economic analysis In table 4, an annual exergoeconomic assessment for the three chosen cities is presented. As it is shown in this table, the system in Tabriz has the highest coverage of solar heat, electricity generation, thermal and exergy efficiency among the cities. Table 4. Annual exergoeconomic results for the three cities. Location

Tabriz

Shiraz

Esfahan

Solartiltedradiation(kWh/m^2)

2178

2448

2396

SolarheatcoveredbyPV/T(kWh/m^2)

1132

1992

1245

Totalelectricityproduced(kWh)

1078

1185

1170

Thermalefficiencyofcollector(%)

52.0%

51.6%

51.9%

ExergyefficiencyofPV/T(%)

9.7%

9.6%

9.6%

PVefficiency(%)

8.7%

7.5%

8.6%

NPV(Replacingelectricity)(€)

241

206

194

NPV(Replacingnaturalgas)(€)

100

66

56

In a separate analysis, the economic parameters of Athens (Table 2) are substituted for Iran and the results are shown in Table 5. It is clear that if the economic parameters in Iran would be the same as that in Athens, the system in various cities selected in Iran would have higher NPV and thus would be more profitable.

455

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456 Table 5. Analysis results considering economic data of Athens for Iran. Parameter 2 NPV (Replacing natural gas) (€/m ) 2 NPV (Replacing electricity)(€/m )

Shiraz 1385 2589

Esfahan 1358 2547

Tabriz 1418 2630

Athens 230.8 558.8

A comparison has been made between the three cities of reference [12] and the three cities in Iran for the selected parameters as illustrated in Table 6. It is clear that both energy and electricity production are favourable for Iran than those in Europe due to high level of solar insolation. The only unfavourable factor is NPV which can become desirable if a reduction is made in capital cost or bank loan interest rate or discount rate. Table 6. Comparison of energy and economic parameters for the three cities of Iran and the three cities of Ref. [12] in Europe Parameters

Shiraz

Tabriz

Esfahan

Athens

Munich

Dundee

Usefulsolarheatgain(kWh/m^2)

350.6

310.5

342.9

304.9

127.6

69.5

Annualelectricityyield(kWh/kWp)

1749.3

1591.3

1727.3

1390.3

1063.1

916.1

NPV(Replacingelectricity)(€/m^2)

36.2

42.4

34.2

558.8

164.7

Ͳ15.8

NPV(Replacingnaturalgas)(€/m^2)

11.6

17.6

9.9

230.8

Ͳ159.6

Ͳ152.5

4. Conclusion An investigation was performed on exergy and economic feasibility of a commercially available PV/T collector for the three cities having various climates. It was found that, 1. 2.

3. 4.

5.

PV/T system performance is greatly affected by climatic condition and monetary policy of the country under investigation. PV/T systems can play a significant role in electricity and hot water production for residential applications in Iran. For cold months where thermal energy is more needed than electricity, Shiraz and Esfahan mutually are better locations for PV/T system. On the other hand in hot months where electricity is needed, Tabriz shows a suitable location for investment. Economic parameters like capital cost and auxiliary energy price, affects the performance of PV/T collectors considerably. For Iran, the only issue regarding using PV/T collectors, is the economic factor; economic parameters in Iran challenges the viability of the PV/T systems, on the other hand, if the same economic conditions of Athens be considered for Iran, these systems would be more economically investible projects than for Athens. Considering the fact that changing discount rate or bank loan interest rate may be difficult for the government, putting subsidies on the capital cost or mass production of PV/T collectors is recommended in order to make these systems economically feasible.

Acknowledgements: The authors appreciate supports from Iran’s National Elites Foundation and South Pars Gas Complex research and development department of phase 1. Mr. Nemati greatly appreciates full cooperation of Mr. M. J. Nafehfeshan.

456

S. Nemati Jahromi et al. / Energy Procedia 75 (2015) 444 – 456

References [1]

Zondag HA. De vries DW.,Vanhelden WGJ., Van zolingen RJC.,Vansteenhoven AA.,.The yield of different combined PV-

[2]

Chow TT., Chan ALS., Fong KF., Lin Z., He W., Ji J. Energy and exergy analysis of photovoltaic-thermal collector with and

[3]

Huang BJ., Lin TH., Hung WC., Sun FS., Performance evaluation of solar photovoltaic/thermal systems. Solar Energy

[4]

Kalogirou SA., Tripanagnostopoulos Y., Hybrid PV/T solar systems for domestic hot water and electricity production.

[5]

Daghigh R., Ruslan MH., Sopian K., Advances in liquid photovoltaic/thermal (PV/T) collectors. Renewable and Sustainable

[6]

Ibrahim A., Othman MY.,Ruslan MH., Mat S., Sopian K. Recent advances in flat plate photovoltaic/thermal (PV/T) solar

[7]

Tyagi VV., Kaushik SC., Tyagi SK. Advancement in solar photovoltaic/ thermal (PV/T) hybrid collector technology,

[8]

Aste N., Del Pero C., Leonforte F. Water flat plate PV-thermal collectors: A Review, Solar Energy 2014;102:98-115

[9]

Makki A., Omer S., Sabir H. Advancements in hybrid photovoltaic systems for enhanced solar cells performance. Renewable

thermal collector designs. Solar Energy 2003;74:253–269. without glass cover. Applied Energy2009;86:310–316. 2001;70:443-448. Energy Conversion and Management 2006;47:3368-3382. Energies Reviews 2011;15:4156-4170. collectors. Renewable and Sustainable Energies Reviews 2011;15:352-365. Renewable and Sustainable Energies Reviews 2012;16:1383-1398.

and Sustainable Energies Reviews 2015;41:658-684. [10] Dupeyrat P., Menezo C., Fortuin S. Study of thermal and electrical performances of PVT solar hot water system. Energy and Buildings 2014;68:751-755. [11] Bakos GC., Soursos M., Tsagas NF., Technoeconomic assessment of a building-integrated PV for electrical energy saving in residential sector. Energy and Buildings 2003;35:757-762. [12] Axaopoulos PJ., Fylladitakis ED. Performance and economic evaluation of a hybrid photovoltaic/thermal solar system for residential applications. Energy and Buildings 2013;65:488-496. [13] Sarhaddi F., Farahat S., Ajam H., Behzadmehr A. Exergetic performance assessment of a solar photovoltaic thermal (PV/T) air collector. Energy and Buildings 2010;42:2184-2199. [14] Sobhnamayan F., Sarhaddi F., Alavi MA., Farahat S., Yazdanpanahi J. Optimization of a solar photovoltaic thermal (PVT) water collector based on exergy concept. Renewable Energy 2014;68:356-365. [15] Duffie JA., Beckman WA. Solar engineering of thermal processes. 2nd ed. New York: John Wiley & Sons; 1991. [16] Sabziparvar A. A., Shetaee H. Estimation of global solar radiation in arid and semi-arid climates of east and west Iran.Energy 2007;32:649-655. [17] K. Jafarpour, M. Yaghoubi. Solar radiation for Shiraz, Iran. Solar & Wind technology 1989;6:177-179. [18] Www.financeformulas.net/Loan_Payment_Formula.html

Biography M. Yaghoubi is professor of mechanical engineering , Shiraz university, Shiraz, Iran A.Vadiee is post-doctoral student, Shiraz university, Shiraz, Iran S. Nemati is master degree program student in mechanical engineering, Shiraz university, Shiraz, Iran and operator engineer at Phase 1 of South Pars Gas Complex, Asalouye, Bushehr, Iran.