ENERGY AND EXERGY ANALYSIS OF A SOLAR PHOTOVOLTAIC PERFORMANCE IN BAGHDAD

Photovoltaic modules usually generate electricity from a specific range of light frequencies and cannot cover the whole solar range of infrared, ultraviolet and diffused light. Hence, much of the striking sunlight energy is wasted by the solar modules. Thus, energy and exergy analysis were conducted to determine the performance of a solar photovoltaic module in Baghdad, Iraq. An engineering equation solver (EES) software has been using to develop the mathematical model. The environmental parameter of solar radiation, ambient temperature, and wind speed were obtained using Meteonorm software. The operating parameters of a PV module includes normal operation cell temperature, open-circuit voltage, and short-circuit current were obtain from manufacturer data sheet. The results showed that, the exergy efficiency ranged from 10.8% to 15.8 %, while the energy efficiency varies between 15.71% to 15.74 % and the exergy destruction varied from 182.8 to 352.3 W/m2 throughout the year. It has been found that, the first law efficiency was greater than second law efficiency. The differences between the two efficiencies from January to December are (25.6%, 31.1%, 25.1%, 25.6%, 17.8%, 9.6%, 9.6%, 1.2%, 0.5%, 0.45%, 2.5%, and 14.6%) respectively. While the exergy destruction through the same 12months are (195.4, 233.5, 304.3, 352.3, 333.8, 292.9, 309.3, 274.6, 249.8, 215.9, 187.4, and 182.8) W/m2.


INTRODUCTION
Renewable energy, also known as clean energy, comes from natural sources or processes that are continually replenished. It is the main alternative to fossil fuels nowadays for their low air pollution and CO2 emissions. A solar photovoltaic is a standout amongst the hugest and quickly developing technology that converts the solar radiation into direct current electricity by using semiconductors. Photovoltaic solar panel performance depends on solar cell temperature, output voltage, current, module area, ambient temperature and solar radiation intensity [1]. Among different renewable energy technologies, the photovoltaic (PV) is the best technology known and widely used for generating electricity. The use of photovoltaic for generating electricity developed from 400 to 600 billion kilowatt-hours from 2010 to 2017 [2]. A group of researchers evaluated the energy and exergy performance of a photovoltaic/thermal (PV/T) collector integrated with a greenhouse in India [3]. The results showed that yearly exergy thermal has been obtained to be 12.8 kWh, yearly exergy input to the greenhouse was calculated to be 21291 kWh and the total exergy output during 2006-2007 was 728.8 kWh. The exergy efficiency for the PV/T system was 4%. From the analysis, it was found that maximum monthly electrical generation occurs in March while the minimum occurs in August. A researcher analyzed a (PV/T) collector with and without glass cover by using energy and exergy model [4]. It is clear that the energetic efficiency of the glazed collector was found always better than the unglazed collector. To maintain high exergy efficiency, unglazed PV/T system would be favorable when the packing factor, ratio of water mass to collector area, and wind velocity increased. In other hand, the increase of on-site radiation or ambient temperature led to choose a glazed PV/T system. The energy and exergy analysis for four different Indian cities of a hybrid micro-channel photovoltaic thermal (MCPVT) module and a single channel photovoltaic thermal (SCPVT) module were investigated by a previous scholar [5]. The results showed that the thermal gain of MCPVT increased over SCPVT by (70.62% -74.05%).
The overall annual exergy gains of MCPVT ranged from (60.19% -63.47%) higher than SCPVT module. The exergy efficiency of MCPVT was higher than SCPVT by (57.61% -63.19). A researcher investigated the performance of the photovoltaic system under full and no-load conditions for a DC refrigerator. For no load condition, the average photovoltaic energy and exergy efficiencies in May were found to be 8.4 and 11.4% respectively. In the case of a full load condition, the average photovoltaic efficiencies of energy and exergy were 8.2 and 11.2% respectively in the same month [6]. A previous researcher theoretically analyzed the exergy life cycle and compared the performance of three unique setups, nanofluids-based PV/T, a standard PV and PV/T [7]. They announced that the nanofluids-based PV/T demonstrated the best execution contrasted with the standard PV and PV/T. At the ideal estimation of solar radiation, nanofluid-based PV/T created 1.3 MW h/m2 of high-grade exergy every year while PV and PV/T were 0.36, 0.79 MW h/m2, respectively. The lowest exergy payback time of 2 years was due to the nanofluid-based PV/T. A recent scholar investigated two grid-connected photovoltaic systems monocrystalline silicon (c-Si) and copper-indium-diselenide (CIS) that located in Malaysia [8]. Results have demonstrated that the CIS system had a higher efficiency than the c-Si system by 23. efficiency occurred in September for c-Si with 9.3 % and in August for CIS with 11.3 %. The maximum efficiency occurred in February for c-Si with 12.3 % and 14.4 % for CIS. This work aims to evaluate the performance of a photovoltaic solar for the whole year in Baghdad according to energy and exergy analysis.

CASE STUDY
The study was conducted in Iraq, Baghdad (33.3 N latitude, 44.2 E longitude). The analysis has been developed by using (EES) software. The environmental parameter of solar radiation, ambient temperature, and wind speed were obtained using Meteonorm software. The operating parameters of (infinity KD -P260) PV module were obtain from manufacturer data sheet as listed in Table 1.

ENERGY AND EXERGY ANALYSIS
Electrical efficiency is quantifying as the ability of a solar panel to convert the sunlight into electricity. This is done when sunlight interacts with silicon cells inside a solar panel to generate the electrical current. The electrical efficiency of a solar panel can be calculated as the electrical power that has been converted by the panel to the maximum power that comes from the solar radiation if it was all converted to electricity [9,10].
Where is the solar radiation, A is the panel's area and power can be calculated by: The current and voltage of the PV module can be expressed as: Where Isc is the short circuit current while Voc is the open circuit voltage. The solar panel temperature Tc can be expressed by: Temperature of PV module (TC) can be estimated as [10] = + −20 The fill factor represents the most extreme power transformation effectiveness of the PV moduls and it can be calculated using the below equation [11].
Where Vm and Im are the voltage and the current of the PV module at maximum power.
On the other hand, the second law of the thermodynamics was basically deals with the Exergy, is characterized as maximum helpful work that is extracted from a system. The electrical power of the PV modules is the result of the current and the voltage output from the device. This transformation productivity is anything but a steady. In any case, there is a most power, where the voltage is Vm, which is not as much as the opencircuit voltage, Voc yet near it, and the current is Im, which is less the cut off, Isc however near it too (Fig. 1)

Figure 1: I-V curve
Exergy investigation procedure use for energy and mass conservations standards with the 2 nd law for the investigation outline and change of energy and different system. Exergy is characterized as the greatest measure of useful work that can be delivered by a device as it comes to equilibrium with a reference condition [12]. The general type of exergy for a control volume for the Pv modules as Where Exout , , and ℎ are the exergy of output , electrical, and thermal respectively.
Where Q represents heat losses from the PV cell, can be estimation by The overall heat transfer coefficient of PV module (U) includes convection heat transfer coefficient (ℎ ) and radiation heat transfer coefficient Convective coefficient Where is the wind speed. And radiation heat transfer coefficient between PV module and atmosphere ℎ = * * ( + ) * ( 2 + 2 ) The exergyy input for a PV module is given by the petela theorem it [13] = * * [1 − Sun temperature ( = 6000 ) As detailed in the exergy efficiency is given as [14,15]:

RESULT AND DISCUSSION
The PV module was analysis by applied energy and exergy models. Exergy efficiency is most convenient, reliability, effective, and more efficient tool than the energy efficiency for estimation the efficiency of the PV module. All figures from 2 to 13 show the destruction of solar PV exergy, energy and exergy efficiencies for the PV module through the year, for all figured constant value of energy efficiency even though the solar intensity was changed through the year. The augmentation in the quantity of photons attracting solar PV module prompts increment the current. The solar PV module performance is adversely influenced by the module temperature. As increase in the temperature of module, the short circuit current was increase while rapidly decreasing happing in open-circuit voltage. This is on the grounds that the expansion in temperature prompts the decrease in the band hole of the characteristic semiconductor. The energy efficiency was almost constant due to the fact that the power increases with the increase of the solar radiation. The exergy efficiency is inversely proportional to the exergy destruction. The exergy destruction represents the thermal losses of the system due to the increase of ambient and cell temperatures. Also the clouds, dust and gases that contained in air effect on its. The variation of the destruction of solar PV exergy, energy and exergy efficiencies (Ex_des , , ) -January was show in figure 2, It can be seen that the maximum values of (Ex_des , , ) were 337.3 W/m 2 , 15.74%, 16.9 % respectively, while the minimum values were 89.5 W/m 2 15.73%, 5.8% respectively.   The maximum and minimum variation of (Ex_des, , ) -Jule was show in figure 8, the results indicated that the maximum values were 354.1 W/m 2 , 15.71%, 17.6 %respectively, while the minimum values were 218.2 W/m 2 , 15.7 %, 10.2 %respectively.     It can be seen from Figure 12 that the maximum values of (Ex_des, , ) -November were 310.4 W/m 2 , 15.74%, 18.3 % respectively, while minimum values were 190.8 W/m 2 , 15.72%, 9.7% respectively. Figure 13 shows that the maximum values of (Ex_des , , )-December were 290.6 W/m 2 , 15.74%, 17.3 % respectively, while the minimum values were 111.9 W/m 2 , 15.73%, 8.2% respectively.  The variation of the destruction of solar PV exergy, energy and exergy efficiencies (Ex_des , , ) -throughout the year was show in figure 14, the results indicated that the (Ex_des) throughout the whole year from January to December are are (195. 4 Also, it can be indicated from the figure that the energy performance was greater than that of exergy throughout the year, where the efficiency differences between them throughout the whole year from January to December are (25.6%, 31.1%, 25.1%, 25.6%, 17.8%, 9.6%, 9.6%, 1.2%, 0.5%, 0.45%, 2.5%, and 14.6%) respectively.

Figure 14:
The variation of destruction of solar PV exergy, energy and exergy efficiencies (Ex_des, η, η_ex) -throughout the year