Solar Cells Thin Film Technologies Part 8 doc

Power Output Characteristics of Transparent a-Si BiPV Window Module 199 Fig. 14. Power output data calibration by comparing the experimental data to the computed data obtained from the simulation program (TRNSYS). Power performance analyses were performed of PV modules facing south (azimuth = 0 º) depending on the different inclined angles of 0 º, 10 º, 30 º, 50 º, 70 º, and 90 º. The data set consisted of the experimental data for 0 º, 30 º, and 90 º and the computed data for 10 º, 50 º, and 70 º. Figure 15 illustrates the monthly power output depending on the inclined angle ranging from 0 º to 90 º south (azimuth = 0 º). PV modules that were tilted at an angle below 30 º showed a relatively good power performance of over 6 kWh in the summer, while those with an inclined angle above 50 º demonstrated a power performance of less than 6 kWh. The most effective annual power output data of 977 kWh/kWp was obtained at an inclined angle of 30 º (SLOPE_30), as shown in Figure 16. On the other hand, the lowest annual power output of 357 kWh/kWp was obtained from the PV module with a slope of 90 º (SLOPE_90), which was 37 % of the annual power output of SLOPE_30. From Figure 16, it can be seen that the annual power output performance was effective in the order of SLOPE_10 (954 kWh/kWp), SLOPE_0 (890 kWh/kWp), SLOPE_50 (860 kWh/kWp), and SLOPE_70 (633 kWh/kWp). The power generation performance depending on the angle of the azimuth was also estimated for PV modules with different inclined slopes, as shown in Figure 17. Similarly, a PV module inclined at an angle of 30 º showed the most effective power output data for all directions in terms of azimuth angles, and the lowest data was obtained from that with an inclined angle of 90 º. For the PV module inclined at an angle of 30 º, the best power performance among the analyzed PV modules facing various directions was obtained for the PV module that was installed to the south (azimuth = 0 º). It can be seen from Figure 17 that different azimuth angles affected the power performance of PV modules: that is, the power performance decreased as the direction of the PV module was changed from the south to the east and west, in comparison to the PV modules that were inclined at the slope of 30 º, as listed in Table 2. Solar Cells – Thin-Film Technologies 200 Fig. 15. Monthly power output data of PV module depending on the slope, and facing south (azimuth = 0). Fig. 16. Annual power production of PV module depending on the slope, and facing south (azimuth = 0). Power Output Characteristics of Transparent a-Si BiPV Window Module 201 Fig. 17. Annual power production of PV modules with various slopes depending on the angle of azimuth ranging from 0 to 90 Angle of azimuth (º) Direction Power performance efficiency a (%) 0 South 100 30 Southwest 30 º 99 60 Southwest 60 º 93 90 West 83 270 East 78 300 Southeast 60 º 88 330 Southeast 30 º 96 a. Power performance efficiency was calculated from the percent of power output at each azimuth angle on the basis of the power output data of PV module to the south. Table 2. Power performance efficiency of PV module with a slope of 308 depending on azimuth angle It can be seen from Figure 17 that for the annual power performance of several PV modules, the power output increased with an increase of the inclined angle below 30 º, and decreased with an increase of the inclined angle above 30 º. In particular, at inclined slopes above 60 º there was a steep decline of power performance with the increase of the inclined slope, as shown in Figure 17. This could be due to the incidence angle modifier correlation (IAM) of glass attached to the PV module, which showed a similar tendency in IAM depending on the inclined angle [11], as can be seen in Figure 18. Actually, IAM should be computed as a function of incidence angle () when estimating the power output of the PV module, by using the following Equation (1) [11]: Incidence Angle(D egrees) 0 100 200 300 400 500 600 700 800 900 1000 1100 Power(kWh/kWp/year) South Azimuth 330 Azimuth 300 Azimuth 270 Azimuth 90 Azimuth 60 Azimuth 30 01030507090 Solar Cells – Thin-Film Technologies 202 IAM = 1 – (1.098×10 -4 ) - (6.267×10 -6 )  + (6.583×10 -7 )  - ×10 -8    (1) Fig. 18. Correlation of incidence angle modifier given by King et al. (1994). Accordingly, a characteristic of the glass attached to the PV module is considerably influential so that the solar transmittance (Tsol) remarkably decreases with an increase in the inclined slope of the PV module from the higher incidence angle. Therefore, the solar transmittance efficiency can significantly affect the power output of the PV module. 6. Power efficiency of PV module 6.1 Hourly based analysis of the power efficiency The power efficiency can be calculated by multiplying total irradiation by the PV window area. Annual averaged power efficiency is illustrated in Fig. 19. η , =  ,   Х  η S, τ ; Power Efficiency E use,τ ; Power Output(Wh) A a ; PV windows area (m 2 ) H τ ; Total irradiation on the PV windows Annual average power efficiencies of the inclined slope of 30 º (SLOPE_30), horizontal PV module (SLOPE_0) and vertical PV module (SLOPE_90) turned out to be 3.19%, 2.61% and 1.77%, respectively, indicating that the inclined slope of 30 º showed the greatest efficiency. On the other hand, the horizontal PV showed the highest instantaneous peak power efficiency of 6.0% followed by those of the inclined slope of 30 º (5.6%) and vertical PV (4.0%) angles. In terms of the monthly average power efficiency depending on each inclination angle, the inclined slope of 30 º (SLOPE_30) showed 3.82% in June and the horizontal PV (SLOPE_0) showed 3.63% in July. The inclined slope of 30 º showed 2.15 % of efficiency and the horizontal PV showed 0.81% in December. On the other hand, the vertical Power Output Characteristics of Transparent a-Si BiPV Window Module 203 PV (SLOPE_90) showed the peak efficiency of 2.38% in February and lowest efficiency of 0.80% in June. The inclined slope of 30 º (SLOPE_30) showed the greatest annual average power efficiency of 3.19%, followed by horizontal and vertical PV modules showing efficiencies of 2.61% and 1.77%, respectively. Fig. 19. Annual hourly averaged power efficiency 6.2 Effect of power efficiency by the intensity of solar irradiance Assuming the solar irradiance of 900 W/m 2 , the power efficiencies of the inclined slope of 30º and horizontal PV reached 5%, while the vertical PV partially exceeded 3%. The inclined slope of 30 º and horizontal PV showed relatively high power efficiency even under high solar irradiance conditions, while the efficiency of vertical PV significantly dropped after reaching 500W/m 2 . The inclined slope of 30 º and horizontal PV can obtain relatively uniform solar irradiance throughout the year and thus the high power efficiency can be achieved over the large range of solar irradiance, while the vertical PV absorb the low solar irradiance during the winter period and thus the power efficiency is reduced in those low irradiance conditions. 6.3 Power efficiency by the temperature variation The correlation between the power efficiency and the PV surface temperature variation is illustrated. Under the low solar irradiance, the data is scattered and thus did not show the clear correlation. However, it showed the clear correlation between PV efficiency and the surface temperature under the solar irradiance higher than 600W/m 2 , i.e., the PV efficiency is improved at higher surface temperature. This is due to the fact that the higher surface temperature enhances the power efficiency in case of amorphous PV as opposed to crystalline silicon solar cell (c-Si solar cell). 5 6 7 8 9 10111213141516171819 Ti m e ( H ) 0 1 2 3 4 5 6 7 PV_Efficiency(%) SLOPE_30 SLOPE_90 SLOPE_ 0 Solar Cells – Thin-Film Technologies 204 Fig. 20. Correlation between solar insolation and power efficiency (SLOPE_90°, SLOPE_30°, SLOPE_0°) Fig. 21. Correlation between the surface temperature and power efficiency (SLOPE_90°) Power Output Characteristics of Transparent a-Si BiPV Window Module 205 Fig. 22. Correlation between the surface temperature and power efficiency (SLOPE_30°) Fig. 23. Correlation between the surface temperature and power efficiency (SLOPE_0°) Solar Cells – Thin-Film Technologies 206 6.4 Power efficiency by the solar incidence angle The PV efficiencies of each inclination angle under different solar incidence angle and solar irradiance are illustrated in the figures below. In case of vertical PV module (SLOPE_90), the power efficiency showed constant value until the solar incidence angle of 65° and it started to rapidly drop after 65°. These characteristics are considered to be the effect of absorbed solar insolation (incident angle modifier) depending on the solar incidence angle reaching the PV module glass wall. This phenomenon did not take place in case of the inclined slope of 30 º (SLOPE_30) due to the low PV efficiency at the solar incidence angle higher than 65°. Likewise, the horizontal PV module was not affected by incident angle modifier as well in most of the solar radiation conditions except for the high solar incidence angle of greater than 65° and the low solar insolation of less than 400W/m 2 where the efficiency was rather decreased. It turns out that the power efficiency of PV module is largely affected by the solar incidence angle, solar azimuth and altitude. Furthermore, the rapid decrease in the PV efficiency during the summer period is due to the reduced solar transmittance through the window system at the solar incidence angle higher than 70°, showing the impact of the front glass of PV module on the power efficiency. Fig. 24. PV module power efficiency vs. solar incidence angle (SLOPE_90°) Power Output Characteristics of Transparent a-Si BiPV Window Module 207 Fig. 25. PV module power efficiency vs. solar incidence angle (SLOPE_30°) Fig. 26. PV module power efficiency vs. solar incidence angle (SLOPE_0°) Solar Cells – Thin-Film Technologies 208 7. Conclusion This study evaluated a transparent PV module in terms of power generation performance depending on installation conditions such as the inclined slope (incidence angle) and the azimuth angle. The objective of this evaluation was to provide useful data for the replacement of traditional building windows by BIPV system, through the experimental results measured in the full-scale mock-up system. 1. The annual power output of the PV module was measured through the mock-up model. The PV module that was installed at a slope of 30 º exhibited a better performance of 844.4 kWh/kWp annual power output than the vertical PV module with a slope of 90 º. 2. The experimental data was compared with the computed data obtained from the simulation program. The computed data is considered to be reliable with a relative error of 8.5 %. The best performance of annual power output was obtained from the PV module with a slope of 30 º facing south, at an azimuth angle of 0 º. The inclined angle was one of the factors that significantly influenced the power generation performance of the PV module, which varied within a range of 24 % on average and provided a maximum difference of 63% in the power output at the same azimuth angle. 3. In terms of the computed power output from a slope of 30 º depending on the azimuth angle, the PV module facing south exhibited the most effective performance compared to other azimuth angles. The direction in which the PV module faces can also be a very important factor that can affect the power performance efficiency by 11 % on average and by a maximum of 22 %, depending on the azimuth angle. 8. References [1] Y. Kuwano, Progress of photovoltaic system for houses and buildings in Japan, Renewable Energy 15 (1998) 535–540. [2] A. Ja¨ger-Waldau, Photovoltaics and renewable energies in Europe, Renewable and Sustainable Energy Reviews 11 (2007) 1414–1437. [3] A. Stoppato, Life cycle assessment of photovoltaic electricity generation, Energy 33 (2008) 224–232. [4] A. Hepbasli, A key review on exergetic analysis and assessment of renewable energy resources for a sustainable future, Renewable and Sustainable Energy Reviews 12 (2008) 593–661. [5] A. Zahedi, Solar photovoltaic (PV) energy; latest developments in the building integrated and hybrid PV systems, Renewable Energy 31 (2006) 711–718. [6] S. Teske, A. Zervos, O. Schafer, Energy revolution, Greenpeace International, European Renewable Energy Council (EREC) (2007). [7] R.W. Miles, G. Zoppi, I. Forbes, Inorganic photovoltaic cells, Materials Today 10 (2007) 20–27. [8] S. Guha, Amorphous silicon alloy photovoltaic technology and applications, Renewable Energy 15 (1998) 189–194. [9] J.H. Song, Y.S. An, S.G. Kim, S,J. Lee, Jong-Ho Yoon, Y.K. Choung, Power output analysis of transparent thin-film module in building integrated photovoltaic system(BIPV), Energy and Building, Volume 40, Issue 11, (2008) 2067-2075 [10] TRNSYS, A transient system simulation program version 14.2 Manual. Solar Energy Laboratory: University of Wisconsin, Madison, USA, 2000. [11] D.L. King, et al., Measuring the solar spectral and angle of incidence effects on photovoltaic modules and irradiance sensors, in: Proceedings of the IEEE Photovoltaic Specialists Conference, 1994, pp. 1113–1116. [...]... of the HCF2Cl partial pressure The most efficient device obtained by 212 Solar Cells – Thin- Film Technologies this procedure, corresponding to 40 mbar HCF2Cl partial pressure in the 400mbar Ar total pressure, has =14 .8% , JSC=26.2mA/cm2, VOC = 82 0mV and ff=0.69 The solar cells were then submitted to an etching procedure in a Br–methanol mixture at 10% to eliminate the back contacts and part of the CdTe... the film Eb =8 keV - Re=0. 38 m Eb=12 keV - Re=0.69 m Eb= 18 keV - Re=1.24 m Eb=24 keV - Re=1.9 m Eb=30 keV - Re=2 .8 m Eb=36 keV - Re=3.7 m CL Intensity (a.u.) 10 8 1.4 eV / NBE Intensity ratio (a.u.) 12 20 CL spectra at T=77K injection density per unit volume constant 16 14 10 36 keV 8 6 0,5 1,0 1,5 2,0 2,5 3,0 3,5 Maximum penetration depth (m) 4,0 12 18 4 24 36 2 0 1,0 8 12 0,0 6 8 keV 18 30... CSS allows to obtain CdTe film with a very high crystalline quality and grains of about one order of magnitude larger (~10m) than films deposited by other deposition techniques (Sputtering, HVE, etc.) and, for this reason, with a low lattice defect density (Romeo A et al., 2009) 214 Solar Cells – Thin- Film Technologies Fig 2 Picture of the CSS setup used for growing the CdTe films studied (left); Detail... the untreated CdTe and of the samples annealed with 40 mbar HCF2Cl partial pressure were shown The preferential orientation of each film is analyzed by using the texture coefficient Chkl, calculated by means of the following formula (Barret & Massalski 1 980 ): C hkl  1 N I hkl /I 0 hkl ,  I hkl /I0 hkl N (4) 220 Solar Cells – Thin- Film Technologies where Ihkl is the detected intensity of a generic peak... Treatment on the Opto-Electronic Properties of Materials for CdTe/CdS Solar Cells Nicola Armani1, Samantha Mazzamuto2 and Lidice Vaillant-Roca3 1IMEM-CNR, Parma University of Parma, Parma 3Lab of Semicond and Solar Cells, Inst of Sci and Tech of Mat., Univ of Havana, La Habana 1,2Italy 3Cuba 2Thifilab, 1 Introduction Thin film solar cells based on polycrystalline Cadmium Telluride (CdTe) reached a record... temperature (77K) CL spectra (Eb=15keV) of the 40 mbar HCF2Cl partial pressure etched solar cell (a) (b) (c) Fig 14 40 mbar HCF2Cl partial pressure CdTe CL mapping; a) SEM image of the surface morphology; b) monoCL image at the NBE emission energy (E=1.57eV); c) monoCL at E=1.4eV emission energy 2 28 Solar Cells – Thin- Film Technologies (Fig.14 c) a complementary CL intensity distribution has been observed... appeared as tetragonal pyramids with the vertex aligned on the growth direction (Fig 8 a) This shape justified their high preferential orientation along the (111) direction This grain shape appeared clearly modified in the HCF2Cl annealed films They were more rounded and the pyramids seem to 222 Solar Cells – Thin- Film Technologies be made up by a superposition of “terraces” (Fig 6 b) This morphology... at 25keV have been summarized in Fig 10 224 Solar Cells – Thin- Film Technologies 80 CL Intensity (a.u.) 1.4 eV Eb=25 keV T=77 K NBE 1.57 eV 60 40 50 mbar 40 mbar 20 0 30 mbar y band 1.47 eV untreated 1,1 1,2 1,3 1,4 1,5 1,6 Energy (eV) Fig 9 Comparison among the low temperature (77 K) CL spectra (Eb=25keV) of untreated CdTe and samples annealed at a HCF2Cl partial pressure of 30, 40 and 50 mbar 25 1.4... volume by increasing the electron beam energy allows us a depth-dependent analysis The CL analysis of 6 -8 m thick CdTe thin films, as the active layers used in the fabrication of solar cells, has particular advantages: the maximum penetration depth of the exciting electrons of the SEM beam can reach 4 .8 m by using 36 keV energy This depth is higher than the few hundreds of nanometers probed by the commonly... of the photovoltaic market Up to now two companies (Antec Solar and First Solar) have a noticeable production of CdTe based modules, which are assessed as the best efficiency/cost ratio among all the photovoltaic technologies Since the record efficiency of such type solar cells is considerably lower than the theoretical limit of 28- 30% (Sze, 1 981 ), the performance of the modules, through new advances . crystalline silicon solar cell (c-Si solar cell). 5 6 7 8 9 1011121314151617 181 9 Ti m e ( H ) 0 1 2 3 4 5 6 7 PV_Efficiency(%) SLOPE_30 SLOPE_90 SLOPE_ 0 Solar Cells – Thin- Film Technologies. (SLOPE_0°) Solar Cells – Thin- Film Technologies 206 6.4 Power efficiency by the solar incidence angle The PV efficiencies of each inclination angle under different solar incidence angle and solar. power efficiency vs. solar incidence angle (SLOPE_30°) Fig. 26. PV module power efficiency vs. solar incidence angle (SLOPE_0°) Solar Cells – Thin- Film Technologies 2 08 7. Conclusion