PV Power Plant Performance under Dessert Conditions: Lessons Learnt

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Cory Miller
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1 PV Power Plant Performance under Dessert Conditions: Lessons Learnt K Dr. Abdulrahman M. Alamoud Professor of Microelectronics and Solar Energy Leader, Solar PV Group (SPVG) Sustainable Energy Technologies (SET) Center Riyadh, Saudi Arabia

2 Factors contributing to higher PV system efficiency: Photonic Energy: Solar Spectrum Solar Cells: Innovative new materials PV modules: Minimize losses due to temperature and dust. Kingdom of Saudi Arabia PV manufacturing: Improved technologies.

3 Kingdom of Saudi Arabia PV Module Causes of Degradation High Temperature Dust Accumulation

5 PV Module degradation Temperature Degradation Roots I o A qd L N e e A qd L N h h D n 2 i V oc kt I L ln 1 q Io

6 Effect of Temperature on V oc dv oc dt V go V oc T kt /q dv oc dt = 2.3 mv/ C

10 Modified Module Fabrication Improved PV module fabrication for high Temperature Thermal Cycling High Humidity Prolonged Ultraviolet Radiation Cyclic Pressure Loading

11 T cell ( C) = T ambient ( C) intensity (in m W/cm 2 )

14 Solar Irradiance during a day

16 Properties of PV modules under test Private test unit # No. of Cells Rated power (W) at SRC A M (m 2 ) A TA (m 2 ) TU TU TU TU TU

17 Parameters Kingdom of Saudi Arabia Output parameters for TU13. H/T = 1049/38 (Base) I-V output H/T = 1000/25 (extrapolated) P mp, watts V mp, volts I mp, amps FF (%) I sc, amps V sc, volts T am, C

18 PV module Degradation: output parameters after one year Module NO. A M (m 2 ) % change in output parameters I sc V sc P mp FF TU TU TU TU TU

21 Physical Module Degradation

22 Dust Accumulation on PV Modules Must clean Modules at least weekly Ground and surrounding dust Sand Storm Dust storm mixed with little rain

23 Cleaning a small system: no problem A need to devise an innovative method for cleaning large PV systems: low cost & efficient In most cases cleaning with water is sufficient Stubborn spots of dust: need detergent Minimize the dust accumulation: film coating Two-axis tracking: dust accumulation is less

24 Clean PV Modules

25 PV Module with Dust Accumulation

27 The Solar Village Start of Operation (9/1981) A 350 kw CPV Power Plant The first and largest in the World 160 two-axis tracking pedestal CPV (33x) Solar Cells 1100 kwh lead acid batteries 300 kva, 40 VAC, 3 phase, Inverter

28 Simplified schematic of half-module connection in the 350 kw PV field.

29 Temperature effect on the 350 kw PV System High temperature causes degradation of all PV system parameters Higher wind speed lowers the temperature effect DNI values higher than 650 W/m sq causes the module temperature to rise This implies poor module thermal recycling

30 The variation of the output power of the PVPS with the direct normal insolation for: (a) T = C and V = 5 7 ms 1, (b) T = C and V = 1 3 ms 1, (c) T = C and V = 1 3 ms 1.

31 The variation of the conversion density of the PVPS with the direct normal insolation for: (a) T = C and V = 5 7 ms 1, (b) T = C and V = 1 3 ms 1, (c) T = C and V = 1 3 ms 1.

32 The percentage rate of change of the output power density of the PVPS with respect to the direct normal insolation as a function of the DN insolation for: (a) T = C and V = 5 7 ms 1, (b) T = C and V = 1 3 ms 1, (c) T = C and V = 1 3 ms 1.

33 The percentage rate of change of the conversion efficiency of the PVPS with respect to the direct normal insolation as a function of the DNI insolation for: (a) T = C and V = 5 7 ms 1, (b) T = C and V = 1 3 ms 1, (c) T = C and V = 1 3 ms 1.

34 The variation of the output power of the PVPS with the ambient air temperature for the wind speed range of 1 3 ms 1 and: (a) DN = 900 Wm 2 ± 2.5%, (b) DN = 700 Wm 2 ± 2.5%, (c) DN = 500 Wm 2 ± 2.5%, and (d) DN = 300 Wm 2 ± 2.5%.

35 The variation of the conversion efficiency of the PVPS with the ambient air temperature for the wind speed range of 1 3 ms 1 and: (a) DN = 550 Wm 2 ± 2.5%, (b) DN = 400 Wm 2 ± 2.5%, (c) DN = 750 Wm 2 ± 2.5%, and (d) DN = 900 Wm 2 ± 2.5%.

36 The rate of change of the output power of the PVPS with respect to both the wind speed and the ambient air temperature as a function of the direct normal insolation.

37 The rate of change of the conversion efficiency of the PVPS with respect to both the wind speed and the ambient air temperature as a function of the direct normal insolation.

38 The variation of the output power of the PVPS with the wind speed for the ambient air temperature range of and: (a) DN = 900 Wm 2 ± 2.5%, (b) DN = 700 Wm 2 ± 2.5%, (c) DN = 500 Wm 2 ± 2.5%, and (d) DN = 300 Wm 2 ± 2.5%.

39 The variation of the conversion efficiency of the PVPS with the wind speed for the ambient air temperature range of and: (a) DN = 150 Wm 2 ± 2.5%, (b) DN = 300 Wm 2 ± 2.5%, (c) DN = 650 Wm 2 ± 2.5%, (d) DN = 700 Wm 2 ± 2.5%, (e) DN = 800 Wm 2 ± 2.5%, and (f) DN = 900 Wm 2 ± 2.5%.

40 Minimum and maximum values of each measured parameter of the PVPS during the test period Parameter Minimum Maximum Ambient air temperature (T), C Wind speed (V), ms Direct Normal Insolation (DNI), Wm Input Power (P i ), KW Output Power (P o ), KW Conversion Efficiency ( ), % Note: The total effective area of the 160 arrays is equal to 3807 m 2.

41 Number of defective modules versus time ( best line, experimental points).

42 Dust Accumulation on PV System PV System cleaned once a week Manual cleaning using pressurized Water jet Water and soap is used for stubborn stains Cleaning twice a week- Storm season

45 The I-V characteristics of the photovoltaic cells at different dust deposition densities.

48 Conclusion The output power and efficiency of the photovoltaic power system (PVPS) increases linearly with increasing direct normal insolation up to approximately 550 Wm -2 with minor changes due to the variations of the ambient air temperature and the wind speed. The changes in the output power due to the variation of the ambient air temperature and the wind speed become noticeable at direct normal insolation values greater than 550 Wm -2. The practical range of the direct normal insolation which is corresponding to the maximum conversion efficiency for this PVPS is from 550 Wm -2 to 650 Wm -2 at ambient air temperature range of C and wind speed range of 1-7 ms -1. Dust accumulation is a problem that needs to be addressed, however solution will add to the cost of a PV system.