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1. Solar Photovoltaic Theory

1. Solar Photovoltaic Theory. 1-3. System configuration. 1-3.System configuration. Contents.

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1. Solar Photovoltaic Theory

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  1. 1. Solar Photovoltaic Theory 1-3. System configuration

  2. 1-3.System configuration • Contents 1-3. System configuration1-3-1. Cells, Modules and Arrays1-3-2. Type of system ( Grid interconnection or not )1-3-3. Power conditioner (Control system)1-3-4. Batteries1-3-5. Wiring1-3-6. Some tips on system design

  3. Volt Ampere Watt Size Cell 0.5V 5-6A 2-3W about 10cm Module 20-30V 5-6A 100-200W about 1m Array 200-300V 50A-200A 10-50kW about 30m 1-3-1. Cells,Modules and Arrays • Hierarchy of PV Array 10 - 50 kW Module,Panel 100 - 200 W Cell 2 – 3 W 6x9=54 (cells) 100-300 (modules)

  4. Easy estimation 0.4911V x 72cells = 35.36 V35.36V x 4.95A = 175.03 W 1-3-1. Cells,Modules and Arrays • Module • Specification- Configuration 12x6=72 Cells- Inner wiring All Serial wiring- Max Power 175 W ( 2.4306w/cell ) - Vopen 44.4V - Vpmax 35.36V ( 0.4911 V/cell) - Ishort 5.55 A - Ipmax 4.95 A- Size 1574 x 826 x 46 mm- Weight 17.0 Kg 175W 1574mm To obtain high voltage, cells are serially wired in most of module. 826mm

  5. 1-3-1. Cells,Modules and Arrays • Module Module intersection Rubber packing Reinforced grass 46mm Plastic film PV cell( plastic molded ) Aluminum angle 826mm

  6. 1-3-1. Cells,Modules and Arrays • Module Back side view of Module 1574mm Cableconnector 862mm Terminalbox Cable Terminal box Attachment angle Bypass Diodeis inside

  7. 1-3-1. Cells,Modules and Arrays • Module connecting

  8. 1-3-1. Cells,Modules and Arrays • Array structure Side View Locallatitude • PV modules are mounted on frame that is tilted the same angle as local latitude. • Face should be truly to North or South. • Frame should be strong enough to withstand weight of modules and wind force by storm. Front View

  9. + - Without Diode Reverse current V= 0.5 x 2 = 1.0 V V= 0.5 x 4 = 2.0 V Partially shaded 1-3-1. Cells,Modules and Arrays • Arrays electrical structure • Serial connected modules form a “String”. • Parallel connected string form “Array”. • Each strings are connected with “Reverse-Current blocking Diode” • Parallel connected Array Units form “Array-system” String Array Module

  10. + - 1-3-1. Cells,Modules and Arrays • How many modules for a string? ( For 30kW system ) ModuleVpmax=35.36VPower=175W 175WModule • Number of serially connecting modules “m” is determined by Power Cont-roller’s input voltage. • Typical input voltage of 200V AC power controller is about 300V (190 – 450V. See 3-3 ) String voltage should be adjusted to this. • Consider voltage drop caused by partially shading, PV string’s voltage should add 10% more. • 300 x 1.1 = 330V • If module voltage is 35.36V, • m = 330 / 35.36 = 9.33 => 9 serial • Then string voltage is • 35.36 x 9 = 318.24V • String power is • 175 x 9 = 1,575W m

  11. + - 1-3-1. Cells,Modules and Arrays • How many strings for an array? ( For 30kW system ) ModuleVpmax=35.36VPower=175W 175WModule • Number of parallel-connecting strings “n” is determined by total output power. • At 9 modules per string, string output power is • 175 x 9 = 1,575 W • For a 30kW system • n = 30,000 / 1,575 = 19.05 => 20(parallel) • Total system power is • 1,575 x 20 = 31.5 kW m = 9 n

  12. + 175W - 1574mm 826mm 1-3-1. Cells,Modules and Arrays • Array layout ( For 30kW system ) ModuleVpmax=35.36VPower=175W 9 x 20 = 180 modules 175WModule 30kW system 1 module m = 9 n=20

  13. 1-3-1. Cells,Modules and Arrays • Array layout ( For 30kW system ) 9 x 2 Modules 3.5 m 8 m 30 kW system( 9 x 20 Modules) 25 m With working space, maintenance roadTotal area = 15 x kW (m2) 20 m

  14. 10 arrays + - + - + - 1-3-1. Cells,Modules and Arrays • Array-System Surge Arrester DC Switch Power Conditioner

  15. PV PV PV DG DG DG Main Grid( > 500kW) G 1-3-2. Type of system • Type of system ( Grid interconnection or not ) (a) Off-grid individual power system (Capacity:50W ) (b) Micro grid power system (Capacity:10 to 50kW ) (c) Small grid power system (Capacity:50 to 500 kW ) (d) Normal grid power system (Capacity: > 500kW ) • Install a renewable energy system in each household separately • This system is applied mainly for a non-electrified region or a rural area. • Install a renewable energy system in a small community by combining with diesel generators • It aims to save diesel fuel consumption and to enhance power supply. • Same as (b), but the system capacity is bigger. • Install a renewable energy system to the main grid.

  16. DC 12V DC 12V Battery Controller(DC) Module For every household Battery Power Conditioner(DC -> AC) AC 200V DC 300V Array For Community Battery 1-3-1. Cells,Modules and Arrays • System Structure 50 – 70 WSolar Home System(SHS) 1 to 50 kWStationary PV system

  17. DC-ACInverter(PWM) DC-DCConverter(Voltage Regulator) PWM (Pulse Wise Modulation) (A) Chop by thirstier For PMW, input voltage should be maintained 282.2V(300V) Smoothing Current(I) AC200V (V) Voltage 1-3-3. Power conditioner • Diagram of power conditioner ConvertDC to AC Seek MaxPower of PV Power Conditioner DC190to450V AC200V DC300V Voltage is example one To Seek Pmax point.Input voltage is automatically controlled Battery

  18. DC-ACInverter(PWM) DC-DCConverter(Voltage Regulator) (A) Current(I) (V) Voltage 1-3-3. Power conditioner • Basic voltage control rules Power Conditioner DC190to450V AC200V DC300V Seeking Pmax point. Width control Seeking ideal charge voltage PWM (Pulse Wise Modulation) Chop by thirstier Battery Smoothing AC200V

  19. (A) DC190to450V DC300V Narrow for voltage High intensity insolation Acceptable input zone of DC-DC Conv.(Typical example) DC-DCConverter(Voltage Regulator) Current(I) Wide for current Low intensity insolation See 3-5 (V) 190V 300V 450V 1-3-3. Power conditioner • Voltage allowance of DC-DC Converter • Due to the converter loss, DC-DC converter’s voltage allowance is narrow.

  20. DC 30 kWConv. 80 kWAC Output 10 kWPanel 10 kWPanel 10 kWPanel 10 kWPanel 10 kWPanel 10 kWPanel 10 kWPanel 10 kWPanel 10 kW x 3 = 30 kW Data LinkforParallel Operation DC 50 kWConv. 10 kW x 5 = 50 kW 1-3-3. Power conditioner • “Unit style” power conditioner • PV system is built based on unit capacities such as • 10 kW, 30 kW, 50 kW, and 100 kW units. • If you need a 80 kW system, you can parallel 30 and 50 kW units.

  21. 30kW powerconditioner 10kW Display unit PV array I/O Unit 10kW 1950 mm 10kW I/O unit Display unit 10kW Unit power conditioners 1-3-3. Power conditioner • “Unit style” power conditioner • Typical “Unit style” power conditioner. • Each unit is 10kW. • Left side photo is 30kW system.

  22. 1-3-3. Power conditioner • Small power conditioner for SHS • Load of SHS is DC, power conditioner is not include inverter. • Main function of power conditioner is “battery charge controller” to avoid over charging or over discharging.

  23. 1-3-3. Power conditioner • Small power conditioner for SHS

  24. 1-3-3. Power conditioner • Small power conditioner for SHS DC type fluorescent lamp

  25. Power Shifting Excess Power Demand Demand PV Power ＋　　－ Battery 1-3-4. Batteries • why battery is necessary? • In an SHS or Independent small grid system, PV’s output power does not meet with demand. • PV’s can generate in daytime only. But demand, such as lighting television, is almost nighttime load. • In main grid interconnected system, other diesel generator compensate this unbalance. So battery is not necessary. • Most systems of this type require “power shifting” by battery. • But batteries are expensive and their lifetime is not enough for PV’s. Therefore, batteries need replacing.

  26. 1-3-4. Batteries • Technical requirements for battery To allow optimal use of battery storage in a PV system, the following requirements should be met: • High efficiency (ratio between supply energy and storage energy); • Long lifecycle in frequent charge/discharge regimes; • High resistance at high temperature environments; ( 0 to 50deg.C); • Low self-discharge; • High ratio capacity/volume; • Low cost; • Rare maintenance processes.

  27. Lead-Acid battery • NiCd battery ( Nickel Cadmium) • NiMH battery ( Nickel metal hydrant ) • Li battery ( Lithium ) Rechargeable battery Shielded style Clad style Automotive 1-3-4. Batteries • Various type of battery • The below rechargeable batteries are available, but lead -acid batteries are used most often for power-shifting with solar cells because of their price and reliability. • Outlook of Lead-Acid batteries

  28. FullCharged100% DOD 75% DOD 100% DOD 50% 50% DOD(Depth of discharge) Remaining power in battery Empty Discharge/Charge sequence 1-3-4. Batteries • DOD (Depth Of Discharge) • Lifetime shortens if the battery is completely discharged, therefore discharging is limited in use. • The ratio of discharge level to the battery’s full capacity is called as DOB (%). • If DOD is kept shallow, the amount of chargeable energy will be low, even with the same kind of battery. However, lifetime will be longer.

  29. Capacity range (Ah) Expected lifetime Water Refilling Expected life cycle type Shieldedstyle Shieldedlead-acid 50 – 3000 150 - 3000 7 - 9 years 12 - 15 years(long life type) DOD 50% - 1000 - No (Maintenance free) Miniature shieldedlead-acid 0.7 – 144 50 - 130 3 - 5 years 5 - 6 years(long life type) DOD 50% - 500 DOD 50% - 700 Clad style Cladlead-acid for PV system 50 - 3000 - DOD 75% - 1800 Necessary 12 - 15 years Other Automotive lead-acid 21 - 160 Ah (5 hr rate) 4 - 5 years DOD 50% 300 Necessary 1-3-4. Batteries • Comparison of battery type DOD : Depth of discharge

  30. 200kWh System ( MSE500x2P ) 13 tones 900mm Acid-resistant floor 1200mm 1400mm 1-3-4. Batteries • Battery installation housing • Actual battery size is big and weight is very heavy. • Floor and lower part of wall should be covered with acid-resistant paint. • Ventilate air continuously to avoid hydrogen explosion.

  31. 1-3-4. Batteries • Automotive battery ( Conventional battery ) • For conventional SHS system, automotive battery is widely applied. • Mainly for DC-Load. (no Inverter) • Cheap but cycle life time is short(about 2 to 3 years) • Capacity of one module is 12V x 100Ahabout $90 12V x 100A x 0.75 = 900 Wh

  32. Row-wise serial Column-wise Serial Array Building 1-3-5. Wiring • Module wiring in arrays • There are may kind of wiring rules. Witch is better? ( 8 Serial 4 Parallel ) In the mid day, some part of array is shaded by Building !

  33. (A) Narrow for voltage High intensity insolation Current(I) Wide for current Low intensity insolation (V) 190V 300V 450V 1-3-5. Wiring • Module wiring in arrays • About characteristic of power conditioner, voltage allowance is narrow. • If array voltage goes down under 190V, power conditioner cannot maintain operation. (in this case) Acceptable input zone of Power conditioner(Typical example) Max Power

  34. 1-3-5. Wiring • Module wiring in arrays “Lost-Voltage” causes shutdown Column-wise serial - Voltage will be half. - Out of operational region. (A) Without shadow, both wiring are same as Max-power point Half voltage Half current Current(I) Row-wise serial - Current will be half. - Operation continue. (V) 190V 300V 450V

  35. 1-3-6. Some tips for system design • Surrounding environment and anticipated damage Falling nuts Falling leaf Stone throwing Sand breeze • Sand scratch(like frosted grass) Sea breeze • Contamination • Electrically grounding Animal bait

  36. 1-3-6. Some tips for system design • Surrounding environment and anticipated damage RainLightning Lightning rod Strong enough for stormy wind Heat up Enough ventilationfor cooling Trench for heavy rein

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