1. Solar Photovoltaic Theory

1
1. Solar Photovoltaic Theory

• 1-3. System configuration

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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
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1-3-1. Cells,Modules and Arrays

• Hierarchy of PV

Array
10 - 50 kW
Module,Panel
100 - 200 W
Cell
2 3 W
6x954 (cells)
100-300 (modules)
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1-3-1. Cells,Modules and Arrays

• Module

• Specification- Configuration 12x672 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
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1-3-1. Cells,Modules and Arrays

• Module

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

• Module connecting

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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
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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
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1-3-1. Cells,Modules and Arrays

• How many modules for a string? ( For 30kW system )

ModuleVpmax35.36VPower175W

• Number of serially connecting modules m is
  determined by Power Cont-rollers 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 strings voltage should add 10 more.
• 300 x 1.1 330V
• If module voltage is 35.36V,
• m 330 / 35.36 9.33 gt 9 serial
• Then string voltage is
• 35.36 x 9 318.24V
• String power is
• 175 x 9 1,575W

175WModule
m
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1-3-1. Cells,Modules and Arrays

• How many strings for an array? ( For 30kW system )

ModuleVpmax35.36VPower175W

• 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 gt 20
  
  (parallel)
• Total system power is
• 1,575 x 20 31.5 kW

175WModule
m 9
n
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1-3-1. Cells,Modules and Arrays

• Array layout ( For 30kW system )

ModuleVpmax35.36VPower175W
9 x 20 180 modules
175WModule
30kW system
1 module
m 9
n20
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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 road Total area
15 x kW (m2)
20 m
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1-3-1. Cells,Modules and Arrays

• Array-System

Surge Arrester
DC Switch
Power Conditioner
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1-3-2. Type of system

• Type of system ( Grid interconnection or not )

(a) Off-grid individual power system (Capacity50W
) (b) Micro grid power system (Capacity10 to
50kW ) (c) Small grid power system
(Capacity50 to 500 kW ) (d) Normal grid power
system (Capacity gt 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.

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1-3-1. Cells,Modules and Arrays

• System Structure

50 70 WSolar Home System(SHS)
1 to 50 kWStationary PV system
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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
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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
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1-3-3. Power conditioner

• Voltage allowance of DC-DC Converter

• Due to the converter loss, DC-DC converters
  voltage allowance is narrow.

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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.

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1-3-3. Power conditioner

• Unit style power conditioner

• Typical Unit style power conditioner.
• Each unit is 10kW.
• Left side photo is 30kW system.

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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.

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1-3-3. Power conditioner

• Small power conditioner for SHS

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1-3-3. Power conditioner

• Small power conditioner for SHS

DC type fluorescent lamp
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1-3-4. Batteries

• why battery is necessary?

• In an SHS or Independent small grid system, PVs
  output power does not meet with demand.
• PVs 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 PVs. Therefore, batteries need
  replacing.

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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.

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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

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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 batterys
  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.

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1-3-4. Batteries

• Comparison of battery type

DOD Depth of discharge
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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.

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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
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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 !
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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(Typica
l example)
Max Power
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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)
300V
190V
450V
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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
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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