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Photo voltaic principal
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1. Solar Photovoltaic Theory1. Solar Photovoltaic Theory
1-1. Basic principles of PV
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1-1.Basic principle of PV 1-1.Basic principle of PV
1-1. Basic principles of PV
1-1-1. Mechanism of generation
1-1-2. Various type of PV cell
1-1-3. Installation example
1-1-4. Basic characteristic
1-1-5. Case sturdy
• Contents
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+
+
++
--
-
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Photo Voltaic cell
Electrode
P-Type Semiconductor
N-Type Semiconductor
Reflect-Proof Film
Electrode
Solar Energy
Load
Ele
ctric
Cur
rent
1-1-1. Mechanism of generation1-1-1. Mechanism of generation
• Mechanism of generationThe solar cell is composed of a P-type semiconductor and an N-type semiconductor. Solar light hitting the cell produces two types of electrons, negatively and positively charged electrons in the semiconductors.Negatively charged (-) electrons gather around the N-type semiconductor while positively charged (+) electrons gather around the P-type semiconductor. When you connect loads such as a light bulb, electric current flows between the two electrodes.
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1-1-1. Mechanism of generation1-1-1. Mechanism of generation
• Direction of current inside PV cell
P
N
Current appears to be in the
reverse direction ?
• Inside current of PV cell looks like “Reverse direction.” Why?
?
• By Solar Energy, current is pumped up from N-pole to P-pole.
• In generation, current appears reverse. It is the same as for battery.
P
N
Looks like reverse
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1-1-1. Mechanism of generation1-1-1. Mechanism of generation
• Voltage and Current of PV cell ( I-V Curve )
(V)
(A)
Voltage(V)
Cu
rre
nt(I
)
P
N
A
Short Circuit
Open Circuit
P
N
V
about 0.5V (Silicon)
High insolation
•Voltage on normal operation point0.5V (in case of Silicon PV)
•Current depend on- Intensity of insolation- Size of cell
•Voltage on normal operation point0.5V (in case of Silicon PV)
•Current depend on- Intensity of insolation- Size of cell
Low insolation
Normal operation point(Maximum Power point)
I x V = W
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1-1-1. Mechanism of generation1-1-1. Mechanism of generation
• Typical I-V Curve
(V)
(A)
Voltage(V)
Cu
rre
nt(I
)
0.49 V
Standard insolation 1.0 kWh/m2
0.62 V
4.95A
5.55A
Depend ontype of cell or cell-material( Si = 0.5V )
Depend on cell-size
Depend onSolar insolation
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CrystallineCrystalline
Non-crystallineNon-crystalline
Single crystalSingle crystal
Poly crystallinePoly crystalline
AmorphousAmorphous
Gallium Arsenide (GaAs)Gallium Arsenide (GaAs)
Conversion Efficiency of Module
Conversion Efficiency of Module
10 - 17%10 - 17%
10 - 13%10 - 13%
7 - 10%7 - 10%
18 - 30%18 - 30%
Conversion Efficiency =Electric Energy Output
Energy of Insolation on cellx100%
Dye-sensitized TypeDye-sensitized Type
Organic Thin Layer TypeOrganic Thin Layer Type
7 - 8%7 - 8%
2 - 3%2 - 3%
1-1-2. Various type of PV cell1-1-2. Various type of PV cell
• Types and Conversion Efficiency of Solar Cell
Silicon SemiconductorSilicon Semiconductor
CompoundSemiconductorCompoundSemiconductor
Solar CellSolar Cell
OrganicSemiconductorOrganicSemiconductor
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• Crystal cell (Single crystal and Poly crystalline Silicon)
Single crystal Poly crystalline
1-1-2. Various type of PV cell 1-1-2. Various type of PV cell
Formed by melting high purity silicon like as Integrated Circuit
For mass production, cell is sliced from roughly crystallized ingot.
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• Surface of PV cell
1-1-2. Various type of PV cell 1-1-2. Various type of PV cell
Front Surface(N-Type side)
• Aluminum Electrode (Silver colored wire)
• To avoid shading, electrode is very fine.
Anti reflection film(Blue colored film)
• Back surface is P-type.
• All back surface is aluminum electrode with full reflection.
Example of Poly Crystalline PV
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Single crystal Poly crystalline
120W
(25.7V , 4.7A)
1200mm
800mm800mm
1200mm
1-1-2. Various type of PV cell 1-1-2. Various type of PV cell
• PV Module (Single crystal, Poly crystalline Silicon)
(3.93ft)
( 2.62ft )
( 3.93ft )
(2.62ft)
128W
(26.5V , 4.8A)
Efficiency is higher Efficiency is lower
Same size
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1-1-2. Various type of PV cell1-1-2. Various type of PV cell
• Hierarchy of PV
2 – 3 W
100 - 200 W
10 - 50 kW
Cell
Array
Module,Panel
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
6x9=54 (cells) 100-300 (modules)
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1-1-2. Various type of PV cell1-1-2. Various type of PV cell
• Roughly size of PV Power Station.
How much PV can we install in this conference room?
1 kw PV need 10 m21 kw PV need 10 m2 Please remember
10m(33feet)
20m
(66f
eet)
ConferenceRoom
(We are now)
Our room has about 200 m2
We can install about
20 kW PV in this room
(108 feet2)
(2,178 feet2)
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1-1-3. Installation example1-1-3. Installation example
• Roof top of residence ( Grid connected )
Most popular installation style in Japan.(Almost 85% PV in Japan )
Owner can sell excess power to power utility.
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1-1-3. Installation example1-1-3. Installation example• Roof top of school ,community-center building.
(For education and emergency power)
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1-1-3. Installation example1-1-3. Installation example
• Distant and independent power supply ( Off grid )
Relay station on top of mountain
Advertising sign beside highway
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1-1-3. Installation example1-1-3. Installation example
• Mountain lodge ( Off grid )
1.2kW system
Inverter and controller
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1-1-3. Installation example1-1-3. Installation example
• Stationary power station (Grid connected )
Site: Funafuti TuvaluInstallation: Feb. in 2008Capacity: 40kWPurpose: Grid connected power supply for fuel conservation
and CO2 reduction.
e8 & PPA project in Tuvalu
30kW array 10kW array
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1-1-3. Installation example1-1-3. Installation example
• Stationary power station (Off grid or mini grid )
Solar cell capacity: 3.4kWWind Power capacity: 1.8kW Inverter capacity: 5kVA
Site: Mongolia
Installation: May & June in 1999
Purpose: For lighting, refrigerator
and outlet in a hospital.
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1-1-3. Installation example1-1-3. Installation example
• Solar Home System (SHS)
Solar array
Solar arraySolar array
Solar array
Controller
Light
Storage battery
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1-1-4. Basic Characteristic1-1-4. Basic Characteristic
• I / V curve and P-Max control
P
N
A
V
• To obtain maximum power, current control (or voltage control) is very important.
(V)
(A)
Voltage(V)
Cu
rre
nt(I
)
I x V = W
P2
PMAX
P1
Vpmax
Ipmax
I/V curve
P- Max controlP- Max control
• “Power conditioner” (mentioned later) will adjusts to be most suitable voltage and current automatically.
Power curve
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1-1-4. Basic Characteristic1-1-4. Basic Characteristic
• Estimate obtained power by I / V curve
(V)
(A)
Voltage(V)
Cur
rent
(I)
12
10
8
6
4
2
0
0 0.1 0.2 0.3 0.4 0.5 0.6
P
N
A
)(05.0 R
PV character( I/V curve )
If the load has 0.05 ohm resistance, cross point of resistance character and PV-Character will be following point.
Then power is 10x0.5=5 W
)(05.0 R
Resistance character
05.0/VI R
VI
Ohm’s theory
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1-1-4. Basic Characteristic1-1-4. Basic Characteristic
• I / V curve vs. Insolation intensity
P
NP
N
Mismatch
5A
1A
P
NP
N
BypassDiode
5A
1A 4A(V)
(A)
Cu
rre
nt(I
)
High intensity insolation
Low intensity insolation
I x V = W
5A
1A
•Current is affected largely by change of insolation intensity.
•Partially shaded serial cell will produce current mismatch.
Bypass Diode
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1-1-4. Basic Characteristic1-1-4. Basic Characteristic
• Temperature and efficiency
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6
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10
12
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0 10 20 30 40 50 60 70 80 90 100Module Temperature (deg.C)
Eff
icie
ncy
(%
)
Crystalline cell
Amorphous cell
0.25 (%/deg)
Typical(25C)
Summer timeon roof top
(65C)
2%down 0.4 – 0.5 (%/deg)
•When module temperature rises up, efficiency decreases.
•The module must be cooled by natural ventilation, etc.
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1-1-5. Case sturdy1-1-5. Case sturdy
1.Maximum power control
P
N
P
N
P
N
)(05.0 R
)(10.0 R
)(02.0 R
Q : Calculate how much power you can get by following three resistance. ( I / V curve is next page)
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1-1-5. Case sturdy1-1-5. Case sturdy
1.Maximum power control
(V)
(A)
Voltage(V)
Cu
rre
nt(I
)
12
10
8
6
4
2
00 0.1 0.2 0.3 0.4 0.5 0.6
R
VI
I/V curve of current insolation.
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1-1-5. Case sturdy1-1-5. Case sturdy
2.Temperature vs. Efficiency
4
6
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10
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0 10 20 30 40 50 60 70 80 90 100
Q: There is 50 kW Crystalline PV system. If surface temperature rises from 25ºC to 65ºC, How much the capacity will be?