1-1Basic Principle of PV(Day1).ppt

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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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+

+

++

--

-

-

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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• 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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• 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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• 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


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


• 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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• 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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• 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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• Distant and independent power supply ( Off grid )

Relay station on top of mountain

Advertising sign beside highway

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• Mountain lodge ( Off grid )

1.2kW system

Inverter and controller

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• 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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• 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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• 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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• 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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• 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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• Temperature and efficiency

4

6

8

10

12

14

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.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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2.Temperature vs. Efficiency

4

6

8

10

12

14

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?

1-1Basic Principle of PV(Day1).ppt

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