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PV Cell Working Principleand Applications
1/Dec/2008Ir Dr Edward LO
Associate Professor Department of Electrical Engineering
The Hong Kong Polytechnic University2
How Powerful is Solar Power? Solar power intensity just outside the
atmosphere of the Earth: 1.353 kW/m 2.This value is also called solar constant .
With the known radius of Earth ~=6380km, solar power falling on The Earth~=173000TW
While the current global power consumption average over a year is only ~16TW as in 2005
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Solar power intensity ~ 1kW/m 2 atsea level in sunny day
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First application of PV cells
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How PV generates
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Common Types of PV cells
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Different PV technology
mono-crystalline (m-Si)typical efficiency: 15%+
poly-crystalline /multi-crystalline (p-Si)
typical efficiency: 10-15%
Copper Indium Diselenide(CIS)typical efficiency: 9-12%
Amorphous Silicon (a-Si)typical efficiency: 4-7%
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crystalline PV cells
m-Si14.46%
p-Si12.62%
p-Si8.29%
p-Si12.68% p-Si
13.66%
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Semi-transparent PV cells
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Cell,Module, Array
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Typical I-V & P-V Curve of a PVCell at a given solar irradianceI
V
1000W/m2
Power
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Typical I-V Curve of a PV Cell atdifferent values of solar irradiance
I
V
1000W/m2
800 W/m2
600 W/m2
400 W/m2
200 W/m2
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Electrical properties, I-V curveI
V
Load curve of maximum power point
resistive load 1000 W/m2
800 W/m2
600 W/m2
400 W/m2
200 W/m2
STC MPP
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Effect of cell temperature on the V-ICurve (at given solar irradiation)
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Name Plate Rating of a PV Panel
It is themaximumpower outputat STC(Standard TestCondition)
Usually STC =1000 W/m 2,25 C PanelTemperature
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efficiency characteristics
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Effect of partial shading onperformance of PV array
100% irradiance
10% irradiance
Very low output fromthe PV system,althoughOnly of themodules are shaded
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100% irradiance
10% irradiance
Must maintain 3/4full output from thePV system, when of the modules areshaded
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BlockingDiodes
BypassDiodes
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BIPV Building IntegratedPhotovoltaic System
Act as other building functions other thangenerating electricity
No harmful side effects No moving parts silent, solid state device No (low) maintenance
Modular format /non-intrusive Versatile
Locations Rural/Urban Applications for stand alone applications
Water pump, Lighting, Desalination plants
The Plus Points:
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Barriers to BIPV application
Relatively high capital cost of the PV panels. Module efficiency is still relatively low
Little understanding of PV system design Less real experience of installations Incentives (in HK) not yet in place
The HK scenario:
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Why BIPV? (1) Replace conventional building materials
concept of avoided cost Does not require any extra land area Does not require any additional support or
infrastructure installation
The above three points smallincremental cost for BIPV systems
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Why BIPV? (2) May cover part of the electricity consumption of
the building. Can provide electricity during peak demand time
times and thus reduce the utility's speak deliveryrequirements.
May reduce transmission and distribution loss.
These points reduce the electricity bills of thebuilding and delay the need for construction of new power plants.
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Time of day N oo n
kW
Po we r co ns um pti on by a bu ild in g
Po w er ge ne ra tio n by PV pa ne ls
Consumption Curve and Generation Curve
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Why BIPV ? (3) Can provide an improved aesthetic
appearance in an innovative way. Can integrated with maintenance, control
and operation of the other installations andsystems in the building.
Can provide reduced planning costs.
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With grid connection, the system cantotally eliminate the storage batteries andits associated problems.
Hence lower capital, replacement andmaintenance cost.
Why BIPV ? (4)
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PV system: stand-alone vs.grid-connected
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Grid-connected systems(G-BIPV) PVs connected to the public grid via an
inverter. Eliminate the expensive and bulky
batteries. Involve local regulatory issues. Must compete against the cost of the
conventional energy source used to supplythe grid.
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Block diagram of G-BIPV Loc al l oads
Power conditioning subsystemco-ordinated with the electromechanical
safety disconnect subsystem
from utility grid
electromachanical sa fetydisconnect
manual disconnect sw itch / electromachanical safe ty disconnect
PV arra ys DC
AC
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Grid-connecting inverter
2kW2kW
convert DC to AC
capacity ranges from 100W to 500kW
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New generation inverters (stringinverter)
100W
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Characteristics of an inverter
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inverter selection
high efficiency (of course) selection of inverter nominal P in with array's
rated kW p (e.g. vertical facade array) read the data-sheet carefully
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BIPV system at Wan Chai Tower
Three systems: Rack type at the roof Sun shading type at mid-floors Skylight type at the lift lobby of ground floor
The site: 22 16 50 N and 114 10 30 EOrientation: south facing about 5 degree off
south toward east
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Wanchai Tower of HKGovernment Building
3 BIPV Systems
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Wan Chai Tower Roof Rack BIPV SystemLocation Roof
Orientation 10 degree to horizontal,facing south
Type of panels Polycrystalline
No. of panels per string 18
No. of strings 7 strings per group, 2 groups
Total no. of panels 252
Total PV panel area 164.70 m 2
System rated power 20.16 kW
No. of inverters 1 inverter per group
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WanChai Tower: Roof Polycrystalline 20 kWpeak
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Wan Chai Tower Sun Shade BIPV System
Location Middle section of the building
Orientation Vertically facing south
Type of panels Monocrystalline
No. of panels per string 21
No. of strings 8 strings per group, 2 groups
Total no. of panels 336
Total PV panel area 231.84 m 2
System rated power 20.16 kW
No. of inverters 1 inverter per group
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WanChai Tower: Sun ShadingBIPV system
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Wan Chai Tower Skylight BIPV System
Location Ground floor lobby
Orientation Vertically facing south
Type of panels Monocrystalline
No. of panels per string 5
No. of strings 7 strings
Total no. of panels 35
Total PV panel area 95.98 m 2
System rated power 10.08 kW
No. of inverters 1 inverter per group
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WanChai Tower: Skylight BIPVsystem
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Science Park 1 BIPV System
Type:PV /grid-connectedPVtechnology:m-SiPV nos/area:1380 / 3019.8m2kWp= 198kW
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The End For This Part Thanks for your attention
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Possible Talks from PolyU EE Dept: Electricity generation, transmission & distribution Renewable Energies Energy Efficiency Intelligent Buildings Electric Vehicles LED Lighting and other new lighting systems Power electronics & drives Railway and its signaling systems Application of photonic devices in engineering Etc..
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