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PV: The Path from Niche to Mainstream Source of Clean Energy
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Transcript of PV: The Path from Niche to Mainstream Source of Clean Energy
PV: The Path from Niche to Mainstream Source of Clean Energy
Dick Swanson
Outline
• History of PV– Satellites to Mainstream (almost)
• PV Market Dynamics– Growing fast
• PV Applications– Grid-connected distributed generation
• How Solar Cells Work– It’s simple
Sun Day, May 5, 1978, SERI
Don’t worry Mr. President, solar will be economical in 5 years!
I can’t believe he said that.
The 1970s oil crises sparked interest in PV as a terrestrial power source
Situation in 1975
$300/kg
3 inches in diameter
Sawn one at a time
0.5 watts each
$100/watt
$200/watt
Wafered Silicon Process
Polysilicon Wafer Solar Cell Solar Module SystemsIngot
1975 View
Wafered Silicon Hopelessly Too Expensive
Breakthrough Needed
Thin Films Concentrators
Remote Habitation Solar Farms
What Actually Happened
Wafered Silicon Emerges as the Dominant Technology
Breakthrough Needed
Thin Films Concentrators
Remote Habitation Solar Farms
DOEWaferedSilicon
Program
Residential/Commercial
Grid connected
PV Market Growth
95% Wafered Silicon
1
10
100
1000
10000
1975 1980 1985 1990 1995 2000 2005 2010
Year
MW
/yr
Rapid Growth in Subsidized,Grid-Connected Market.41% CAGR
Early period of rapid innovationand growth
Historical PV LandscapeEra Main Players Characteristics
1975-1885 Small Start-ups•Solar Technology International → ARCO•Solar Power Corp. → Exxon•Solarex → BP•Tyco → Mobile
•Rapid Growth•Development of technology paradigm
1985-1995 Oil Companies•ARCO•Exxon•BP•Mobile•Shell
•Moderate growth•Search for market•Massive losses•Few start-ups
Historical PV LandscapeEra Main Players Characteristics
1995 - 2005 Japanese Companies•Sharp•Sanyo•Kyocera
•Emergence of residential roof market•Improved manufacturing
2000 - Entrepreneurial Co’s•Q-Cells (Germany)•Scanwafer (Norway)•Solar World (Germany)•Evergreen (US)•SunPower (US)•Suntech (China)•MiaSole (US)
•Explosive growth•Profitability•Technology evolution
Market Share Trends
0%
5%
10%
15%
20%
25%
30%
94 95 96 97 98 99 00 01 02 03 04 05 06
Ma
rke
t Sh
are
Sharp
BP
Kyocera
Shell /SolarWorld
RWE
Sanyo
Mitsubishi
Q-cells
SunTech
SunPower
Recent Industry Milestones
• 1999 1 GW accumulated module production
• 2001 More square inches of silicon used than in entire microelectronics industry
• 2004 1 GW production during year
• 2006 More tons of silicon used than in microelectronics
History of SunPower
• Founded in 1985-9 to commercialize technology developed at Stanford
• Utility-scale solar dish application• High performance required• All-back-contact cell developed• NASA & Honda early customers• Great technology, high cost• Merged with Cypress
Semiconductor in 2001• Went public in 2005
SunPower Growth
-100
0
100
200
300
400
500
600
700
2004 2005 2006 2007 F
Mill
ion
$
RevenueNet Income
2007 forecast non-GAAP net income as presented in Q4 conference call
Distributed Generation Strategies are Shaping the Future
Residential Retrofit
New Production Homes Commercial & Public
Power Plants
PV Applications
Shell Sustained Growth Scenario
18801860
500
0
1000
1500
1900 1920 1940 1960 1980 2000 2020 2040 2060
Surprise
Geothermal
Solar
Biomass
Wind
Nuclear
Hydro
Gas
Oil &NGL
Coal
Trad. Bio.
Exa
jou
les
Source: Shell, The Evolution of the World’s Energy Systems, 1995
Renewable Energy Drivers:•Climate Change•Fossil Fuel Depletion•Energy Security
Polysilicon
Wafer Solar Cell Solar Panel SystemIngotPolysilicon
Value Chain Cost Distribution
20%30%
50%
2006 US Solar System Cost Allocation by Category
2006 2016
Downstream Savings (50%)
Panel Savings (50%)
Cell Savings (25%)
Silicon Savings (50%)
Conversion Efficiency (15%)
Downstream
Panel
Cell
Silicon
60% Drop in System Cost
50%+ cost reduction from CA system cost is achievable50%+ cost reduction from CA system cost is achievable
SAMPLE APPLICATIONS
Commercial Roofs New Production Homes
Commercial Ground Power Plants
Systems Business Segment
Santa Barbara, California – 12.6 kW
Walldürn, Germany – 8.0 kW
Osaka, Japan – 5 kW
Walnut Creek, CA
New York City – 27 kW
Los Altos Hills, California – 35 kW
Market Opportunity for PV Roof Tiles
• Product enables homeowner to integrate PV into the roof of the building:– Lower profile than traditional
modules means better aesthetics
– Potential cost savings over traditional PV system
– Traditionally targeted at new home construction
PowerLight SunTileTM
New York City – 27 kW
Microsoft Silicon Valley Campus
Arnstein, Germany – 12 MW
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Factory Assembled Unitary Product Reduces CostTracking improves Energy Delivery
15 MW PlantNellis AFB
Television for 1st Time
Energy from the Desert, Kosuke Kurokawa, ed., James & James, London, 2003.
•Advanced Crystalline?•Thin film?•Concentrating PV?
The Terrawatt Future
35
How Solar Cells Work
36
H 2O
Energy as light
The Hydropower Analogy to PV Conversion
37
Solar Cell Operation
e
h
Electron-HoleProduction
Electron Collection
Hole Collection
Light
38
Solar Cell OperationStep 1: Create electron at higher energy
phE
Thermalization loss
Conduction Band
Valence Band
Bandgap
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Solar Cell OperationStep 2: Transfer electron to wire at high energy(voltage/electrochemical potential/Fermi level)
phE outV
Thermalization loss
Collection loss
40
Step 3: Deliver Energy to the External Circuit
phE outV
phoutout EqVE
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Recombination Loss
• Any outcome of the freed electron and hole other than collection at the proper lead is a loss called “recombination loss.”
• This loss can occur in several ways
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Bulk Recombination LossA) Radiative recombination
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Bulk Recombination LossB) Defect mediated recombination
(SRH recombination)
Defect related mid-gap energy level
44
Surface and Contact Recombination Loss
45
Cell Current
recphout JJJ
46
Cell Voltage
outVn
p
npoutV
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1.8%
0.4%
1.4%
1.54% 3.8%
2.6%
2.0%
0.4%
0.3%
I2R LossReflection Loss
Generic Solar Cell Loss Mechanisms
RecombinationLosses
Back LightAbsorption
Limit Cell Efficiency 29.0%
Total Losses -14.3%
Generic Cell Efficiency
14.7%
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SunPower’s Backside Contact Cell
PassivatingSiO2 layer• Reduces top and bottom recombination loss
N-type Silicon – 270 um thickN-type FZ Silicon – 240 um thick• reduces bulk recombination
P+ P+ P+N+ N+ N+
TextureTexture + OxideTexture + SiO2 + ARC
Backside Gridlines• Eliminates shadowing•Thick, high-coveragemetal reduces resistance loss
Lightly doped front diffusion• Reduces recombinationloss
Localized Contacts• Reduces contact recombination loss
Backside Mirror• Reduces backlight absorption• Causes light trapping
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SunPower Cell Loss Mechanisms
N-type Silicon – 270 um thick
TextureTexture + Oxide
0.5%
0.2%
0.8%
1.0%
1.0%
0.2%
0.3%0.2%
I2R Loss0.1%
Limit Cell Efficiency 29.0%
Total Losses -4.4%
Enabled Cell Efficiency 24.6%