solar energy physics 52. outline basics of today’s power generation the sun photovoltaic cell...
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Solar Energy
Physics 52
Outline
• Basics of today’s power generation• The Sun• Photovoltaic Cell• Modules and systems• A little economics• Conclusion• Quiz
Power Generation
Current energy usage by mankind
7 x 1012 W
Renewable and Non-Renewable energy Sources
• Non-Renewable– Oil– Natural Gas– Coal– Nuclear
• Renewable– Hydro-electric– Wind– Bio Fuels– Solar
• Direct heating• Photo-Voltaic
Current World Energy Sources
39%
23%
23%
7%7% 1%
Oil
Gas
Coal
Nuclear
Hydro
Other
Other includes wind and solar power
The Sun
Solar Power
The total power from the sun is about 4 x 1026W
a) How much total power hits the earth?
b) What is the power density (W/m2)at the top of the earth’s atmosphere?
References on Solar energy: 1) Review paper by L. Kazmerski, of National Renewable Energy Laboratory, Golden, CO 2) Fundimentals of Renewable Energy ProcessesBy Also DaRosa (Stanford)
Solar Power
a) How much total power hits the earth?
Powere = PSRe2/4D2
Pe= 1.7 x 1017W
Total human energy usage = 7 x 1012W
Solar Power
b) What is the solar power density (W/m2)at the top of the earth’s atmosphere?
Power Densitye = PS/4D2
Power Densitye = 1360 W/m2
(Solar Constant)
Solar Power
c) What is the solar power density at the surface of the earth?
Step 1: Average over all latitudes, day and night is ¼ solar constant
Step 2: Average attenuation due to clouds and other absorption is about 50%
Average Insolation = 1360W/m2 x ¼ x ½
= 174W/m2
Average Insolation
Photovoltaic Cells
Photovoltaic Cell
Photovoltaic Cell
• Semiconductor material that absorbs photons with energy greater than the material bandgap
• pn junction with bias allows current to be generated from the electron hole pair that is generated by the absorbed material
• > 95% of todays cells are simple silicon
The silicon solar cell, invented in 1955, quickly became the standard for space power.
Solar Cells
Solar Power
d) What size (m2) photovoltaic cell would you need to power your house or apartment?
Need to assume something for Photovoltaic efficiency
Efficiency of PV Cells
Historical Silicon PV Efficiency
Manufacturers Concentrated on Cost Reduction During this Period
Photovoltaic Cells
Multi-junction cells now have demonstrated efficiencies approaching 40% and are for sale at rated efficiency of >25%
Multi-junction cells lead to high cost semiconductor devices. Concentrator systems allow dramatic reduction in the amount of active material
Concentrating Solar Power
Example of a concentrator system for solar cells comes from SolFocusAllows for a 500x reduction in the amount of PV area needed
Solar Power
d) What size (m2) photovoltaic cell would you need to power your house or apartment?
Power Generation = Insolation x PV efficiency
= 200W/m2 x 0.25
=50W/m2
Energy/Day= 50W/m2 x 24 hr =1.2KW-hr/m2
My house uses 1000KW-hr/mo. or 33KW-hr/day
Area = 33KW-hr/day/1.2KW-hr/day m2
Area = 28m2
Solar Power
One More Idea
Off Grid: Your power system must store energy for use at night and cloudy days. Leads to expensive battery systems. It must also be robust enough to meet peak demand (Examples: Boats, Satellites, very remote sites)
On Grid: Your power system shares its power with the public or private utility, selling power when generation exceeds demand and buying power when generation is less than demand.
Distributed Generation Strategies are Shaping the FutureDistributed Power Generation will be the Future Architecture
1900’s 2000’s
Economics and projections
Silicon Roadmap Cost
1
10
100
1 10 100 1,000 10,000 100,000
Cumulative Production (MW)
Module Price ($/W) ($2002)
Historical
Projected
1980$21.83/W
1990$6.07/W
2000$3.89/W
2010$1.82/W
2013$1.44/W2002 Roadmap
Solar Panel Price Drops by 19% With Each Doubling in Manufacturing Capacity
PV Experience Curve
Rough Rules of Thumb
• Prices halve every decade• Market size increases
ten-fold every decade Silicon Shortage
2006$3.50/W
Silicon Roadmap Cost1
10
100
1 10 100 1,000 10,000 100,000
Cumulative Production (MW)
Module Price ($/W) ($2002)
Historical
Projected
1980$21.83/W
1990$6.07/W
2000$3.89/W
2010$1.82/W
2013$1.44/W2002 Roadmap
Incremental Improvements in Silicon Technology will Continue to Drive Solar Panel Price Reduction
Continuous Cost Reduction
Retail Parity
Photovoltaic Production
Market Growth
0
500
1,000
1,500
2,000
2,500
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Industry Shipments (MW)
On-Grid Utility
On-Grid Commercial
On-Grid Residential
Indoor
Consumer Power
Remote Habitation
Remote Industrial
Source: Strategies Unlimited
Walldürn, Germany – 8.0 kW
Osaka, Japan – 5 kW
Microsoft Silicon Valley Campus
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
Sources of Energy 50 years from now
Conclusions
Solar power future
• Environmental– With the pressure to reduce greenhouse gasses
people and governments will invest in solar energy to reduce costs and expand deployment
• Political– Strong desire in US to reduce dependence on foreign
sources of energy (oil)
• Economic– Cost of oil and natural gas will continue to increase
lowering the bar for alternative energy to compete economically
Venture Capital want into the act
• New Solar Energy companies– Better materials for the cell– More efficient cell production– Less us of silicon material– New mounting techniques
• Over next decade start-up companies will compete with multi-national companies until technology settles down to a pure production cost race
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