Solar Voltaic Energy. Outline Overview of Solar Power How Photo-voltaic (PV) Cells Work How Solar PV...
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Transcript of Solar Voltaic Energy. Outline Overview of Solar Power How Photo-voltaic (PV) Cells Work How Solar PV...
Solar Voltaic Energy
Outline
• Overview of Solar Power• How Photo-voltaic (PV) Cells Work• How Solar PV Cells are Made• Solar PV
– Applications– Efficiencies– Economics– Facts & Trends– Research
Solar Power Overview
http://en.wikipedia.org/wiki/Image:The_Sun_w920607.jpg
PV Solar Radiation
http://en.wikipedia.org/wiki/Solar_cells
Photon Energy
Light & the Photovoltaic Effect
• Certain semiconductor materials absorb certain wavelengths – The shorter the wavelength the greater the energy– Ultraviolet light has more energy than infrared light
• Crystalline silicon – Utilizes all the visible spectrum plus some infrared
radiation• Heat vs. electrical energy
– Light frequencies that is too high or too low for the semiconductor to absorb turn into heat energy instead of electrical energy
How PV Cells Work
Florida Solar Energy Center
Cross Section of PV Cell
http://en.wikipedia.org/wiki/Solar_cells
How Solar Cells are Made
Solar Cell Construction
• Materials– Crystalline Silicon– Gallium Arsenide (more expensive)
• Grown into large single-crystal ingots
• Sawed into thin wafers
• 2 wafers are bonded together (p-n junction)
• Wafers grouped into panels or arrays
http://en.wikipedia.org/wiki/Solar_panel
Creating Silicon Wafers
Growing Silicon Ingots
http://en.wikipedia.org/wiki/Czochralski_process
Czochralski Process
Drawing a Silicon Ingot
http://www.answers.com/topic/silicon
Silicon Ingots & Wafers
http://www.sumcosi.com/english/products/products2.html
Creating PV Cells
Computer Chips on Wafer
http://d0server1.fnal.gov/projects/silicon/www/svxwafer.jpeg
Silicon Solar Cell
http://en.wikipedia.org/wiki/Image:Solar_cell.png
Florida Solar Energy Center
PV Cells have efficiencies approaching 21.5%
Solar Modules and Arrays
Solar PV Systems• Cells are the building block of PV systems
– Typically generate 1.5 - 3 watts of power• Modules or panels are made up of multiple cells• Arrays are made up of multiple modules
– A typical array costs about $5 – $6/watt• Still need lots of other components to make this work• Typical systems cost about $8/watt
Florida Solar Energy Center
Florida Solar Energy Center
PV Modules have efficiencies approaching 17%
Florida Solar Energy Center
Solar Panel
http://en.wikipedia.org/wiki/Solar_panel
Solar panel by BP Solar at a German autobahn bridge
Florida Solar Energy Center
Florida Solar Energy Center
Florida Solar Energy Center
Florida Solar Energy Center
Solar PV Applications
Spacecraft
Hubble Telescope
Mars Rover
International Space Station
Recreational Use (Sailboat)
Remote Areas (Mexico)
http://en.wikipedia.org/wiki/Solar_panel
A solar panel in Marla, Cirque de Mafate, Réunion
Residential
http://www.californiasolarco.com/photos_html/grid_tied/rootop_system/nevada-city-2-4.html
Commercial
http://www.c-a-b.org.uk/projects/tech1.htm
Solar Centre at Baglan Energy Park in South Wales
Solar PV Efficiency
Solar Cell Efficiencies
• Typical module efficiencies ~12%– Screen printed multi-crystalline solar cells
• Efficiency range is 6-30%– 6% for amorphous silicon-based PV cells– 20% for best commercial cells– 30% for multi-junction research cells
• Typical power of 120W / m2 – Mar/Sep equinox in full sun at equator
http://en.wikipedia.org/wiki/Solar_cells
Solar Panel Efficiency
• ~1 kW/m2 reaches the ground (sunny day)
• ~20% efficiency 200W/m2 electricity
• Daylight & weather in northern latitudes– 100 W/m2 in winter; 250 W/m2 in summer– Or 20 to 50 W/m2 from solar cells
• Value of electricity generated at $0.08/kWh– $0.10 / m2 / day OR $83,000 km2 / day
http://en.wikipedia.org/wiki/Solar_panel
Solar PV Facts & Trends
DC Peak Power
Location Description MW·h/year
6.3 MW Mühlhausen, BDR 57,600 solar modules 6,750 MWh
5 MW Bürstadt, BDR 30,000 BP solar mods 4,200 MWh
5 MW Espenhain, BDR 33,500 Shell solar mods 5,000 MWh
4.59 MW Springerville, AZ 34,980 BP solar mods 7,750 MWh
4 MW Geiseltalsee, BDR 25,000 BP solar modules 3,400 MWh
4 MW Gottelborn, BDR 50,000 solar modules 8,200 MWh
4 MW Hemau, BDR 32,740 solar modules 3,900 MWh
3.9 MW Rancho Seco, CA, n.a. n.a.
3.3 MW Dingolfing, BDR Solara, Sharp & Kyocera 3,050 M·h
3.3 MW Serre, Italy 60,000 solar modules n.a.
World Largest PV Solar Plants
http://en.wikipedia.org/wiki/Solar_panel
World Solar Power Production
Country
PV Capacity
Cumulative Installed in 2004
Off-grid PV [kW] Grid-connected [kW] Total [kW] Total [kW] Grid-tied [kW]
Australia 48,640 6,760 52,300 6,670 780Austria 2,687 16,493 19,180 2,347 1,833Canada 13,372 512 13,884 2,054 107France 18,300 8,000 26,300 5,228 4,183Germany 26,000 768,000 794,000 363,000 360,000Italy 12,000 18,700 30,700 4,700 4,400Japan 84,245 1,047,746 1,131,991 272,368 267,016Korea 5,359 4,533 9,892 3,454 3,106Mexico 18,172 10 18,182 1,041 0Netherlands 4,769 44,310 49,079 3,162 3,071Norway 6,813 75 6,888 273 0Spain 14,000 23,000 37,000 10,000 8,460Switzerland 3,100 20,000 23,100 2,100 2,000United Kingdom 776 7,386 8,164 2,261 2,197United States 189,600 175,600 365,200 90,000 62,000
http://en.wikipedia.org/wiki/Solar_panel
Solar Cell Production Volume
http://sharp-world.com/solar/generation/images/graph_2004.gif
Sharp Corporation
Solar PV Cell Research
Solar PV Components• Inverter
– Converts DC power from solar array to AC for use in your home
• Wiring– Connects the system
components• Batteries
– Used to store solar-produced electricity for nighttime or emergency use
– Mainly used for remote sites that aren’t tied into the electrical grid
• Charge controller– Prevents batteries from
being over charged
• Disconnect switches– Allows power from a PV
system to be turned off
• Electrical meter– Measures electrical
production and use– Often runs backward if
system is attached to the electrical grid
Total system cost = ~$8.00 / watt
BATTERY
Stand Alone Solar PV System
Grid Connected Solar PV System
Connecting PV to the Grid
Net Metering
• When your system produces more electricity than your home uses– electricity flows backward out to the grid
• Meter runs backward and you get credit for the electricity you sell to the utility
Florida Solar Energy Center
Florida Solar Energy Center
Siting & Designing Solar PV
Solar PV Dependencies• Location, Location, Location !• Latitude
– Lower latitudes better than higher latitudes• Weather
– Clear sunny skies better than cloudy skies– Temperature not important
• Direction solar arrays face– South preferred, east and west acceptable
• Absence of shade– Trees, Flatirons, etc.
Solar PV Design – Key Factors
• Location– How much solar radiation does the system
receive?
• DC rating– How big is the system
Solar PV Design – Module
• Module Efficiency– How efficiently does the solar system convert
solar radiation into DC power– Best retail systems approaching 17%– Holy Grail of solar PV research
• DC to AC derate factor– How efficient is the system converting DC to
AC power
Solar PV Array Design
• Array Flat Panel– Remains in a constant fixed position
• Array tilt (equal to latitude best)– Increase solar radiation by 10-20%
compared to 0% tilt– Sunnier locations benefit more
• Array azimuth (180° best)– Directly south
Solar PV Array Tracking
• Array 1-axis tracking– Tracks sun across the sky during each day– Stays at a constant tilt– Increase solar radiation by 25-30% compared to no
tracking– Sunnier locations benefit more
• Array 2-axis tracking– Tracks sun across the sky during each day– Adjusts tilt – more in winter, less in summer– Increase solar radiation by 33-38% – Sunnier locations benefit more
PV Design Website
• National Renewable Energy Lab
• PVWATTS• http://rredc.nrel.gov/solar/calculators/PVWATTS/version2/
• Examples– Portland (97229)– Phoenix (85034)– Boulder (80309)
Solar PV Economics
Solar PV Energy Payback
• Expected lifetime of 40 years
• Payback of 1-30 years– Typically < 5 years
• Solar cells 6-30× energy required to make them
http://en.wikipedia.org/wiki/Solar_cells
Cost Analysis
• US retail module price = ~$5.00 / W (2005)• Installations costs = ~$3.50 / W (2005)• Cost for a 4 kW system = ~$17,000 (2006)
– Without subsidies– Typical payback period is ~24 years
• Honda 4 kW system = ~$12,500 (2007)• With subsidies
– Payback is ~12 years
http://en.wikipedia.org/wiki/Solar_cells
Economic Example 1/3
• 4000 watt system @ 40o fixed tilt
• $32,000 initial cost
• 4000 watt (4 kW) system is about 23.5 m2
– Assume 5.5 kWh / m2/day
• 23.5 x 5.5 = 129.25 DC kWh/day – hitting the solar modules
Economic Example 2/3
• Module Efficiency = 17%– 129.25 kWh/day x 0.17 = 21.97 DC kWh/day
• Derate factor – 77%– Takes into account inefficiencies in the DC/AC
conversion and internal module components– 21.97 DC kWh/day x 0.77 = 16.92 AC kWh/day
• Output = ~17 kWh / day
Economic Example 3/3
• Pay $32,000, save $555/year– 16.92 kWh/day x $0.09/kWh x 365 days/year
• 1.7% return
• Over 20 years @ 6%– Cost of Energy = $0.452/kWh– Compared to $0.09/kWh from Xcel– EXPENSIVE!
Solar PV Policy
CO Amend. 37 Solar Provision
• $4.50 rebate/watt up to 10 kW
• Combination rebate/REC for larger systems– REC = “Renewable Energy Credits”
• Funded by a $0.63/month surcharge on all Xcel customer bills
• $20 million/year program for 10 years
CO Amend. 37 Solar Provision
• On-site solar requirement– 2007 – 2010: 0.06% of a retail electricity sales – 2011 – 2014: 0.12% of a retail electricity sales– 2015 – On: 0.2% of a retail electricity sales– Focus on Xcel
• 44,000 kW of on-site solar by 2015• 1500 to 2000 new on-site solar installations
– Depending on average size– $352 million in PV solar installation sales– $200 million in rebates
Federal Tax Credit
• 30% tax credit – Max of $2,000 for residential installations– No maximum for businesses
CO Cost Analysis
• 4,000 watt system• $32,000 initial cost• $18,000 Amendment 37 rebate
– 4000 x $4.50
• $2,000 Federal Tax Credit– ($32,000 - $18,000) x 0.30 = $4,200– However, maximum of $2,000
• After rebate/tax credit cost– $32,000 - $18,000 - $2,000 = $12,000
Return on Investment
• For $12,000 you can save $555/year– 4.6% return
• Over 20 years @ 6%– Cost of Energy = $0.169/kWh– Compared to $0.09/kWh from Xcel– Still EXPENSIVE! – $$$
Solar PV Cell Research
Emerging PV Techologies
• Cells made from gallium arsenide– molecular beam epitaxy– 35% efficiencies have been achieved
• Non-silicon panels using carbon nanotubes– Quantum dots embedded in special plastics– May achieve 30% efficiencies in time
• Polymer (organic plastics) solar cells – Suffer rapid degradation to date
http://en.wikipedia.org/wiki/Solar_cells
Thin Film Solar Cells
• Use less than 1% of silicon required for wafers
• Silicon vapor deposited on a glass substrate
• Amorphous crystalline structure– Many small crystals vs. one large crystal
http://en.wikipedia.org/wiki/Solar_cells
Florida Solar Energy Center
Flexible PV Cells
http://www.princeton.edu/~chm333/2002/spring/SolarCells/potential%20images/flexible_pv_cell.jpg
http://en.wikipedia.org/wiki/Image:Nrel_best_research_pv_cell_efficiencies.png
Benefits/Costs of Solar PV
• Reduces pollution
• Stabilizes electricity costs
• Lessens dependence on fossil fuels
• Increases self-reliance
• Can size for small, on-site installations
• Not grid dependent
• Currently expensive $$$$$
Solar Thermal Energy
Solar Thermal Collectors
• Focus the sun to create to create heat– Boil water– Heat liquid metals
• Use heated fluid to turn a turbine
• Generate electricity
Solar Thermal Dish Collector
http://www.eia.doe.gov/cneaf/solar.renewables/page/solarthermal/solarthermal.html
Solar Thermal Dish Schematic
Solar Power Towers
http://solstice.crest.org/renewables/re-kiosk/solar/solar-thermal/case-studies/central-receiver.shtml
Solar Trough Scheme
http://solarbridge.org/pedestrians.html
Parabolic Trough Cross-Section
http://www.irishsolar.com/howdoes/how_does_1.htm
Solar Thermal Collector Trends
Year
Number ofCollector Shipments
(Thousand Square Feet)
Companies Totalb Imports Exports
1995 36 7,666 2,037 530
1996 28 7,616 1,930 454
1997 29 8,138 2,102 379
1998 28 7,756 2,206 360
1999 29 8,583 2,352 537
2000 26 8,354 2,201 496
2001 26 11,189 3,502 840
2002 27 11,663 3,068 659
2003 26 11,444 2,986 518
2004 P 24 14,114 3,723 813
http://www.eia.doe.gov/cneaf/solar.renewables/page/solarthermal/solarthermal.html
Next week:
Geothermal Energy