Title: Solar Voltaic Energy
1Solar Voltaic Energy
2Outline
- Overview of Solar Power
- How Photo-voltaic (PV) Cells Work
- How Solar PV Cells are Made
- Solar PV
- Applications
- Efficiencies
- Economics
- Facts Trends
- Research
3Solar Power Overview
4http//en.wikipedia.org/wiki/ImageThe_Sun_w920607
.jpg
5PV Solar Radiation
http//en.wikipedia.org/wiki/Solar_cells
6Photon Energy
7Light 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
8How PV Cells Work
9Florida Solar Energy Center
10Cross Section of PV Cell
http//en.wikipedia.org/wiki/Solar_cells
11How Solar Cells are Made
12Solar 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
13Creating Silicon Wafers
14Growing Silicon Ingots
Czochralski Process
http//en.wikipedia.org/wiki/Czochralski_process
15Drawing a Silicon Ingot
http//www.answers.com/topic/silicon
16Silicon Ingots Wafers
http//www.sumcosi.com/english/products/products2.
html
17Creating PV Cells
18Computer Chips on Wafer
http//d0server1.fnal.gov/projects/silicon/www/svx
wafer.jpeg
19Silicon Solar Cell
http//en.wikipedia.org/wiki/ImageSolar_cell.png
20PV Cells have efficiencies approaching 21.5
Florida Solar Energy Center
21Solar Modules and Arrays
22Solar 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
23Florida Solar Energy Center
24PV Modules have efficiencies approaching 17
Florida Solar Energy Center
25Florida Solar Energy Center
26Solar Panel
Solar panel by BP Solar at a German autobahn
bridge
http//en.wikipedia.org/wiki/Solar_panel
27Florida Solar Energy Center
28Florida Solar Energy Center
29Florida Solar Energy Center
30Florida Solar Energy Center
31Solar PV Applications
32Spacecraft
33Recreational Use (Sailboat)
34Remote Areas (Mexico)
A solar panel in Marla, Cirque de Mafate, Réunion
http//en.wikipedia.org/wiki/Solar_panel
35Residential
http//www.californiasolarco.com/photos_html/grid_
tied/rootop_system/nevada-city-2-4.html
36Commercial
Solar Centre at Baglan Energy Park in South
Wales
http//www.c-a-b.org.uk/projects/tech1.htm
37Solar PV Efficiency
38Solar 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
39Solar 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
40Solar PV Facts Trends
41World Largest PV Solar Plants
edit
http//en.wikipedia.org/wiki/Solar_panel
42World Solar Power Production
http//en.wikipedia.org/wiki/Solar_panel
43Solar Cell Production Volume
Sharp Corporation
http//sharp-world.com/solar/generation/images/gra
ph_2004.gif
44Solar PV Cell Research
45Solar 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 arent 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
46Stand Alone Solar PV System
47Grid Connected Solar PV System
48Connecting PV to the Grid
49Net 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
50Florida Solar Energy Center
51Florida Solar Energy Center
52Siting Designing Solar PV
53Solar 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.
54Solar PV Design Key Factors
- Location
- How much solar radiation does the system receive?
- DC rating
- How big is the system
55Solar 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
56Solar 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
57Solar 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
58PV Design Website
- National Renewable Energy Lab
- PVWATTS
- http//rredc.nrel.gov/solar/calculators/PVWATTS/ve
rsion2/ - Examples
- Portland (97229)
- Phoenix (85034)
- Boulder (80309)
59Solar PV Economics
60Solar PV Energy Payback
- Expected lifetime of 40 years
- Payback of 1-30 years
- Typically lt 5 years
- Solar cells 6-30 energy required to make them
http//en.wikipedia.org/wiki/Solar_cells
61Cost 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
62Economic Example 1/3
- 4000 watt system _at_ 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
63Economic 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
64Economic 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 _at_ 6
- Cost of Energy 0.452/kWh
- Compared to 0.09/kWh from Xcel
- EXPENSIVE!
65Solar PV Policy
66CO 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
67CO 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
68Federal Tax Credit
- 30 tax credit
- Max of 2,000 for residential installations
- No maximum for businesses
69CO 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
70Return on Investment
- For 12,000 you can save 555/year
- 4.6 return
- Over 20 years _at_ 6
- Cost of Energy 0.169/kWh
- Compared to 0.09/kWh from Xcel
- Still EXPENSIVE!
71Solar PV Cell Research
72Emerging 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
73Thin 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
74Florida Solar Energy Center
75Flexible PV Cells
http//www.princeton.edu/chm333/2002/spring/Solar
Cells/potential20images/flexible_pv_cell.jpg
76http//en.wikipedia.org/wiki/ImageNrel_best_resea
rch_pv_cell_efficiencies.png
77Benefits/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
78Solar Thermal Energy
79Solar Thermal Collectors
- Focus the sun to create to create heat
- Boil water
- Heat liquid metals
- Use heated fluid to turn a turbine
- Generate electricity
80Solar Thermal Dish Collector
http//www.eia.doe.gov/cneaf/solar.renewables/page
/solarthermal/solarthermal.html
81Solar Thermal Dish Schematic
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83Solar Power Towers
http//solstice.crest.org/renewables/re-kiosk/sola
r/solar-thermal/case-studies/central-receiver.shtm
l
84Solar Trough Scheme
http//solarbridge.org/pedestrians.html
85Parabolic Trough Cross-Section
http//www.irishsolar.com/howdoes/how_does_1.htm
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94Solar Thermal Collector Trends
http//www.eia.doe.gov/cneaf/solar.renewables/page
/solarthermal/solarthermal.html
95Next weekGeothermal Energy