1. Solar Voltaic Energy

2. 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

3. Solar Power Overview

4. http://en.wikipedia.org/wiki/Image:The_Sun_w920607.jpg

5. PV Solar Radiation http://en.wikipedia.org/wiki/Solar_cells

6. Photon Energy

7. 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

8. How PV Cells Work

9. Florida Solar Energy Center

10. Cross Section of PV Cell http://en.wikipedia.org/wiki/Solar_cells

11. How Solar Cells are Made

12. 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

13. Creating Silicon Wafers

14. Growing Silicon Ingots http://en.wikipedia.org/wiki/Czochralski_process Czochralski Process

15. Drawing a Silicon Ingot http://www.answers.com/topic/silicon

16. Silicon Ingots & Wafers http://www.sumcosi.com/english/products/products2.html

17. Creating PV Cells

18. Computer Chips on Wafer http://d0server1.fnal.gov/projects/silicon/www/svxwafer.jpeg

19. Silicon Solar Cell http://en.wikipedia.org/wiki/Image:Solar_cell.png

20. Florida Solar Energy Center PV Cells have efficiencies approaching 21.5%

21. Solar Modules and Arrays

22. 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

23. Florida Solar Energy Center

24. PV Modules have efficiencies approaching 17%

25. Florida Solar Energy Center

26. Solar Panel http://en.wikipedia.org/wiki/Solar_panel Solar panel by BP Solar at a German autobahn bridge

27. Florida Solar Energy Center

31. Solar PV Applications

32. Spacecraft Hubble Telescope Mars Rover International Space Station

33. Recreational Use (Sailboat)

34. Remote Areas (Mexico) http://en.wikipedia.org/wiki/Solar_panel A solar panel in Marla, Cirque de Mafate, Réunion

35. Residential http://www.californiasolarco.com/photos_html/grid_tied/rootop_system/nevada-city-2-4.html

36. Commercial http://www.c-a-b.org.uk/projects/tech1.htm Solar Centre at Baglan Energy Park in South Wales

37. Solar PV Efficiency

38. 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 / m 2 –Mar/Sep equinox in full sun at equator http://en.wikipedia.org/wiki/Solar_cells

39. Solar Panel Efficiency ~1 kW/m 2 reaches the ground (sunny day) ~20% efficiency  200W/m 2 electricity Daylight & weather in northern latitudes –100 W/m 2 in winter; 250 W/m 2 in summer –Or 20 to 50 W/m 2 from solar cells Value of electricity generated at $0.08/kWh –$0.10 / m 2 / day OR $83,000 km 2 / day http://en.wikipedia.org/wiki/Solar_panel

40. Solar PV Facts & Trends

41. DC Peak Power LocationDescriptionMW·h/year 6.3 MWMühlhausen, BDR57,600 solar modules6,750 MWh 5 MWBürstadt, BDR30,000 BP solar mods4,200 MWh 5 MWEspenhain, BDR33,500 Shell solar mods5,000 MWh 4.59 MWSpringerville, AZ34,980 BP solar mods7,750 MWh 4 MWGeiseltalsee, BDR25,000 BP solar modules3,400 MWh 4 MWGottelborn, BDR50,000 solar modules8,200 MWh 4 MWHemau, BDR32,740 solar modules3,900 MWh 3.9 MWRancho Seco, CA,n.a. 3.3 MWDingolfing, BDRSolara, Sharp & Kyocera3,050 M·h 3.3 MWSerre, Italy60,000 solar modulesn.a. [edit]edit World Largest PV Solar Plants http://en.wikipedia.org/wiki/Solar_panel

42. World Solar Power Production Country PV Capacity CumulativeInstalled in 2004 Off-grid PV [kW]Grid-connected [kW]Total [kW] Grid-tied [kW] Australia48,6406,76052,3006,670780 Austria2,68716,49319,1802,3471,833 Canada13,37251213,8842,054107 France18,3008,00026,3005,2284,183 Germany26,000768,000794,000363,000360,000 Italy12,00018,70030,7004,7004,400 Japan84,2451,047,7461,131,991272,368267,016 Korea5,3594,5339,8923,4543,106 Mexico18,1721018,1821,0410 Netherlands4,76944,31049,0793,1623,071 Norway6,813756,8882730 Spain14,00023,00037,00010,0008,460 Switzerland3,10020,00023,1002,1002,000 United Kingdom7767,3868,1642,2612,197 United States189,600175,600365,20090,00062,000 http://en.wikipedia.org/wiki/Solar_panel

43. Solar Cell Production Volume http://sharp-world.com/solar/generation/images/graph_2004.gif Sharp Corporation

44. Solar PV Cell Research

45. 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

46. BATTERY Stand Alone Solar PV System

47. Grid Connected Solar PV System

48. Connecting PV to the Grid

49. 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

50. Florida Solar Energy Center

52. Siting & Designing Solar PV

53. 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.

54. Solar PV Design – Key Factors Location –How much solar radiation does the system receive? DC rating –How big is the system

55. 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

56. 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

57. 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

58. PV Design Website National Renewable Energy Lab PVWATTS http://rredc.nrel.gov/solar/calculators/PVWATTS/version2/ Examples –Portland (97229) –Phoenix (85034) –Boulder (80309)

59. Solar PV Economics

60. 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

61. 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

62. Economic Example 1/3 4000 watt system @ 40 o fixed tilt $32,000 initial cost 4000 watt (4 kW) system is about 23.5 m 2 –Assume 5.5 kWh / m 2 /day 23.5 x 5.5 = 129.25 DC kWh/day –hitting the solar modules

63. 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

64. 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!

65. Solar PV Policy

66. 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

67. 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

68. Federal Tax Credit 30% tax credit –Max of $2,000 for residential installations –No maximum for businesses

69. 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

70. 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! – $$$

71. Solar PV Cell Research

72. 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

73. 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

74. Florida Solar Energy Center

75. Flexible PV Cells http://www.princeton.edu/~chm333/2002/spring/SolarCells/potential%20images/flexible_pv_cell.jpg

76. http://en.wikipedia.org/wiki/Image:Nrel_best_research_pv_cell_efficiencies.png

77. 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 $$$$$

78. Solar Thermal Energy

79. 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

80. Solar Thermal Dish Collector http://www.eia.doe.gov/cneaf/solar.renewables/page/solarthermal/solarthermal.html

81. Solar Thermal Dish Schematic

83. Solar Power Towers http://solstice.crest.org/renewables/re-kiosk/solar/solar-thermal/case-studies/central-receiver.shtml

84. Solar Trough Scheme http://solarbridge.org/pedestrians.html

85. Parabolic Trough Cross-Section http://www.irishsolar.com/howdoes/how_does_1.htm

94. Solar Thermal Collector Trends Year Number of Collector Shipments (Thousand Square Feet) CompaniesTotal b ImportsExports 1995367,6662,037530 1996287,6161,930454 1997298,1382,102379 1998287,7562,206360 1999298,5832,352537 2000268,3542,201496 20012611,1893,502840 20022711,6633,068659 20032611,4442,986518 2004 P 2414,1143,723813 http://www.eia.doe.gov/cneaf/solar.renewables/page/solarthermal/solarthermal.html

95. Next week: Geothermal Energy