Solar Voltaic Energy: Solar Voltaic Energy


Outline: 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: Solar Power Overview


Slide4: http://en.wikipedia.org/wiki/Image:The_Sun_w920607.jpg


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


Photon Energy: Photon Energy


Light & the Photovoltaic Effect: 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: How PV Cells Work


Slide9: Florida Solar Energy Center


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


How Solar Cells are Made: How Solar Cells are Made


Solar Cell Construction: 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: Creating Silicon Wafers


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


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


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


Creating PV Cells: Creating PV Cells


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


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


Slide20: Florida Solar Energy Center PV Cells have efficiencies approaching 21.5%


Solar Modules and Arrays: Solar Modules and Arrays


Solar PV Systems: 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


Slide23: Florida Solar Energy Center


Slide24: Florida Solar Energy Center PV Modules have efficiencies approaching 17%


Slide25: Florida Solar Energy Center


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


Slide27: Florida Solar Energy Center


Slide28: Florida Solar Energy Center


Slide29: Florida Solar Energy Center


Slide30: Florida Solar Energy Center


Solar PV Applications: Solar PV Applications


Spacecraft: Spacecraft


Recreational Use (Sailboat): Recreational Use (Sailboat)


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


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


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


Solar PV Efficiency: Solar PV Efficiency


Solar Cell Efficiencies: 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: 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: Solar PV Facts & Trends


World Largest PV Solar Plants: [edit] World Largest PV Solar Plants http://en.wikipedia.org/wiki/Solar_panel


World Solar Power Production: World Solar Power Production http://en.wikipedia.org/wiki/Solar_panel


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


Solar PV Cell Research: Solar PV Cell Research


Solar PV Components: 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


Stand Alone Solar PV System: Stand Alone Solar PV System


Grid Connected Solar PV System: Grid Connected Solar PV System


Connecting PV to the Grid: Connecting PV to the Grid


Net Metering: 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


Slide50: Florida Solar Energy Center


Slide51: Florida Solar Energy Center


Siting & Designing Solar PV : Siting & Designing Solar PV


Solar PV Dependencies: 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: 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: 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: 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: 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: 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 Economics


Solar PV Energy Payback: 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: 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: 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: 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: 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: Solar PV Policy


CO Amend. 37 Solar Provision: 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: 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: Federal Tax Credit 30% tax credit Max of $2,000 for residential installations No maximum for businesses


CO Cost Analysis: 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: 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: Solar PV Cell Research


Emerging PV Techologies: 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: 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


Slide74: Florida Solar Energy Center


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


Slide76: http://en.wikipedia.org/wiki/Image:Nrel_best_research_pv_cell_efficiencies.png


Benefits/Costs of Solar PV: 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 Energy


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


Solar Thermal Dish Schematic: Solar Thermal Dish Schematic


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


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


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


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


Next week:Geothermal Energy: Next week: Geothermal Energy