Solar Voltaic Energy Associate Professor Mazen Abualtayef Environmental Engineering Department Islamic University of Gaza, Palestine
Adapted from a presentation by Professor S.R. Lawrence Leeds School of Business, Environmental Studies University of Colorado, Boulder, CO, USA
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 Video Photo means light Voltaic means electricity Photovoltaic means getting electricity from light
The Sun provides 1,400 watts/m² at the distance of the Earth's orbit, but less at ground level http://en.wikipedia.org/wiki/image:the_sun_w920607.jpg
PV Solar Radiation http://en.wikipedia.org/wiki/solar_cells
PV Solar Radiation Palestine Solar Radiation Map Gaza: >1900 kwh/m 2 /year
Photon Energy A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation Visible light has a wavelength in the range of about 380 nanometres to about 740 nm
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, which 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
What are PV Cells? Si Si Si Si Si Si Si Si P Si Si n-type Si Si B Si Si p-type
Cross Section of PV Cell Video http://en.wikipedia.org/wiki/solar_cells
How Solar Cells are Made Video
Solar Cell Construction Materials Crystalline Silicon الغاليوم زرنيخيد expensive) Gallium Arsenide (more 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 فحم الكوك فرن قوس التقطير بوليكريستال السيليكون رقائق السيليكون التلميع كريستال السيليكون
Growing Silicon Ingots http://en.wikipedia.org/wiki/czochralski_process سبائك السيليكون سيليكون منصهر قطع السيليكون Czochralski Process The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, platinum, silver, gold) and salts.
Drawing a Silicon Ingot http://www.answers.com/topic/silicon
Silicon Ingots & Wafers Special high-speed saws slice the ingots into wafers about the thickness of a dime 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 21.6%
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 $1.2 $1.5/watt (Chinese) Still need lots of other components to make this work Typical systems cost about $5-$6/watt
Florida Solar Energy Center
Florida Solar Energy Center PV Modules have efficiencies approaching 17% الصفيحة Laminate:
Solar Panel Solar panel by BP Solar at a German autobahn bridge http://en.wikipedia.org/wiki/solar_panel
Florida Solar Energy Center
Florida Solar Energy Center
Florida Solar Energy Center
Florida Solar Energy Center الفناء Patio:
Solar PV Applications
Spacecraft International Space Station Hubble Telescope Mars Rover
Recreational Use (Sailboat) In 1999-2000 two people sailed Rusalka Mist from the island of Jersey in the English Channel, via Tenerife to the Caribbean and back via the Azores. The solar panels and a towed, water-power generator provided selfsufficiency in electrical energy during this trip, both at sea and at anchor during the year.
Remote Areas (Mexico) A solar panel in Marla, Cirque de Mafate, Réunion http://en.wikipedia.org/wiki/solar_panel
Residential http://www.californiasolarco.com/photos_html/grid_tied/rootop_system/nevada-city-2-4.html
Commercial Solar Centre at Baglan Energy Park in South Wales http://www.c-a-b.org.uk/projects/tech1.htm
Solar PV Efficiency
Efficiencies
Solar Cell Efficiencies Typical module efficiencies ~12% 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 120 W/m 2 Mar/Sep equinox in full sun at equator http://en.wikipedia.org/wiki/solar_cells تساوي الليل والنهار Equinox:
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 cell Value of electricity generated at $0.1/kWh 1 km 2 would generate up to 50 MW Sahara desert is over 9 million km 2 72-83MW/km 2, or 650-750 TW (Global power rate is 15 TW) http://en.wikipedia.org/wiki/solar_panel
Solar PV Facts & Trends
World Solar Power Production
World Solar Power Production
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 solarproduced 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 = $3.00~$4.00 / watt
Stand Alone Solar PV System BATTERY
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! خط عرض 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% 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 زاوية السمت best) Array azimuth (180 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
http://pvwattsbeta.nrel.gov/pvwatts.php
Off grid solar system design 1. Load Calculation Room Load Quantity Working hours [hrs] Energy [Wh] Guest room 25W PL 1 4 100 Living room 25W PL 2 10 500 Master bedroom 25W PL 1 4 100 Boys bedroom 25W PL 1 3 75 Girls bedroom 25W PL 1 3 75 Balcony 25W PL 1 3 75 Bathroom 25W PL 1 2 50 Corridors 25W PL 1 6 150 Kitchen 25W PL 1 7 175 Fridge 1 24 2200 Total Energy [Wh/day] 3500
Off grid solar system design 2. Solar System Sizing: PV sizing = Load / sunny hours / derate factor = 3500 / 5 / 0.70 = 1000 Wp System is used 250W / 24V panels 1 kw PV array (1000 DC watts) 1000/250 (watts per panel) = 4 panels 4 series strings of 1 panels = 4 modules with each string producing 24 volts
Off grid solar system design 3. Battery Bank Sizing: System is used GEL battery 12V/100 Ah C10 kwatts of PV array required = kwh / daily sun hours / derate factor 1 kwp = kwh / 5 / 0.7 kwh = 1k * 5 * 0.7 = 3.5 kwh
Off grid solar system design 3. Battery Bank Sizing: Battery Bank Capacity = kwh per day * Day of Autonomy / (losses * DOD * 24 (system voltage)) Battery Bank Capacity (1 day) = 3.5k * 1 / (0.85 * 50% * 24) = 343 Ah No. of Batteries 1 set to get 24V = 24/12 = 2 with 100Ah C10 No. of Batteries to get 686 Ah = (343/100) * 2 = 6
Off grid solar system design 4. Charge controller sizing: System is used MPPT Solar controller charger VT-65 1000W / 24V = 40 A No. of MPPT = 1 5. Inverter Sizing: AC system watts = DC watt x derate factor = AC system watts= 1 kwp * 0.7 = 0.7 kw No. of inverter = 1 =1 kva
Off grid solar system design 6. Economics: Cost of PV system = US$ 3500 Annual electricity cost = 1456*0.125 = $182 Payback period = = 19 yrs Cost of Energy = ($3500)/(1456*25) = US$0.10 / kwh
PV Calculator A solar photovoltaic calculator was developed by Mazen Abualtayef and you can find it at http://site.iugaza.edu.ps/mabualtayef/files/pv-calculator.xlsx
Solar PV Economics
Solar PV Energy Payback Expected lifetime of 40 years Payback of 1-30 years For 1.0 kw 2-Axis Tracking panels the Payback = $3,500 / (1,962 kwh/year $0.125) = 14 years For 1.0 kw fixed tilt panels the Payback = $3,500 / (1,456 kwh/year $0.125) = 19 years http://en.wikipedia.org/wiki/solar_cells
Cost Analysis Module price = ~$3.00-3.50 / W Installations costs = ~$0.50 / W Cost for a 1 kw system = ~US$3,500-4,000 Typical payback period is 25~30 years http://en.wikipedia.org/wiki/solar_cells
Economic Example 1/3 1000 watt system $4,000 initial cost 1000 watt (1 kw) system is about 7.25 m 2 Assume 5.40 kwh/m 2 /day for fixed tilt Or 7.00 kwh/m 2 /day for 2-axis tracking 7.25 x 5.40 = 39.15 DC kwh/day (solar radiation) hitting the solar modules Cost from http://www.solar.co.il/electricity.htm
Economic Example 2/3 Module Efficiency = 15% 39.15 kwh/day x 0.15 = 5.87 DC kwh/day Derate factor 76% Takes into account inefficiencies in the DC/AC conversion and internal module components 5.87 DC kwh/day x 0.76 = 4.46 AC kwh/day Output = 4.46 kwh/day 1640 kwh/year (fixed tilt) 5.65 kwh/day 2060 kwh/year (Tracking)
Economic Example 3/3 Pay $4,000, save $205/year 1640kWh/year x $0.125/kWh for fixed tilt Cost of Energy = ($4000)/(1640*25) = $0.10/kWh Compared to $0.125/kWh from PEC
Solar PV Cell Research
Emerging PV Techologies Cells made from gallium arsenide 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 slice Amorphous crystalline structure Many small crystals vs. one large crystal it is more efficient to absorb the visible part of the solar spectrum, but it fails to collect the infrared http://en.wikipedia.org/wiki/solar_cells
Florida Solar Energy Center
Flexible PV Cells Gerrit Kroesen, Eindhoven University of Technology, the Netherlands 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 يقلل Lessens
Solar Thermal Energy
Solar Thermal Collectors Focus the sun to create heat: Concentrating Solar Power, CSP: Boil water Heat liquid Use heated fluid to turn a turbine Generate electricity
How does solar power station work?
Types of CSP: Parabolic Trough Capacity Range: 10-200MW. Thermal Cycle Efficiency: 30 40%, Land Use: 60 80 MW/km 2. Operating Temperature: 390 C; LEC ~$0.13 kwh. Thermal storage with oversized solar field allow plant to dispatch power during nonsolar times of day increase annual capacity factor ~ 50%.
http://en.wikipedia.org/wiki/solar_energy_generating_systems
Types of CSP: Linear Fresnel Reflector 177 MW Compact Linear Fresnel Reflector (LFR) proposed in California. LFR uses about 100-125 MWe per km 2 of land. Current LEC $0.08~$0.10/kWh, operating temperature 265 C.
Linear Fresnel Reflector, AREVA North America us.arevablog.com
Types of CSP: Parabolic Dishes New solar-to-grid system conversion efficiency record of 31.25% set in Feb 2008. Capacity Range: 0.01-0.4 MW, Thermal Cycle Efficiency: 30~40%, Land Use: 80~120 MW/km 2 ; Engine Operating Temperature: 700 C; LEC ~$0.30/kWh http://en.wikipedia.org/wiki/solar_thermal_collector
Types of CSP: Solar Towers Commercial 20 MWe PS-20 plant constructed in Spain. Capacity Range: 10-150 MW. Thermal Cycle Efficiency: 30 40%, Land Use: 80 120 MW/km 2 ; Operating Temperature: 567 C; LEC ~$0.30/kWh Efficient commercial-scale power towers are >>30 MW. Power Towers with molten salt thermal storage are expected to have annual capacity factor > 65% and LEC $0.07/kWh.
Solar Power Towers ps20 is the world first power tower plant, Spain http://en.wikipedia.org/wiki/file:ps20andps10.jpg
Examples of Solar Power Towers
CSP vs. PV Panels What is? CSP Mirrors are used to concentrate sunlight onto receivers that convert the solar energy to heat. Steam is created from that heat and goes through a turbine to generate electricity. PV A photovoltaic solar panel converts solar radiation into direct current electricity.
CSP vs. PV Panels Efficiency Differences CSP CSP efficiency increases with temperature (good for hot sunny places). Power Tower has reached a peak efficiency of 77%. The mean annual thermal collection efficiency for Solar Tres (Spain) is 41%. CSP is relatively new and improvement is still needed. PV Efficiency decreases with temperature (good for cold sunny places). At 0 c, maximum efficiency is 24-28% (depending what type of metal used. At room temperature, efficiency (for silicon) is 12%. Efficiency has been increasing over time.
CSP vs. PV Panels Efficiency Differences CSP Heat can be stored as thermal energy and converted to usable energy later. Can provide 24 hour/day electricity using energy storage. Uses a lot of water. PV Energy can be stored in batteries (not a sufficient amount). No energy produced without sunlight.
CSP vs. PV Panels Economic Considerations CSP Currently, it takes longer and is more expensive to build CSP plants... Cost estimates vary, but CSP is still not perfected. The price of CSP power production is expected to drop significantly in the next five years. PV which leaves photovoltaic as the leader in solar power. Photovoltaic has the advantage of being the more developed technology right now. Government subsidies for photovoltaic panels make it the current cheaper option.
CSP vs. PV Panels Economic Considerations CSP Current CSP projects are running around 19-21 cents per kwh. PV A photovoltaic power plant would cost around 17 cents per kw. Technology for CSP is improving. It is still cheaper to use photovoltaic panels because their production time is lower and they cost less.
CSP vs. PV Panels Summary and Conclusion There are pros and cons to photovoltaic and concentrated solar power. Photovoltaic is cheaper to build and use, but CSP is newer and rapidly improving. CSP can store power for several hours and has an extremely high thermal efficiency.
CSP vs. PV Panels Summary and Conclusion Photovoltaic is the best choice for now. Research is still being done to continually improve efficiency. CSP is improving more rapidly and they will probably be equal competitors in the future. Location will play a large factor in the future of these two technologies. Photovoltaic and CSP technology may be combined for maximum efficiency in the future.
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