Chapter 2 Solar Energy to Earth and the Seasons Robert W. Christopherson Charlie Thomsen.
Solar Energy Robert Kinzler .
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Transcript of Solar Energy Robert Kinzler .
History of Solar Technologies 1830’s – Solar thermal collector box 1954 – First Photovoltaic Cell Late 1950’s – Power for satellites Small consumer electronics Off-grid power Government incentives in 1990’s More recently?
Background Information World’s electricity demand: 20 *109 MWh/yr
US electricity demand: 4.7*109 MWh/yr
Sun supplies ~1000W/m2 to atmosphere Which roughly becomes 4±2 kWh/m2/day at
the surface for most places in the world This means we would need to recover all the
energy that hits 15000 km2
Basics of Solar Solar energy can be converted into heat
or electricity Air and water heating Direct electricity and steam generation
Pros and Cons Operation produces no pollution Can have minimal impact on
environment
Potentially hazardous fluids Can kill birds and insects May require water
Limitations of Solar Amount of sunlight is not constant
Varies with location, time of day, time of year, and weather
Large surface area required for useful amounts of energy
Solar Thermal Collectors Heating water Storage tank
http://en.wikipedia.org/wiki/Solar_thermal_collector
Solar Thermal Collectors Heating Air Active or passive
http://en.wikipedia.org/wiki/Solar_thermal_collector
Concentrating Solar Power Parabolic Troughs Solar Dish Solar Power Tower
http://www.eia.gov/kids/energy.cfm?page=solar_home-basics
Parabolic Trough Looks like what it sounds like Focuses sunlight on an absorber pipe of
transfer fluid Can focus 30-100 times normal sun
intensity Reaches temperatures higher than
750oF Solar Energy Generating Systems
(SEGS) in Mojave Desert, CA (354 MW)
Solar Dish Reflects light to a point rather than a
line Tracks sun as in passes Higher focus than trough Fluid temperatures higher than 1380oF
http://en.wikipedia.org/wiki/Solar_thermal_collector
Solar Power Tower Idea similar to Solar Dish Thousands of sun-tracking mirrors Concentrates sun’s energy up to 1500
times normal Energy losses minimized
Left: http://energy.gov/articles/celebrating-completion-worlds-largest-concentrating-solar-power-plantRight: Http://www.eia.gov/kids/energy.cfm?page=solar_home-basics
Ivanpah Solar Plant (392 MW)
http://energy.gov/articles/celebrating-completion-worlds-largest-concentrating-solar-power-plant
Photovoltaic (PV) Cells Convert sunlight directly to electricity 4% of the world’s desert could meet all
our needs Generate DC current Three Generations
First Generation PV Cells Silicon or Germanium Doped with Phosphorus and Boron P and N layers 10-15% efficiency commercially Close to 30% efficient in research
http://en.wikipedia.org/wiki/Solar_cell#/media/File:From_a_solar_cell_to_a_PV_system.svg
Electrical Current
Left: http://www.thesolarplanner.com/images/solar_cell.jpgRight: http://education.mrsec.wisc.edu/SlideShow/images/pn_junction/pn_junction_solar_heat.jpg
Band Gap of Silicon (1.11eV)
http://upload.wikimedia.org/wikipedia/commons/4/4c/ShockleyQueisserFullCurve.svg
Shockley-Queisser Limit
Second Generation Thin-film solar cells Amorphous silicon, CIGS, and CdTe 99% absorption in first μm Can be flexible
http://www.alternative-energy-tutorials.com/images/stories/solar/thin-film.jpg
Second Generation
Efficiency of 10-15% Lower material costs Consumes lots of energy Scarce resources
http://org.ntnu.no/solarcells/pages/generations.php
Band Gaps of Materials
Silicon (1.11eV)
GaAs (1.43eV) and
CdTe (1.44eV) CIS(1.0 eV) CGS(1.7 eV)
http://upload.wikimedia.org/wikipedia/commons/4/4c/ShockleyQueisserFullCurve.svg
Third Generation Many kinds
Organic materials High performance multi-layer solar cells Quantum Dot (QD) solar cells
Focus on breaking efficiency barrier as well as cheaper, abundant materials
Organic Solar Cells Polymer materials Simple, quick and inexpensive Readily available materials Roll-to-roll fabrication
Right: http://www2.imec.be/content/user/Image/Press_releases/organic.jpgLeft: http://cdn.greenpacks.org/wp-content/uploads/2010/02/polymer-solar-cells.jpg
Roll-to-Roll Fabrication Similar to printing newspapers
Right: http://www.risoe.dk/News_archives/News/2010/~/media/Risoe_dk/News/2010/Images/plastsolceller-inden-indkapsling-web.ashx
Left: http://3.bp.blogspot.com/_vfImvyorvjQ/S_jg_ZPHwtI/AAAAAAAAEe0/aAw6lHWFTyw/s1600/glass+fig+4.png
Multi-junction Solar Cells Each layer can absorb light at different
wavelengths Surpasses the 33.7% efficiency limit Currently up to ~45% efficiency Expensive materials
http://www.photonics.com/images/Web/Articles/2008/10/1/SpectoLab_Fig3.jpg
Quantum Dot Solar Cells Doped onto a nanostructure which is
then connected to transparent electrode Very thin Cascade of electrons
http://cdn.phys.org/newman/gfx/news/2008/quantumdotsolarcells.png
Photovoltaic Economics
http://image.slidesharecdn.com/solar-cell-19187/95/solar-cell-15-728.jpg?cb=1180442697
References "Solar." EIA Energy Kids -. Web. 18 Mar. 2015. http
://www.eia.gov/kids/energy.cfm?page=solar_home-basics Madsen, Morten. "Solar- The Three Generations." Web. 18 Mar. 2015. http
://plasticphotovoltaics.org/lc/lc-solarcells/lc-introduction.html Lund, H. et al. "Solar Cells." Web. 20 Mar. 2015. http
://org.ntnu.no/solarcells/pages/generations.php Streetman, Ben G.; Sanjay Banerjee (2000). Solid State electronic Devices (5th
ed.). New Jersey: Prentice Hall. p. 524. "Part 2: Solar Energy Reaching The Earth's Surface." ITACA RSS. Web. 21 Mar.
2015. http://www.itacanet.org/the-sun-as-a-source-of-energy/part-2-solar-energy-reaching-the-earths-surface/