Solar Energy Robert Kinzler http://www.eia.gov/kids/energy.cfm?page=solar_home-basics

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)

SEGS http://en.wikipedia.org/wiki/Solar_power_plants_in_the_Mojave_Desert

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-plant Right: 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

http://www.eia.gov/kids/energy.cfm?page=solar_home-basics

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.jpg Right: http://education.mrsec.wisc.edu/SlideShow/images/pn_junction/pn_junction_solar_heat.jpg

Band Gap of Silicon (1.11eV) Shockley-Queisser Limit http://upload.wikimedia.org/wikipedia/commons/4/4c/ShockleyQueisserFullCurve.svg

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

Cadmium Telluride http://www.nrel.gov/continuum/spectrum/images/graphic_innov_01_large.jpg

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 Left: http://cdn.greenpacks.org/wp-content/uploads/2010/02/polymer-solar-cells.jpg Right: http://www2.imec.be/content/user/Image/Press_releases/organic.jpg

Roll-to-Roll Fabrication Similar to printing newspapers Left: http://3.bp.blogspot.com/_vfImvyorvjQ/S_jg_ZPHwtI/AAAAAAAAEe0/aAw6lHWFTyw/s1600/glass+fig+4.png Right: http://www.risoe.dk/News_archives/News/2010/~/media/Risoe_dk/News/2010/Images/plastsolceller-inden-indkapsling-web.ashx

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

https://betterarchitecture. files. wordpress https://betterarchitecture.files.wordpress.com/2013/04/pveffrev130307.jpg

Three Generations Overview http://www.novaled.com/typo3temp/pics/OPV_market_tab1_01_f4e45e4594.png

Photovoltaic Economics http://image.slidesharecdn.com/solar-cell-19187/95/solar-cell-15-728.jpg?cb=1180442697

Questions?

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/