Solar Energy Collectors

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    03-Nov-2014

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discussion of solar energy and the device used to collect those energy for many purposes like electricity generation

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  • 1. Integral Collector Storage

2. ntegral collector storage (ICS)Integral collector storage is a method ofstoring thermal energy within thecollector itself. Although a standardthermal collector has some storagecapacity in its piping, ICS employs eitheroversize piping or large formedrectangular box channels, to increasethe stored liquid capacity within thecollector. This allows for additionalthermal capacity without requiring aseparate insulated storage tank 3. Flat Plate Collectors 4. Flat platecollectorsFlat-plate collectors, developed by Hotteland Whillier in the 1950s, are the mostcommon type. They consist of (1) a darkflat-plate absorber of solar energy, (2) atransparent cover that allows solar energyto pass through but reduces heat losses,(3) a heat-transport fluid (air, antifreezeor water) to remove heat from theabsorber, and (4) a heat insulatingbacking. 5. Evacuated tube collectors 6. Evacuated tube collectorsMost vacuum tube collectors in use in middle Europeuse heat pipes for their core instead of passing liquiddirectly through them. Direct flow is more popular inChina. Evacuated heat pipe tubes (EHPTs) arecomposed of multiple evacuated glass tubes eachcontaining an absorber plate fused to aheat pipe. Theheat from the hot end of the heat pipes is transferredto the transfer fluid (water or anantifreezemixtypicallypropylene glycol) of a domestic hot waterorhydronicspace heating system in a heat exchangercalled a "manifold". The manifold is wrapped ininsulation and covered by a sheet metal or plastic caseto protect it from the elements. 7. Solar Air Heat Collector 8. Solar air heatcollectorsheat air directly, almost always for space heating. Theyare also used for pre-heating make-up air incommercial and industrialHVACs stems. They fall intotwo categories: Glazed and Unglazed.Glazed systems have a transparent top sheet as well asinsulated side and back panels to minimize heat loss toambient air. The absorber plates in modern panels canhave anabsorptivityof more than 93%. Air typicallypasses along the front or back of the absorber platewhile scrubbing heat directly from it. Heated air canthen be distributed directly for applications such asspace heating and drying or may be stored for lateruse. 9. Solar Bowl 10. Solar bowlis a type of solar thermal collector that operatessimilarly to aparabolic dish, but instead of usinga tracking parabolic mirror with a fixed receiver,it has a fixed spherical mirror with a trackingreceiver. This reduces its efficiency but makes itcheaper to build and operate. Designers call itafixed mirror distributed focus solar powersystem. The main reason for its development wasto eliminate the cost of moving a large mirror totrack the sun as with parabolic dish systems 11. Types of SolarCollectors forElectricity Generation 12. Parabolic Trough 13. This type of collector is generallyused insolar power plants. A trough-shapedparabolic reflectoris used toconcentrate sunlight on an insulatedtube (Dewar tube) orheat pipe,placed at thefocal point,containingcoolantwhich transfersheat from the collectors totheboilersin the power station.Parabolic trough 14. Parabolic Dish 15. Parabolic dishWith a parabolic dish collector, one ormoreparabolicdishes concentratesolar energy at a single focal point, similar to the way areflectingtelescopefocuses starlight, or a dishantennafocuses radio waves. Thisgeometry may be used insolarfurnacesand solar power plants 16. Solar Tower 17. Concentrated solar power(alsocalledconcentrating solarpower,concentrated solar thermal, andCSP)-systems use mirrors or lenses to concentrate alarge area of sunlight, orsolar thermal energy,onto a small area. Electrical power is producedwhen the concentrated light is converted toheat, which drives aheat engine(usuallyasteam turbine) connected to an electricalpower generator or powers an, experimental asof 2013, thermochemical reaction- is surrounded by tracking mirrorscalledheliostats. These mirrors alignthemselves and focus sunlight on the receiverat the top of tower, collected heat istransferred to a power station below. 18. Advantages of Solar Tower-Very high temperatures reached. High temperatures are suitablefor electricity generation using conventional methods likesteamturbineor a direct high temperature chemical reaction such as liquidsalt.-Good efficiency. By concentrating sunlight current systems can getbetter efficiency than simple solar cells.-A larger area can be covered by using relatively inexpensive mirrorsrather than using expensivesolar cells.-Concentrated light can be redirected to a suitable locationviaoptical fiber cable for such uses as illuminating buildings.-Heat storage for power production during cloudy and overnightconditions can be accomplished, often by underground tank storageof heated fluids.Molten saltshave been used to good effect. 19. Disadvantages of Solar Tower-Concentrating systems requiresun trackingtomaintain Sunlight focus at the collector.-Inability to provide power indiffusedlightconditions. Solar Cells are able to providesome output even if the sky becomes a little bitcloudy, but power output from concentratingsystems drop drastically in cloudy conditions asdiffused light cannot be concentrated passively. 20. DarkEnergy 21. Why is the universe speeding up?In 1998, two teams of astronomersstudying distant supernovae madethe remarkable discovery that the expansion of the universe is speedingup. Yet, according to Einsteins theory of General Relativity, gravityshould lead to a slowing of the expansion. To explain cosmicacceleration, cosmologists are faced with two possibilities: Either 75%of the universe exists in an exotic form, now called dark energy, thatexhibits a gravitational force opposite to the attractive gravity ofordinary matter, or General Relativity must be replaced by a new theoryof gravity on cosmic scales.The Dark Energy Survey (DES)is designed to probe the origin of theaccelerating universe and help uncover the nature of dark energy bymeasuring the 14-billion-year history of cosmic expansion with highprecision. More than 120 scientists from 23 institutions in the UnitedStates, Spain, the United Kingdom, Brazil, and Germany are working onthe project. This collaboration is building an extremely sensitive 570-Megapixel digital camera, DECam, and will mount it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high inthe Chilean Andes. Starting in Sept. 2012 and continuing for five years,DES will survey a large swath of the southern sky out to vast distancesin order to provide new clues to this most fundamental of questions. 22. Albert Einstein,1947. Einstein usedhis "cosmologicalconstant" to helpdescribe a staticuniverse. When helearned the universewas expanding, hediscarded it. 23. Einsteintheorized thatmass warpsthe shape ofspace,creating theforce we callgravity.Einsteintheorized thatmass warpsthe shape ofspace,creating theforce we callgravity. 24. Supernova 1994D in NGC4526 25. The Corpuscular TheoryThe Corpuscular TheoryThe Corpuscular TheoryThe Corpuscular TheoryThe Corpuscular TheoryThe Corpuscular Theory--- Created in the seventeenth century by SirIsaac Newton--- States that light emitted by luminous objectsconsist of tiny particles of mattercalled corpuscles. When corpuscles hit a surface,each partice is reflected.--- Thought that light traveling from air into waterwill increase the speed, while light enteringwater will decrease the speed. 26. The Wave Theory--- Discovered by Christian Huygens, a Dutch scientist, also in theseventeenth century--- States that light is emitted in a series of waves that spread outfrom a light source in all directions. These waves are not affectedby gravity.--- Furthermore, he disagreed with Newton and said that lighttraveling from air to water will decrease the speed, and vice versa.Huygens was proved later to be correct.--- 100 years later, Englishman Thomas Young completelydisproved the corpuscular theory by showing that light waves caninterfere with each other. 27. The Electromagnetic Theory--- Discovered in the nineteenth centurybyJames Maxwell--- Proposed that light waves do not requirea medium for transmission.--- Light waves posses electrical andmagnetic properties and can travel though avacuum. Light waves are a part of a largerfamily of electromagnetic waves and makeup the electromagnetic spectrum. 28. THE QUANTUM THEORY---discovered by Max Planck, a German scientist in 1990--- Stated that light waves travel asseparate packets of energycalled quanta or photons. --- Merged thesubjects of the Corpuscular, Wave, andElectromagnetic Theories together.Later, it was proved that the correct andmost accurate theory was the QuantumTheory. 29. Speed of LightThe speed of light is much greater than the speed of sound.Olaus Roemer--- Danish Scientist, 1st method to find the speed oflight, used the planets, he calculated the speed of light was 227,000kilometers per secondAlbert A. Michelson--- 1926, developed a more modern method todetermine the speed of light, used mirrors, calculated the speed of light to be186,285 miles per second (299,796 kilometers per second)The wavelength of any electromagnetic vibration x its frequency = the speedof the electromagnetic vibrationScientists have determined that the speed of any electromagnetic vibration =the speed of light (approximate value of the speed of light is 300,000kilometers per second)The speed of an electromagnetic wave is not affected by temperature, but itis affected by the medium through which it travels. 30. Transmission of LightLight can travel through a vacuum.Opaque Objects--- completely block lightand through which you cannot seeTransparent Objects--- readily transmitlight and through which you can see clearlyTranslucent Objects--- allow light to passthrough partially or that distort the light so thatyou cannot see through them 31. Behavior of LightLight travels in a straight line.Pinhole Camera--- the object that is viewed isupside-downShadow--- the dark space behind an object that isformed when light is blocked by that opaque objectUmbra--- the darker central portion of the shadowthat receives no light from the sourcePenumbra--- the lighter shadow that surrounds theumbra and receives some light from outer edges of thelight source