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
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.
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 a heat pipe. Theheat from the hot end of the heat pipes is transferredto the transfer fluid (water or an antifreeze mix—typically propylene glycol) of a domestic hot wateror hydronic space 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.
Solar air heat collectors heat air directly, almost always for space heating. Theyare also used for pre-heating make-up air incommercial and industrial HVACs 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 an absorptivity of 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.
Solar bowlis a type of solar thermal collector that operatessimilarly to a parabolic 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 ita fixed 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
Types of SolarCollectors forElectricity Generation
This type of collector is generallyused in solar power plants. A trough-shaped parabolic reflector is used toconcentrate sunlight on an insulatedtube (Dewar tube) or heat pipe,placed at the focal point,containing coolant which transfersheat from the collectors tothe boilers in the power station.Parabolic trough
Parabolic dishWith a parabolic dish collector, one ormore parabolic dishes concentratesolar energy at a single focal point, —similar to the way a reflectingtelescope focuses starlight, or a dishantenna focuses radio waves. Thisgeometry may be used in solarfurnaces and solar power plants
Concentrated solar power (alsocalled concentrating solarpower, concentrated solar thermal, and CSP)-systems use mirrors or lenses to concentrate alarge area of sunlight, or solar thermal energy,onto a small area. Electrical power is producedwhen the concentrated light is converted toheat, which drives a heat engine (usuallya steam turbine) connected to an electricalpower generator or powers an, experimental asof 2013, thermochemical reaction- is surrounded by tracking mirrorscalled heliostats. These mirrors alignthemselves and focus sunlight on the receiverat the top of tower, collected heat istransferred to a power station below.
Advantages of Solar Tower-Very high temperatures reached. High temperatures are suitablefor electricity generation using conventional methods like steamturbine or 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 expensive solar cells.-Concentrated light can be redirected to a suitable locationvia optical 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 salts have been used to good effect.
Disadvantages of Solar Tower-Concentrating systems require sun tracking tomaintain Sunlight focus at the collector.-Inability to provide power in diffusedlight conditions. 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.
Why is the universe speeding up?In 1998, two teams of astronomers studying 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.
Albert Einstein,1947. Einstein usedhis "cosmologicalconstant" to helpdescribe a staticuniverse. When helearned the universewas expanding, hediscarded it.
Einsteintheorized thatmass warpsthe shape ofspace,creating theforce we callgravity.Einsteintheorized thatmass warpsthe shape ofspace,creating theforce we callgravity.
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.
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.
The Electromagnetic Theory--- Discovered in the nineteenth centuryby James 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.
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.
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 second Albert 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 vibration Scientists 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.
Transmission of LightLight can travel through a vacuum. Opaque Objects --- completely block lightand through which you cannot see Transparent Objects --- readily transmitlight and through which you can see clearly Translucent Objects --- allow light to passthrough partially or that distort the light so thatyou cannot see through them
Behavior of LightLight travels in a straight line. Pinhole Camera --- the object that is viewed isupside-down Shadow --- the dark space behind an object that isformed when light is blocked by that opaque object Umbra --- the darker central portion of the shadowthat receives no light from the source Penumbra --- the lighter shadow that surrounds theumbra and receives some light from outer edges of thelight source