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Ch 20107 solar energy


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  • Hello! I'm PHUC Truong The. I am currently a Master of thermoelectric cooler technology Polytechnic University of Da Nang Vietnam. I need all the information in your slides for reference. I need information on radiation coefficients at page 39 (Information in the table). This information you get somewhere, maybe give me reference source for this information is not     Your slides were reported at scientific conferences or was posted notice yet? Can you give me information on this article is not? Purpose: to listed in the references cited    Thank you so much!
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Ch 20107 solar energy

  1. 1. 7. SOLAR ENERGYTopics: Solar Energy: Solar radiation measurements, Solar Thermal: Flat plate and focusing collectors, solar space heating and cooling, solar pond, Solar Photovoltaic: Solar cells and storage
  2. 2. SUNEnergy received from the sun in 30 days exceeds total energy available in fossil fuels
  3. 3. HIGHLY DYNAMICInfrared Black spots
  4. 4. THE EARTH Moon’s Shadow(at the time of solar eclipse)
  5. 5. SOLAR ENERGYSun is the prime source of all renewable energy
  6. 6. SOLAR RADIATION Energy from the sun reaches earth’s surface in the form of solar radiation. The Sun is a sphere of intensely hot gaseous matter, continuously generating heat by thermo-nuclear fusion reactions, which convert hydrogen atoms to helium atoms. This energy radiated from the sun in all directions and a very small fraction of its reaches the earth. The maximum intensity of solar radiation known as solar constant which is defined as the total energy received from the sun, per unit time on a surface of unit area kept perpendicular to the radiation, in space, just outside the earth’s atmosphere when the earth is at its mean distance from the sun. The value of solar constant is 1366 W/m2.
  8. 8. SOLAR RADIATION SPECTRUMOriginates with the thermonuclear fusion reactions occurring in the sun.Represents the entire electromagnetic radiation (visible light, infrared,ultraviolet, x-rays, and radio waves).
  9. 9. Total Energy ReceivedPer unit surface area(Solar Insolation) 1366 W/m2 Outside atmosphere Earth surface
  11. 11. SOLAR INSOLATION The solar radiation received on a flat, horizontal surface at a particular location on earth at a particular instant of time is called the solar insolation and usually expressed in W/m2. For a given flat horizontal surface, the parameters of the solar insolation are:  Daily variation (Hour angle).  Seasonal variation and geographical location of the particular surface.  Atmospheric clarity.  Shadows of trees, tall structures, adjacent solar panels, etc.  Degree of latitude for the location.  Area of surface, m2.  Angle of tilt.
  12. 12. ANGLE OF INCIDENCE (θ )  The angle between the incident beam (Ibn) and normal (ON) to surface (S).  If surface S is fixed, angle of incidence θ has hourly variation due to changing position of the sun.  Equivalent Incident Flux (IN) normal to the surface S = component of Ibn along ON. IN = Ibn cos θ Angle of Incidence θ depends on several variables such as angle of declination, tilt angle, hour angle, latitude , azimuth angle associated with the location and orientation of the surface (S) and the direction of sun rays. The fixed type collector surface ‘S’ should be so oriented that it collects maximum energy during the year.
  13. 13. TILT ANGLE OR SLOPE ANGLE (β) The angle between the collector surface plane and the horizontal plane is called the tilt angle or the slope angle and is designated by β.  For vertical surface β = 900  For horizontal surface β = 00  β is always positive. For sun tracking collectors/reflectors, the angle β is changed automatically to track the sun. For fixed type collectors/reflectors, angle β is constant.
  14. 14. ANGLE OF DECLINATION (δ)  The angle between the line joining centers of the sun and earth and the equatorial plane.  The angle of declination (δ) varies with season from maximum value of +23.45° on June 21 to minimum value of –23.45° on December 21. The angle δ is zero at two equinoxes, i.e., March 21 and September 21.  The declination angle can be calculated from the following expression: Declination angle (δ)=23.45sin{(360/365) (284 + n)} where, n = the day of year counted from first January.
  15. 15. HOUR ANGLE (ω) Angle traced by sun in 1 hour with reference to 12 noon (Local Solar Time) and is equivalent to 15° per hour. ω= 15×(ST-12),where ST is local solar time At 9 am ω = 15×(9-12) = - 45° At 6 pm ω = 15×(18-12) = 90°
  16. 16. LATITUDE (Φ) The angle made by the radial line joining the given location and the center of the earth, with equatorial plane. Tilt Angle (β) and Angle of Latitude (φ)
  17. 17. SOLAR RESOURCES The Earth receives at an average of 1366 W/m2 energy (January: 1412 W/m², and July: 1321 W/m²) in the form of electromagnetic radiation from the Sun This is equivalent to over 43 thousand times the entire power generation rate on the Earth But…  Large portion of this energy is absorbed in the atmosphere.  Not available all the time at one particular place.  Needs to be collected (absorbed) before its utilization.
  18. 18. SOLAR ENERGY CONVERSION To use solar energy, some part of the electromagnetic spectrum must be converted into two other farms:  Heat (Thermal Energy)  Electricity The amount of heat or electricity produced depends upon the technology used and its efficiency.
  19. 19. TECHNIQUES FOR USING SOLAR ENERGYSolar energy is used in three different ways:1. By converting solar energy to thermal energy through solar heater (thermal conversion)2. By direct conversion of solar energy to electricity through photovoltaic (PV) approach3. By converting solar energy to chemical energy (photosynthesis)
  20. 20. SOLAR ENERGY CONVERSION OPTONS Heating CO SC 2Sugar O H e- 2 2 HO 2 O 2 H2O Photosynthesis Semiconductor/Liquid Photovoltaics Junctions
  21. 21. APPLICATIONS OF SOLAR ENERGY Water heating Air heating for agricultural and industrial applications Heating and cooling of buildings Cold storage for preservation of food Cooking of food Green houses Distillation of water Water pumping Solar furnaces Power generation Solar photovoltaic
  22. 22. ADVANTAGES AND DISADVANTAGES Advantages  All chemical and radioactive pollutants of the thermonuclear reactions remain behind on the Sun, while only pure radiant energy reaches the Earth.  Energy reaching the earth is incredible. By one calculation, 30 days of sunshine striking the Earth have the energy equivalent of the total of all the planet’s fossil fuels, both used and unused! Disadvantages  Solar energy is not available round the clock.  Available Solar energy is diffused. Required to be focused at one point before using (particularly for thermal conversion).  Three step approach is required: 1) collection, 2) conversion, 3) storage.
  23. 23. SOLAR THERMAL TECHNOLOGIES Solar thermal is the oldest solar energy technology – has been used for centuries Solar thermal technologies can be divided in three types:  Passive solar building design  Thermal collectors for water heating, space heating and other uses  Solar thermal power plants
  24. 24. PASSIVE SOLAR DESIGN Passive solar design is a set of practices that accommodate the local climate by:  Letting the sun into the building in the winter  Keeping the sun out in the summer The most important aspect of passive solar design are  Building and window orientation  Insulation and building materials  Shading
  25. 25. HEATING OF LIVING SPACES Best design of a building is to act as a solar collector and storage unit for the purpose of heating. This is achieved through three elements: collection, storage, and insulation. Efficient heating starts with proper Collection of solar energy that can be achieved by keeping south-facing windows and appropriate landscaping (location of tree, tall building, etc.). Insulation on external walls, roof, and the floors. The doors, windows, and vents must be designed to minimize heat loss (double layer panels). Storage: Thermal mass holds heat. Water= 62 BTU per cubic foot per degree F. Iron= 54, Wood (oak) = 29, Brick = 25, concrete = 22, and loose stone = 20
  26. 26. HEATING OF LIVING SPACES (contd…)Passive Solar Trombe Wall Passively heated home
  27. 27. HEATING OF LIVING SPACES (contd…) A passively heated home uses about 60-75% of the solar energy that hits its walls and windows. The Center for Renewable Resources estimates that in almost any climate, a well-designed passive solar home can reduce energy bills by 75% with an added construction cost of only 5-10%. About 25% of energy is used for water and space heating. Major factor discouraging solar heating is low price of electricity!!!
  28. 28. SOLAR THERMAL COLLECTORS Thermal collectors convert solar radiation into heat Main uses are water heating and space heating for homes and businesses Many different types, but they can be categorized as:  Flat plate collectors  Concentrating collectors
  29. 29. FLAT PLATE COLLECTOR  A flat-plate collector is used to absorb the sun’s energy to heat (mostly water).  Two methods of heating: passive (no moving parts) and active (using pumps). In passive collectors water circulates throughout the closed system due to convection currents. Tanks of hot water (insulated) are used for storage.
  30. 30. FLAT PLATE COLLECTORS (contd…) Flat-plate solar collector absorbs sunlight and transfer the heat to water or a mixture of anti-freeze and water The hot fluid can be used directly or indirectly for hot water and space heating Generally used for low temperature applications like residential hot water heating
  31. 31. FLAT PLATE COLLECTORS (contd…) A flat-plate solar collector is one of three main types of solar collectors, which are key components of active solar heating systems. The other main types are evacuated tube collectors and batch solar heaters (also called integrated collector-storage systems). Flat-plate collectors are the most common solar collectors for use in solar water-heating systems in homes and in solar space heating. A flat-plate collector consists basically of an insulated metal box with a glass or plastic cover (the glazing) and a dark-colored absorber plate. Solar radiation is absorbed by the absorber plate and transferred to a fluid that circulates through the collector in tubes. In an air-based collector the circulating fluid is air, whereas in a liquid-based collector it is usually water. Flat-plate collectors heat the circulating fluid to a temperature considerably less than that of the boiling point of water and are best suited to applications where the demand temperature is 30-70°C and for applications that require heat during the winter months.
  32. 32. EVACUATED TUBE SOLAR THERMAL COLLECTORS  Evacuated tube collectors use a “thermos bottle” type of collector that prevent freezing and can achieve higher temperatures  Used when large volumes high temperature water are needed like commercial laundries, hotels and hospitals
  33. 33. HEATING WATER: ACTIVE SYSTEMActive System uses antifreeze so that the liquid does not freeze ifoutside temperature drops below freezing point.
  34. 34. FLAT PLATE SOLAR COLLECTORS PERFORMANCE Useful energy gain QuCollector efficiency,η = Solar radiation incident on collector Ac ITAc = Collector areaIT = Incident solar radiation on collector (kW/m2 )
  35. 35. FLAT PLATE SOLAR COLLECTORS PERFORMANCE (contd…)Qu = in − Eout = R Ac ατ IT − UL (Tf , O − Ta )   E F  FR = Collector efficiency factorα = Absorptivity of collectorτ = Transmissivity of glass coverUL = Overall loss coefficientTf , O = Temperature of fluid in the tubesTa = Ambient temperature
  38. 38. HEATING WATER—LAST THOUGHTS Efficiency of solar heating system is always less than 100% because:  % transmitted depends on angle of incidence,  Number of glass sheets (single glass sheet transmits 90- 95%), and  Composition of the glass By using solar water heating in place of a gas water heater, a family will save 500 kg of pollutants each year. Market for flat plate collectors grew in 1980s because of subsidy. While solar water heating is relatively low in the India, in other parts of the world such as Cyprus (90%) and Israel (65%), it proves to be the predominate form of water heating.
  39. 39. CONCENTRATING SOLAR THERMALCOLLECTORS: CONCENTRATION RATIO S. Concentration Concentrator-Receiver CombinationNo. Ratio 1. Plane reflector – plane receiver 1 to 42. Conical reflector – cylindrical receiver 4 to 10 Parabolic cylindrical reflector-cylindrical3. 10 to 100 receiver4. Paraboloidal reflector-spherical receiver Up to 10000 kW/m2 insolar radiation on surfaceConcentration Ratio = kW/m2 on surface of focus of collector
  41. 41. CONCENTRATING SOLAR THERMAL COLLECTORS (contd…) Parabolic dish collectors use optical mirrors to focus sunlight on a target can achieve very higher temperatures, but are more expensive and complex Small size Collectors are more economical in hilly area (Ladakh)
  43. 43. CONCENTRATING SOLAR THERMAL COLLECTORS Parabolic trough collectors also use optical mirrors to focus sunlight on a linear target, usually a tube with a circulating fluid in it Used for power generation
  44. 44. PARABOLIC DISHES AND TROUGHS Collectors in southern CABecause they work best under direct sunlight, parabolic dishesand troughs must be steered throughout the day in the directionof the sun.
  45. 45. SOLAR-THERMAL ELECTRICITY: PARABOLIC DISHES AND TROUGHS Focus sunlight on a smaller receiver for each device; the heated liquid drives a steam engine to generate electricity. The first of these Solar Electric Generating Stations (SEGS) was installed in CA by an Israeli company, Luz International. Output was 13.8 MW; cost was $6,000/peak kW and overall efficiency was 25%. Through federal and state tax credits, Luz was able to build more SEGS, and improved reduced costs to $3,000/peak kW and the cost of electricity from 25 cents to 8 cents per kWh, barely more than the cost of nuclear or coal-fired facilities. The more recent facilities converted a remarkable 22% of sunlight into electricity.
  46. 46. MIRRORS
  47. 47. CONCENTRATING SOLAR THERMAL COLLECTORS Tracking mirrors focus sunlight on a stationery “power tower” to generate very high temperatures (~1000o F) Used to generate electricity
  49. 49. BINARY CYCLE SOLAR THERMAL POWER PLANT 1. Solar collector 2. Hot water reservoir 3. Head exchanger 4. Cold water reservoir 5. NH3 Gas Turbine 6. Generator 7. NH3 condenser 8. NH3 Pressuriser 9. Cooling Tower
  50. 50. SOLAR-THERMAL ELECTRICITY General idea is to collect the light from many reflectors spread over a large area at one central point to achieve high temperature. Example is the 10-MW solar power plant in Barstow, CA.  1900 heliostats, each 20 ft by 20 ft  a central 295 ft tower An energy storage system allows it to generate 7 MW of electric power without sunlight. Capital cost is greater than coal fired power plant, despite the no cost for fuel, ash disposal, and stack emissions. Capital costs are expected to decline as more and more power towers are built with greater technological advances. One way to reduce cost is to use the waste steam from the turbine for space heating or other industrial processes.
  52. 52. DIRECT CONVERSION INTO ELECTRICITY Photovoltaic cells are capable of directly converting sunlight into electricity. A simple wafer of silicon with wires attached to the layers. Current is produced based on types of semiconductor (n- and p-types) used for the layers. Each cell produces 0.5 V. Battery may be needed to store electrical energy No moving parts, no pollution, do not wear out, but because they are exposed to the weather, their lifespan is about 20 years.
  53. 53. PHOTOVOLTAIC TECHNOLOGY - BACKGROUND  Photovoltaic (PV) converts sunlight to DC electricity using a semiconductor cell.  The PV effect was discovered in 19th century by Alexander Becquerel  Bell labs pioneered early application, especially for satellites, in the 1960s  Very small, remote applications emerged in the 1970s and early 1980s  As cost declined, PV became more common for larger applications in late 1980s and early 1990s
  54. 54. SOLAR PANELS IN USE Because of their current costs, only rural and other customers far away from power lines use solar panels. Subsidy is given for these panels by Central and State nodal agencies. The costs may go down in coming years in view of ongoing R&D work worldwide
  55. 55. PHOTOVOLTAIC EFFECT Electromagnetic radiation can be viewed as photons Each photon has energy E = hν = h c/λ Photons travel at speed c = ν λ Photons having an sufficient energy can dislodge an electron from silicon (1.12 eV = 1.794 x 10-22 kJ) The electron is accelerated by the electric field If a circuit is provided a current will flow
  56. 56. PHOTOVOLTAIC CELLS When sunlight strikes the solar cell, it “knocks loose” electrons, which generates a flow of DC current
  57. 57. PHOTOVOLTAIC CELL EFFICIENCYThe most commonly used material crystalline silicon, absorbs energy in a small part ofthe spectrum. Efficiency depends on how much of the available spectrum can beconverted to electricity.
  59. 59. PV CELLS IN SERIES AND PARALLEL Series arrangement: voltages add Parallel arrangement: currents add
  60. 60. PV CELL MATERIALS The most common PV cells are made from crystalline silicon wafers Other types of materials include thin films like Cadmium Telluride (CdTe), Copper-Indium-Gallium- Diselenide (CIGS), amorphous silicon (a-Si) The main goals for manufacturers are to minimize the amount of materials and maximize efficiency Today, the best crystalline silicon cells are about 15% efficient, the best thin films are about 8% efficient.
  61. 61. PV CELLS, MODULES AND ARRAYS PV cells are connected like batteries to increase voltage and current output and are assembled in to modules Modules become part of larger arrays
  62. 62. HOW ARE PV SYSTEM RATED? PV modules are rated based on the maximum power produced in Watts when the amount of sunlight is 1,000 W/m2 PV systems are rated based on the maximum combined power output of the PV modules Since the amount of sunlight changes, the power output of the system will vary
  64. 64. EFFICIENCIES OF PHOTOVOLTAIC DEVICES 25 20 15 Efficiency (%) 10 crystalline Si amorphous Si nano TiO2 5 CIS/CIGS CdTe 1950 1960 1970 1980 1990 2000 Year
  65. 65. BATTERIES Primary Batteries  can store and deliver electrical energy, but can not be recharged. Typical carbon-zinc and lithium batteries commonly used in consumer electronic devices are primary batteries. Primary batteries are not used in PV systems because they can not be recharged. Secondary Batteries  can store and deliver electrical energy, and can also be recharged by passing a current through it in an opposite direction to the discharge current. Common lead-acid batteries used in automobiles and PV systems are secondary battery.
  66. 66. SECONDARY BATTERY TYPES AND CHARACTERISTICS Deep Cycle Battery Type Cost Maintenance PerformanceFlooded Lead-Acid Lead-Antimony Low Good High Lead-Calcium Open Vent Low Poor Medium Lead-Calcium Sealed Vent Low Poor Low Lead Antimony/Calcium Hybrid Medium Good MediumCaptive Electrolyte Lead-Acid Gelled Medium Fair Low Absorbed Glass Mat Medium Fair LowNickel-Cadmium Sintered-Plate High Good None Pocket-Plate High Good Medium
  67. 67. BATTERIES FOR PV Battery Capacity  It is a measure of battery’s ability to store or deliver electrical energy, commonly expressed in units of ampere-hours. Ampere-Hour Definition  It is the common unit of measure for a battery’s electrical storage capacity, obtained by integrating the discharge or charge current in amperes over a specific time period. An ampere-hour is equal to the transfer of one ampere over one hour, equal to 3600 coulombs of charge. For example, a battery which delivers 5 amps for 20 hours is said to have delivered 100 ampere-hours.
  68. 68. BATTERIES FOR PV (contd…) Discharge rate affects capacity Typical discharge times  Industrial, motive applications 10 hours  Photovoltaic applications 100-300 hours Maximum Recommended Depth of Discharge for Lead Acid Batteries  Shallow cycling types 50%  Deep cycling types 80% Time to fully discharge Days of reserve × 24 hours(1 day)  Time to discharge (rating) = Maximum Depth of Discharge (%)
  69. 69. BATTERY SELECTION CRITERION Nominal system voltage Charging requirement Required capacity Ampere-hour capacity at discharge rate Daily and maximum depth of discharge Self-discharge rate Gassing characteristics Efficiency Temperature effects Size, weight and structural needs Susceptibility to freezing Electrolyte type and concentration Maintenance requirements Terminal configurations Battery life (cycles/year) Availability and servicing Cost and warranty
  70. 70. PV SYSTEMS A complete PV system may also include a device to convert DC to AC power (inverter), batteries to store energy, and a back up generator PV systems can be connected to the electric utility and can be used to reduce the amount of electricity purchased from the local utility without using batteries or generators
  71. 71. LOW EFFICIENCY AND OTHER DISADVANTAGES Efficiency is far lass than the 77% of usable solar spectrum (theoretical efficiency). Only 43% of photon energy is used to warm the crystal. Efficiency drops as temperature increases (from 24% at 0°C to 14% at 100 °C.) Light is reflected off the front face Internal electrical resistance are other factors. Overall, the efficiency is about 10-14%. Underlying problem is weighing efficiency against cost.  Crystalline silicon-more efficient but more expensive to manufacture  Amorphous silicon-half as efficient, less expensive to produce.
  72. 72. FUTURE OF SOLAR ENERGY Solar thermal energy is already very cost- effective for providing low temperature heat almost anywhere PV is very cost effective for providing electricity in remote areas and in niche applications As the costs of fossil fuels and electricity increase, PV is becoming more cost effective compared to electricity from conventional sources The costs of all solar technologies are declining
  73. 73. SOLAR ENERGY ISSUES AND BARRIERS ‘Fuel’ is free but the systems are not. Can be costly to install compared to grid supplied electricity and fossil fuels Certain technologies, like PV, can require large areas Some PV technologies use toxic materials, although in very small amounts Energy storage must be used in some cases
  74. 74. FINAL THOUGHT Argument that sun provides power only during the day is countered by the fact that 70% of energy demand is during daytime hours. At night, traditional methods can be used to generate the electricity. Goal is to decrease our dependence on fossil fuels. Currently, 75% of our electrical power is generated by coal-burning and nuclear power plants. Mitigates the effects of acid rain, carbon dioxide, and other impacts of burning coal and counters risks associated with nuclear energy. Pollution free, indefinitely sustainable.