Lecture Note of Photovaltaic Technology.docx

1、Lecture Note of Photovaltaic TechnologyPHOTOVOLTAIC TECHNOLOGY PHOTOVOLTAIC TECHNOLOGY LESSON 1Reference Textbooks (1) “Applied Photovoltaics” by S.R. Wenham, M.A. Green, M.E. Watt and R Corkish. (2) “ Practical Photovoltaics electricity from solar cells” by Richard J.Komp (3) “ Energy Systems and s

2、ustainabiliy- Power for a substainable future” by G Boyle, B Everett and J Ramage (4) “Renewable Energy- Power for a sustainable future” by G Boyle (5) “ Solar cells, materials, manufacture and operation” by Tom Markvart and Luis Castaner (6) “ The physics of solar cells” by Jenny Nelson (7) “ Semic

3、onductors for solar cells” by Hans Joachim Moller Course outline 2 hrs of lecture 2 hrs of lab and mini assignment with presentation 1 hr of tutorial Common Test 20% Lab 10% Mini Assignment 15% Tutorial 10% Exam 45% Couse contents Energy demand and global climate changes, Properties of sunlight, sem

4、iconductor properties, p-n junctions, solar cell operation, solar cell design solar module design module interconnection PV systemsEnergy demand and global climate changesThe Greenhouse effect Increasing levels of CO2 in Earths atmosphere (primarily from burning of fossil fuels). 280 ppm before 1860

5、, 355 ppm today. Other Greenhouse gases are also increasing due to human activity (methane). Ozone (near the Earths surface), nitrous oxides, and CFC. Could potentially increase the Earths average temperature by 2-3C over the next 100 years. Potentially disastrous for many eco-systems (e.g. corals,

6、low lying islands, river deltas) Rise in sea level . Lost of sea coast areas, population affected http:/ukinjapan.fco.gov.uk/en/newsroom/?view=Speech&id=15027013 lost of fresh water supply lost of fertile landsMajor contributor to greenhouse gas : burning of fossil fuel for electricity generation an

7、d transport Conclusion: society progress increase global climate changes instability etc Solutions : 1) reduce our pollution by using alternative energy sources that are eco-friendly and sustainable eg hydro, wind, geothermal, tidal, solar . 2) change in lifestyle 3) invest and invent energy saving

8、appliances and machinesChallenges face by RE : cost/ kWh generation, geographical dependence, intermittent supply and changing climate causes RE supplies unpredictable.Wind powerVertical axis wind turbine (VAWT) Advantages: harness wind from all direction position of rotor stays excellent power in s

9、low winds. wind resource isnt critical so can be installed closer to buildings Disadvantages: not as efficient as the HAWT in high winds. require big space for guy wires to keep them stable. Other types of VAWTHorizontal-axis wind turbine (HAWT)Hydro power Tidal powerBiomass Energy crops: Woody crop

10、s, agricultural crops Wastes: wood residues, animal wastes, municipal solid waste, landfill gas Geothermal Heat from geothermal reservoirs ( collection of hot water) provides the forces that spin the electrical generators Two major type of reservoirs-dry steam &hot water reservoirs Hotspot Theories

11、- Yellowstone National Park Fuel cell Solar energy Annual amount of solar incident on Earth : equivalent to X 160 energy stored in proven reserves of fossil fuel equivalent to X 5,000 Earth consumption of fossil, nuclear and hydro power Thermall PV Solar thermal Direct conversion of solar heat to sp

12、ace heating, water heating Solar Cooking Electricity generation via heat turbine eg solar tower, solar pond Solar collector & solar cooker Solar trough and solar tower Photovoltaics Evolve from space technology Rapid advancement through the semiconductor technology about a little over 20 per kilowat

13、t hour. Energy from solar cell incident light surface area Efficiency at present : 13-15% Solar module ( many solar cells connected to firm a module) Many size of solar madules available, typically 50W, 75W or 80W Make up of many solar cells connected together in series Modules can be add up to meet

14、 the needs of the users PV applicable to areas with plenty of sunlight and windy ( ideal) Types of PV systems:Stand alone, hybrid and grid connection. PHOTOVOLTAIC TECHNOLOGY LESSON 2 Photovoltaics Process that convert sunlight to electricity Device that carry out this process is called PV cells/ mo

15、dules Note direct heating is not photovoltaic process eg solar collector, solar cooker, solar pond Particle/wave duality of light Light behaves as both a wave and a particle E = hf = hc/ ( E=energy, h = Plancks constant, c = velocity of light)Particles properties : blackbody Radiation Blackbody - id

16、eal absorber and emitter of electromagnetic radiation . The hotter the blackbody the more radiation it emits, and the peak of the spectrum moves to higher energy (lower wavelength). Planks formula K Boltzmanns constant (1.38 x 10 -23 J/K) - Energy density in interval f to f + df Js/m3 Intensity emit

17、ted into a hemisphere I = intensity (W/m2) s- Stefan Boltzmanns constant (5.67 x 10-8 W/m2K 4 ) radiation distributions from perfect black bodies at different temperatures. Power emitted per unit area of the blackbody per unit wavelength at 6000K, 4500K, 3000K.Sun and its Radiation Suns energy is de

18、rived by the fusion of H. This forms He and large amounts of energy. Total output of the Sun = 4 x 1026 W Power reaching earth = 1.78 x 1017 W Intensity outside Earths atmosphere = 1367 W/m26000K blackbodyAM 0AM1.5Solar Radiation at the Earths surface Atmosphere attenuates sunlight - scattering and

19、adsorption. The maximum radiation reaches the Earths surface when the sun is directly overhead and the sky is clear The intensity decreases as the pathlength of light through the atmosphere increases. Described using the concept of: Air Mass = 1/ cos () where is the angle between sunlight and the ve

20、rtical (zenith). Expression loses accuracy when 75 due to curvature of the Earth.Air Mass (AM) AM1.5 is often used as a standard reference spectrum (1000 W/m2). Just outside the atmosphere is defined as: Air Mass zero: AM0 (1367 W/m2)AM = 1/cos Direct and Diffuse Radiation The atmosphere attenuates

21、sunlight by 30% due to: Rayleigh scattering by air molecules (very strong at short wavelengths due to 1/ l4 dependence). Scattering by aerosols and dust particles. Absorption by gases such as O2, ozone, H2O & CO2 (reduces the intensity of the sunlight). Effect 1 and 2 give rise to blue sky, sunset,

22、diffuse light. The total radiation has two components: direct and diffuse i.e. AM global = AM direct + AM diffuse For example when the sun is directly overhead (AM1.0), the diffuse component is about 10% of the total (or global) AM1.0 spectrum. This percentage increases with increasing AM or when sk

23、ies are not clear. Under clear sky conditions, the diffuse radiation is typically “more blue”. On a cloudy day then the spectrum is 100% diffuse, and the diffuse intensity is about 20% of the maximum possible. PHOTOVOLTAIC TECHNOLOGY LESSON 3The Greenhouse effect Increasing levels of CO2 in Earths a

24、tmosphere (primarily from burning of fossil fuels). 280 ppm before 1860, 355 ppm today. Other Greenhouse gases are also increasing due to human activity (methane). Ozone (near the Earths surface), nitrous oxides, and CFC. Could potentially increase the Earths average temperature by 2-3C over the nex

25、t 100 years. Potentially disastrous for many eco-systems (e.g. corals, low lying islands, river deltas).Apparent motion of the Sun The Earth orbits the sun with its axis of rotation inclined at an angle of = 23.45 to the normal to the plane of the orbit. This means that the Suns apparent motion acro

26、ss the sky varies throughout the year (seasons )Direct and Diffuse Insolation Data If data is available giving the direct and diffuse components on a horizontal plane, the corresponding insolation on a tilted surface at an angle b to the horizontal can be calculated. We can assume the diffuse compon

27、ent is independent of the tilt angle (valid for b 45). S = S sin ( + )/sin () Dec = 23.45 sin (d-81) X 360/365 = 90 dec south hemisphere = 90 + dec north hemisphere S - direct component on the tilted surface S - direct component on the horizontal plane a - solar noon time altitude of the sun Dec: de

28、clination of the sun (The attitude at which the Sun is directly overhead), = latitude. d = day number Solar panel If direct and diffuse components are not available and only the global insolation on a plane is known: Then you need to know the number of “sunny” and “cloudy” days per month.(i) intensi

29、ty for “sunny: days I intensity of direct component incident on a plane perpendicular to the suns rays. Diffuse component = 10% of I Total intensity = 110% I(ii) intensity for “ cloudy” days Assume all light is diffuse I = 20% ISolar Radiation in Singapore Radiation in Singapore in the month of Janu

30、arySingapore insolation Singapore receives 2/3 of the solar radiation Mean daily sunshine hours for different months of the year vary from 33% to 55% of the maximum possible February, March and July with 6.2 hours of bright sunshine (highest) November and December with 4.5 and 4.4 hours, respectively (lowest) Average max solar radiation is in February (484.4