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Fundamentals of Solar PV System

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Fundamentals of Solar PV System

  1. 1. Fundamentals of Solar PV system
  2. 2. Solar Energy Basics and solar spectrum Photovoltaic Cell: Construction and working principleSolar photovoltaic technologies Types of solar photovoltaic systems Designing of a solar photovoltaic system Advantages and disadvantages of solar energy and systems Applications of solar energy Outline
  3. 3. What is Solar Energy?  Originates with the thermonuclear fusion reactions occurring in the sun.  Represents the entire electromagnetic radiation (visible light, infrared, ultraviolet, x-rays, and radio waves).  This energy consists of radiant light and heat energy from the sun.  Out of all energy emitted by sun only a small fraction of energy is absorbed by the earth.
  4. 4. http://en.wikipedia.org/wiki/File:Breakdown_of_the_incoming_solar_ener The surface receives about 47% of the total solar energy that reaches the Earth. Only this amount is usable. Breakdown of incoming solar energy
  5. 5. Air Mass  Amount of air mass through which light pass  Atmosphere can cut solar energy reaching earth by 50% and more
  6. 6.  Solar Thermal Energy  Solar Heating  Solar Water Heating  Solar Space Heating  Solar Space Cooling  Solar Photovoltaic  Solar Concentrators Solar Energy Harvesting Using Different Paths
  7. 7. Electricity Generation From Solar Energy Solar Energy can be used to generate electricity in 2 ways:  Solar Thermal Energy: Using solar thermal technologies for heating fluids which can be used as a heat source or to run turbines to generate electricity.  Solar Photovoltaic Energy: Using solar energy for the direct generation of electricity using photovoltaic phenomenon.
  8. 8. Technology Options for Solar Power Parabolic Dish Solar Power Thermal Low Temperature <100°C. Solar Water Heating Solar Chimney Solar Pond Med Temp <400°C High Temp. >400°C Central Tower PV Technology Mono Crystalline Silicon Polycrystalline Silicon Amorphous Silicon Production Process Wafer Thin Film
  9. 9. Energy Band Diagram of a Conductor, Semiconductor and Insulator conductor semiconductor insulator Semiconductors are interested because their conductivity can be readily modulated (by impurity doping or electrical potential), offering a pathway to control electronic circuits.
  10. 10. Semiconductors used for solar cells II III IV V VI B C (6) Al Si (14) P S Zn Ga Ge (32) As Se Cd In Sb Te Semiconductors:  Elementary – Si, Ge.  Compound – GaAs, InP, CdTe.  Ternary – AlGaAs, HgCdTe, CIS.  Quaternary – CIGS, InGaAsP, InGaAIP.
  11. 11. Silicon - Si Si Si Si SiSi Si Si Si Shared electrons  Silicon is group IV element – with 4 electrons in their valence shell.  When silicon atoms are brought together, each atom forms covalent bond with 4 silicon atoms in a tetrahedron geometry.
  12. 12. Intrinsic Semiconductor  At 0 ºK, each electron is in its lowest energy state so each covalent bond position is filled. If a small electric field is applied to the material, no electrons will move because they are bound to their individual atoms.  At 0 ºK, silicon is an insulator.  As temperature increases, the valence electrons gain thermal energy.  If a valence electron gains enough energy (Eg), it may break its covalent bond and move away from its original position. This electron is free to move within the crystal.  Conductor Eg <0.1eV, many electrons can be thermally excited at room temperature.  Semiconductor Eg ~1eV, a few electrons can be excited (e.g. 1/billion)  Insulator, Eg >3-5eV, essentially no electron can be thermally excited at room temperature. Energy of a photon,
  13. 13. Extrinsic Semiconductor, n-type Doping Electron - Si Si Si Si SiSi Si Si As Extra Valence band, Ev Eg = 1.1 eV Conducting band, Ec Ed ~ 0.05 eV  Doping silicon lattice with group V elements can creates extra electrons in the conduction band — negative charge carriers (n-type), As- donor.  Doping concentration #/cm3 (1016/cm3 ~ 1/million).
  14. 14. Valence band, Ev Eg = 1.1 eV Conducting band, Ec Ea ~ 0.05 eV Electron - Si Si Si Si SiSi Si Si B Hole  Doping silicon with group III elements can creates empty holes in the valence band positive charge carriers (p-type), B-(acceptor). Extrinsic Semiconductor, p-type doping
  15. 15. V I R O F p n p n V>0 V<0 Reverse bias Forward bias p-n Junction diode  A p-n junction is a junction formed by combining p-type and n-type semiconductors together in very close contact.  In p-n junction, the current is only allowed to flow along one direction from p-type to n-type materials. i p n V<0 V>0 depletion layer - +
  16. 16.  Get image from book Efficiency – The Band Gap Problem
  17. 17. Photo+voltaic = convert light to electricity
  18. 18.  A PV cell is a light illuminated pn- junction diode which directly converts solar energy into electricity via the photovoltaic effect.  A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (n-type) silicon on top of a thicker layer of boron- doped (p-type) silicon.  When sunlight strikes the surface of a PV cell, photons with energy above the semiconductor bandgap impart enough energy to create electron-hole pairs. Photovoltaic Cell
  19. 19. Photovoltaic Cell: Operating Principle  There are three basic steps for generation of electricity using PV cells which are following:  First is absorption of solar radiation,  Second is generation of free charge carriers and  Third is transport and then collection of charge carriers at PV cell terminals.
  20. 20. Structure of a Solar Cell
  21. 21. 1) Non absorbed photons 2) Lattice thermalization 3) Junction voltage drop 4) Contact voltage drop 5) Recombination Standard PV cell Efficiency Losses
  22. 22. Blocking Diodes  During sun shine, as long as the voltage produced by the panels is greater than that of the battery, charging will take place.  In the dark, the voltage of the battery would cause a current flow in reverse direction through the panels, which can lead to the discharging of battery.  A blocking diode is used in series with the panels and battery in reverse biasing to prevent reverse flow of the current.  Normal p-n junction diodes can be used as blocking diodes.  To select a blocking diode, following parameters should be kept in mind:  The maximum current provided by the panels.  The voltage ratings of the diode.  The reverse breakdown voltage of the diode.
  23. 23. Hot- Spot and Bypass Diodes  Hot Spot phenomenon happens when one or more cells of the panel is shaded while the others are illuminated.  The shaded cells/panels starts behaving as a diode polarized in reverse direction and generates reverse power. The other cells generate a current that flows through the shaded cell and the load.
  24. 24.  Any solar cell has its own critical power dissipation Pc that must not be exceeded and depends on its cooling and material structures, its area, its maximum operating temperature and ambient temperature.  A shaded cell may be destroyed when its reverse dissipation exceeds Pc. This is the hot spot.  To eliminate the hot-spot phenomenon, a bypass diode is connected parallel to the module or group of cells in reverse polarity which provides another path to the extra current. Hot- Spot and Bypass Diodes
  25. 25.  When part of a PV module is shaded, the shaded cells will not be able to produce as much current as the unshaded cells.  Since all cells are connected in series, the same amount of current must flow through every cell.  The unshaded cells will force the shaded cells to pass more current through it. Bypass diode working phases Bypass Diodes working
  26. 26.  The only way the shaded cells can operate at a current higher than their short circuit current is to operate in a region of negative voltage i.e. to cause a net voltage loss to the system.  The voltage across the shaded or low current solar cell becomes greater than the forward bias voltage of the other series cells which share the same bypass diode plus the voltage of the bypass diode thus making the diode to work in forward bias and hence allowing extra current to pass through it, preventing hot-spot.  For an efficient operation, there are two conditions to fulfill:  Bypass diode has to conduct when one cell is shadowed.  The shadowed cell voltage Vs must stay under its breakdown voltage (Vc).  Ideally, a bypass diode should have a forward voltage (VF) and a leakage current (IR) as low as possible. Bypass Diodes working
  27. 27. Bypass Diodes  Two types of diodes are available as bypass diodes in solar panels and arrays:  p-n junction silicon diode  Schottky barrier diode  To select a bypass diode, following parameters should be checked:  The forward voltage and current ratings of the diode.  The reverse breakdown voltage of the diode.  The reverse leakage current.  Junction Temperature Range
  28. 28. 2 – 3 W 100 - 200 W 10 - 50 kW Cell Array Module,Panel Volt Ampere Watt Size Cell 0.5V 5-6A 2-3W about 10cm Module 20-30V 5-6A 100-200W about 1m Array 200-300V 50A-200A 10-50kW about 30m 6x9=54 (cells) 100-300 (modules) Hierarchy of PV
  29. 29. Solar cells are composed of various semiconducting materials  Crystalline silicon  Cadmium telluride  Copper indium diselenide  Gallium arsenide  Indium phosphide  Zinc sulphide Materials for Solar cell
  30. 30. Cell Technologies Crystalline silicon Mono- crystalline Pure and efficient 15-19% efficiency Multi- crystalline 12-15% efficiency Thin film Non Silicon based CdTe 8.5% efficiency CIGS 9-11% efficiency Silicon based Amorphous 5-7% efficiency
  31. 31. Technology Differences Optical Properties • Band gap (direct, indirect) • Absorption Coefficient • Absorption length Electrical Properties • Carrier Lifetime • Mobility • Diffusion length Manufacturing • Absorber material • Cells • Modules Performance • Efficiency • Current, Voltage and FF • Effect of temperature and radiation
  32. 32. Optical Properties: Band Gaps Fixed band gap of c-Si material (mono, multi). Tunable gaps of thin film compound semiconductors.
  33. 33. Optical Properties: Material absorption lengths Absorption Length in Microns (for approx. 73% incoming light absorption) Wavelength (nm) c-Si a-Si CIGS GaAs 400 nm (3.1eV) 0.15 0.05 0.05 0.09 600 nm (2eV) 1.8 0.14 0.06 0.18 800 nm (1.55eV) 9.3 Not absorbed 0.14 1.1 1000nm(1.24eV) 180.9 Not absorbed 0.25 Not absorbed  Absorption length is much higher for Si because of lower absorption coefficient.  Longer wavelength photons require more materials to get absorbed.
  34. 34. Electrical Properties Mobility Ease with which carriers move in semiconductor. Lifetime Average time carriers spend in excited state. Diffusion Carrier movement due to concentration difference. Diffusion Length Average length travelled by carrier before recombining due to concentration difference. Drift Carrier movement due to electric field. Drift length Average length travelled by carrier before recombination under electric field.
  35. 35. Electrical Properties: Drift and Diffusion lengths High quality material scenario Low quality material scenario  Carrier are transported by diffusion to the junction.  Large diffusion length.  Junction is very thin.  Diffusion length are small.  Drift length is about 10 times greater than diffusion length.  Intrinsic layer is thicker.
  36. 36. Three generations of solar cells 1. First Generation  First generation cells consist of high quality and single junction devices.  First Generation technologies involve high energy and labour inputs which prevent any significant progress in reducing production costs. 2. Second Generation  Second generation materials have been developed to address energy requirements and production costs of solar cells.  Alternative manufacturing techniques such as vapour deposition and electroplating are advantageous as they reduce high temperature processing significantly.  Produced from cheaper polycrystalline materials and glass  High optical absorption coefficients  Bandgap suited to solar spectrum
  37. 37. 3. Third Generation  Third generation technologies aim to enhance poor electrical performance of second generation (thin-film technologies) while maintaining very low production costs.  Current research is targeting conversion efficiencies of 30-60% while retaining low cost materials and manufacturing techniques.  They can exceed the theoretical solar conversion efficiency limit for a single energy threshold material, 31% under 1 sun illumination and 40.8% under the maximal artificial concentration of sunlight (46,200 suns).  Approaches to achieving these high efficiencies including the use of multijunction photovoltaic cells, concentration of the incident spectrum, the use of thermal generation by UV light to enhance voltage or carrier collection, or the use of the infrared spectrum for night-time operation.
  38. 38. Monocrystalline Silicon Modules  Most efficient commercially available module (14% - 17%)  Most expensive to produce  Circular (square-round) cell creates wasted space on module
  39. 39. Front Surface (N-Type side) • Aluminum Electrode (Silver colored wire) • To avoid shading, electrode is very fine. Anti reflection film (Blue colored film) • Back surface is P-type. • All back surface is aluminum electrode with full reflection. Poly Crystalline PV Polycrystalline Silicon Modules
  40. 40. Polycrystalline Silicon Modules  Less expensive to make than single crystalline modules  Cells slightly less efficient than a single crystalline (10% - 12%)  Square shape cells fit into module efficiently using the entire space
  41. 41. PV Module (Single crystal, Poly crystalline Silicon) Single crystal Poly crystalline 120W (25.7V, 4.7A) 1200mm 800mm800mm 1200mm (3.93ft) (2.62ft) (3.93f) (2.62ft) 128W (26.5V ,4.8A) Efficiency is higher Efficiency is lower Same size
  42. 42. Amorphous Thin Film  Most inexpensive technology to produce  Metal grid replaced with transparent oxides  Efficiency = 6 – 8 %  Can be deposited on flexible substrates  Less susceptible to shading problems  Better performance in low light conditions that with crystalline modules
  43. 43. Solar Panel Manufacturing Technologies Mono-Si Solar Panels  Mono-Si is manufactured by Czochralski Process.
  44. 44. Si boule for the production of wafers. Solar Panel Manufacturing Technologies  Since they are cut from single crystal, they gives the module a uniform appearance. Advantages  Highest efficient module till now with efficiency between 13 to 21%.  Commonly available in the market.  Greater heat resistance.  Acquire small area where ever placed. Disadvantages  More expensive to produce.  High amount of Silicon.  High embodied energy (total energy required to produce).
  45. 45. Poly-Si Solar Panels  Polycrystalline (or multicrystalline) modules are composed of a number of different crystals, fused together to make a single cell.  Poly-Si solar panels have a non-uniform texture due to visible crystal grain present due to manufacturing process. Advantages  Good efficiency between 14 to 16%.  Cost effective manufacture.  Commonly Available in the market. Visible crystal grain in poly-Si Solar Panel Manufacturing Technologies
  46. 46. Disadvantages  Not as efficient as Mono-Si.  Large amount of Si.  High Embodied Energy. Visible difference between Mono-Si and Poly-Si Panels Mono-Si solar cells are of dark color and the corners of the cells are usually missing whereas poly-Si panels are of dark or light blue color. The difference between the structure is only due to their manufacturing process. Mono-Si Panel Poly-Si Panel Solar Panel Manufacturing Technologies
  47. 47. Thin Film Solar Panels  Made by depositing one or more thin layers (thin film) of photovoltaic material on a substrate.  Thin Film technology depend upon the type of material used to dope the substrate.  Cadmium telluride (CdTe), copper indium gallium selenide (CIGS) and amorphous silicon (A-Si) are three thin-film technologies often used as outdoor photovoltaic solar power production. Solar Panel Manufacturing Technologies
  48. 48. Amorphous-Si Panels  Non-crystalline allotrope of Si with no definite arrangement of atoms. Advantages  Partially shade tolerant  More effective in hotter climate  Uses less silicon - low embodied energy  No aluminum frame - low embodied energy Disadvantages  Less efficient with efficiency between 6 to 9% .  Less popular - harder to replace.  Takes up more space for same output .  New technology - less proven reliability. Solar Panel Manufacturing Technologies
  49. 49. Thin Film Silicon Solar Cells
  50. 50. CdTe/CdS Solar Cell  CdTe: Bandgap 1.5 eV; Absorption coefficient 10 times that of Si  CdS: Bandgap 2.5 eV; Acts as window layer  Limitation: Poor contact quality with p- CdTe (~ 0.1 Wcm2) Cadmium Telluride Solar Cell  Toxicity of Cd is an issue.  Best lab efficiency = 16.5%.
  51. 51.  NREL has demonstrated an efficiency of 19.9% for the CIGS solar cell.  Typically requires relatively high temperature processing (> 500C). Copper-Indium-Gallium-Diselenide Cell
  52. 52. Comparison of Si on the basis of crystallinity
  53. 53. Comparison of Mono-Si, Poly-Si and Thin film Panels Mono-Si Panels Poly-Si Panels Thin Film Panels 1. Most efficient with max. efficiency of 21%. 1. Less efficient with efficiency of 16% (max.) 1. Least efficient with max. efficiency of 12%. 2. Manufactured from single Si crystal. 2. Manufactured by fusing different crystals of Si. 2. Manufactured by depositing 1 or more layers of PV material on substrate. 3. Performance best at standard temperature. 3. Performance best at moderately high temperature. 3. Performance best at high temperatures. 4. Requires least area for a given power. 4. Requires less area for a given power. 4. Requires large area for a given power. 5. Large amount of Si hence, high embodied energy. 5. Large amount of Si hence, high Embodied energy. 4. Low amount of Si used hence, low embodied energy. 6. Performance degrades in low- sunlight conditions. 6. Performance degrades in low- sunlight conditions. 5. Performance less affected by low-sunlight conditions. 7. Cost/watt: 1.589 USD 7. 1.418 USD 7. 0.67 USD 8. Largest Manufacturer: 8. Suntech (China) 8. First Solar (USA)
  54. 54.  Efficiency,  = (VocIscFF)/Pin  Voc is proportional to Eg,  Isc is proportional to # of absorbed photons  Decrease Eg, absorb more of the spectrum  But not without sacrificing output voltage hv > Eg Semiconductor Material Efficiencies: The Impact of Band Gap on Efficiency
  55. 55.  Direction of current inside PV cell • Inside current of PV cell looks like “Reverse direction.” Why? P N Current appears to be in the reverse direction ? ? • By Solar Energy, current is pumped up from N-pole to P-pole. • In generation, current appears reverse. It is the same as for battery. P N Looks like reverse
  56. 56. Current-Voltage (I-V) Curve   0 exp 1S S ph C Sh q V IR V IR I I I kT A R                 max , mp mp OC SC en PV in PV PV V IP V I FF P A G A G     RL + - Equivalent circuit of practical PV cell
  57. 57. •Voltage on normal operation point 0.5V (in case of Silicon PV) •Current depend on - Intensity of insolation - Size of cell (V) (A) Voltage(V) Current(I) P N A Short Circuit Open Circuit P N V about 0.5V (Silicon) High insolation Low insolation Normal operation point (Maximum Power point) I x V = W Open circuit voltage and short circuit current
  58. 58. (V) (A) Voltage(V) Current(I) 0.49 V 0.62 V 4.95A 5.55A Depend on type of cell or cell-material ( Si = 0.5V ) Depend on cell-size Depend on Solar insolation
  59. 59.  To obtain maximum power, current control (or voltage control) is very important. P N A V (V) (A) Voltage(V) Current(I) I x V = W P2 PMAX P1 Vpmax Ipmax I/V curve P- Max control Power curve
  60. 60. (V) (A) Voltage(V) Current(I) 12 10 8 6 4 2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 P N A )(05.0 R PV characteristics ( I/V curve ) If the load has 0.05 ohm resistance, cross point of resistance character and PV-Character will be following point. Then power is 10x0.5=5 W )(05.0 R 05.0/VI  R V I  Ohm’s theory Estimate obtained power by I / V curve
  61. 61. P N P N Mismatch 5A 1A P N P N Bypass Diode 5A 1A 4A (V) (A) Current(I) High intensity insolation Low intensity insolation I x V = W 5A 1A  Current is affected largely by change of insolation intensity.  Partially shaded serial cell will produce current mismatch. I / V curve vs. Insolation intensity Voltage(V)
  62. 62. Effects of Temperature  As the PV cell temperature increases above 25º C, the module Vmp decreases by approximately 0.5% per degree C
  63. 63.  As insolation decreases amperage decreases while voltage remains roughly constant Effects of Shading/Low Insolation
  64. 64. Shading on Modules  Depends on orientation of internal module circuitry relative to the orientation of the shading.  Shading can half or even completely eliminate the output of a solar array
  65. 65. Series Connections  Loads/sources wired in series  VOLTAGES ARE ADDITIVE  CURRENT IS EQUAL
  66. 66. Parallel Connections Loads/sources wired in parallel:  VOLTAGE REMAINS CONSTANT  CURRENTS ARE ADDITIVE
  67. 67.  Roughly size of PV System How much PV can we install in a given area? 1 kw PV need 10 m2 (108 feet2) Please remember 10m(33feet) 20m(66feet) Room Area = 200 m2 (2,178 feet2) We can install about 20 kW PV
  68. 68. Solar Panel specifications Mechanical Specifications 1. Solar Cell Type: Defines the type of module or cell used in the module. e.g.- Mono-Si, Poly-Si or Thin Film. Design Implication: This determines the class of conversion efficiency of the module. 2. Cell Dimension (in inches/mm.): Defines the size of cell used in the module. e.g.- 125(l) × 125 mm(b) (5 inches). Design Implication: This determines the output power of a single solar cell. 3. Module Dimension (in inches/mm.): Defines the size of the panel. e.g.- 1580 (l)× 808 (b) × 35 (h) mm. Design Implication: Determines the number of cells accommodated in the module. Across length: 1580/125 = 12.64 ~ 12 [least integer]. Across breadth: 808/125 = 6.4 ~ 6. This means number of cell be 72 (6*12).
  69. 69. Solar Panel specifications Mechanical Specifications 4. Module Weight (in kgs./lbs.): Defines the weight of the module. e.g.- 15.5 kgs. (34.1 lbs.) Design Implication: Determines the maximum number of panels which can be installed. 5. Glazing or front Glass: Defines the type and width of the front glass used. e.g.- 3.2 mm (0.13 inches) tempered glass. Design Implication: Width determines the strength of the covering. The type of glass used depends upon thermal insulation requirements or strength requirement. 6. Frame: Defines the type of frame used in the module. e.g.- Anodized aluminium alloy Design Implication: Frame material is chosen so that it can Withstand the environmental effects such as corrosion, hard Impact etc.
  70. 70. Mechanical Specifications 7. Output Cables: Defines the type of cables and sometimes their dimensions provided at output to connect with connector specifications. e.g.- H+S RADOX® SMART cable 4.0 mm2 of length 1000 mm (39.4 inches) with RADOX® SOLAR integrated twist locking connectors. Design Implication: The rating of the cable is as per rating of the PV module and of optimum length generally required by the customers. 8. Junction Box: Defines the protection level of electrical casing at the back of panel. Also includes the no. of bypass diodes (if used). e.g.- IP67 rated with 3 bypass diodes. Solar Panel specifications
  71. 71. Electrical Specifications 1. Peak Power (W): Defines the maximum power of the panel. e.g.- P: 195 Wp 2. Optimum operating Voltage: Defines the highest operating voltage of panel at the maximum power at STC. e.g.- Vmp: 36.6V Design Implication: Determines the number of panels required in series. 3. Optimum operating current: Defines the highest operating current of panel at the maximum power at STC. e.g.- Imp: 5.33A Design Implication: Determines the wire gauge. Used to calculate the voltage drops across the modules or cells. Solar Panel specifications
  72. 72. Electrical Specifications 4. Open Circuit Voltage: Defines the output voltage when no load is connected under STC. e.g.- Voc : 45.4V Design Implication: Determines the maximum possible voltage. Determines the maximum number of modules in series. 5. Short Circuit Current: Defines the protection level of electrical casing at the back of panel. Also includes the no. of bypass diodes (if used). e.g.- Isc: 5.69A Design Implication: Determines the current rating of fuse which is to be used for protection. Determines the conductor size. Solar Panel specifications
  73. 73. Electrical Specifications 7. Module Efficiency: Defines the conversion efficiency given by a given module (which is generally lesser than the single solar cell used in the module). e.g.- 15.3% Design Implication: This parameter helps in solving the problem of choosing a module. 8. Operating Temperature: Defines the range of temperature for which the module can function. e.g.- -40°C to 85°C Design Implication: Determines the temperature range for the environment in which the panel can be kept. 9. Max. Series Fuse Rating: Defines the max. current which can be handled by the module without damage. e.g.- 15 A Design Implication: This defines the rating of fuse to be used with the module. Solar Panel specifications
  74. 74. Electrical Specifications 10. Power Tolerance: Defines the range of power deviation from its stated power ratings due to change in its operating condition. It is defined in %. e.g.- 0/+5 % Design Implication: This parameter determines the upper limit for power of a module. 11. Parameters defined under NOCT: These parameters are same as defined under STC conditions with different values. Difference between STC and NOCT: STC (Standard Test Conditions): Irradiance 1000 W/m2, Module temperature 25 °C, Air Mass=1.5 NOCT(Nominal Operating Cell Temperature): Irradiance 800 W/m2, Ambient temperature 20 °C, Wind speed 1 m/s Solar Panel specifications
  75. 75. Electrical Specifications 12. Temperature Coefficients: These coefficients are defined to show the possible rate of change of values under varying module temperature and irradiance. Design Implication: These parameters can be used to calculate the power, current and voltage of the module. Temperature Coefficient of Voc can also be used to determine the maximum panel voltage at the lowest expected temperature. Solar Panel specifications
  76. 76. Parameters at STC Sanyo (HIP-190DA3) Suntech (STP190S-24/Ad+) Trina (TSM-190DC01A) Optimum Operating Voltage (Vmp) 55.3 V 36.5 V 36.8 V Optimum Operating Current (Imp) 3.44 A 5.20 A 5.18 A Open - Circuit Voltage (Voc) 68.1 V 45.2 V 45.1 V Short - Circuit Current (Isc) 3.7 A 5.62 A 5.52 A Maximum Power at STC (Pmax) 190 W 190 W 190 W Module Efficiency 15.7% 14.9% 14.9% Maximum Series Fuse Rating 15 A 15 A 10 A Maximum System Voltage 600 VDC 1000 V DC 1000VDC Power Tolerance +10/-0% 0/+5 % 0/+3 Temperature Coefficient of Pmax -0.34% / °C -0.48 %/°C - 0.45%/°C Temperature Coefficient of Voc -0.191 V / °C -0.34 %/°C - 0.35%/°C Temperature Coefficient of Isc 1.68 mA / °C 0.037 %/°C 0.05%/°C Module Dimension 53.2 x 35.35 x 2.36 in. (1351 x 898 x 60 mm) 62.2 × 31.8 × 1.4 inches (1580 × 808 × 35mm) 62.24 x 31.85 x 1.57in. (1581 x 809 x 40mm) Warranty : 90% power output 80% power output 20 Years 20 Years 12 years 25 years 10 years 25 years Cost: $570.00 $285.00 $459.00 Comparison between Suntech, Trina and Sanyo 190W Monocrystalline modules
  77. 77. Parameters at STC Monocrystalline (S.C. Origin) Polycrystalline (Moserbaer) Thin Film (a-si) (China Solar) Optimum Operating Voltage (Vmp) 17.82V 17 V 18 V Optimum Operating Current (Imp) 0.285A 0.29A 0.278 A Open - Circuit Voltage (Voc) 21.396V 21V 26.7 V Short - Circuit Current (Isc) 0.315A 0.35A 0.401 A Maximum Power at STC (Pmax) 5W 5 W 5 W Module Efficiency 16.2% 14% Not Available Temperature Coefficient of Pmax -0.549% (°K) -0.43 (°K) -(0.19±0.03)%/°C Temperature Coefficient of Voc -0.397% /°K -0.344 %/°K -(0.34±0.04)%/°C Temperature Coefficient of Isc 0.06% /°K 0.11 %/ °K 0.08±0.02)%/°C Maximum System Voltage 1000 VDC 600VDC 600 VDC Module Dimension 350x176x34mm 359x197x26 mm 385 x322 x18 mm Warranty: 90% power output 85% power output 10 years 25 years 10 years 15 years 10 years 15 years Comparison between Mono-, Poly- and Amorphous Si Solar Panels (5 W)
  78. 78. How to choose a solar panel? Critical parameters to be considered for solar panel evaluation 1. Selecting the right technology : The selection of solar panel technology generally depends on space available for installation and the overall cost of the system. 2. Selecting the right manufacturer for better warranty. 3. Check operating specifications beyond STC ratings 4. Negative Tolerance can lead to a lower system performance and reduced capacity. 5. Solar Panel efficiency under different conditions and over time.
  79. 79.  Stand-alone systems - those systems which use photovoltaics technology only, and are not connected to a utility grid.  Hybrid systems - those systems which use photovoltaics and some other form of energy, such as diesel generation or wind.  Grid-tied systems - those systems which are connected to a utility grid. Types of Solar Photovoltaic System
  80. 80. Stand Alone PV System
  81. 81. Stand Alone PV System Water pumping system
  82. 82. Hybrid PV System
  83. 83. Hybrid PV System Ranching the Sun project in Hawaii generates 175 kW of PV power and 50 kW of wind power from the five 10 kW wind turbines
  84. 84. Grid-Tied PV System
  85. 85. Balance of System (BOS) The BOS typically contains  Structures for mounting the PV arrays or modules  Power conditioning equipment that massages and converts the do electricity to the proper form and magnitude required by an alternating current (ac) load.  Sometimes also storage devices, such as batteries, for storing PV generated electricity during cloudy days and at night.
  86. 86. 1. Collect some data viz. Latitude of the location, and solar irradiance (one for every month). 2. Calculation of total solar energy. 3. Estimate the required electrical energy on a monthly/weekly basis (in kwh): Required Energy= Equipment Wattage X Usage Time. 4. Calculate the system size using the data from ‘worst month’ which can be as follows: a) The current requirement will decide the number of panels required. b) The days of autonomy decides the storage capacity of the system i.e. the number of batteries required. How to design a PV Off-grid system?
  87. 87. Designing a PV System 1. Determine the load (energy, not power) The load is being supplied by the stored energy device, usually the battery, and of the photovoltaic system as a battery charger. 2. Calculating the battery size, if one is needed 3. Calculate the number of photovoltaic modules required 4. Assessing the need for any back-up energy of flexibility for load growth
  88. 88. Determining Load  The appliances and devices (TV's, computers, lights, water pumps etc.) that consume electrical power are called loads.  Important : examine power consumption and reduce power needs as much as possible.  Make a list of the appliances and/or loads to be run from solar electric system.  Find out how much power each item consumes while operating.  Most appliances have a label on the back which lists the Wattage.  Specification sheets, local appliance dealers, and the product manufacturers are other sources of information.
  89. 89. Determining Loads II  Calculate AC loads (and DC if necessary)  List all AC loads, wattage and hours of use per week (Hrs/Wk).  Multiply Watts by hrs/Wk to get Watt-hours per week (WH/Wk).  Add all the watt hours per week to determine AC Watt Hours Per Week.  Divide by 1000 to get kW-hrs/week
  90. 90.  Decide how much storage is provided by battery bank as per requirement (0 if grid tied)  expressed as "days of autonomy" because it is based on the number of days the system should provide power without receiving an input charge from the solar panels or the grid.  Also consider usage pattern and critical nature of application.  Alternatively, if a solar panel array is added as a supplement to a generator based system, the battery bank can be slightly undersized since the generator can be operated in needed for recharging. Determining the Batteries
  91. 91.  Once the storage capacity has been determined, consider the following key parameters:  Amp hours, temperature multiplier, battery size and number  To get Amp hours :  daily Amp hours  number of days of storage capacity ( typically 5 days no input )  1 x 2 = A-hrs needed  Note: For grid tied – inverter losses Determining the Batteries
  92. 92. Determining Battery Size  Determine the discharge limit for the batteries ( between 0.2 - 0.8 )  Deep-cycle lead acid batteries should never be completely discharged, an acceptable discharge average is 50% or a discharge limit of 0.5  Divide A-hrs/week by discharge limit  Determine A-hrs of battery and # of batteries needed - Round off to the next highest number.  This is the number of batteries wired in parallel needed.
  93. 93.  Divide system voltage ( typically 12, 24 or 48 ) by battery voltage.  This is the number of batteries wired in series needed.  Multiply the number of batteries in parallel by the number in series.  This is the total number of batteries needed. Total Number of Batteries Wired in Series
  94. 94. Determining the Number of PV Modules  First find the Solar Irradiance at the location.  Irradiance is the amount of solar power striking a given area and is a measure of the intensity of the sunshine.  PV engineers use units of Watts (or kiloWatts) per square meter (W/m2) for irradiance.  http://rredc.nrel.gov/solar/old_data/nsrdb/
  95. 95. Peak Sun Hours  Peak sun hours is defined as the equivalent number of hours per day, with solar irradiance equaling 1,000 W/m2, that gives the same energy received from sunrise to sundown.  Peak sun hours only make sense because PV panel power output is rated with a radiation level of 1,000W/m2.  Many tables of solar data are often presented as an average daily value of peak sun hours (kW-hrs/m2) for each month.
  96. 96.  Determine total A-hrs/day and increase by 20% for battery losses then divide by “1 sun hours” to get total Amps needed for array  Then divide your Amps by the Peak Amps produced by your solar module  The peak amperage can be determined if the module's wattage is dividedby the peak power point voltage  Determine the number of modules in each series string needed to supply necessary DC battery Voltage  Then multiply the number (for A and for V) together to get the amount of power you need  P=IV [W]=[A]x[V] Calculating Energy Output of a PV Array
  97. 97. Charge Controller  Charge controllers are included in most PV systems to protect the batteries from overcharge and/or excessive discharge.  The minimum function of the controller is to disconnect the array when the battery is fully charged and keep the battery fully charged without damage.  The charging routine is not the same for all batteries: a charge controller designed for lead-acid batteries should not be used to control NiCd batteries.  Size by determining total Amp max for the array.
  98. 98. Wiring  Selecting the correct size and type of wire will enhance the performance and reliability of the PV system.  The size of the wire must be large enough to carry the maximum current expected without undue voltage losses.  All wire has a certain amount of resistance to the flow of current.  This resistance causes a drop in the voltage from the source to the load. Voltage drops cause inefficiencies, especially in low voltage systems ( 12V or less ).  See wire size charts here: www.solarexpert.com/Photowiring.html
  99. 99. Inverters  For AC grid-tied systems you do not need a battery or charge controller if the back up power is not needed– just the inverter.  The Inverter changes the DC current stored in the batteries or directly from the PV into usable AC current.  To size increase the Watts expected to be used by AC loads running simultaneously by 20%
  100. 100. Off-Grid Design Example Step 1: Determine the DC Load DC Device Device Watts Hours of daily use DC Watt-hrs per Day (Device Watts x Hours of daily use) Refrigerator 60 24 1440 Lighting fixtures 150 4 600 Device A 12 8 96 Total DC Watt-hrs/Day = 2,136
  101. 101. Total AC Watt-hrs/Day = 1,440 Divided by 0.85 (Inverter, losses) Total DC Whrs/Day = 1,694 AC Device Device Watts Hours of daily use AC Watt-hrs per Day (Device Watts x Hours of daily use) Device B 6175 6 1050 Pump 80 0.5 40 Television 175 2 350 Total AC Watt-hrs/Day = 1440 Step 2: Determine the AC Load, Convert to DC
  102. 102. Step 3: Determine the Total System Load Total DC Loads [A] 2,136 Total DC Loads [B] 1,694 Total System Load 3,830 Whrs/Day Step 4: Determine Total DC Amp-hours/Day Total System Load / System Nominal Voltage = (3,830 Whrs/Day) / 12 Volts = 319 Amp-hrs/Day Step 5: Determine Total Amp-hr/Day with Batteries Total Amp-hrs/Day X 1.2(Losses and safety factor) 319 Amp-hrs/Day X 1.2 = 382.8 or 383 Amp-hrs/Day
  103. 103. Step 6: Determine Total PV Array Current Total Daily Amp-hr requirement / Design Insolation* =383 Amp-hrs / 5.0 peak solar hrs = 76.6 Amps * Insolation Based on Optimum Tilt for Season Step 7: Select PV Module Type Choose BP Solar-Solarex MSX-60 module: Max Power = 60 W (STP) Max Current = 3.56 Amps Max Voltage = 16.8 Volts Nominal Output Voltage 12 Volts
  104. 104. Total PV Array Current / (Module Operating Current) X (Module Derate Factor) = 76.6 Amps / (3.56 Amps/Module)(0.90) = 23.90 modules = (Use 24 Modules) Step 8: Determine Number of Modules in Parallel Step 9: Determine Number of Modules in Series System Nominal Voltage / Module Nominal Voltage 12 Volts / (12 Volts/module) = 1 Module Step 10: Determine Total Number of Modules Number of modules in parallel X Number of modules in Series = 24 X 1 = 24 modules
  105. 105. Step 11: Determine Minimum Battery Capacity [Total Daily Amp-hr/Day with Batteries (Step 5) X Desired Reserve Time (Days)] / Percent of Usable Battery Capacity =(383 Amp-hrs/Day X 3 Days) / 0.80 = 1,436 Amp-hrs Step 12: Choose a Battery Use an Interstate U2S – 100 Flooded Lead Acid Battery Nominal Voltage = 6 Volts Rated Capacity = 220 Amp-hrs
  106. 106. Step 13: Determine Number of Batteries in Parallel Required Battery Capacity (Step 11) / Capacity of Selected Battery =1,436 Amp-hrs / (220 Amp-hrs/Battery) = 6.5 (Use 6 Batteries) Step 14: Determine Number of Batteries in Series Nominal System Voltage / Nominal Battery Voltage = 12 Volts / (6 Volts/Battery) = 2 Batteries Step 15: Determine Total Number of Batteries Number of Batteries in Parallel X Number of Batteries in Series =6 X 2 = 12 Batteries
  107. 107. Series: Voltage is additive Parallel: Current is additive + - + - - + 3 A 12 V 3 A 12 V 3 A 24 V 6 A 12 V 3 A 12 V 3 A 12 V + + - - + -
  108. 108. Step 17: Complete Balance of System a. Complete the design by specifying the: Charge Controller Inverter Wire Sizes (Battery will have larger gage due to higher currents) Fuses and Disconnects Standby Generator, if needed Battery Charger, if needed Manual Transfer Switch, if needed. b. Determine mounting method: Roof mount Ground mount with racks Ground mount with pole. c. Assure proper grounding for safety. d. Obtain permits as required. Step 16: Determine the need for a Standby Generator to reduce other Components (number of Modules and Batteries). Several iterations may be necessary to optimize costs.
  109. 109. Advantage 1.It is free, clean and non-polluting 2.It is a renewable and sustainable energy 3.Solar cells do not produce noise and they are totally silent. 4.Provide electricity to remote places 5.High power-to-weight ratio 6.They require very little maintenance 7.They are long lasting sources of energy which can be used almost anywhere 8.They have long life time 9.There are no fuel costs or fuel supply problems
  110. 110. Disadvantage 1.Soar power can be obtained in night time 2.Soar cells (or) solar panels are Less efficient and very expensive 3.Energy has not be stored in batteries 4.Reliability Depends On Location 5.Environmental Impact of PV Cell Production 6.Air pollution and whether can affect the production of electricity 7.They need large are of land to produce more efficient power supply. 8. Solar energy is a diffuse source.
  111. 111. USES OF SOLAR ENERGY  Heaters Green houses  Cars water pumps  Lights Desalination  Satellites Chilling  Dryers Solar ponds  Calculators Thermal Commercial use  On an office building , roof areas can be covered with solar panels .  Remote buildings such as schools , communities can make use of solar energy.  In developing countries , this solar panels are very much useful.  Even on the highways , for every five kilometres ,solar telephones are used.
  112. 112. Solar Map of India About 5,000 trillion kWh per year energy is incident over India’s land area with most parts receiving 4-7 kWh per square meter per day.
  113. 113. Thank You!! Need Help? Feel Free To Get In Touch contact@sunrator.com 011-41605551

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