Solar photovoltaic technology
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- 3. outline Introduction of PV system Solar cell Solar panel Components of SPV system: Charge controller, Inverter, Batteries Applications of SPV system Advantages / disadvantages Design of PV system 3
- 4. INTRODUCTION Photovoltaics (PV) is the science of direct conversion of light to D.C. electricity, based on the fundamental principle of “photovoltaic effect”. This phenomenon is exhibited in semiconductor materials The photovoltaic effect is defined as the generation an electromotive force as result of absorption of ionizing radiation. Photovoltaic devices which convert solar energy into electricity are called SOLAR CELLS 4
- 5. Solar cell It consist of a) Semi-conductor in which electron hole pairs are created by absorption of incident solar radiation, b) Region containing a drift field for charge separation, and c) Charge collecting front and back electrodes. 5
- 6. DEVELOPMENT OF SOLAR CELL First Generation Single crystal silicon wafers (c-Si) Second Generation Amorphous silicon (a-Si) Polycrystalline silicon (poly-Si) Cadmium telluride (CdTe) Copper indium gallium di-selenide (CIGS) alloy 6 Third Generation Nanocrystal solar cells Photo electrochemical (PEC) cells • Polymer solar cells Dye sensitized solar cell (DSSC) Fourth Generation Hybrid - inorganic crystals within a polymer matrix
- 7. Types of Solar Cells Silicon Solar Cells: Single Crystal Si Cells: Commonly used. Usual efficiency of 20%. Long lifetime (>20 yrs.). Approaching the theoretical limit of 29%. Poly Crystal Si Cells: Less expensive. Efficiency is usually less than 15%. Amorphous thin film Si Cell: thin non- crystalline Si layers are printed on a substrate. Lightweight and less expensive. Efficiency around 10%. 7
- 8. Cadmium Telluride Thin Film Cells Inexpensive to produce;. Best efficiency reported is 25%. Popular for solar panel arrays. Copper Indium Gallium Selenide Thin Film Cell: Efficiency around 20%. Manufacturing costs are higher that amorphous Si thin film cells, but dropping fast. Gallium Arsenide Multi junction Cells: Maximum reported efficiency of 42.4%. Much more expensive to produce. Limited to scientific and high cost commercial usage. 8
- 9. PROPERTIES OF SILICON AS A SOLAR CELL MATERIAL Advantages – Unlimited supply of raw material. – Well developed materials and device technology. – Well developed understanding of physics. – High solar cell efficiency. – Well established long term solar cell stability. Disadvantages – Low light absorption coefficient. – Large thickness of material required. – High cost of silicon wafers 9
- 10. Solar Panels A single solar cell has very limited output capacity, e.g. a single crystal Si cell output is about 0.5V. Cells are joined in series and parallel to increase their output capacity, e.g. 36 solar cell-Si cells are connected to produce a ~24v module. Further increase in output capacity, require joining panels into solar arrays. 10 + Cells Panel Array
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- 12. Solar cell module In actual usage, the solar cells are interconnected in certain series/parallel combination to forms modules. These modules are hermetically sealed for protection against corrosion, moisture, pollution and weathering. A combination of suitable modules constitutes an array. Solar PV system can produce an output only if sunlight is present. If it is required to be used during non sunshine hours, a suitable system of storage batteries will be required. 12
- 13. Types of Arrays: 1. Tracking arrays or modules 2. Fixed arrays Flat-plate arrays Concentrating arrays 13 Solar cell concentrating arrengements: • Cells may be connected in parallel to achieve the desired current and then stacked in series to achieve the desired voltage. • The optimum operating voltage of a PV cell is about 0.45 V at normal temp. & the current full sunlight may be taken to be 270 A/sq. m. 10
- 14. pv controller The PV controller works as a voltage regulator. The primary function of a controller is to prevent the battery from being overcharged by the array. PV charge controller constantly monitors the battery voltage. Size- from a few amp to 80 amps. Types of controllers 1. Shunt controllers 2. Single stage series controllers 3. Diversion controllers 4. Pulse width modulation(PWM) controllers 14
- 15. batteries -Main component of SPV system. -Solely generated electrical energy stored. Types of batteries: Lead acid battery -Liquid vented - Sealed (VRLA-valve Regulated Lead Acid ) Alkaline batteries - Nickel-cadmium -Nickel- Iron 15
- 16. Batteries specifications Days of autonomy Battery capacity Rate and depth of discharge Life expectancy Environmental conditions Price and warranty Maintenance schedule 16
- 17. Inverters/converters Device usually solid state, which change the array DC to AC of suitable voltage, frequency & phase to feed PV generated power into the power grid or local load. Inverter Types: 1. Square Wave Inverters 2. Modified Square Wave Inverters 3. Sine Wave Inverters 17 Standard Inverter Features: oHigh efficiency oLow standby losses oFrequency Regulation oHarmonic Distortion oReliability oPower connection factors oLight weight
- 18. Application of SPV System The terrestrial application of these systems include provision of power supply to: 1.Water pumping sets for micro irrigation and drinking water supply 2.Radio beacons (signal fire) for ship navigations at ports 3.Community radio and television sets 4.Cathodic protection of oil pipe lines 5.Weather monitoring 6.Railway signaling equipment 7.Battery charging 8.Street lighting 9.Remote home lighting 10.Farm Equipment's 11.Air-conditioning and remote vaccine storage 18 11
- 19. Advantages & disadvantages of sPV energy conversion ADVANTAGES: • Direct room temp. conversion of light to electricity through the simple solid state device. • Absence of moving parts. • Ability to function unattended for long periods as evidence in space programme. • Modular in nature. • Maintenance cost is low. • Easy to operate. • Do not create pollution. • Long effective life. • Highly reliable. • wide power handling capabilities from microwatts to kilowatts. 19 DISADVANTAGES: • Higher cost. • Energy storage is required because of no insolation at night. • Effort are being made world-wise to reduce costs through various technological innovations.
- 20. Design of Pv system 20 PV system are already economically viable system in isolated location < 1 kW. In that cases system is generally low voltage DC system used to charge storage batteries. It consist of one/more arrays of solar cells, storage battery, blocking diode & battery charge limiter. Design involves: • Calculation of array size • Calculation of battery capacity
- 21. Depends on technical several factors: location, required availability, duty cycle, energy demand. 1. Calculation of array size PV array kilowatts needed: (including factors for battery losses, temp losses, and miscellaneous system losses ): 2. Calculation of battery capacity Battery capacity (AH) B= 𝟕𝟑𝟏.𝟔 𝟎.𝟕𝟓 × Imean × 𝑯𝒎 −𝑯𝒐 𝑯𝒎 Where Imean = 𝑳𝒐𝒂𝒅 (𝒌𝑾) 𝑩𝒂𝒕𝒕𝒆𝒓𝒚 𝑽𝒐𝒍𝒕𝒂𝒈𝒆 (𝑽) , 𝑯𝒎 −𝑯𝒐 𝑯𝒎 = daily avg. insolation Ho is < annual mean value 21
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