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1. Solar Photovoltaic Theory

1. Solar Photovoltaic Theory. 1-2. Potential assessment. 1-2.Potential assessment. Contents. 1-2. Potential assessment 1-2-1. Basic principle of assessment 1-2-2. Insolation measurement 1-2-3. Estimation of annual power generation 1-2-4. Case practice. Sun light from any direction. PV.

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1. Solar Photovoltaic Theory

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  1. 1. Solar Photovoltaic Theory 1-2. Potentialassessment

  2. 1-2.Potential assessment • Contents 1-2. Potential assessment1-2-1. Basic principle of assessment1-2-2. Insolation measurement1-2-3. Estimation of annual power generation1-2-4. Case practice

  3. Sun light from any direction PV REFLECTED 1m 1m Horizontal plane 1-2-1 Basic principle of assessment • Insolation Solar radiation (Insolation ) is “light energy” from sun. • Solar radiation (insolation) reaches the ground as: • direct radiation • diffused radiation Global Radiation(Insolation) Energy received within a unit time Energy: kWh/m2 Power: kW/ m2

  4. 1.00 kW/m2( 0.093 kW/f2 ) 1.35 kW/m2(0.125 kW/f2 ) Green Out of atmosphere( 1.35 kW/m2 = 0.125 kW/feet2) Ground surface on the equator( 1.00 kW/m2 = 0.093 kW/feet2 ) Absorbed by H2O , O2 , O3, CO2 Visible 1-2-1 Basic principle of assessment • Insolation spectrum on the surface of ground

  5. 1-2-1 Basic principle of assessment • Various effects for insolation • Local latitude effect • “Air mass” effect ( Atmospheric path length effect) • Seasonal effect • Weather effect • Face rotation effect • Surrounding obstacles effect( Shading effect )

  6. : Local latitude I0 I0 I0 I0 Earth -90 deg(S pole) 0 deg(Equator) +90 deg(N pole) 1-2-1 Basic principle of assessment • Effect of Local Latitude Actually, you can measure this value Local Horizontal Insolation mathematical Cosine curve 1.0 kW/m2(0.093 kW/feet2) about 1.0 kW/m2(0.093 kW/feet2)

  7. (kW/m2) I0 (kW/m2) 1 m m 1 m 1-2-1 Basic principle of assessment • Effect of Local Latitude Rectangle plane towed sun light Meaning of convert equation Horizontal plane Insolation energy of the tilted plane(yellow) and the horizontal plane(blue) is same. Tilted plane(yellow plane) Horizontal plane(blue plane)

  8. B c a A C b Appendix • A-2 Triangle Function ( Cosine Function ) Please calculate by your handy computer Example

  9. Ideal tilt angle = local latitude Ideal PV plane Your horizontal plane I0 You are here I0 Local latitude is Earth 1-2-1 Basic principle of assessment • Best tilt angle Best tilt angle is almost same as “local latitude”

  10. Lp (Light pass length) Air Air Mass = I0 At (thickness of air) I0 mathematical Cosine curve I0 With Air mass effect I0 Earth -90 deg(S pole) 0 deg(Equator) +90 deg(N pole) 1-2-1 Basic principle of assessment • Effect of “Air mass” ( Atmospheric path length ) At Lp about 1.37 kW/m2( 0.125 kW/f2 ) about 1.0 kW/m2( 0.093 kW/f2 ) • “Atmospheric path length” depend on its latitude. Air mass effect

  11. Latitude Max. Min. Japan +35deg Jun. Dec. Singapore 0deg Mar.Sep. Jun.Dec. Australia - 35deg Dec. Jun. 1-2-1 Basic principle of assessment • Effect of Season

  12. 1-2-1 Basic principle of assessment • Effect of Season Seasonal effect is more strong in high latitude -13 Samoa +1 Kiribath -17 Vanuatu -21 Cook Is. kWh/m2day -8 Tuvalu. +34 Japan Month

  13. Data in JAPAN Fine day Cloudy day Actual output / Rated capacity Rainy day Time 1-2-1 Basic principle of assessment • Effect of Weather Daily output curve of various weather condition

  14. Key factor of solar resource • Latitude • Atmospheric path length • Length of daytime • Opportunity of fine day. Almost same in PPA countries Depend on the geographical aspect. Insoration 6822 (MJ/m2year)Utilization 15.8% Fine day 77.5%Cloudy day 17.9% Nandi Fiji Insoration 6131 (MJ/m2year)Utilization 14.2% Fine day 68.4%Cloudy day 21.2% Suva 1-2-1 Basic principle of assessment • Effect of Weather

  15. Location = 35N Face to S W E Face to SE Face to SW S Insolation 6 10 12 14 18 Time 1-2-1 Basic principle of assessment • Face-rotation effects on daily insolation curve • If you rotate PV module face to East, output peak will shift to earlier. • If you rotate PV module face to West, output peak will shift to later. Northern hemisphere

  16. Face to S Face to SE Face to SW Insolation Face to S Face to SE Face to SW Insolation Face to S Face to SE Face to SW Insolation 6 10 12 14 18 1-2-1 Basic principle of assessment • Face-rotation effects on daily insolation curve • This effect is more strong in high latitude. • Low latitude area (under 15deg), this effect is negligible. Latitude15N Latitude35N Latitude60N

  17. Latitude effect • Seasonal effect(depended on sun height angle) • Air mass effect Insolation • Weather effect Summer • Seasonal effect Winter Time 6 12 18 Day light time 1-2-1 Basic principle of assessment • Various effects on daily insolation curve

  18. 1-2-1 Basic principle of assessment • Necessity of on site insolation measuring Key factor of solar resource • Latitude dependent • Atmospheric path length • Length of daytime • Seasonal sun height-angle • Weather dependent • Opportunites of fine day • Mist in the air • Site situation • Shade of mountain, tree, buildings • Contamination by dust, salty gusts Easy to estimate Easy to estimate Easy to estimate Un-known Un-known Difficult Un-known On site insolation measuring is necessary before planning.(at least 1 – 3 years. Use meteorological observatory data)

  19. PV 1-2-1 Basic principle of assessment • Basic theory of PV panel adjustment Basic theory of PV panel adjustment • You cannot avoid these effect. • The best things you can do are to: Latitude effect Air Mass effect Seasonal effect Daily effect Weather effect Obstacle shad effect - Tilt PV plane the same as your latitude.- Face true north or true south. Face to N or S (as possible as you can) same angle as latitude Avoidable. Try to find good location

  20. +deg At 45N point, Optimum tilt angle is45 – 7 = 38 deg 45 deg local latitude difference between local latitude and optimum tilt -7deg under In low latitude region such as 10 to 20 deg, error is negligible -deg 1-2-1 Basic principle of assessment • Basic theory of PV panel adjustment (Note) • In high latitude locations, the optimum tilting angle is slightly lower than the local latitude. By using computer, you can calculate accurate tilting angle easily.

  21. 1-2-1 Basic principle of assessment • Insolation of the world

  22. 1 (kW/m2) Output 1 kW Rated Capacity “1 kW” 1 (kW/m2) Generate 1 kWh for 1 hour Rated Capacity “1 kW” 1-2-1 Basic principle of assessment • Definition of PV’s Rated Capacity Note: This is the definition that, we use metric system here. “Rated capacity 1kW” means ( Power ) If insolation is 1 kW/m2, this PV can output 1 kW. ( Energy ) If PV has 1 kW/m2 insolation in 1 hour, this PV can generate 1 kWh

  23. 1 (kWh/m2day) Generate 1 kWh for a day Rated Capacity “1 kW” 1-2-1 Basic principle of assessment • Definition of PV’s Capacity “Rated capacity 1kW” means ( Accumulated Energy ) If PV has 1 kWh/m2day, this PV can generate 1 kWh for a day In resource assessment, “Accumulated Insolation (energy)” is used widely. Daily accumulated insolation kWh/m2day Monthly accumulated insolation kWh/m2month Annual accumulated insolation kWh/m2year

  24. 1 (kW/m2) Generate 1 kW Rated Capacity “1 kW” 1 (kW/m2) Generate 1 kW Rated Capacity “1 kW” 1-2-1 Basic principle of assessment • Definition of PV’s Capacity “Efficiency” parameteris already included in “Rated Capacity”. • High-efficiency PV ( Single crystal PV 15% ) If you use “rated capacity”, you don’t have to consider about efficiency. • Low-efficiency PV (Amorphous PV 8 %) Module is larger.

  25. 1-2-2 Insolation measurement • How to observe Insolation Pyranometer for Horizontal Global Solar Radiation (Insolation) Pyranometer Horizontal plane

  26. 1-2-2 Insolation measurement • How to observe Insolation Pyranometer for Horizontal Global Solar Radiation (Insolation) Sun window (receives light from all directions) • Place Pyranometer on thehorizontal plane. • Make sure no shadow is cast all day long. • Clean upper window frequently. 20 cm Instant value XX.XX (kW/m2) orAccum. value XX.XX (kWh/m2) Data logger Insolation data is very common in meteorology. Ask your meteorological observatory for local insolation data.

  27. Metric(m) Imperial(feet) MJ MJ / m2year MJ / feet2year kWh kWh / m2year kWh / feet2year x 3.60 x 1 / 10.76 Pyranometer for Global Solar Radiation 1-2-2 Insolation measurement • There are many units of Insolation data. Be sure to note which unit your pyranometer is using.

  28. 1-2-2 Insolation measurement • Example of raw data (monthly data) Date January Accumulating Time Average Insolation for a day (kWh/m2day)

  29. 1-2-2 Insolation measurement • Example of raw data ( Annual data) Daily average Insolation Summarize Annual total insolation

  30. I0 I0 I0 Earth 1-2-2 Insolation measurement • Convert “horizontal insolation” to “tilted insolation” Raw insolation data( Horizontal insolation ) Horizontal to Tiltedconversion Plane ofPV Panel(Tilted same as local latitude) I0 Hj I0 I0 Earth Hj : Tilted insolation

  31. Hj(kWh/m2year) PV Module Plane(Tilted as local Latitude) I (kWh/m2year) Measured Plane (Horizontal) (kWh/m2year) (kWh/m2year) 1-2-2 Insolation measurement • Convert “horizontal insolation” to “tilted insolation” (Note) This conversion can be used in low latitudes (less than 20deg.)

  32. 1-2-2 Insolation measurement • Convert “horizontal insolation” to “tilted insolation” Meaning of convert equation (kW/m2) I Hj(kW/m2) 1 m Insolation energy of the tilted plane(yellow) and the hori-zontal plane(blue) is same. m 1 m Tilted plane(yellow plane) Horizontal plane(blue plane)

  33. Local Latitude = -10 (deg) Horizontal Insolation I = 2,000 (kWh/m2Year) (kWh/m2year) (kWh/m2year) (kWh/m2year) 1-2-2 Insolation measurement • Convert “horizontal insolation” to “tilted insolation” (Example) Hj = 2,031 kWh/m2year( Tilted insolation ) I = 2,000 kWh/m2year(Measured raw data) 10 deg.

  34. Actual generation energy Hg = 70% (System Efficiency) • Converter Loss 8% • Surface Contamination 7% • Temperature Rise 15% Pu = Rated Capacity of PV Module (=1.0 kW)hg = System efficiency (= 0.7 depending on type of PV cell)H = Tilted Plane Insolation in kWh unit. 1-2-3. Estimation of annual power generation • Actual generation energy of PV (Example) Tilted Insolation Hj = 2,031 (kWh/m2Year) PV rated capacity Pu=10 (kW) (kWh/year)

  35. 1-2-3. Estimation of annual power generation • Calculate “Load Factor ( Syaytem Utilization parameter)" • To estimate various capacities of PV system, calculate Unified Parameter,called"Load Factor (System Utilization Parameter )". • This parameter means “Annual average output power” of unit capacity of the PV system. p = Annual Available power for Unit Capacity of PV Module Pu = Unit Capacity of PV Module (=1.0) (Example) Annual power generation p= 14,217 (kWh/Year) PV rated capacity Pu=10 (kW) 16.3 (%)

  36. (kWh/year) 1-2-3. Estimation of annual power generation • Calculate annual power by System Utilization Parameter (Example) If you install a 50kW PV system in this place, how much power can you generate? System utilization parameter Ug= 0.158 (%) PV rated capacity Pu=50 (kW)

  37. Local Latitude = -15 (deg) Horizontal Insolation I = 1,800 (kWh/m2Year) PV Capacity Pu = 5kW 1-2-3. Estimation of annual power generation • Exercise (Insolation data) Step1Convert “horizontal insolation” to “tilted insolation” Step2Calculate annual earned energy

  38. Local Latitude = -15 (deg) Horizontal Insolation I = 1,800 (kWh/m2Year) PV Capacity Pu = 5kW (kWh/m2year) (kWh/m2year) (kWh/m2year) (kWh/year) 1-2-3. Estimation of annual power generation • Exercise (Insolation data) Step1Convert “horizontal insolation” to “tilted insolation” Step2Calculate annual earned energy

  39. 1-2-3. Estimation of annual power generation • Exercise Step3Calculate “Load Factor" Step4If you install 50kW PV system in this place, how much energy (kWh) can you earn?

  40. 14.9 (%) (kWh/year) 1-2-3. Estimation of annual power generation • Exercise Step3Calculate “Load Factor" Step4If you install 50kW PV system in this place, how much energy (kWh) can you earn?

  41. 1-2-4. Case practice Case Practice

  42. 1-2-4. Case practice February has 28 days

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