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Solar Electric Power Systems

Solar Electric Power Systems. ELEG 620 Electrical and Computer Engineering University of Delaware March 4, 2010. ELEG 620 Outcomes. Understanding the nature of Solar Radiation 2 . Design of a solar cell from first principles 3. Design of a top contact system

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Solar Electric Power Systems

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  1. Solar Electric Power Systems ELEG 620 Electrical and Computer Engineering University of Delaware March 4, 2010 ELEG 620 Solar Electric Power Systems March 4, 2010

  2. ELEG 620 Solar Electric Power Systems March 4, 2010

  3. ELEG 620 Outcomes • Understanding the nature of Solar Radiation • 2. Design of a solar cell from first principles • 3. Design of a top contact system • 4. Design, construction and test of a solar power system ELEG 620 Solar Electric Power Systems March 4, 2010

  4. Solar Cell Design Silicon Solar Cell Design Homework Due: March 9, 2010 Design a silicon solar cell. Calculate the following: Light generated current at short circuit Open circuit voltage Maximum power (show voltage and current at maximum power) Efficiency Thickness and doping of each layer Show key equations ELEG 620 Solar Electric Power Systems March 4, 2010

  5. Solar Cell Design • Silicon Solar Cell Design Homework Due: March 9, 2010 • Design a silicon solar cell. • Following assumptions can be used • Structure is N on P • There is no surface recombination • There is no surface reflection • Series resistance = 0 ohms • Shunt resistance is infinite (shunt conductance = 0) • Sunlight = AM 1.5 global ELEG 620 Solar Electric Power Systems March 4, 2010

  6. I-V Curve of a Well Behaved Solar Cell I + ILight 60 Current (mA) IDiode V 40 20 _ Voc -1 -0.5 0.5 1 Voltage(V) -20 -40 Isc -60 (Vmp,Imp) I-V curve of a well behaved solar cell ELEG 620 Solar Electric Power Systems March 4, 2010

  7. ELEG 620 Solar Electric Power Systems March 4, 2010

  8. ELEG 620 Solar Electric Power Systems March 4, 2010

  9. ELEG 620 Solar Electric Power Systems March 4, 2010

  10. Solar Cell Design ELEG 620 Solar Electric Power Systems March 4, 2010

  11. Dp ni2 Xj Dn ni2 Xj q + tanh tanh Lp Nd Lp Ln Na Ln Jo = q ELEG 620 Solar Electric Power Systems March 4, 2010

  12. Dp ni2 Dn ni2 q + Lp Nd Ln Na Jo = q ELEG 620 Solar Electric Power Systems March 4, 2010

  13. ELEG 620 Solar Electric Power Systems March 4, 2010

  14. ELEG 620 Solar Electric Power Systems March 4, 2010

  15. Design rules for high performance • For a high solar cell efficiency, simultaneously need high absorption, collection, open circuit voltage and fill factor. • Absorption and collection are typically achievable by “clever” engineering & innovation. • Voltage is controlled by worst, localized region, NOT the same region which absorbs the light – this is fundamentally why single crystal solar cells are highest efficiency. • Predictive models and design rules for all characteristics are necessary for the device parameters. ELEG 620 Solar Electric Power Systems March 4, 2010

  16. Solar Cell Operation • Key aim is to generate power by: • (1) Generating a large short circuit current, Isc • (2) Generate a large open-circuit voltage, Voc • (3) Minimise parasitic power loss mechanisms (particularly series and shunt resistance). ELEG 620 Solar Electric Power Systems March 4, 2010

  17. I Front contact Emitter Voc Pmax Base 0 V Back contact Isc Structure, Equivalent circuit and IV curve of solar cell + Ilight V I-V Characteristic of Solar Cell Equivalent circuit of solar cell ELEG 620 Solar Electric Power Systems March 4, 2010

  18. Maximizing efficiency h = Isc Voc FF Pin •  Isc • EG •  Reflection • Surface • Metal •  Ln, Lp •  Sr • xj optimum •  Voc • EG •  doping •  Ln, Lp •  Sr •  FF • Series R • Metal • Emitter •  doping • Thick emitter Doping and diffusion length are related ELEG 620 Solar Electric Power Systems March 4, 2010

  19. dn dp + qDn Jn = qun n E dx dx - qDp Jp = qup p E ELEG 620 Solar Electric Power Systems March 4, 2010

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