Solar Electric Power Systems
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Transcript of Solar Electric Power Systems
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ELEG 620 Solar Electric Power Systems March 4, 2010
Solar Electric Power Systems
ELEG 620Electrical and Computer Engineering
University of DelawareMarch 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
ELEG 620 Outcomes
1.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
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ELEG 620 Solar Electric Power Systems March 4, 2010
Solar Cell Design
Silicon Solar Cell Design Homework Due: March 9, 2010 Design a silicon solar cell. Calculate the following: 1. Light generated current at short circuit2. Open circuit voltage3. Maximum power (show voltage and current at maximum
power)4. Efficiency5. Thickness and doping of each layer Show key equations
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ELEG 620 Solar Electric Power Systems March 4, 2010
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
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I-V Curve of a Well Behaved Solar Cell
I-V curve of a well behaved solar cell
Voltage(V)C
urre
nt (m
A)
0.5-0.5-1 120
4060
-20
-40
-60
(Vmp,Imp)
Voc
Isc
)1(exp0
kTVqIIDiode
IDiode
_
+
VILight
I
LightIkTVqII
)1(exp0
in
mpmp
PowerIV
Efficiency
ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
Solar Cell Design
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Jo = q tanh tanhDp ni
2
Lp Nd Xj
Lp+
Dn ni2
Ln Na Xj
Ln
q
ELEG 620 Solar Electric Power Systems March 4, 2010
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Jo = q Dp ni2
Lp Nd +Dn ni
2
Ln Na q
ELEG 620 Solar Electric Power Systems March 4, 2010
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1ln
0JJ
qkTVoc L
Lifetime Voltage (mV)
1 ms 561
100us 506
10us 467
Wn(um)
Wp(um)
S(cm/s)
De(cm2/s)
Dh(cm2/s)
ND(cm-3)
NA(cm-3)
Jsc(mA/cm2)
10 500 0 35 12 1e15 1e14 43.6
ELEG 620 Solar Electric Power Systems March 4, 2010
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1ln
0JJ
qkTVoc L
Wn(um)
Wp(um)
S(cm/s)
De(cm2/s)
Dh(cm2/s)
ND(cm-3)
NA(cm-3)
Jsc(mA/cm2)
10um 500 0 35 12 1e15 1e14 43.6
1 500 0 35 12 1e16 1e15 43.6
Lifetime Voltage (mV)
1 ms 561 620
100us 506 565
10us 467 526
ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
Design rules for high performanceFor 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.
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ELEG 620 Solar Electric Power Systems March 4, 2010
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).
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Structure, Equivalent circuit and IV curve of solar cell
Ilight
Equivalent circuit of solar cell
I-V Characteristic of Solar Cell
+
V
Base
Emitter
Back contact
Front contact
( 1)qVkT
D oI I e
I
V0
Isc
Voc
Pmax
0 (exp( ) 1)qVJ JkT
0 (exp( ) 1) scqVJ J JkT
ELEG 620 Solar Electric Power Systems March 4, 2010
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ELEG 620 Solar Electric Power Systems March 4, 2010
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
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Jn = qun n E qDndn
dx+
Jp = qup p E qDpdp
dx-
ELEG 620 Solar Electric Power Systems March 4, 2010