The document discusses photovoltaic (solar) cells and their efficiency. It explains that efficiency is the most important characteristic and is defined as the fraction of incident light energy converted to electrical energy. The efficiency depends on factors like the semiconductor material, device structure, temperature, and sun spectrum. It also notes that cost and lifetime are important beyond just efficiency alone. The document then examines I-V characteristics of solar cells and how efficiency is calculated using measurements of short circuit current, open circuit voltage, and maximum power point from the I-V curve. It provides an example calculation of efficiency for a specific solar cell operating under a resistive load.

1. Photovoltaic Cells:
Solar Cells
EBB 424
Dr. Sabar D. Hutagalung
USM

2. Efficiency
 Efficiency = Fraction of incident light energy converted to electrical
energy.
 Efficiency is the most important characteristic because it allows the
device to be assessed economically in comparison to other energy
devices.
 For a given solar spectrum, the efficiency depends on:
 Semiconductor material
 Device structure
 Ambient conditions (temperature)
 High radiation damage
 Sun spectrum
 Efficiency alone is not enough, the cost of the cell is also important
and the life time.

3. I-V characteristics & Efficiency
in dark (diode)
under illumination
Typical I-V characteristic of solar cells

4. I-V characteristics & Efficiency
As the intensity
increases, the short-
circuit current ISC
increases linearly,
but the open circuit
voltage VOC increases
sublinearly.
The I-V characteristics of a solar cell with varying
illumination as a parameter.

5. I-V characteristics & Efficiency

6. I-V characteristics & Efficiency
(II) (I)
(III) (IV)
The I-Va characteristic of a solar cell.
The maximum power is obtained at Pm = ImVm

7. I-V characteristics & Efficiency

8. I-V characteristics & Efficiency

9. I-V characteristics & Efficiency
The I-V characteristics of a solar cell with varying illumination

10. I-V characteristics & Efficiency

11. Calculation, η
Consider a solar cell driving a 30Ω resistive load. The cell has area = 1
cm x 1 cm and is illuminated with light of intensity = 600Wm-2 and has I-V
characteristic as shown below.
0.425V
14.2mA
Q: What are the current and voltage in the circuit?
A: I’ = 14.2mA , V’ = 0.425V
Q: Calculate the power delivered to the load (Pout)
A: Area under the I’, V’ rectangular = P
P= 14.2 x 10-3A x 0.425V = 6.035mW

12. Calculation, η
Q: Calculate the input sun-light power
A: Pin = (light intensity x surface area)
Pin = 600Wm-2 x (0.01m)2 = 0.06W
Q: Calculate the efficiency of the device
A: η = 100x (Pout/Pin)
Pin = 0.06W
Pout = 6.035mW
η = 10.06%
Q: State why the efficiency is very small?

14. Solar Spectrum

15. Conversion Efficiency
 The most efficient PV modules usually
employ single-crystal Si cells, with
efficiencies up to 15%.
 Poly-crystalline cells are less expensive to
manufacture but yield module efficiencies of
about 11%.
 Thin-film cells are less expensive still, but
give efficiencies to about 8% and suffer
greater losses from deterioration.

16. Solar Photovoltaic Plants

17. How PV Cells Work
Photovoltaic cells, modules, panels and
arrays
Diagram of a photovoltaic cell
Major photovoltaic system components.

18. Problem
 Suppose that a particular family house in a sunny
geographic location consumes a daily average electrical
power of 1500 W supply by an 50 m2 are of solar panel. The
average solar intensity incident per day is about 6 kWh m-2.
What is the efficiency of solar cell?
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19. Solution
 Total sunlight energy per day:
= intensity x area
= 6 kWh m-2 x 50 m2
= 300 kWh
 Solar cell output = 1.5 kW x 24 h = 36 kWh
 Efficiency = Output/Total energy light
= 36 kWh/300 kWh
= 12 %
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20. Solar Cells