• ENGR 1181 First-Year Engineering Program

College of EngineeringEngineering Education Innovation Center

First-Year Engineering Program

Solar Cell Lab

• ENGR 1181 First-Year Engineering Program

Solar Cells – Current Applications

• Calculators that never need batteries• Emergency road signs or call boxes, on buoys, even in

parking lot lights• Satellites where they are used to power the electrical systems• Yard Lights• Residential• Limited commercial

Solar Cells

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab - Materials

• Silicon (not doped) is basically an insulator

(with 4 valence electrons, all used in bonding crystal lattice => no 'free electrons)

• Solar Cell consists of 2 differently doped semiconductors layers (silicon)

• N-doping introduces free 'electrons' (introduce impurity into lattice with 5 valance electrons => 1 free electron per atom)

• P- doping introduces free 'holes' (introduce impurity into lattice with 3 valance electrons => 1 free 'hole' per atom)

POSITIVE

NEGATIVE

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab – Electrical

• Concentration difference of holes and electrons – The important fact to note on the next slide is that when N and P doped materials are layered, a surplus of positive and negative charge carriers are produced so that when photons(light) hit the solar cell these additional charge carriers, which were initially in equilibrium, now cause an external voltage whose value is dependent upon the employed materials.

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab - Electrical

For more information refer to: http://science.howstuffworks.com/environmental/energy/solar-cell.htm

Depletion Region

Sunlight or Light Source

In Solar Cell Lab, Load = Resistor

• ENGR 1181 First-Year Engineering Program

P. 6

Solar Cell Lab - Device

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Solar Cell Lab - Characteristics

Energy generated by the solar cell is

– Proportional to the intensity of the incident light

– Dependent upon the load applied to the solar cell

– Temperature dependent

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab - EvaluationAdvantages

– Energy source is FREE (sun)– No emissions (earth friendly)– No moving parts (low maintenance)

Disadvantages– Technology is presently very expensive– Low power conversion efficiency (5 – 17 %)– Intensity of light source impacted by

geographical location and local weather conditions

– Energy source available for limited time (daylight)

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab - Schematic

red banana plug lead

( resistive lead – negligible impact )

Light Source

Indicates probe ends

black banana plug lead

( resistive lead – negligible impact )

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab Setup

• ENGR 1181 First-Year Engineering Program

Solar Cell Lab

Circuit Diagram

Wire connections Resistor Board

Solar CellDMM

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Solar Power Conversion Efficiency

V

When sunlight strikes the surface of a Solar Cell, it develops a voltage (V) and that voltage can be used to power any electrical device (like an iPhone charger).

Electrically, the Solar Cell acts like a battery that supplies Voltage (V) and Current (I) to power any device (like the Resistor R) in the circuit diagram.

The Solar Cell generates power from sunlight and delivers that power to the Resistor, where it ends up being dissipated as heat, or:

The power conversion efficiency of the Solar Cell is:

Where the Power Input to the Solar Cell from sunlight falling on it

15 Volts

BATTERYR = 5 Ohms

Current, I

• ENGR 1181 First-Year Engineering Program

Solar Cell Output as a function of Incident Light Angle

The Power output of a solar cell as a function of the angle Φ of the incident light is given by:

P(

Where the Power output of the Solar Cell when = 0 degrees.

• ENGR 1181 First-Year Engineering Program

Solar Cell - Procedure

Please note that you should use the on-line version of the Solar Cell Procedure in

the lab since it is in color and thus is much easier to view and understand the various connections. You can use your hard copy as a reference when you are writing your memo.

• ENGR 1181 First-Year Engineering Program

Solar Cell – Procedure, one last hint

Very slight changes of the solar cell location in the x and y directions are needed to maximize the voltage reading and thus the incident light!

xy

Voltage reading