The Solar Cell

Peter Said:

How does different coloured light affect solar cell output?

We Answered:

This is the photoelectric effect! The photo electric effect states that:

KE = h*f -h*fo where h is planck’s constant
h*fo = the work function of the metal).
f is the frequency of light.

You can clearly see that the KE (Kinetic energy) is directly proportional to the frequency of light.

So, light with a short wavelength (high frequency) will produce more output that a longer wave (low frequency).

The colors of light that would have to most output would be:

1.- Blue
2.- Green
3- Yellow
4,- Red

Eileen Said:

What are 3 ways a plant and solar cell are similar and 3 ways they differ?

We Answered:

1. They both use solar energy to carry out their tasks.
2. They both stay rooted in the same place.
3. They both help mankind.

1. Plant uses solar energy to bond chemicals (to create glucose), solar cell generates electricity.
2. Plant can grow towards the sunlight while solar cell cannot
3. Plant needs water and air to survive while solar cell does not.
4. Solar cell is man-made while the plant is not.

Sorry the answer is pretty bad 🙁

Lester Said:

What is a small and cheap solar cell?

We Answered:

Interesting project. Radio shack sells a couple in the form (wires already attached) that would be easy for a beginner to play with. Go into any store and ask for one and they’ll show you where they are.

The thing you’re going to want to measure is probably current, rather than voltage. The voltage is more or less just a function of the materials the cell is made of (about .5V), while the current is proportional to the solar flux. A cheap multimeter will make this measurement by just putting it across the wires of the cell.

What you should find is that the power coming out of a cell varies with the sine of the angle of incidence.

Electrical power, in watts, is the volts times the amps. So you would multiply .5volts times lets say for example 50milliamps with direct on sun and get 25milliwatts.

Also, you will be measuring the amount of solar energy CONVERTED, not absorbed. To measure the amount absolbed, you would need to know the amoubnt of solar energy incident on the cell, but not reflected, and that isn’t so easy.

Melanie Said:

How do you screen print a solar cell?

We Answered:

see: http://www.udel.edu/igert/pvcdrom/MANUFA…

Not something for the home hobbyist

Greg Said:

Is it possible to make a solar cell utilizing a p-n junction at home?

We Answered:

Bell labs actually made a kit that had the silicon wafer and most of the chemicals needed.

http://www.porticus.org/bell/belllabs_ki…

Tanya Said:

What total solar cell area would you need to provide energy needs? Mastering Physics problem?

We Answered:

The correct rate is 11kWhr per day. 11kw would be a horrendous amount of power.(maybe Al Gore uses it at this rate)

I will calc it at your rate for problem sake. (this is not real life by the way, there are lots more variables, length of day, etc)

200W/m^2 * 15% = 30w/meter

11kw / 30w/meter = 366m^2

On a side note I think mastering physics is a crappy program, made for lazy physics teacher that dont ever care about application of knowledge.

Ramon Said:

What do they expect solar cell efficiency to increase to and what impact would this have on the use of solar?

We Answered:

There is more than one type of solar technology and it is getting more efficient all the time. All I know for sure is my PV system generates more energy than I was quoted and I will break even in about 6 years so I’ll have about 18 years of free energy which will save me well over $50K. That’s efficient enough for me.

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