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Working Of Solar Cell

Susan Said:

Solar Panel - Cell Resources and Calculations?

We Answered:

The two wiki links below provide basic explanations that are good starters. They also lead to other information. You do not mention much about the actual project, so I can only guess what level to pitch the answer.

In practical situations you will not be able to work out Solar panel performance by a formula, but by looking up the manufacturer's specification (data sheet). From that you have the power in watts that can be drawn from the panel for "standard sun" which is taken as 1000W/m^2 at a standard temperature, usually 25C. Derate the panel for the temperature when it operates in the sun (50-60C). This means a reduced voltage, which may or may not be of significance.

Determine how many hours a day of "full sun equivalent" are relevant for your region. In the tropics it may be 5 hours. This takes into account the changes in sun angle to the panel over the day or year, as well as the geographic region. There are usually on line charts for this. Greater output can be obtained by tracking the sun, though this is not common.

After that calculate the losses of each step in the process towards providing output from an inverter. These could be cables, charge controller, battery, inverter. There are on line calculators that allow these figures to be estimated, and provide the net output. There are two main groups, grid connected (no battery required) and stand alone systems (with batteries). The charge controller is an important item for efficiency, as it should be able to maximise the power from the panel by adjusting the load for a given illumination (MPPC controller). The V-I curves for a panel (in the data sheet) illustrate that aspect. The maximum power occurs at the knee of this curve.

Using some of the words above for key words in on line searches will help. WIth a better understanding of your needs you can ask further questions.

On points to ponder:
It takes about 6 million tons of arsenic to manufacture enough solar PV panels to power the world, and there is only 1 million tons of known reserves. The efficiency of solar panels maxes out well under 50%. Solar trackers using heat for generators (see Sun Catcher), absorption refrigeration, even solar hot water represent a more effective approach, also offer long term sustainability. So why is everyone so focussed on PV electricity? Is it because it is seen as backyard "doable".

Claire Said:

What type of solar cell is the Cuprous Oxide-Copper cell? Can you tell me how it works?

We Answered:

The cell works the same as a silicon wafer or any other solar cell.

When photons strike the surface, an electron in the Cu(II) oxide plate is promoted to a higher electronic state in the conduction band,

Being attached to free Cu, electrons in thier conduction band allows the electrons mobility and flow as current when there is a circuit load. Drawing off this current leaves holes n the Cu conduction band.

See. Electrons in the atoms of each material reside in bands, much like the floors in a "two story" building with a flat roof. When light strikes the electrons, they gain energy and are promoted to the roof, where they can move around (conduction) . siphoning off these electrons (electrical load) leaves more room on the roof, for more electrons to be promoted from below.

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Roger Said:

How do you make a circut with a solar cell?

We Answered:

To operate this motor requires that you have an adequate voltage AND current supply. The two AA cells you have can supply both of these, but it would appear that your solar cells can't. The voltage appears okay but they can't supply the current, at least, not for this motor anyway.

You see, a motor requires power in order to work, and power is voltage times current. You have the volts but the current capability of your solar cells is far too low. You can test this out for yourself by doing a little experiment:

Measure the solar cell voltage in full sun with nothing connected to it; you should get 4V as you said before. Now, connect your motor and measure the voltage again; this time you should find that it has fallen maybe to less than one volt.

Try using a smaller motor- one that uses less power. Typically it would be one that is about the diameter of your thumb. If you can afford it use more solar cells.

Jorge Said:

A silicon solar cell array works at an efficiency of 8.1% in sunlight and is exposed to an average solar insol?

We Answered:

That average insolation value is low enough that it's probably averaged over a 24-hour period already.

So I would do

3600 seconds / hour * 24 hours / day * 365 days / year * 8 years * 230 W/m^2 * 8.1% efficiency = a certain number of W-seconds/m^2.

1 watt-second = 1 J (Joule)

Elmer Said:

Adding a second solar cell to a kit?

We Answered:

Yes. But you need to wire positive to negative.

Lisa Said:

I am working on some solar cell technology and working on some photoconductivity (current-time) graph.?

We Answered:

I can think of 2 ways.

1. For the rise time, find the 'minimum' value and find the 'maximum' settled value. Take the difference. (If the minimum value is zero, then the difference is the settled max.) Take 36.8% of the difference. Find the time where the value is at 36.8%. From the time the rise starts until the time where the value is at 36.8% of max. -- that's the rise time constant.

For the fall time constant, use 63.2% (which is 100% - 36.8%)

2. Enter the data from the graph into an Excel spreadsheet. Graph the appropriate portions using X-Y scatter. Do a trendline analysis on those portions of the graph using the exponential function. The time constant will be displayed in the equation.

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