Understanding Solar Cell Specifications: Voltage, Current, and Efficiency

In summary: The current rating is the maximum current that the cell can deliver when exposed to a rated light source at a rated load.
  • #1
fisico30
374
0
Hello Forum,
I am trying to perform a solar cell experiment. I went to several websites and they list their small solar cells panels as having an output of 0.5 volts, 100mA.
The cell size is 1 3/4" X 1"...

Does 0.5 V represent the open circuit voltage, when the cell receives the max energy from the sun?
his is the max voltage that the cell can produce. What if we placed the solar cell in front of something stronger that the sun, with a higher irradiance? the open circuit voltage would be higher...

Does anyone know at what wavelength a silicon solar cell has the highest efficiency?

Does 100mA represent the short circuit current (when the load resistance is almost zero and the sun is giving the max energy)?

Some cells have the same output voltage but higher output current? Why? For instance, 0.5 V and 300 mA or 0.5 V and 400 mA...

Thanks,
fisico30
 
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  • #2
Or are they the voltage and current when max power is emitted?
 
  • #3
maybe the voltage and current that give the max power under 1000 W/m^2 solar illumination and 25 degrees temperature?
 
  • #4
The silicon junction has a voltage drop of .5 VDC. A silicon solar cell will deliver no more than .5 VDC when open. It will produce 100 ma of current when exposed to a rated light source at a rated load at close to .5 VDC.
Cells made from other materials produce different voltages and power levels. GaAr cells typically produce .3 VDC.
 
  • #5
Does anyone know at what wavelength a silicon solar cell has the highest efficiency?


the energy of a photon is E=hf where h is planks constant (6.63*10-34J/S) and f is the freq of the photon (f=c/λ)

In modern physics, the longest wavelength that can liberate an electron from a metal is known as the 'threshold wavelength' , and is denoted by KEmax=hf-phi with phi being the work function in electron volts. For silicon, it has a Work function of 4.52eV (from http://environmentalchemistry.com/yogi/periodic/Si.html)

with that the longest wavelength is 2.74*10-7m (f=1.09*1015hz)
 
  • #6
fisico30 said:
Some cells have the same output voltage but higher output current? Why? For instance, 0.5 V and 300 mA or 0.5 V and 400 mA...
Bigger area of exposed silicon contribute more current. If you want higher voltage, you have to add them in series and expose them to the same intensity of sunlight.
 
  • #7
Silicon solars are said to be able to produce 0.5V and can supply up to 0.1 A when exposed to bright light.

For a silicon cell, the open circuit voltage is 0.5 V and the short circuit current is 50 mA.

The maximum power the solar cell can emit is the product of the current and voltage at the max power point. The current and voltage needed for the max power are not the short circuit current and open circuit current...
Both the voltage and current change depending on the resistance of the load...

So when they say that the current they can supply is 0.1 A they assume that the load has resistance close to zero...

If you gain in current you lose in voltage. You cannot have both high...
 
  • #8
As I recall, there was on open voltage rating and a shorted current rating. You could multiply the two, but it wouldn't give you the max power. That was described by the peak power number.

A solar cell has a family of curves showing current versus voltage. Each curve is somewhat rectangular, with the corner rounded off a bit. Thus, they do move towards having P = V_rating x I_rating, but they fall just a bit short.

The different curves are based on operating temperature with the output voltage dropping as the temperature increases. Thus a cell that's really hot has less efficiency.

Then, you have to compute the captured sunlight versus time of day and sum those effects, since the cells typically don't get direct light in the morning and evening. Take the sum of all that energy and divide over the number of hours in the day, and the poor cell doesn't get much energy overall.
 
  • #9
Hello Mike,
thanks for your reply. I agree with what you say, but when we go online and look for a solar cell, they always give you a voltage (0.5 V) and a current rating...

I am still wondering what that current rating is...Max current allowed, is that the current needed achieve the max power (for V=0.5 V)...?
 

What is the efficiency of solar cells?

The efficiency of solar cells refers to the percentage of sunlight that is converted into electricity. The efficiency can vary depending on the type of solar cell and its design, but most commercially available solar cells have an efficiency between 15-20%.

What is the maximum power output of a solar cell?

The maximum power output of a solar cell is determined by its size and efficiency. For example, a standard 6x6 inch solar cell with an efficiency of 18% can produce about 4.5 watts of power. However, the maximum power output can also be affected by external factors such as temperature and shading.

What is the difference between monocrystalline and polycrystalline solar cells?

Monocrystalline solar cells are made from a single crystal of silicon, while polycrystalline solar cells are made from multiple fragments of silicon. Monocrystalline solar cells tend to have a higher efficiency but are more expensive, while polycrystalline solar cells are cheaper but have a lower efficiency.

How long do solar cells last?

The lifespan of solar cells can vary, but most manufacturers offer warranties of 20-25 years. With proper maintenance and care, solar cells can last even longer. Over time, the efficiency of solar cells may decrease, but they can still continue to produce electricity.

Can solar cells work in cloudy weather?

Solar cells can still generate electricity in cloudy weather, although their efficiency may decrease. Some types of solar cells, such as thin-film solar cells, are also more efficient in low light conditions. However, the amount of electricity produced will be significantly less compared to sunny weather.

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