Question by ME: Would it be possible to power an energy star light bulb using the light it produces and photo-voltaic cells?
Follow-up. Say you have a lightbulb on a seperate power source shining its light on a single photovoltaic cell. If you added a second cell to the first, does that multiply the output x2, exponetially, or only slightly? I guess my question is does the amount of power generated by photocells depend on the strength of the light source or just the number of cells?
Best answer:
Answer by ioerr
No you can’t power a light bulb this way.
Even if you completely surrounded the light bulb with photovoltaic cells, their combined output still would be less than what the bulb takes to create the light they’re capturing.
The power in the light that the bulb creates is itself less than the power the bulb requires to make that light. In other words, the bulb is not 100% efficient at turning power into light. No bulb is, or can be.
Likewise, the cells are not 100% efficient at turning the light they capture into power, far from it. And no cell can be.
Likewise, even the wires in the circuits involved are not 100% efficient at transmitting the power from one end of their lengths to the other.
No real machine is 100% efficient at converting power to work, or ever will be.
The law of physics that deals with this is called the conservation of energy. It just means, there’s only so much energy in a system. You can’t create or destroy it, you can only change it from one form to another. In order to power the bulb with the output from a cell capturing light from it, energy would have to be created that wasn’t originally in the system. This would violate the law of conservation of energy.
This is why perpetual motion machines are impossible.
As for the 2nd question, the output goes up arithmetically with the number of cells. 2 cells put out 2x the power, 3 put out 3x the power and so on. As long as the light on each is equal. Yeah the brightness of the light makes a difference too. But in every case the total output will still always be less than the energy required to create the light they’re converting.
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