Won't this work, theoretically?

Question

My friend and I have been toying with this idea for a long time. He is a little dubious about my asking this online as someone could "steal the idea", but I think if it works, it would have been thought of a long time ago.

The idea is for a solar powered light, which shines on the very solar cells that power it. The sun would power it initially, but when the light shines, it could be removed from the sunlight. Provided that the cells always collected enough power to keep the light on, it would run itself until the bulb needed to be changed.

The question is, could this be done, even on a small scale? I'm a little skeptical that the light would provide enough energy to the cells to keep itself on, especially as solar cells are only 30% efficient or something like that.

Answer 1

Let's assume the cells are only 30% efficient. Then, each time the cells are recharged, they only get 30% of the remaining energy. After time, the energy remaining decreases (exponentially, I might add).

The only way your idea will work completely is if the efficiency were 100%, which in theory, is not possible.

Answer 2

It won't work, and for exactly the reason that you suppose. Typical solar cells are only about 11% efficient, but as long as the efficiency is less than 100%, some energy will be lost every time around the loop, so the light will die out quickly. Also, the light source is less than 100% efficient.

Answer 3

Everyone's answers are great, and your question is thought-provoking.

Here's the loophole. First, you could have that work IF 100% of the beams of light pointed at the cells and no light went anywhere else (and that's only possible with a laser so that wouldn't work) AND 100% of the energy that powered the light went to the creaton of light.

But when energy goes through a lightbulb, only part of it goes to the creation of light. The rest, a large bit of it, is "wasted" through heat.

So no, even in theory it wouldn't work. However, a light could be used to save energy by collecting some of its energy back. But that'd be very expensive and probably not worth it. And the energy it would save would be so small!

Answer 4

What you are asking is, will our perpetual machine idea work? The answer is no. The efficiency of the solar panels is such that it would not be enough to keep the lamp lit. The panel does not store energy either. You would need a storage battery to store the energy the panel converts from sunlight. The lamp would not keep the panel operating to keep the battery charged either.

Answer 5

Not practically because you will continue to lose some of this initial sun energy through inefficiency/loses in the system.
But theoretically --
If you could make a perfect system with no leakage what good would it do since the minute you wanted to use some energy you would start losing per normal. ( kind of like a battery but even those lose their initial charge through shelf life.

Answer 6

The efficiency is less very much less than 1 and basic radiometry will show you that much of the energy will leave the system. Therefore each cycle more energy is lost.

Answer 7

No, it can work as this would violate several of the laws of thermodynamics. You would have a perpetual motion machine, in a sense, which isn't allowed by the laws of nature.

Answer 8

That would be wasteful. You would be converting your solar energy into heat instead of storing it.