# Could we replace humans in this picture with robots to generate electricity? [closed]

My idea is to replace the humans with robots on magnets - like the maglev trains or just a couple smart wheels. Simple mathematical algorithms would adjust the robots to keep the contraption spinning constantly. Another idea along the same lines would be a smart track that simply moves a weight along the circle at the appropriate time.

Men turning a hamster wheel

## closed as unclear what you're asking by AndreiROM, Kromey, bowlturner, Hohmannfan, GianlucaApr 7 '16 at 20:51

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• Why not just have the solar panels power the device? – Lacklub Apr 7 '16 at 19:28
• Yes, just use the energy from the solar panels. If you are just trying to generate electricity, as your title says, the whole robot contraption would just add unnecessary loss. Now, if you need the circular motion for something else, like grinding grain or pumping water, a humanoid robot pushing a wheel is not terribly efficient, but I could conceive cultural/historical reasons for a world to evolve to that point. – user11864 Apr 7 '16 at 19:32
• what you are hinting at is a perpetual motion machine. It simply is not possible for them to generate more power that way than they would consume. Conservation of energy and entropy are inescapable facts of life. – user11864 Apr 7 '16 at 19:40
• gravity would not contribute anything to the equation. the potential energy (energy from gravity) exchanged to kinetic energy when any part of the contraption is going down is then exchanged right back to potential energy when that same part of the contraption has to go back up to the starting point. And you would lose some of it to friction in the wheel bearings and wind resistance. Wish it were that easy to generate electricity. If the output was more than what the robots consume, all you would have to do is use some of the output to power the robots and you'd have perpetual motion. – user11864 Apr 7 '16 at 20:16
• I am wondering if you are a young person (don't answer that). The thing is, I would not want to discourage you. If you are, this sort of thinking - "what if..." is exactly the sort of thinking that will make a good scientist, and as you learn more about physics, you will learn about some of what has already been figured out as "won't work", but hopefully you will retain that "what if..." mentality that is so crucial for an innovator in science or any field. – user11864 Apr 7 '16 at 20:26

## Yes, but...

Although it would be possible to generate power this way (using humans, hamsters, or robots), it will always require a higher energy input than it can output.

Furthermore, you often get much better efficiencies by removing intermediate steps. As the comments mentioned, you get better results if you go straight from PV panels to electrical power by removing the hamster wheel and hamster (robot).

This resource describes the laws of thermodynamics

### Zeroth law of thermodynamics

– If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

### First law of thermodynamics

– Energy can neither be created nor destroyed. It can only change forms. In any process, the total energy of the universe remains the same. For a thermodynamic cycle the net heat supplied to the system equals the net work done by the system.

### Second law of thermodynamics

– The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

### Third law of thermodynamics

– As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

Of all the laws in science, this set of laws is probably the most inviolate of them all. If we ever find that these laws can be broken, then most of our understanding of how the Universe works is very broken. Basically you must throw out almost all theories and engineering design.

A humorous lay persons version of these laws is:

1. You can't win
2. You can't break-even
3. You can't quit the game
• I thought the First Law of Thermodynamics was, "You don't talk about thermodynamics." :-) – Jay Apr 8 '16 at 3:58