Has expanding metal ever been configured into a solar type device for generating electricity? I believe it would have slow movement with relatively high torque. Does anyone have any suggestons how this possibly could be configured to generate electricty?
It seems a solar heated thermal coiled spring could be geared up to spin generators if used in unison in large groups. It also seems possible to use cold water to cool them back down and harvest the energy of contraction as well.
I this crazy or does it have some viable merit?
You’re essentially describing a Stirling cycle engine, but using a solid medium instead of a gas filled chamber.
Not likely to be very effective because the coefficient of expansion of metals is only moderate, and their heat capacity means the expansion/contraction cycle would be slow.
The energy that goes into expanding the metal is heat. Why not employ it directly? What is the advantage of putting in extra steps?
Plus, slow movement but high torque is really difficult to make a practical device out of. Gearing the other way is generally much more efficient.
There’s nothing wrong with the idea of using a heat source (in this case, the sun) to power a mechanical engine, then use this to run an electrical generator - solar steam turbine projects do it, arguably, all fossil fuel power stations do it (just from solar energy that’s been stored).
This particular mechanism doesn’t sound particularly practical though.
You mean like an atmos clock?
A what?
I vaguely recall seeing a device once that used that effect to make a wheel spin*. Sloooowwwwly. I don’t think it would have generated anywhere near as much power as could have been harvested from the heat by a more efficient method.
*It was a long time ago, and I don’t remember enough details to find a video with Google. Sorry.
I don’t believe that steel springs absorb or conduct heat effieciently enough but it would seem if it were configured kind of like a card on a bicycle wheel the energy could be stored with a ratchet device and then quickly released. Some kid of cooling would be needed to increase the cycling or just have one long slow cycle that reversed at night.
an atmos clock is a clock that gets wound up by atmospheric pressure on a bellows. the clock has to be very specially made to run on such a small energy input.
to have something run on low grade heat the Stirling engine, hot air engine, is already good and compact for this.
Do you mean like a rubber band heat engine? https://www.youtube.com/watch?v=OW6aEmOsXv0
Yeah, something like that, only there were a lot more bands, and they were flat and twisted a 1/4 turn. The twist was what distorted the wheel when one side was heated and the bands expanded.
ETA: It was a long time ago, so my memory may be off on the degree of twist. It may have been 1/2 or more.
I think, instead of gearing, one would want to use piezoelectric crystals. I don’t know how much electricity one can get that way.
This sounds like one of those perpetual motion inventions. I seem to remember something about a device like that.
Perpetual, as long as you keep the heat source turned on. It stopped when you turned that off.
Sounds more like the 10,000 year clock.
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So how does the Clock keep going if no one visits it for months, or years, or perhaps decades? If it is let to run down between visits, who would keep resetting it? The Clock is designed to run for 10,000 years even if no one ever visits (although it would not display the correct time till someone visited). If there is no attention for long periods of time the Clock uses the energy captured by changes in the temperature between day and night on the mountain top above to power its time-keeping apparatus.
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There is a pretty fundamental reason why you wouldn’t want to do this if you cared about efficiency. There would not be much of a temperature swing, because it’s hard to heat and cool metals repeatedly and over a large temperature range, and they tend to conduct away the temperature difference you are creating. But you want a large temperature swing.
If this is all based on heating a metal and letting it cool back down to room temperature, then ask yourself what percentage, in absolute temperature terms, room temperature is, relative to the highest temperature your heat engine sees. Chances are it’s a pretty big percentage. Well, the best your engine could do would still leave that same percentage of the total heat energy to remain as heat energy. That is, the low engine temperature as a fraction of the high engine temperature will tell you the fraction of your initial heat input that will be discarded at the end, as a bare minimum. This is entropy and the Carnot cycle we’re talking here.
Better to use gasses or phase changes, and large temperature changes.