Here's the idea. There's lot of available energy in the atmosphere, and all around us in general in the form of heat. Just a few degrees temperature difference represents an appreciable amount of kinetic energy, even in something as lightweight as air. And, everyday ambient temperatures, or even arctic temperatures for that matter, are hundreds of degrees Kelvin.
I'm writing about what's potentially a vast untapped renewable energy source. Even more renewable because of conservation of energy. Most mechanical enrgy we use ends up deteriorating into heat energy anyways. There's no reason I can think of that we can't just round it up again and re-use it.
I suppose one way would be to just take a typical heat engine like a steam engine, and design it to operate by exploiting ambient heat. Having a steam engine work at room temperature in this way would I imagine require it not using steam. This, I suppose, offers an engineering challenge as these engines, I understand, often exploit the phase change of water to improve efficiency.
One question that arises from that is, can such an engine efficiently boil water using only heat pumps or the like? Another question is, can a fluid heat engine efficiently operate without boiling, just only the recirculation of warm and warmer water (or an alternative coolant)?
And, as long as were discussing alternative coolants, why not a coolant that can achieve a liquid to gas phase change at room temperature? Or would the operating temperature being bound by the boiling point of that coolant limit such an application? On the other hand, don't boiling liquids typically remain at their boiling points, at least until they all boil away? Could that be exploited? Would the boiling away problem be too much?
Another idea I had was a coil of unevenly spaced myriad bi-metallic springs (like the ones you find in bi-metallic thermometers) attached to a drive train and all the springs pushing up against a ratchet. I like this idea partly because it's sooo steampunk clockwork, but also, from an engineering stand-point it actually does three jobs. It can act as an engine, a heat sink, and a spring energy storage device. Granted springs are not well known for their energy storing capacity. But, a machine that can mult-task is nifty nonetheless. I suppose limiting it to doing all three jobs at once would limit it's available applications though.
I also recall a piston engine that uses heat differential. It's bugging me because I can't remember the name of it and it's inventor, nor can I think where to start data mining for it. I think I saw it on a Modern Marvels. Points if you can find it. I recall that it really didn't matter whether it was hot or cold so long as one side of the piston was significantly hotter or colder than the other. You could get it to work sitting on a cup of steaming tea, or a glass full of ice cubes, as was demonstrated on the show. This implies it was mechanically motivated by heat exchange from one side of the piston to the other. I understand this concept has already been thoroughly explored and found to be not viable. But, who knows, your thoughts?
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