When the topic of renewable energy comes up I cant help but think that since anything greater in temprature than absploute zero has some level of thermal energy, why are we not able to harness it? I get the law of entropy and heat and whatnot but even if its inefficient, why can we not use heat, only heat differences, to generate electricity. I get how RTGs and nuclear power works, but those both require some kind of thing that is cool in addition to what is hot. Why not just use the energy in the heat of whatever we have? If you believe in the concept of the universe having a “heat death” then you also get that its not that one part of the universe loses it heat and one part gains it, its that every atom in the universe loses heat. If thats the case then why cant we have uniform heat loss on earth?
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Heat is a form of energy.
Another form of energy would be the potential energy in a gravity well. If you hold a basketball at arm’s length, that basketball has a potential energy based on the fact you’re holding it above ground. So what power can you harvest from holding that basketball at arm’s length? None.
Power is energy differential transferred over time. If you drop that basketball, you’re harvesting its potential energy into kinetic energy that will eventually be harvested into the impact when it strikes the ground. To gain that power, you must transform the energy in some fashion.
Heat is no different. Unless you’re moving from hot to cold or vice versa, you’re not moving the energy at all. You’re not producing work from it. It’s just a feature of the system like the basketball suspended above the ground.
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