Is it possible to use some volatile liquid with a low melting point (like ammonia) and atmospheric heat to make energy? Can we make a volatile liquid like ammonia to evaporate due to atmospheric heat and make it rotate turbines to make electrical energy? Is this possible?

PS: I'm new to such the topic of energy making and hope there aren't any errors.

Its very much like a thermal power-plant except that in place of coal we use atmospheric heat and in place of water we use a liquid with a low melting point- seems crazy, but I'm curious if this is scientifically and economically feasible. Thank you!

  • $\begingroup$ A heat engine needs a temperature difference. So yes you can use atmospheric heat, but you also need something colder than the atmosphere to send the heat to. $\endgroup$ – PM 2Ring Apr 10 '18 at 16:44
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    $\begingroup$ What would your system do when all the ammonia has evaporated? $\endgroup$ – BowlOfRed Apr 10 '18 at 16:47

You cannot use such a system to make energy. That would violate the conservation of energy.

You can use it to convert energy from thermal energy to mechanical energy though. I believe this is what you really intended.

An engine that converts heat to mechanical work is a Heat engine. You can see there are many types of heat engines. They run off different cycles and have various applications. One with ammonia like you describe would be a form of phase change heat engine.

The specific application you're looking for may not be possible though; because you suggest running an engine off atmospheric heat. The thing is, for a heat engine, you need a hot and cold resovior. The heat transfer to run the engine requires a temperature difference. If all your surroundings are the same temperature, you cannot extract the heat as work. If one end were a little warmer, it would be possible to use ammonia as a phase change substance in the thermodynamic cycle.

Another potential topic of interest might be exergy which is the available energy. Air at the same temperature has no exergy. when there's a temperature difference, the act of the systems trying to reach equilibrium can do work, which is what we utilize in thermodynamics.

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  • $\begingroup$ Thank you sir! but can we use thet mechanical energy to create electrical energy? $\endgroup$ – Mayur Apr 11 '18 at 6:55
  • $\begingroup$ Can we use atmospheric heat on one side and cold ocean water on the other side to create a temperature difference? $\endgroup$ – Mayur Apr 11 '18 at 6:58
  • $\begingroup$ @Mayur Sure, but you won't get a lot of power that way, since the temperature difference is usually quite small, and the ocean isn't always colder than the air. $\endgroup$ – PM 2Ring Apr 14 '18 at 4:56
  • $\begingroup$ @PM2Ring Is there some way to make this system more efficient? $\endgroup$ – Mayur Apr 23 '18 at 6:02
  • $\begingroup$ @Mayur I'm afraid not. For example, let's say the air is at 300 kelvin, around 27 Celsius, and the water is 5 degrees colder. The energy difference for air between those temperatures is around 6 joules per litre. But according to Carnot's theorem only 5/300 of that energy can be converted to work under perfect ideal conditions. In a real heat engine, the efficiency will be significantly lower, since there are no perfect heat conductors or insulators, and there are losses due to friction, etc. $\endgroup$ – PM 2Ring Apr 23 '18 at 7:19

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