Efficient Energy Transfer from Heat?

  • #1

Main Question or Discussion Point

Hi,

I was wondering, for a process that produces a large amount of heat, are there any efficient systems out there to transform this into different types of energy (chemical potential, electrical, mechanical, etc) with a high efficiency (80-90%+)

Thanks.
 

Answers and Replies

  • #2
251
10
I'd suggest reading (and understanding) the second law of thermodynamics, as well as the limit nature imposes when we attempt to convert heat into work
 
  • #3
RonL
Gold Member
1,096
215
I'd suggest reading (and understanding) the second law of thermodynamics, as well as the limit nature imposes when we attempt to convert heat into work
Hi Gordianus,
I understand your comment and agree to a point, but in a quest to understand my own thoughts, can you (or anyone) put in simple words an explanation to "the limit nature imposes" ?
When reading the 1st and 2nd law statements, it seems (to me) that my brain is the only limit.
In my search for understanding, there have been a couple of things that stand out, at least to me.

First a statement made long ago.

http://en.wikipedia.org/wiki/Aeolipile

"It is not known whether the aeolipile was put to practical use as an 'engine' in ancient times. Hero's drawing shows a stand-alone device, and was presumably intended as a temple 'wonder', like many of the other devices described in Pneumatica. [3]

Vitruvius, on the other hand, mentions use of the aeolipile for demonstrating the physical properties of the weather. He describes the aeolipile as

…a scientific invention [to] discover a divine truth lurking in the laws of the heavens.[5]
After describing the device's construction (see above) he concludes:

…Thus from this slight and very short experiment we may understand and judge of the mighty and wonderful laws of the heavens and the nature of winds.[5]"

Then I learned a little about "physical ontology" and found this.

http://en.wikipedia.org/wiki/Physical_ontology

"Richard Feynman (1918–1988) was not only a very important physicist of the 20th century, but he was also in some way a philosopher. His reflections on the value of theories in physics referred to human ideas about the universe and then about its being. Feynman won the 1965 Nobel Prize in Physics and in traditional lecture he said:

Perhaps rightly so, for possibly the chance is high that the truth lies in the fashionable direction. But, on the off-chance that it is in another direction - a direction obvious from an unfashionable view of field theory - who will find it? Only someone who has sacrificed himself by teaching himself quantum electrodynamics from a peculiar and unusual point of view; one that he may have to invent for himself. I say sacrificed himself because he most likely will get nothing from it, because the truth may lie in another direction, perhaps even the fashionable one.
But, if my own experience is any guide, the sacrifice is really not great because if the peculiar viewpoint taken is truly experimentally equivalent to the usual in the realm of the known there is always a range of applications and problems in this realm for which the special viewpoint gives one a special power and clarity of thought, which is valuable in itself.[citation needed]

Tony Hey and Patrick Walters in their "The New Quantum Universe" (2003) report the following Feynman's speech:

A poet once said "The whole universe is in a glass of wine." We will probably never know in what sense he meant that, for poets do not write to be understood. But it is true that if we look at a glass closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflections in the glass, and our imaginations adds the atoms. The glass is a distillation of the Earth's rocks, and in its composition we see the secret of the universe's age, and the evolution of the stars. What strange array of chemicals are there in the wine? How did they come to be? …. How vivid is the claret, pressing its existence into the consciousness that watches it! If our small minds, for some convenience, divide this glass of wine, this universe, into parts—physics, biology, geology, astronomy, psychology, and so on — remember that Nature does not know it![citation needed]"

In my simple mind, almost all things energy related can find a path connection to the wind and weather. Hero's Turbine was a steam machine, why was the connection made to the wind (by Vitruvius) ? I believe I understand.

Thanks for any responses
Ron
 
Last edited:
  • #4
russ_watters
Mentor
19,319
5,355
Hi Gordianus,
I understand your comment and agree to a point, but in a quest to understand my own thoughts, can you (or anyone) put in simple words an explanation to "the limit nature imposes" ?
When reading the 1st and 2nd law statements, it seems (to me) that my brain is the only limit.
The limiting factor is that the heat needs to flow.

Consider a moving river. It has a certain amount of kinetic energy, but if you try to harness all of it, you'll just stop the flow of the river and your device will only work for a moment. So too, a thermodaynamic device must be able to harness heat while still allowing it to flow through the device. As a result, it can only harness some of the energy. Exactly how much requires doing a thermodynamic analysis of the particular thermo cycle -- putting numbers to a 1st and 2nd law analysis.

Now there are other process, such as using a semiconductor to convert heat or light directly to electrical energy, but it so happens that these devices have similar limitations. A solar panel, for example, works better when it is cold, but when put out in the sun, it gets hot. Some of the energy will always be dissipated as heat.

I don't see any relevant content in the rest of your post to respond to...
 

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