Re: Stirling engines

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Posted by Davis Landstrom (195.92.194.17) on April 23, 2002 at 07:05:17:

In Reply to: Re: Stirling engines posted by Scott Ellis on April 22, 2002 at 10:23:26:

It is an interesting idea, yes, and indeed one which I have thought about. The MM6 does work off as little as 2 degrees temperature difference, and I feel could be adapted to exploit naturally occuring thermal gradients, (like those you mentioned), however as the low delta T Stirling engines produce little dynamic touque, I feel it's prospects for large scale power generation are non existant as it stands. However as I mentioned NASA are developing a Stirling cycle engine that runs off of the heat given out freely by decaying radioisotopes and minerals, and from what I have heard this engine produces quite a large amount of dynamic touque.
The heat engine of the future so to speak has to be the wheel of Wally Minto, this 7 foot wheel exploits the small temperature gradient that exists between the air and a solar heated pond, in order to exploit it, the wheel has a series of gas cylinders, each containing a liquid whose boiling point is 1 or 2 degrees above room temperature, arranged around the circumference of the wheel, the liquid becomes a gas when the cylinder is heated by the pond, and it condenses again when the cylinder is exposed to the cooler atmosphere making the wheel constantly top heavy and over balancing, the wonder wheel (as it is often known) rotates very slowly but unlike the Stirling engine, it produces a very large amount of dynamic touque. I like this wheel as it reminds me of a hybrid between a Bessler wheel and a Stirling engine.

: Hi Davis, thanks for your very interesting post.

: I had no idea that Stirling engines could operate at such low delta T's. It makes me wonder...

: Because of the spin of the earth and the different heat retaining characteristics of earth, air, and water, there is almost always a difference of 2 degrees to be tapped from the natural world. For example, during the daytime, the air temperature is usually at least 2 degrees warmer than the earth's surface (just a few inches down) or a body of water. At night, the reverse is usually true.

: Do you think a strirling engine could be built that produces useful power from these natural and inexhaustible temperature differentials?

: -Scott

:
: : Although Stirling engines are not perpetual motion, because of their incrediable efficiency they can be made to work close to them. Take for example the MM6 which is a low delta T (Temperature) stirling engine, this fine piece of engineering can be made to run off a temperature difference of as little as 2 degrees C!, it will sit there on your hand or on a sun warmed surface at room temerature performing 100-200 RPMs!
: : I have only just heard about the MM6 from the American Stirling engine company and am saving for one. (Unless someone re-invents Bessler's wheel or some other self powering free energy perpetual motion device this is probably as close as I will get)
: : I bought my first Stirling engine about a week ago, it is quite a high delta T model, but boasts being the smallest stirling around (It's called the micro-stirling). It's a shame that it is high delta T and not coffe cup compatable, (It requires an alcohol burner) but it is so elegantly crafted and vintage Victorian looking (+ gold plated!) that I simply had to have it.
: : The reason that it isn't low delta T is because it is desighned to show the user (begginer) how the stirling cycle works in the engine, rather than have a flexable 'bellows' it has a much more inefficiant glass tube and reciprocator (so you can peer inside) but none the less it goes at about 800 RPMs when it has heated up.
: : The Stirling thermodynamic cycle has been calculated to be the most efficient cycle, (it approaches closest to the Carnot theoretical limit of thermodynamic efficiency for a heat engine)
: : The Stirling engine was invented by the Stirling brothers in 1816, it 'grew up' with steam, and for a good many years Stirling engines were a popular alternative to steam engines which in the early part of the 19th centuary had a nasty tendancy to blow up all the time. But by the 1840s-50s the steam the foundations for the development of things like Stirling cryocoolers which were developed for use with the immaging systems on many satalites by NASA, today NASA are developing a Stirling engine that will run off the heat given off from decaying radioisotopes, this engine could power equipment in space and could even have implications for terrestrial power generation, (because of the thermodynamic efficiency of the Stirling cycle you can use much less radioisotopes to produce energy out puts that rival those of the much more inefficient radiothermal generators).
: :
: :

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Comments:	: It is an interesting idea, yes, and indeed one which I have thought about. The MM6 does work off as little as 2 degrees temperature difference, and I feel could be adapted to exploit naturally occuring thermal gradients, (like those you mentioned), however as the low delta T Stirling engines produce little dynamic touque, I feel it's prospects for large scale power generation are non existant as it stands. However as I mentioned NASA are developing a Stirling cycle engine that runs off of the heat given out freely by decaying radioisotopes and minerals, and from what I have heard this engine produces quite a large amount of dynamic touque. : The heat engine of the future so to speak has to be the wheel of Wally Minto, this 7 foot wheel exploits the small temperature gradient that exists between the air and a solar heated pond, in order to exploit it, the wheel has a series of gas cylinders, each containing a liquid whose boiling point is 1 or 2 degrees above room temperature, arranged around the circumference of the wheel, the liquid becomes a gas when the cylinder is heated by the pond, and it condenses again when the cylinder is exposed to the cooler atmosphere making the wheel constantly top heavy and over balancing, the wonder wheel (as it is often known) rotates very slowly but unlike the Stirling engine, it produces a very large amount of dynamic touque. I like this wheel as it reminds me of a hybrid between a Bessler wheel and a Stirling engine. : : Hi Davis, thanks for your very interesting post. : : I had no idea that Stirling engines could operate at such low delta T's. It makes me wonder... : : Because of the spin of the earth and the different heat retaining characteristics of earth, air, and water, there is almost always a difference of 2 degrees to be tapped from the natural world. For example, during the daytime, the air temperature is usually at least 2 degrees warmer than the earth's surface (just a few inches down) or a body of water. At night, the reverse is usually true. : : Do you think a strirling engine could be built that produces useful power from these natural and inexhaustible temperature differentials? : : -Scott : : : : : : Although Stirling engines are not perpetual motion, because of their incrediable efficiency they can be made to work close to them. Take for example the MM6 which is a low delta T (Temperature) stirling engine, this fine piece of engineering can be made to run off a temperature difference of as little as 2 degrees C!, it will sit there on your hand or on a sun warmed surface at room temerature performing 100-200 RPMs! : : : I have only just heard about the MM6 from the American Stirling engine company and am saving for one. (Unless someone re-invents Bessler's wheel or some other self powering free energy perpetual motion device this is probably as close as I will get) : : : I bought my first Stirling engine about a week ago, it is quite a high delta T model, but boasts being the smallest stirling around (It's called the micro-stirling). It's a shame that it is high delta T and not coffe cup compatable, (It requires an alcohol burner) but it is so elegantly crafted and vintage Victorian looking (+ gold plated!) that I simply had to have it. : : : The reason that it isn't low delta T is because it is desighned to show the user (begginer) how the stirling cycle works in the engine, rather than have a flexable 'bellows' it has a much more inefficiant glass tube and reciprocator (so you can peer inside) but none the less it goes at about 800 RPMs when it has heated up. : : : The Stirling thermodynamic cycle has been calculated to be the most efficient cycle, (it approaches closest to the Carnot theoretical limit of thermodynamic efficiency for a heat engine) : : : The Stirling engine was invented by the Stirling brothers in 1816, it 'grew up' with steam, and for a good many years Stirling engines were a popular alternative to steam engines which in the early part of the 19th centuary had a nasty tendancy to blow up all the time. But by the 1840s-50s the steam engine had been perfected and the Stirling engine was considered to produce too little power compared to it's weight. The main problem was that Iron was used for their construction and proved inefficient at retaining heat, (had we waited 20-30 years untill the invention of stainless steel we might have seen the Stirling age instead of the steam age). : : : After this time, stirling engines were still in use, but in a much more subdued fashion, you could find them powering things like fans, phonographs and smal boats right up untill the first quarter of the last centuary, when electric motors became practical, and largely replaced the Stirling engine. Science historians often regaurd this period as being the first Stirling age. : : : The second stirling age came when the electronics hardware company, Phillips, developed a series of very small and powerfull Stirling engines (Using more modern materials), between 1940 and 1960, which actually proved more cost effective to run than electric motors of the day, for a small period of time they seemed to catch on, but new advances in electric motor technology quickly put an end to this. However that was not the end of Phillip's Sterling technology program, as they laid the foundations for the development of things like Stirling cryocoolers which were developed for use with the immaging systems on many satalites by NASA, today NASA are developing a Stirling engine that will run off the heat given off from decaying radioisotopes, this engine could power equipment in space and could even have implications for terrestrial power generation, (because of the thermodynamic efficiency of the Stirling cycle you can use much less radioisotopes to produce energy out puts that rival those of the much more inefficient radiothermal generators). : : : : : :
(Archived Message)

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