Author Topic: Stirling Engine energy?  (Read 2579 times)

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Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #25 on: March 09, 2019, 04:01:42 pm »
It's a military application.....  I don't think the military would care about efficiency as long as it provided an advantage.
 

Offline beanflying

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Re: Stirling Engine energy?
« Reply #26 on: March 09, 2019, 04:09:54 pm »
It's a military application.....  I don't think the military would care about efficiency as long as it provided an advantage.


Submarines have finite space so energy density and efficiency do matter. The main engines are Diesel so using what is already on hand is sensible. The Delta T is also better with his option against Seawater as a coolant.
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Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #27 on: March 09, 2019, 04:13:22 pm »
It's a military application.....  I don't think the military would care about efficiency as long as it provided an advantage.


Submarines have finite space so energy density and efficiency do matter. The main engines are Diesel so using what is already on hand is sensible. The Delta T is also better with his option against Seawater as a coolant.

Sterling is all about the delta T.  So maybe they use the LOX in cooling "cycle" and the oxidation in "heat" cycle.
 

Offline beanflying

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Re: Stirling Engine energy?
« Reply #28 on: March 09, 2019, 04:21:30 pm »
Really unlikely they would use LOX for cooling when surrounded by Seawater. I have never seen any reference to it being used that way in anything I have seen or read on the Sub use case.

It doesn't mean you wouldn't maybe send the LOX fluid path past the water lines on their way to the burners for gain a point or two of Delta T but gains would be minimal at best.
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Online IanB

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Re: Stirling Engine energy?
« Reply #29 on: March 09, 2019, 04:57:48 pm »
It's a military application.....  I don't think the military would care about efficiency as long as it provided an advantage.

Of course the military care about efficiency. It's about range and endurance. Why would the military value a sub that can only go 10 miles before refueling instead of 1000 miles?

When considering power sources, you cannot forget the energy balance. This is where "free energy" and "perpetual motion" researchers go awry. They totally forget that to get power out of a system you have to put energy in. How much energy is stored in liquid oxygen in and of itself? None, relatively speaking. It is not a power source, so you cannot use it to power engines.

The same false reasoning goes with "using liquid oxygen to provide cooling". Liquid is oxygen is not cold in and of itself, it is cold because it is stored in highly insulated tanks designed to keep heat out. What happens if you try to cool something with liquid oxygen? You put heat into it, which makes it boil, which means your liquid oxygen becomes gaseous oxygen. So no what are you going to do with all that highly dangerous oxygen gas? You had better vent it to the outside, which will be a total and expensive waste.

It's also wrong to suppose engines are "all about the delta-T". A delta-T cannot power anything. Heat engines work by moving heat energy from a source to a sink. The more heat you move the more power you get out. If you don't move heat, you don't get power, regardless of the delta-T.
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Offline george80

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Re: Stirling Engine energy?
« Reply #30 on: March 09, 2019, 06:48:59 pm »

The Stirling Cycle and similar technologies are likely to remain fringe for plenty of reasons but as energy costs increase then reusing excess or waste hot or cold with them start to make more sense.

Reuse of waste heat or low pressure steam energy even from existing power stations would potentially be an application but at large MW the numbers and plant size would be daunting if not cost prohibitive at present.

And there we have it. What I said all along although one does have to use a couple of brain cells to make the connection. I'll try to spell things out for the readers still in kindy and at the low end of the gene pool in more simplistic terms and more S l o w l y  next time. 
Apologies to the Kiddies that couldn't keep up earlier.

The 2nd grade level of the comprehension and reading abilities on this site are staggering in the pitiful low standard.
No one said they didn't work, just that they had no practical use in everyday applications which made them at best a toy.

Nuke reactors work too but no one is going to be powering vehicles with them for a while yet either so the question of something working or not is irrelevant to whether it is useful except in specific and specialized applications... as you have proven.
 

Offline beanflying

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Re: Stirling Engine energy?
« Reply #31 on: March 09, 2019, 08:40:44 pm »

While being a very interesting process and making for great little  toys, unfortunately the low power output of stirling engines means any real and worthwhile power output would take an impractically sized ( and cost) unit.
Even getting 1 Kw out of these things would take a Very large unit and either a wasteful heat source or a vey big collector of low density heat.

Either way, extremely difficult to make worth while and more importantly, cost effective.

What you actually said was :bullshit: and negative. And again you try and propagate YOUR delusional myth that the technology is flawed. It IS in everyday use just not in everyones everyday use YET.

Placing them in the diminutive of 'toy' is taking debate points from the shallow end of the Gene Pool and would be more at home proving the Earth is Flat. The Sub example is hardly a toy and neither is the device shown in the OP.

Take your head out of the sand and try being positive for a change who knows you just may learn something instead of fighting the new ideas of others.
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Offline apis

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Re: Stirling Engine energy?
« Reply #32 on: March 10, 2019, 03:26:03 am »
High delta T makes heat engines more efficient, but it is indeed the energy that powers the motor. I.e. energy is converted from heat to mechanical energy and most of that will come from the chemical energy released when burning the fuel (burning = fuel + oxidiser). No one would carry around a lot of oxidiser unless they intended to use it to oxidise (burn) stuff, it's too dangerous.
 

Offline jmelson

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Re: Stirling Engine energy?
« Reply #33 on: March 10, 2019, 03:13:07 pm »
It was my understanding the liquid oxygen is used as a coolant for the Sterling Engine.
Why would the need LOX as a coolant when they have the whole ocean?
Quote
Guess what I'm not understanding is why an oxidizer is needed with a Sterling engine. 
A Stirling engine runs on temperature differential.  To propel a submarine, you need  a LOT of energy.  This sub was designed to run VERY quietly, and produce minimal (or maybe zero) exhaust, and have no intake from the surface.  (Supposedly, the Russians went nearly crazy over this design, as it was close to stealth underwater technology.)  So, burning a fuel with a concentrated oxidizer was the way to create the heat to run the engine.

To answer an earlier question, the oxygen generators in some aircraft produce a very small amount of Oxygen.  Enough to keep a couple people alive for 20 minutes, but nowhere near enough to run several hundred HP engines on.  LOX is a WAY more dense form of Oxygen than the stuff in an oxygen generator.

Jon
 

Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #34 on: March 10, 2019, 03:31:29 pm »
It was my understanding the liquid oxygen is used as a coolant for the Sterling Engine.
Why would the need LOX as a coolant when they have the whole ocean?

The temperature delta between seawater and LOX is pretty substantial, isn't it?

Quote
Guess what I'm not understanding is why an oxidizer is needed with a Sterling engine. 
A Stirling engine runs on temperature differential.  To propel a submarine, you need  a LOT of energy.  This sub was designed to run VERY quietly, and produce minimal (or maybe zero) exhaust, and have no intake from the surface.  (Supposedly, the Russians went nearly crazy over this design, as it was close to stealth underwater technology.)  So, burning a fuel with a concentrated oxidizer was the way to create the heat to run the engine.

To answer an earlier question, the oxygen generators in some aircraft produce a very small amount of Oxygen.  Enough to keep a couple people alive for 20 minutes, but nowhere near enough to run several hundred HP engines on.  LOX is a WAY more dense form of Oxygen than the stuff in an oxygen generator.

Jon

Your right,  LOX or solid form of O2 space wise would be about the same.  LOX would be pure and not require any burning.  That makes a lot of sense.

Sterling engines run on temperate differentials.  I would think a Sterling engine could easily run on the temperature diff between LOX and the coldest seawater.  But it appears they burn diesel fuel and use the LOX as the oxidizer.  What happens to combustion byproducts?  Do they use a CO2 absorbent?  Or vent the exhaust into the ocean water?  But if they vent, at say 100 feet underwater that would be around 3 atmospheres.  So wouldn't they need a pump or compressor to pump the exhaust gasses into the seawater?  And then wouldn't the bubble give the sub away if no the pump or compressor?


 

Online IanB

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Re: Stirling Engine energy?
« Reply #35 on: March 10, 2019, 03:55:52 pm »
Your right,  LOX or solid form of O2 space wise would be about the same.  LOX would be pure and not require any burning.  That makes a lot of sense.

It makes no sense at all: "LOX would be pure and not require any burning." What are you trying to say here? Burning combines oxygen with fuel to produce heat. Pure oxygen is more efficient than air as an oxidant (air contains 80% nitrogen), but the oxygen still has to be consumed in a fire to produce the required heat to drive an engine.

Quote
Sterling engines run on temperate differentials.

In fact, all heat engines run on temperature differentials, including the common ones like internal combustion engines, steam turbines in power plants, and jet engines. But always you have to put energy in to get power out.

Quote
I would think a Sterling engine could easily run on the temperature diff between LOX and the coldest seawater.

Again, no. This is the "free energy" trap. You cannot get energy for free. To get power out you need to put heat in, whether it by by burning fuels, or from nuclear fission, or from renewable sources (solar or wind, since wind energy comes from the heat of the sun). If you try to take the required heat energy from the sea it will simply heat up the LOX and boil it away, quickly destroying your cold reservoir.

If they were going to do this, they wouldn't use LOX (highly dangerous), they would use liquid nitrogen or dry ice. But they don't because there is not enough energy available to derive a useful power output. Combustion is the only way to get enough power to drive a useful engine (unless you use batteries).

Quote
But it appears they burn diesel fuel and use the LOX as the oxidizer.  What happens to combustion byproducts?  Do they use a CO2 absorbent?  Or vent the exhaust into the ocean water?  But if they vent, at say 100 feet underwater that would be around 3 atmospheres.  So wouldn't they need a pump or compressor to pump the exhaust gasses into the seawater?  And then wouldn't the bubble give the sub away if no the pump or compressor?

These are good questions. Possibly the sub absorbs the CO2 since venting it would give away the sub's location.
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Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #36 on: March 10, 2019, 04:24:41 pm »
Your right,  LOX or solid form of O2 space wise would be about the same.  LOX would be pure and not require any burning.  That makes a lot of sense.

It makes no sense at all: "LOX would be pure and not require any burning." What are you trying to say here? Burning combines oxygen with fuel to produce heat. Pure oxygen is more efficient than air as an oxidant (air contains 80% nitrogen), but the oxygen still has to be consumed in a fire to produce the required heat to drive an engine.

Quote
Sterling engines run on temperate differentials.

In fact, all heat engines run on temperature differentials, including the common ones like internal combustion engines, steam turbines in power plants, and jet engines. But always you have to put energy in to get power out.

Quote
I would think a Sterling engine could easily run on the temperature diff between LOX and the coldest seawater.

Again, no. This is the "free energy" trap. You cannot get energy for free. To get power out you need to put heat in, whether it by by burning fuels, or from nuclear fission, or from renewable sources (solar or wind, since wind energy comes from the heat of the sun). If you try to take the required heat energy from the sea it will simply heat up the LOX and boil it away, quickly destroying your cold reservoir.

If they were going to do this, they wouldn't use LOX (highly dangerous), they would use liquid nitrogen or dry ice. But they don't because there is not enough energy available to derive a useful power output. Combustion is the only way to get enough power to drive a useful engine (unless you use batteries).

Quote
But it appears they burn diesel fuel and use the LOX as the oxidizer.  What happens to combustion byproducts?  Do they use a CO2 absorbent?  Or vent the exhaust into the ocean water?  But if they vent, at say 100 feet underwater that would be around 3 atmospheres.  So wouldn't they need a pump or compressor to pump the exhaust gasses into the seawater?  And then wouldn't the bubble give the sub away if no the pump or compressor?

These are good questions. Possibly the sub absorbs the CO2 since venting it would give away the sub's location.

No such thing as free energy.  If there was such a think the universe would have burned up from all of the heat millions of years ago.

We are in agreement a sterling engine works off of a temperature difference.  Can be hot or cold.  So LOX could be used with seawater.   The energy put it would be the compressing of the O2 to make LOX.  We have to obey the first law of thermodynamics.  Using the ideal gas law, PV=nRT when LOX turns into a gas and "warms" to seawater temp there would T=PV  (As nR remain the same we can drop them from the equation.)  This cold LOX will draw the energy out of the seawater and power the Sterling Engine.

https://youtu.be/DvD2EJNihm4


 

Online IanB

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Re: Stirling Engine energy?
« Reply #37 on: March 10, 2019, 07:55:50 pm »
We are in agreement a sterling engine works off of a temperature difference.  Can be hot or cold.  So LOX could be used with seawater.   The energy put it would be the compressing of the O2 to make LOX.  We have to obey the first law of thermodynamics.  Using the ideal gas law, PV=nRT when LOX turns into a gas and "warms" to seawater temp there would T=PV  (As nR remain the same we can drop them from the equation.)  This cold LOX will draw the energy out of the seawater and power the Sterling Engine.

While this might work for a short time (although using something less dangerous than LOX such as nitrogen), the amount of stored energy in a liquefied gas is insufficient to provide a meaningful power source. You would get an under-powered motor with a very limited range.
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Offline beanflying

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Re: Stirling Engine energy?
« Reply #38 on: March 10, 2019, 08:08:57 pm »
On Ice maybe a 20-30 Delta T. Mine on Hot Water with maybe 60-70 Delta T. as per the video below from last year. Generally my 'Toy' typically runs 3 or 4 minutes at that sort of rate before slowing down as the Engine and Water reach closer to equilibrium Delta T as I don't run a seawater heat exchanger :box:

Not mathematical by any means but energy out LOX or similar maybe 200C Delta T and Burnt against Diesel maybe 1000C an a resulting energy output far in excess of just decompressing a liquefied gas without looking it up and knowing what burners are in use. Why try and fight what the Submarine case clearly doesn't use and back of a postage stamp non calculations can't make a sensible use case for  :-//

https://youtu.be/sV6oiuq3xKo
« Last Edit: March 10, 2019, 08:16:15 pm by beanflying »
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Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #39 on: March 11, 2019, 05:19:25 am »
You know you just made me think why has no one made a Sterling Engine powered by the heat from Nuclerar fuel.  Seems to me it would be perfect on a submarine,  I’m sure someone has done the math and realized other methods for utilizing the power from nuclear fuel is far more efficient.

This has been an interesting discussion, thank you.
 

Offline apis

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Re: Stirling Engine energy?
« Reply #40 on: March 11, 2019, 05:39:29 am »
Nuclear subs use turbines, which can be quite effective but they are also the main source of noise from the subs. So nuclear powered stirling engines might not be such a bad idea from a military perspective. A nuclear sub runs out of food before it runs out of nuclear fuel, so fuel efficiency isn't as important in that case. I think they just went with turbines for simplicity.
 

Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #41 on: March 11, 2019, 05:44:57 am »
Nuclear subs use turbines, which can be quite effective but they are also the main source of noise from the subs. So nuclear powered stirling engines might not be such a bad idea from a military perspective. A nuclear sub runs out of food before it runs out of nuclear fuel, so fuel efficiency isn't as important in that case. I think they just went with turbines for simplicity.

Can't nuclear subs run for 5 years before need to pull into a nuclear fueling station? 

It is quite impressive the amount of energy that's contained in nuclear fuel comparted to coal, gasoline, wood, solar and wind. 
I which I could remember the fact but I think 1 barrel of gasoline, (55 gallons) has the same amount of energy as four slaves working for a year.
 

Offline apis

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Re: Stirling Engine energy?
« Reply #42 on: March 11, 2019, 06:09:31 am »
 
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Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #43 on: March 11, 2019, 08:07:06 am »
That’s perfect.
 

Offline chickenHeadKnob

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Re: Stirling Engine energy?
« Reply #44 on: March 11, 2019, 11:01:47 am »
Nuclear subs use turbines, which can be quite effective but they are also the main source of noise from the subs. So nuclear powered stirling engines might not be such a bad idea from a military perspective. A nuclear sub runs out of food before it runs out of nuclear fuel, so fuel efficiency isn't as important in that case. I think they just went with turbines for simplicity.

Can't nuclear subs run for 5 years before need to pull into a nuclear fueling station? 

It is quite impressive the amount of energy that's contained in nuclear fuel comparted to coal, gasoline, wood, solar and wind. 
I which I could remember the fact but I think 1 barrel of gasoline, (55 gallons) has the same amount of energy as four slaves working for a year.

Virginia Class boats :
The VIRGINIA-class  reactor plant is designed to last the entire planned 33-year life of the ship without refueling .
  This will help to reduce life-cycle cost while increasing the time the ship is available to perform missions. 


https://www.energy.gov/sites/prod/files/2018/02/f49/nuclear_propulsion_program_8-30-2016%5B1%5D_0.pdf
 

Offline beanflying

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Re: Stirling Engine energy?
« Reply #45 on: March 11, 2019, 11:10:27 am »
Pump and Turbine noise is one of the problems with a Nuclear powered Sub they can be heard even when stationary as the pumps can't be stopped or KaBoom  :o The USA asked to have a proper look at the Swedish Sub after it got past their fleet. Even Australia's Diesel Electrics have got past the USA's fleet before due to the low noise during wargames.
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Offline DougSpindler

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Re: Stirling Engine energy?
« Reply #46 on: March 11, 2019, 11:26:03 am »
Nuclear subs use turbines, which can be quite effective but they are also the main source of noise from the subs. So nuclear powered stirling engines might not be such a bad idea from a military perspective. A nuclear sub runs out of food before it runs out of nuclear fuel, so fuel efficiency isn't as important in that case. I think they just went with turbines for simplicity.

Can't nuclear subs run for 5 years before need to pull into a nuclear fueling station? 

It is quite impressive the amount of energy that's contained in nuclear fuel comparted to coal, gasoline, wood, solar and wind. 
I which I could remember the fact but I think 1 barrel of gasoline, (55 gallons) has the same amount of energy as four slaves working for a year.

Virginia Class boats :
The VIRGINIA-class  reactor plant is designed to last the entire planned 33-year life of the ship without refueling .
  This will help to reduce life-cycle cost while increasing the time the ship is available to perform missions. 


https://www.energy.gov/sites/prod/files/2018/02/f49/nuclear_propulsion_program_8-30-2016%5B1%5D_0.pdf

Do they use energy saving devices like LED to get the 35 years?

And let's not forget the Soviets flew a couple of nuclear powered planes. 

« Last Edit: March 11, 2019, 02:16:18 pm by DougSpindler »
 

Offline jmelson

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Re: Stirling Engine energy?
« Reply #47 on: March 11, 2019, 02:29:32 pm »
You know you just made me think why has no one made a Sterling Engine powered by the heat from Nuclerar fuel.  Seems to me it would be perfect on a submarine,  I’m sure someone has done the math and realized other methods for utilizing the power from nuclear fuel is far more efficient.

This has been an interesting discussion, thank you.
Carnot engines have a loss from the vaporization of a working fluid.  This sets the maximum efficiency of the engine.  Stirling engines do not suffer this loss, but there is another loss from the mixing of hot-side and cold-side working fluid.  This also sets a max eff.
Well, the mixing loss of a Stirling engine is proportional to the temperature difference.  The vaporization loss in the Carnot cycle is NOT proportional to temp diff!  So, for low temp diff, Stirling can get greater efficiency.  But, when large temp difference is available, then the Carnot cycle pulls ahead.  If size and weight are not limited, you can follow a Carnot cycle with a Stirling cycle, which is now done in some steam power plants.

Jon
 

Offline duak

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Re: Stirling Engine energy?
« Reply #48 on: March 12, 2019, 10:10:44 am »
Jon, do you have any more info on Stirling engines following a turbine?  I had understood that steam turbines were the best at extracting energy at the tail end, however, this could be for larger systems.

Cheers,
 

Online IanB

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Re: Stirling Engine energy?
« Reply #49 on: March 12, 2019, 10:42:34 am »
Jon, do you have any more info on Stirling engines following a turbine?  I had understood that steam turbines were the best at extracting energy at the tail end, however, this could be for larger systems.

In a power plant the steam is expanded to the lowest pressure possible to extract the maximum energy from it, but at some point there is an economic limit--as the steam expands the volume naturally increases, which means the turbines have to get bigger and bigger, and there is a point where it is not economically viable to go any further. After the last turbine stage the steam gets condensed and recycled back to the boiler to go round again. Condensing the steam naturally produces waste heat which is dumped into the surrounding environment (river, sea, cooling tower...)

If possible, this waste heat can be used for other purposes. In the Middle East it may be used to run desalination plants to produce drinking water from seawater. In other places it may be used for agriculture, to heat greenhouses for example.

It is conceivable that the waste heat could be used to run a Sterling engine to extract a little more power. I have no knowledge of the economics of this, whether or how often it might make sense to do so.
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