EEVblog Electronics Community Forum
Electronics => Power/Renewable Energy/EV's => Topic started by: mgscheue on January 23, 2019, 04:17:28 pm
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This seems to somehow amplify sound energy without requiring any energy.https://www.forbes.com/sites/johnkoetsier/2019/01/18/this-dutch-startup-converts-heat-into-cold-via-a-stirling-engine-and-could-just-save-the-planet/ (https://www.forbes.com/sites/johnkoetsier/2019/01/18/this-dutch-startup-converts-heat-into-cold-via-a-stirling-engine-and-could-just-save-the-planet/)
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They're playing fast and loose with physics. Stirling engines produce heat through frictional losses. The only way it's going to produce *cold* is through using that Stirling engine to induce some form of evaporative cooling by compression / expansion, similar to a modern refrigeration system.
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They're playing fast and loose with physics. Stirling engines produce heat through frictional losses. The only way it's going to produce *cold* is through using that Stirling engine to induce some form of evaporative cooling by compression / expansion, similar to a modern refrigeration system.
No, unlike a Carnot cycle, a Stirling cycle is fully reversible. You can use it to extract mechanical energy from a heat source (that's a Stirling engine), or to pump heat up from a cold environment to a hotter one (that's a Stirling refrigerator). If you had some nice heat source, like a big solar collector, you could couple two Stirling machines together to make a refrigerator, without any evaporation going on. It is all done by changing the pressure on a gas such that heat flows in/out of the gas in certain environments.
Jon
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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.
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Well NASA managed to get plenty of power out of a Stirling engine in a Chevrolet Celebrity;
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880002196.pdf
Also used in submarines and with large solar mirror/dishes for power generation.
There is more to Stirling engines than the toy ones found on ePay.
David
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Stirling engines were used to pump water, at an iron foundry and to compress air for church organs. But steam was just more powerful and reliable and then along came small gas engines and electric motors. There are a couple applications where it might work, but why when one could use an electric motor? Far less moving parts and far more reliable.
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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.
Yes, Stirling machines that use atmosphere-pressure air as the working fluid are large. But, if you use pressurized Hydrogen or Helium as the working fluid, and allow the machine to run fairly fast, they can be quite compact. There is a Stirling solar power station in, i think, Arizona that has 50 KW Stirling engines mounted on each heliostat - by the hundreds. They are quite compact.
Sunpower built some really cutting-edge free-piston Stirling engines in the 1970's that were very compact. But, they didn't deal with the metallurgy properly, their engines had VERY short life.
Jon
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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.
Yes, Stirling machines that use atmosphere-pressure air as the working fluid are large. But, if you use pressurized Hydrogen or Helium as the working fluid, and allow the machine to run fairly fast, they can be quite compact. There is a Stirling solar power station in, i think, Arizona that has 50 KW Stirling engines mounted on each heliostat - by the hundreds. They are quite compact.
Sunpower built some really cutting-edge free-piston Stirling engines in the 1970's that were very compact. But, they didn't deal with the metallurgy properly, their engines had VERY short life.
Jon
Helium is a limited resource so unlikely that would be used.
Found the company in Az.
This is from 2001 or 18 years ago. And they had been working on it for 15 years. So after 30 years can one buy one?
Stirling Energy Systems, Phoenix, Ariz., has been developing solar dish systems for more than 15 years and is convinced the technology is "ready for mass deployment as soon as sufficient investment makes mass production possible." As with STM Power's 25 kW PowerUnit, then, the key is high-volume production to reduce costs. Stirling Energy Systems estimates the cost to produce electricity from a 1,000 MW solar dish installation would be about 6 cents/kWh. Whether this cost is accurate, and whether similar costs could be achieved in smaller installations, is uncertain.
On 29 September 2011, Stirling Energy Systems filed for Chapter 7 bankruptcy as the Stirling dish technology could not compete against the falling costs of solar photovoltaics, according to media reports.
Just as 200 years ago Stirling engines lost out to steam and electric motors it appears history repeated itself with Stirling engines once again just not being cost effective enough.
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This looks like it is not based on a "Sterling Engine" effect.
It is more like a "Thermo-Acoustic-Engine", as developed in the Los Alamos laboratories.
The only problem they did not solve, was the stack.
Otherwise this engine would probably be running already.
May be this Dutch company solved it?
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On 29 September 2011, Stirling Energy Systems filed for Chapter 7 bankruptcy as the Stirling dish technology could not compete against the falling costs of solar photovoltaics, according to media reports.
Just as 200 years ago Stirling engines lost out to steam and electric motors it appears history repeated itself with Stirling engines once again just not being cost effective enough.
Yep, same old. Good for toys but impractical in the real world.
Everyone is always looking for the magic bullet and to hype up the under dog. I love all this old tech, don't get me wrong. I have a 300Kg toy in the form of a Lister Cs6/1 from the 30's but I'm not under any illusion heavy flywheel slow speed Diesel tech could be made to break land speed records.
As far back as I can remember going to the libary after school as a kid and reading Popular Mechanics and other auto magazines I have read of hundreds of " New breakthrough engine technology that could offer new levels of efficency, performance, economy and power" .
There have been allsorts of weird and Wonderful designs and hyped up promises but none of them, bar mabe 1, the rotary, has ever made it into production. There have been a few that had a limited run like the commer knocker with opposing pistons and the Napier Deltic used in rail road engines with great success but as far as vehicles go..... Nada.... bar the rotary. Which is now dead. Even the knocker and the deltic were just really re configurations of engines with pistons thrashing up and down the same as a Model T or even an Aveling Porter traction engine.
I think some people just have a need and desperation for something to bring hope to their lives and look forward to and will latch onto something and want so badly for it to become a success they get obsessed. There are a lot of engine designs that could be efficent and powerful and light weight and many other things BUT, cost of production, service life, maintence requirements, emissions and a load of other factors are all even more relevant and may make a design or technology unsuitable for the mainstream whether they work or not.
I just turn off when I hear about these new engine breakthroughs now. heard about too many that were nothing more than a PR exercise to raise money for investors to keep inventors and researchers in a job.
When I can see the engine in a showroom sitting in a new vehicle or go down the road and buy one on it's own or in a new piece of equipment , I'll give it some credibility.
Untill such time, it's just more vaporware.
With things like sterling engines, once they are installed in working applications ( other than space which is irrelevant) they will just be interesting tech that isn't practical in the modern age.
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Waffle Waffle Waffle .... With things like sterling engines, once they are installed in working applications ( other than space which is irrelevant) they will just be interesting tech that isn't practical in the modern age.
You really are full of something aren't you. :wtf: You are being negative here and like your climate waffle anti science you spout on the modern use of Stirling Engines denying Science yet again.
Clearly the Swedish should have employed you to tell them where they went wrong on their Submarines https://en.wikipedia.org/wiki/Gotland-class_submarine before they snuck up on the Yanks in war games using your non credible device.
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According to the link you posted the Sterling engines in submarines need a supply of liquid oxygen to work and a large body of water to work. While this might work for submarines wee are not seeing it be used in ships, cars, airplanes or in factories. I don”t think anyone has said Sterling engines do. Not work, we are just saying there are very few applications for them. Clearly you he need for liquid oxygen limits there application.
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According to the link you posted the Sterling engines in submarines need a supply of liquid oxygen to work and a large body of water to work. While this might work for submarines wee are not seeing it be used in ships, cars, airplanes or in factories. I don”t think anyone has said Sterling engines do. Not work, we are just saying there are very few applications for them. Clearly you he need for liquid oxygen limits there application.
The idea of this submarine is to run underwater with no supply from the surface. So, if you can't suck air from the surface with a snorkel, you have to have a tank of oxidizer to burn your fuel with. That is why they need liquid Oxygen. It is just like a rocket, no air in outer space, so you have to carry some oxidizer in tanks.
No other Stirling engine needs this, they just need a heat source.
Jon
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According to the link you posted the Sterling engines in submarines need a supply of liquid oxygen to work and a large body of water to work. While this might work for submarines wee are not seeing it be used in ships, cars, airplanes or in factories. I don”t think anyone has said Sterling engines do. Not work, we are just saying there are very few applications for them. Clearly you he need for liquid oxygen limits there application.
The idea of this submarine is to run underwater with no supply from the surface. So, if you can't suck air from the surface with a snorkel, you have to have a tank of oxidizer to burn your fuel with. That is why they need liquid Oxygen. It is just like a rocket, no air in outer space, so you have to carry some oxidizer in tanks.
No other Stirling engine needs this, they just need a heat source.
Jon
Not the way I understand it. Seems silly to use liquid oxygen, when they could use a solid source like in airplanes for emergency breathing systems.
It was my understanding the liquid oxygen is used as a coolant for the Sterling Engine. Maybe it is used as both an oxidizer and a coolant?
Guess what I'm not understanding is why an oxidizer is needed with a Sterling engine.
Help me out here, what am I missing.
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Some more reading here. The Sub in question has a hybrid drive system. The Stirling Engine / Generator set still need Oxygen while submerged to Burn Fuel. The principal advantage of the Stirling design is it doesn't make anywhere near the noise of more conventional Diesel/Electric subs while submerged.
https://en.wikipedia.org/wiki/Air-independent_propulsion
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You really are full of something aren't you. :wtf: You are being negative here and like your climate waffle anti science you spout on the modern use of Stirling Engines denying Science yet again.
Yeah, Fk me for not just going along blindly with all the other sheeple believing every bit of crap I am told and asking questions and finding answers that do not add up to what all the other morons blindly follow. I'm suce a trouble maker for having a mind of my own snd showing up all the bullshit that's heaped on the general public by big Biz and their Puppet Gubbermints.
I mean if you can't trust the gubbermint who can you trust Right?
Clearly the Swedish should have employed you to tell them where they went wrong on their Submarines https://en.wikipedia.org/wiki/Gotland-class_submarine before they snuck up on the Yanks in war games using your non credible device.
I stand corrected.
Sterling engines are teh be all and end all of everything we need to solve the energy Crisis.
That's why they are planned to be in every Vehicle, aircraft, generator, water pump and small and industrial application out there.
You read about it all the time, Sterling engines are the next big thing going to do away with ICE, electric and every other type of power plant in the next 6 months. All forms of Motorsport and racing are getting ready to re write the recod books once sterling engines come into play.
It's not just specialist applications in the modern world they are suited for like space craft and Military applications where cost is not an issue, oh no, these things are going to be powering everything from your weed wacker to Gigawatt power stations by Christmas.
Please forgive my confusion, I just don't know which flavour of zealot cult Koolaide I am suppose to quaff down next these days!! :-[
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Avoiding yet again the unfortunate fact that this technology works and has practical applications with your waffle. No one said it is a magic solution for all things and only you seem to think it was ever the case to allow you an apparent point to rant about.
I will leave you believing in alternate facts, non engineering and pseudo science as you seem happy ranting and raving about it's powerful and beautiful nature and obvious truths. :-DD
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"It takes 100% of stack-emitted waste energy, or solar thermal ... and converts that for 40-50% [efficiency]."
It's a refrigerator which runs on a heat differential, just like say a gas powered camper fridges.
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Some more reading here. The Sub in question has a hybrid drive system. The Stirling Engine / Generator set still need Oxygen while submerged to Burn Fuel. The principal advantage of the Stirling design is it doesn't make anywhere near the noise of more conventional Diesel/Electric subs while submerged.
https://en.wikipedia.org/wiki/Air-independent_propulsion
Thank you for sharing this. Wikipedia says the liquid O2 and diesel are burned to provide power. Not sure where the exhaust gases go.
Sterling powered subs are apparently stealthier than nuclear subs. But that stealth comes at a high cost. Limited range, and high cost for power.
There are defiantly one off unique applications for Sterling engines and this appears to be one of them. I know of a couple of unique novel applications for Sterling engines.
Would it be safe to say the reason Sterling Engines are not is wide spread use is we have found other technologies over the past 150 years which are less expensive and provide far more power?
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The idea of this submarine is to run underwater with no supply from the surface. So, if you can't suck air from the surface with a snorkel, you have to have a tank of oxidizer to burn your fuel with. That is why they need liquid Oxygen. It is just like a rocket, no air in outer space, so you have to carry some oxidizer in tanks.
No other Stirling engine needs this, they just need a heat source.
Jon
Yup. The goal is to stay under water for a long time so you need to bring with you both oxidiser and fuel. You would need that for a diesel motor as well.
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The idea of this submarine is to run underwater with no supply from the surface. So, if you can't suck air from the surface with a snorkel, you have to have a tank of oxidizer to burn your fuel with. That is why they need liquid Oxygen. It is just like a rocket, no air in outer space, so you have to carry some oxidizer in tanks.
No other Stirling engine needs this, they just need a heat source.
Jon
Yup. The goal is to stay under water for a long time so you need to bring with you both oxidiser and fuel. You would need that for a diesel motor as well.
Correct me if wrong but would just the liquid O2 run the Sterling engine without the need to burn it? Wouldn't the temperature differential between liquid O2 and seawater be enough to power the engine?
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There are defiantly one off unique applications for Sterling engines and this appears to be one of them. I know of a couple of unique novel applications for Sterling engines.
Would it be safe to say the reason Sterling Engines are not is wide spread use is we have found other technologies over the past 150 years which are less expensive and provide far more power?
Being able to recharge the batteries on a sub to keep the occupants alive and not found with some motive power for a few weeks is better than limited.
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.
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The idea of this submarine is to run underwater with no supply from the surface. So, if you can't suck air from the surface with a snorkel, you have to have a tank of oxidizer to burn your fuel with. That is why they need liquid Oxygen. It is just like a rocket, no air in outer space, so you have to carry some oxidizer in tanks.
No other Stirling engine needs this, they just need a heat source.
Jon
Yup. The goal is to stay under water for a long time so you need to bring with you both oxidiser and fuel. You would need that for a diesel motor as well.
Correct me if wrong but would just the liquid O2 run the Sterling engine without the need to burn it? Wouldn't the temperature differential between liquid O2 and seawater be enough to power the engine?
In theory at least, but it would be insignificant amount of energy compared to the chemical energy you can get by burning it.
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It was my understanding the liquid oxygen is used as a coolant for the Sterling Engine. Maybe it is used as both an oxidizer and a coolant?
Guess what I'm not understanding is why an oxidizer is needed with a Sterling engine.
Help me out here, what am I missing.
Correct me if wrong but would just the liquid O2 run the Sterling engine without the need to burn it? Wouldn't the temperature differential between liquid O2 and seawater be enough to power the engine?
Not at all. You are missing the fact that engines are energy converters. They convert a non-mechanical form of energy (heat, electricity) into mechanical energy by the equation:
(power in) = (power out) + (losses)
The amount of power produced by vaporizing liquid oxygen is negligible compared to the amount of power available by burning a fuel.
A Sterling engine does not convert a temperature difference into power, it converts heat energy into power.
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In theory at least, but it would be insignificant amount of energy compared to the chemical energy you can get by burning it.
Correct it is all about Delta T and energy density of the complete fuel available. With Air breathing engines we ignore the Oxygen as part of that equation. Using LOX alone and simply expanding it to produce gas for a piston and scavenge the waste cold in this case would be far less efficient than burning it with a fuel you are already carrying in the case of the Diesel for the Subs main engines.
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It's a military application..... I don't think the military would care about efficiency as long as it provided an advantage.
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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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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.
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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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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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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.
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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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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.
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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?
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
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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?
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?
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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.
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.
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).
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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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.
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.
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).
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
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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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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
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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.
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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.
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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.
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(https://imgs.xkcd.com/comics/log_scale_2x.png)
https://xkcd.com/1162/ (https://xkcd.com/1162/)
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That’s perfect.
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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 (https://www.energy.gov/sites/prod/files/2018/02/f49/nuclear_propulsion_program_8-30-2016%5B1%5D_0.pdf)
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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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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 (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.
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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
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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,
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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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Do they use energy saving devices like LED to get the 35 years?
Umm, after propelling a 100 meter boat at 30+ knots underwater, the power used in lighting is going to be MICROSCOPIC in comparison.
Jon
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I found this article in an old edition of Popular Science by accident last night when searching for something else.
https://books.google.co.uk/books?id=sgAAAAAAMBAJ&lpg=PP1&lr&pg=PA54#v=onepage&q&f=false (https://books.google.co.uk/books?id=sgAAAAAAMBAJ&lpg=PP1&lr&pg=PA54#v=onepage&q&f=false)
I noticed "Philips Stirling cycle" on the front cover and was expecting something about the small generator they made, but was surprised the article was actually about a 4 cylinder 200HP engine for a bus/coach, the heat is provided by burning gas & the speed being controlled by regulating the pressure of the helium inside and like the submarine Stirling engine is quieter than using an internal combustion engine too.
Helium is a limited resource so unlikely that would be used.
The increasing price of helium may be one reason why these engines aren't more common. Helium is vital for things like MRI scanners too, but as the local supermarket started selling small helium cylinders last year for wasting in balloons it can't be rare enough yet.
David
Edit:
Apparently the coach still exists but wasn't as reliable for road use as the magazine article suggests, the Philips Stirling engine got replaced with a 6 cylinder DAF diesel.
http://www.curbsideclassic.com/bus-stop-classic/bus-stop-classic-1970-daf-jonckheere-its-first-power-unit-was-a-philips-stirling-engine/ (http://www.curbsideclassic.com/bus-stop-classic/bus-stop-classic-1970-daf-jonckheere-its-first-power-unit-was-a-philips-stirling-engine/)
More Stirling engines in road vehicles & boats here;
http://stirlingengineforum.com/viewtopic.php?t=1618 (http://stirlingengineforum.com/viewtopic.php?t=1618)
Found a company making 1-5kW piston free Stirling engine;
https://www.qnergy.com/ (https://www.qnergy.com/)
David
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Qnergy only has 20% electrical output, it's only really useful for waste heat or to use when you are just straight burning fuel for heat any way, to get some electrical power as a bonus. Free piston combustion generators can achieve 50% electrical efficiency.