It's a military application..... I don't think the military would care about efficiency as long as it provided an advantage.
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.
It's a military application..... I don't think the military would care about efficiency as long as it provided an advantage.
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.
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.
It was my understanding the liquid oxygen is used as a coolant for the Sterling Engine.
Guess what I'm not understanding is why an oxidizer is needed with a Sterling engine.
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?QuoteGuess 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?
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.QuoteSterling 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.QuoteI 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).QuoteBut 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.
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.
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.
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.
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
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.
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.