gray_sky_guy t1_iulhvnf wrote
Steam isn't an energy source. You need an energy source to boil the water to make the steam. That could be coal, or gas, or oil, or wood, or something else you can burn. Or you can use nuclear energy to create the heat. either way you cant just have water, then convert it to steam magically, then power the ship.
TheNoobsauce1337 t1_iulimzn wrote
Couldn't you use electricity? Basically a system that uses the wires to heat the inside or outside of the tanks (like a space heater) with a startup battery configuration, which the generators can then recharge once the steam gets pressurized and flowing?
Not asking this passive aggressively. As I understand it, so long as you have sufficient power storage on hand, you could heat a boiler with electricity.
Even better, so long as the ship remains immersed in water, just keep the steam flowing once the initial heat systems have been up and running, and let the excess steam bleed off into the atmosphere once all necessary power storage systems are charged.
There's a previous comment here where I mentioned my thought process better. But that would be the gist of it.
I would think that it's possible, especially on cargo ships with extra space.
Mhgglmmr t1_iulj17w wrote
If you have enough electrical power on board already (generated by what exactly?), why would you use that to generate steam to power a turbine to turn generator to generate electricity for an electric motor? Just run the electric motor directly.
TheNoobsauce1337 t1_iulk00d wrote
This is my thought process:
Pre-charged startup batteries to begin boiling process with water brought in from the ocean.
Water begins to boil and is replenished from the ocean periodically.
Steam held at high pressure turns generators that sustain a constant flow of power.
Constant flow of power powers electric engines, boilers and backup batteries. Also recharges startup batteries in case the entire system needs to be restarted.
Engine and boilers relies primarily on generators at this point, which rely on periodic refills from the ocean (though battery backups are installed if something fails).
Basically a self-sustaining reaction so long as the system is started once.
Am I crazy for this? I can see it working, but I haven't built a test model to see if it would actually work.
thegagis t1_iulleq3 wrote
Boiling stops immediately if you stop making the boiling happen with heat. Water boils if and only if you dump a lot of energy into it somehow. It does not produce free energy from nothing.
TheNoobsauce1337 t1_iulltb8 wrote
But that's the thing. Part of the electricity in the generators would be re-routed back to the boilers to maintain the heat. Would that be possible?
Basically the water is constantly boiling, the generators have two circuits. The larger circuit powers the engine, the smaller circuit maintains heat in the boilers.
Would that be possible?
SLR_ZA t1_iulm949 wrote
No, you cannot power a generator with steam then take part of that energy to make as much steam as powered the generator.
You require more energy to make the steam than you can recover from the steam max.
Cut out the electric generator and just imagine boiling water with steam to make steam.
You're trying to do that and get more steam out than went in plus enough to overcome the turbine and battery efficiency and have usable power left over for the ship
TheNoobsauce1337 t1_iulmgzn wrote
Ahh I see.
Believe it or not, I wasn't posting this to troll. I legit had a scientific question and wanted to test the idea out with other like minds.
Contrary to what you see on today's internet, I actually appreciate the criticism. Bouncing ideas back and forth (pending real experimentation) is what I think makes science both great and important. Seeking out truth through hypothesis and experimentation.
TheDawggFather t1_iulqdch wrote
This curiosity you have is great! However, It seems you might be operating without fully understanding some fundamental physical concepts. If your really interested in these kinds of things, im sure you would enjoy taking some time to learn more physics and engineering. I know that YouTube has some awesome video lectures and I've heard good things about Brilliant.com. I hope this helps, never stop being curious and asking questions! 👍
TheNoobsauce1337 t1_iuls1mm wrote
Will do. Definitely need to brush up on my Physics.
dudius7 t1_iulm9q2 wrote
No it would not be possible. You're talking about something like a perpetual motion machine.
If you used a battery to power an internal colandria to generate steam, then used that steam to power a turbine, you would have energy losses. Those losses would prevent you from recharging the battery, powering the colandria, and propelling the ship.
gray_sky_guy t1_iuliqcu wrote
same issue, where's the electric energy come from? a battery? cool, how did you charge it?
TheNoobsauce1337 t1_iulitxh wrote
Charged on land initially upon install, then charged by the generators on the ship once the process gets rolling.
gray_sky_guy t1_iulj54s wrote
so to charge it on land you need some other source of energy. if you're just trying to use the steam as a weird kind of battery, then you'd have to look at energy density of steam, and also consider how well you could insulate the thing. you're probably not gonna get across an ocean with stored steam energy.
for the generators on board, again, how are they generating the electricity? it doesn't come from nowhere
(i'm just gonna ignore the fact that it makes way more sense to use the electrical power you have stored to directly drive an electric motor that drives the propeller)
TheNoobsauce1337 t1_iulkk3z wrote
That's basically the idea. Use water from the ocean to periodically refill the boilers (since water below the waterline automatically generates a positive pressure towards the inside of the ship).
Basically think of it like this:
Water replenished periodically from outside > Boilers > Steam > Generators > Engines and boilers on separate circuits > Process repeats so long as you can keep replenishing water from the ocean into the boilers that are already heated.
The key thing would be to build generators that could generate enough electricity to maintain the heating of the boilers and run the engines simultaneously.
The volume of water in the ocean would be the source of power, provided you could generate enough electricity to keep the water boiling to keep the generators running.
A self-sustaining reaction once started.
Does that make sense? I feel like people keep thinking about this like a Tesla that has to be recharged with a cord. It's not that.
thegagis t1_iullan1 wrote
Its nowhere near self sustaining.
Turning water into steam USES absolutely massive amounts of energy. You need to constantly produce amazing amounts of heat to be able to do that.
Replenishing the water is not an issue, you can just direct the condensed water from the steam cooling back down back to the system.
This is how power plants work. They burn some fuel or run a nuclear reactor to convert massive amounts of energy into heat to heat water which turns into steam and that steam rotates a turbine with its pressure and the turbine rotates a generator.
Steam is not a source of energy, it is a local temporary storage for energy.
TheNoobsauce1337 t1_iullo5z wrote
Makes sense. So the amount of electricity to maintain a boiling temperature would be unrealistic with today's generator technology?
Again, not saying this to troll or be passive aggressive. Literally throwing an idea out in front of other scientific minds and seeing what they have to say and critique.
The water would be the source of the energy. Steam would just be a conversion to transfer that energy to a generator that could then keep the boilers AND engine running.
Basically two primary circuits: 80-90% of the electricity goes to the engine, 20-10% goes back to the boilers to keep the water boiling and steam incoming, reduced to high pressure for high RPMs on the generator.
Not possible or feasible then?
thegagis t1_iulmo3x wrote
Its unrealistic with physics. If entropy was not a thing, you could at best get exactly as much energy back as you used to boil the water with. In reality some of the energy is always wasted and depending on how good your generator is you get some % below 100% out as electricity.
Water is simply not a source of energy. Boiling water requires more energy than you can get by using the pressure of boiled water to drive a generator. Steam is just a way to move that energy from point A to point B.
SLR_ZA t1_iulmsij wrote
No, it's possible to boil the water to make steam
It is impossible to recover nearly as much energy from that that steam as it would take to boil it.
It's not a 'today's technology' thing it's a law of thermodynamics thing.
Water is not a source of energy, it is a medium of energy transfer.
Every kg of water at boiling point being converted to steam takes say 2133 kJ of energy.
You cannot then power a generator with that steam and get more than 2133 kJ of energy out of it. Your actual efficiency of a steam generator is 10-40%
So now you have 2133 x 0.4 = 853 kJ of electric energy.
So you take 20% to the boiler and you have 170 kJ of energy. Which is not enough to boil a kg of water.
Even if you had an impossible 100% efficiency boiler, steam system, turbine and battery system you'd never be able to pull even 1 kJ out without decreasing your steam volume.
MidnightAdventurer t1_iulk0q4 wrote
If you could get enough electricity storage on ship to heat steam to power the engines then why not just use the electricity to run the ship directly? It will be far more efficient that way both because you're not transferring energy from one form to another and back and you don't need to carry all the weight of the water, turbines, generators etc
cheses t1_iulkbl2 wrote
Ok, you want to charge the ship via a landline and when it is away from the harbor, it only runs on its thermal batteries so to speak? We could do the math, but there are two problems: you would need huge storages for the energy (it does not matter if you store the energy in batteries or as steam).
Ok I do the math quick and dirty: A big ship has an engine with 37 MW (megawatt) power (Jahre Viking). You can store 0,2 kWh (kilowatt) per kilo steam (at 100 bar at 500 °C), which means you would need 185 tons of steam an hour to drive your ship. When you are like four weeks at sea, you need 124.000 tons of storage for your steam.
TheNoobsauce1337 t1_iull8yx wrote
Almost, but not exactly.
Basically create a self-sustaining reaction where once you get enough water boiling, you can pressurize the steam to turn a series of generators and then have those generators power both the boilers and the engine. So long as you have a way of replenishing the water in the tanks, steam is constantly being generated and pressurized to where it can make the generators spin at very high RPMs, and then the system just works round-the clock. Basically see if you can create a system where, say, 80-90% of the power goes to the engines, and 20-10% of that power goes to maintaining the heat of the boilers. Water can be added without the need for a pump using the ship's weight and opening valves from pipes beneath the water line, or pumps that don't need as much suction because of that principle.
Basically the water is the power source converted into a form of energy that's more easily pressurized.
It is interesting reading the reactions, though. In my mind this is part of what science is all about -- someone presents an idea, then a bunch of counter-ideas based on learning and experience are presented.
I really do appreciate the feedback. Just wanted to see what people thought and what the limitations would be.
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