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cheses t1_iulkbl2 wrote

Reply to comment by TheNoobsauce1337 in Engineering question: With today's material sciences, why don't ocean liners use pressurized steam to power electric engines? by [deleted]

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.

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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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