Steam power

You should take a good marine engineering course on total plant design. Go read the First Chapter of Marine Engineering by SNAME then go seek out advancements in regeneration lately. For modern similar 30,000 SHP plants, both steam and direct coupled diesel have overall consumption rates of ~0.4 lb/shp-hr. Thermal efficiency of a modern marine steam plant is ~ 35-40% depending on reheat. The 50% thermal efficiency you quote is only the main engine fuel and not total fuel or oil consumption. This is because with the steam plant you get all the other stuff, TG's and pumps, for "free" where a LDS powered vessel has lube oil consumption and needs to run DG sets while only getting minimal waste heat offsets due to stack gas temp issues.

Really, it's a manning and layup economics issue, not an at sea fuel consumption one. And if total thermal efficiency was you goal, we would all be running nuclear plants or multiple small GT-electric systems.

 

Well now that's just rubbish. Show me a ship steam plant that can match diesel for tons of fuel consumed, and the same output. You can't.

And no, total thermal efficiency isn't the goal - profit is (efficiency is just conducive to profit). Nuclear and gas turbines are (currently) too expensive to be the best choice in most cases, except for the military.

 

For folks that pay the fuel bill, efficiency is FREE fuel.

Steam can use free fuel, diesels can not.

 

While that is not 100% true, as diesels can run on some waste oils, which could potentially be free, the dependability of the engine usually suffers, where a steam system won't.

The nice thing about steam, is that they can run on many many fuels, without much risk or major modifications.

Coal is cheap, sometimes wood is as well.
Heavy fuel oil could also work, if you could find a venue to purchase it from.

 

well if you like to tinker with machinery, you could build yourself a fairly compact steam driven boat that uses not just multiple fuels, but could also burn wood or coal, or even waste paper. with a few more processing stepss, you could even burn waste plastic with little to no pollution.

That would be an interesting idea in fact, most municipalities fill the limited landfill space with plastic packageing and bottles. You could use that to power a steam power plant, and get all your plastics for free, some cities might even pay to haul it off. The problem with that is however, it would take up a lot of space in the boat. Even so, if you were doing it as a "demonstration" yacht for personal live aboard pleasure boat, getting paid to pick up your "fuel" might be worth taking up a lot of space in the hull.

 

This is true...
Our landfill even burns branches and wood, a guy could buy a wood chipper and make thousands of pounds of fuel for cheap.
Run wood, plastic, paper, etc all through the wood chipper, and use a hopper / auger system to transfer fuel, then you could also use coal too.

Make a gasification stove and heat a stainless steel coil to flash steam power the thing.

https://www.youtube.com/watch?v=msOH1M8ulxQ

Instead of exhausting the steam out a stack or vent, pipe it into a tank. Have a cooling coil in the tank piped with an electric motor and thermostat. When the temperature reaches a certain level, the pump turns on enough to cause the steam to condense, and thus lowers the temperature just enough to not waste energy heating it more than necessary.

 

Mu dream ride was always a Motorcycle with the steam power plant (boiler) in a sidecar.

As a steam engine makes its best torque at close to 0RPM, think of the acceleration!

The Harley louts would not be impresses with the sound of silence tho.

 

The only noise would be from the thousands of confused and angry and hungry seagulls that would always be around, looking for fries and never getting fries but always smelling the fries.

 

Reminiscent of Jules Verne era. That would be a real showstopper.

 

I don't understand, all nuclear power plants use steam turbines to generate power.