Green boating?

[LondonRascal]

This is going to sound like some sort of bonkers Victorian idea that was patented, tried and failed...Like moving a train through a tunnel through the use of vacuum.

 

Anyway...I was thinking about how one might power something to basically turn a propeller.  You need either something to cause an explosion to turn an engine, or something to store power and let it go (could be batteries – even a rubber band).

 

Anyway I’ve got the solution – Compressed air power.

 

Yep that is it - problem sorted green boated solved in a puff of air...Ok, now you’ve stopped laughing think about this.  A boat unlike a car for example, has rather a lot of space inside it (depending on the boat of course) and while some of this is used for the fuel and water tanks, they are more often than not put down the sides of the boat to equal weight and be kept pout of the way under the side decks.  Batteries might be anywhere from under the seat in the saloon, to outside under a hatch at the stern.

 

Take away the fuel tank and use the space for an air tank - then utilise space under beds, loose a few drawers and the like here and there and your capity will grow.

 

The air is compressed – but not volatile - and would need a hell of a crash to ‘go up like a bomb’ although on a smaller scale commercial vehicles and trains have tanks (though capacity smaller) for their brakes etc. 

 

All the bits you need are right there ‘off the shelf’ no special manufacturing required.  Sure the air tanks would need to be larger and so that would cost more but the principal is easy.  You can then have 'recharge' points along the rivers – basically an air line and compressor. Onboard you can have a couple of extra batteries and a smaller compressor as a sort of ‘emergency backup’.

 

The compressed air can then be injected into an engines cylinders – instead of the explosion of expanding gases (petrol or diesel) driving the engine, the compressed air would be doing it.  Especially with a diesel engine where the PSI of the injected fuel is already very high I recon that would work just find if that was injected air.  (This is not I might add my invention I am pretty sure  compressed air engines have already been thought up).

 

But you get the point that with a boat at a far more constantly speed and load, more space to store more compressed air and river side air recharge points and the only actual thing coming out of the ‘exhaust’ would be – air. The engine would do all that it currently does, recharge domestic batteries and power the boat along the water.

 

Of course there is the cost of installing the recharge points, and electricity to power them – that could be bought from renewable suppliers to keep the green lobby happy – and while it might take longer to ‘recharge’ the air tank than fill a fuel tank it would be a damn sight faster than recharging batteries!

[Guest]

I'm afraid the amount of energy that can be stored as air pressure in tanks would only drive the average 20hp boat engine a few yards !

 

 

I use a portable compressor set in my garage for paint spraying and with a variety of air driven tools, socket wrenches, sanders and metal shears.

 

The receiver tank, like most, is only certified up to a running pressure of 150 psi, (with a safety margin above that). 

 

The average diesel engine compression PSI is 400 and upwards.

 

When using any of the tools or spraying, the automatic pressure switch cuts the 3hp electric motor in after only a few seconds, because the volume in the 3 cu ft tank is depleted very rapidly even with just small hand tools and spray guns.

 

If you tried to get around 20 hp of boat engine power out of compressed air, you would need either a receiver tank the size of a blimp, or you would need to store the air at thousands of PSI.

 

Also, although compressed air is not volatile in itself, when stored in a rigid container it has the same explosive power as a bomb if ruptured, even at only 150 psi. It has often killed.

 

The thought of a boat with high pressure air tanks tucked away inside the accommodation space, together with the various high pressure pipes and connections is frightening ! 

[LondonRascal]

Well, annoyingly the French don't just help make blue engines for Broads boats - they have made a car that runs on compressed air - and this was in 2003!

 

http://www.youtube.com/watch?v=WSq6vb3ztWQ

[Guest]

Yes, another interesting video, (shame about the background music !)   

Quite clever the way they use an extra piston to make use of the car's kinetic energy to initially draw the air in.

A 100km range from a 4500 psi air tank for a very lightweight car.

That's a phenominally high pressure, even Diver's compressed air tanks are less than that.

Wikipedia has chapter and verse on compressed air cars at http://en.wikipedia.org/wiki/Compressed_air_car

As you say, they've been around for over 10 years now, with no market penetration, and few interested developers.

[Hockham Admiral]

The Shorts Belfast I used to fly had a 4000psi hydraulic system and we pressurised the accumulators with Nitrogen (at 4000psi). The Nitrogen came in the heaviest and strongest cylinders you can imagine!

The sheer size and weight which would be necessary would actually probably help a Broads Cruiser by lowering its air-height significantly!