NEW CAR $12,700. New Motor. I want one for my boat!

That's wonderful,but can you smoke it and get ripped?

 

If someone built a compressed air outboard based on this engine, how large and heavy would the compressed air tank have to be to equal the energy stored in a 5-gallon gas tank?

 

At 300 bars or 4,300psi air has an energy content of .2MJ/L
Standard gas has an energy density of 38.6 MJ/L

38.6/.2 = 193

So a five gallon jug of gas would take roughly 965 gallons of compressed air. Which would be completely unreasonable.

In this application though you only need to store enough air for one days operating, since the primary storage medium is actually the diesel stored in the mother ships fuel tanks. Which means you only need around 5 gallons of diesel to equate to the 5 gallons of gas. Obviously there are some limitations on the system, but also some advantages, like not having to have gas on board, deal with storage, ect...

I have been a long time detractor from most alternative energy powered ideas on this forum since I don't see any practical use for them, but this seems to have possibilities. At least for dingies on mother ships that already have diesel generators, and air compressors.

 

It IS interesting to me too!

 

Thanks Stumble.

The application then would be a skiff with a 1 or 2 hp air-outboard?

The van in post 1 has 680 liters of compressed air storage. Dividing by 193, that van would have only 3.5 liters of gas or less than 1 gallon of gas storage if it ran on gas?

 

I'm not sure you can compare to an internal combustion engine and its fuel. Compressed air is more similar to steam, and a lesser degree electric. Air, steam, and electric can apply static torque when stopped. ICEs cannot.

 

If you compared the stored air to how much steam volumne at 4300 psi you could generate with 5 gals of diesel or gasoline...might be a usable comparison.

 

So, we take one pound of water from 60 to 212 degrees and it takes 152 Btu’s. (212 - 60 = 152)
To convert one pound of water from 212 degrees water to 212 degree steam (still one pound by weight) at atmospheric pressure takes another 970 Btu’s. If we contain all of this, as in a boiler, we get a pressure differential (inside vs. outside). That pound of water, at 212 degrees, had occupied only .2 cubic feet. The steam at 212 degrees and at atmospheric pressure (or 14.7 lbs. per square inch) will occupy 27 cubic feet.

http://www.backwoodshome.com/articles/goebel43.html

 

I think the issue here is the difference between available energy, which is what I calculated, and the system's effiency which is what really matters. Gas engines has a realistic 25% efficiency rating, that is they convert 25% of the input energy from fuel into useful power. Steam engines are at around 40%, excluding turbines which seem unacceptable for other reasons. I know nothing about this engine, but I would guess it falls somewhere in between the two.

To me the advantages of this engine however are not efficiency, but fuel availability and ease of use. When I was sitting on the hook in Las Aves for a month, we quickly ran out of gas, but still had significant diesel fuel. So had this engine been available we could have just charged the tank off of our scuba compressor and been fine.

Secondly I hate the idea of storing gas on board a boat. It is flammable, and potentially explosive, and requires a number of specialty procedures to handle safely. Plus refueling small boats from gas cans always results in discharging at least some into the water.

To me this system addresses those problems, even at lower overall efficiency numbers. Since it removes an objectionable material from boats entirely. Assuming it works well enough to give a few mile range for a small outboard it may be a realistic option for cruising boats.

 

I'm not a marine engineer or any other engineer.
I know comparing ICEs to electric motors is like trying to compare apples to oranges. Steam gets even weirder! Compressed air? Where is it's niche? I don't know. I wasn't criticizing your post or your ideas. I'd like to learn.
I'm just wondering if now we're comparing apples to bananas?

I don't want gasoline aboard either!

 

I carry a minimum of one extra gallon of gas in case I need it. Can you have enough compressed-air on a skiff for safety?

 

I don't know yet.
It is a new twist on old technology. I started the thread because I want to learn more. I'm researching but there is little yet available except whats already posted. By instinct tells me it will be similar to steam except cold, and stored pressure instead of created pressure. Therefore limited range. I'm more inclined to think it will be competitive with battery'electric power. Since batteries store rather than generate

 

Me too. Safe and clean is worth looking at if it's enough to power a skiff.
Comparing air to battery weight and power would be interesting.

 

More power with a farther-fetched http://www.boatdesign.net/forums/propulsion/liquid-air-engine-41464.html#post523018?

 

BPL,

I tend to Cary extra gass too, the question though is how much? If my expected trip is 1 mile, then an extra 2 miles worth of fuel is probably enough for near shore use. In a small dingy, that may equate to pint of gas. My guess is that a scuba tank would run this engine just fine, for around 1 gallons equivalent. Perhaps not, and I am truely guessing. In this case a second scuba tank would be pretty easy to bring along.

The liquid air engine requires a whole host of support equipment I just don't see available on a cruising boat, perhaps it would work in place of a large hp fishing boat or ski boat though. Until I see some equivalents I can't begin to guess.

Batteries just don't work. They take too long, and the energy density is crap. It takes around 600lbs of batteries to replace 1 gallon of gass.