Highly efficient vehicles

[ehwatt]

In the 70 and 80's there was much activity around air, hydrogen, CH4(natural gas/methane), propane, steam, wood, even batteries and solar.
It was the OPEC crisis, and solutions were in demand. When OPEC realized that the world may well discover a way to make them irrelevant, they relented.
Really, that's the only reason why. Their market manipulation was triggering much development. Whole countries were on track to switch to other fuels.

And also it made it worth the investment to develop technology for off shore and other sources of fossil fuels. A lot of methane sources were found too. They didn't seem to anticipate those two issues.

I myself was tasked with running a series of engine power dynamic tests using a propane/methane mix. The carburetor was modified so that it could use gas, propane or methane. Methane was cheap but a huge tank had no range. So it was filled 50% with methane and the rest with propane, which was at an OK price, but lots better range, but still not as good a range as regular fuels. When CH4 and propane went low the driver could manually switch to regular fuel.
The switch between the two gasses was automatic. The methane in liquid form, would boil off until it ran out, then only propane was left to boil off.
So, having some electronics background, I used a zirconium oxide sensor to feedback to a restrictor valve which would follow the changing fuel mix.
We produced a SAE paper on the subject, which I still have a copy of.
Range is still one of the biggest issues with these alternatives. In the case of compressed air, efficiency can also be a problem. But that depends to some extent on where and how you are compressing the air. This is also the determining factor in how green it is.

Seems people were even trying to use the expansion of "liquefied air", sort of like a steam engine.

 

[AriLea]

Seems people were even trying to use the expansion of "liquefied air", sort of like a steam engine.

Yes, it's all expanding gases. (TDC=Top Dead Center, ICE=Internal Combustion Engine)
The standard ICE, needs to get rid of excess heat, only after it's been used to push the piston. (up though TDC)
The steam engine (formally speaking, it's really just a motor) needs to retain heat until it exits the cylinders(or just before, starting at TDC).
The air engine(also just a motor), needs to acquire as much heat as possible just after the intake valve(or whatever it has) closes, up though TDC.
Which is a very different proposition from the first two.
Difference between an engine and a motor? The engine generates the pressure (or pressure head) inside, as part of the process.
Motors only convert potential energy into kinetic. So that includes electric motors.

If your compressed air is in the form of liquid-air, it needs to be preheated in a high-pressure trap until used. And then it still benefits from more heat input. In fact, an interesting combination would be using the waist heat from an ICE to heat the cylinders of the air motor(only if using compress air supply). A hybrid of sorts.

The reason you would not use waist heat to expand ambient air, is that energy used in moving the extra weight of that hardware often exceeds the power generated. That is, using a hybrid of ICE and Stirling (or an Ericsson) together, these heat motors are more useful when not in a moving vehicle, and near to an available heat source, that is otherwise being wasted. (called a bottoming cycle, or post-cycle)

And then there is the cost, does all this extra cost of equipment off-set the value of energy saved? Generally not in a moving vehicle.

 

[ehwatt]

Yes, it's all expanding gases. (TDC=Top Dead Center, ICE=Internal Combustion Engine)
The standard ICE, needs to get rid of excess heat, only after it's been used to push the piston. (up though TDC)
The steam engine (formally speaking, it's really just a motor) needs to retain heat until it exits the cylinders(or just before, starting at TDC).
The air engine(also just a motor), needs to acquire as much heat as possible just after the intake valve(or whatever it has) closes, up though TDC.
Which is a very different proposition from the first two.
Difference between an engine and a motor? The engine generates the pressure (or pressure head) inside, as part of the process.
Motors only convert potential energy into kinetic. So that includes electric motors.

If your compressed air is in the form of liquid-air, it needs to be preheated in a high-pressure trap until used. And then it still benefits from more heat input. In fact, an interesting combination would be using the waist heat from an ICE to heat the cylinders of the air motor(only if using compress air supply). A hybrid of sorts.

The reason you would not use waist heat to expand ambient air, is that energy used in moving the extra weight of that hardware often exceeds the power generated. That is, using a hybrid of ICE and Stirling (or an Ericsson) together, these heat motors are more useful when not in a moving vehicle, and near to an available heat source, that is otherwise being wasted. (called a bottoming cycle, or post-cycle)

And then there is the cost, does all this extra cost of equipment off-set the value of energy saved? Generally not in a moving vehicle.

It seems they direct-inject raw, liquid air and rely on a flash, liquid-to-gas expansion. I think they did indeed, have to manage a way to keep piston/cylinder/combustion chamber temperatures elevated to maintain a consistent "flashing" of liquid air.