On the heels of the failed Puegot 208, any other hybrid air cars in development?
 

https://www.caranddriver.com/news/a1...id-technology/

Or is a compressed air hybrid not possible at this time? Some articles had stated 141 mpg, I believe, had it made it into production. But since it’s a subcompact, it probably would never make it to America. Still, a novel approach to decrease gas consumption, without the cons of battery electric hybrids.

Lacks infrastructure. You have to remove heat compressing the air and then heat the decompressed air. I remember discussing a research effort to resolve that a year or two ago.

I could use the site's Search function, but you're the one that cares.

The problem with compressed air is about half the energy is lost to heat compressing the air. That's why batteries rule.

I've always thought of liquid air (or liquid nitrogen) and compressed air vehicles as having cold as a byproduct, which can be used for something like an air-conditioner. This is the opposite of ICEV's that have heat as a byproduct.

EV's don't produce much heat and no cold. So they need to pump heat in or out of the cabin if you want to be comfortable in hot or cold weather.

I had an extra tab open so I tried the Search function. Fruitlessly. There was some University research gone commercial about extracting and storing the heat and using it to warm the decompressed air.

But I did find this article via DDG:

solar.lowtechmagazine.com: History and Future of the Compressed Air Economy:Historical compressed air systems hold the key to the design of a low-tech, low-cost, robust, sustainable and relatively energy efficient energy storage medium.
I've always thought wind powered compressed air is very elegant. The compressed air network in Paris spanned 25 kilometers.
This is what the research I'd seen was about. But there's a necessary link between where the air is compressed and expended. Not so hot for moving vehicles.
This part I thought was cool. I've seen homemade trompes on Youtube made from 2-liter bottles:
That's 3 Megawatts from falling water!

Maybe it's worth mentioning that I keep pointing to the Scuderi Split-Cycle engine.

Scuderi Split-Cycle Engine

That was 2008. IMHO his heirs squandered his intellectual property. Same way as Elio, they tried to develop their own proprietary inline four.

But one could generate compressed air on regenerative braking and recharge at home from that babbling brook.

Battery hybrid solves other problems too, like keeping the AC running while the engine is off. By electrifying everything, all systems can operate regardless of the ICE running. Compressed air would need a similar way to run accessories.

There are non-hybrid vehicles with start-stop systems. Of course those still have the option to idle the engine of need be. But maybe an air motor vehicle could work in a similar way.

Or use a second small air motor for the accessories.

If the tank is filled at home maybe the heat from compression can be used to heat your house or water.

And when operating in hybrid mode heat from the ICE could be put back into the air in multiple stages.

Compressed air is a terrible medium for storing energy.
You lose a lot of energy to heat when compressing air and require heat to expand it somewhat efficiently.
That's why cordless tools and hybrid cars are running on lithium ion cells, not compressed air tanks.

Only advantage of storing energy in compressed air is that pneumatic cylinders can be used for suspension and active aero

I don't think it's all doom and gloom. Hydraulic hybrids normally compress a gas by pumping hydraulic fluid into an enclosed "accumulator" with a gas filled bladder. And those can reach some surprisingly high levels of efficiency: 80% IIRC.

I'd like to see a source on that, I'm genuinly curious how that is supposed to work.

Considering its claimed suitability to operate on a pneumatic hybrid setup.


IIRC the current-generation Volvo D5 engine is coupled to a 48-volt electrical system which provides mild-hybrid capability, so maybe the electric compressor which provides air for the PowerPulse system could be considered analogue to a regenerative braking :D

Here's a little info on UPS (United Postal Service) modifying some of their mail trucks to use a hydraulic hybrid system.

United States Environmental Protection Agency: Hydraulic Hybrid Vehicles

The way they work is pretty simple.

• There's a hydraulic pump-motor connected to the driveline after the transmission. There are hydraulic pump-motors that are completely variable, so you can adjust the amount of regen or power.
• Connected to the hydraulic pump-motor are a reservoir and an accumulator.
  • The reservoir stores hydraulic fluid at ambient pressure.
  • The accumulator is basically a pressure cylinder with a gas bladder (although a piston and spring accumulator could work).
• The gas is already under pressure, so as you pump hydraulic fluid from the reservoir to the accumulator the bladder is compressed even more making it shrink in size as the rest of the accumulator fills up with hydraulic fluid, storing energy.
• Then, when the pump-motor is set into motor-mode, the bladder expands pushing high pressure hydraulic fluid through the pump-motor and into the reservoir which turns the wheels of the vehicle.

The hydraulic hybrid has the following benefits:

• Hydraulic pump motors can be as high as 99% efficient.
• Depending on the design, that efficiency can be basically the same at any RPM or torque load. Even at a dead stop since unlike an electric motor the hydraulic fluid cannot flow until the motor starts turning.
• Hydraulic pump motors allow for efficient regen braking clear down to basically 0RPM.
• Hydraulic hybrid systems can have a higher power to weight ratio than lithium ion electric systems (albeit they can't hold a lot of energy) making them ideal for stop and go traffic, such as postal or public transportation vehicles.
• They aren't hardly affected at all by cold or hot weather.
• In a series hydraulic hybrid vehicle the hydraulic system can replace the transmission much like the "power split device" on a Toyota hybrid.

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

IIRC the first prototype to feature Ford's 6.0 PowerStroke was also fitted with a hydraulic hybrid setup.

That’s incredible. Thanks for sharing, I hadn’t heard about this. Glad to see it implemented in humongous vehicles.

Brilliant solution to braking energy recapture. I hope it’s reliable and safe. Do you know how long UPS has been doing this? I might have missed that part, thanks.

Hope to see cars with a solution that is as efficient also. I’ve seen flywheels, but not sure it’s gained any traction.

I remember an article on a compressed air car targeted at India. They made a big deal that air conditioning was "free" in the car... so I guess nice for hot climes.

Edit: it was Tata
https://trak.in/tags/business/2008/0...r-minicat/amp/

It seems like there was a bit of attention drawn to hydraulic hybrids when UPS deployed their first HHV truck. After that there seemed to be a small amount of news about them until EV's started rolling out. Then the idea seems to have kind of been lost.

Something along the lines of the air-cycling machine featured on pressurized aircraft would be viable on a car too, but I'd take with a grain of salt any claim of "free" air conditioning. Unless the wasted heat gets recovered through a Sterling motor.

The expanding air has to absorb a lot of heat... it requires an exchanger for this purpose.

The air conditioning is "free" the same way heat is free in an IC car.

Even though the air-cycling system applied to airliners may be possible to scale down enough to fit into a pneumatic hybrid, I'd take its suitability with a grain of salt. Vapour-cycle air conditioning is likely to remain more common for such purposes. Unless a heat pump could be applied to a pneumatic hybrid in order to improve its overall efficiency.

I was good on this until I remembered how they get their air.

It is compressor stage heated air that is bypassed from the front of the engine ran down a flex duct in the wing into the cabin then back out to atmosphere through a pressure valve. May or may not be filtered where the circulating air system is filtered with a hepa style filter to get the smell particles reduced. Exchange rate used to be like 3 times per hour but now it's 6.

Would be quite harder to bleed enough air from a turbocharger fitted to a conventional reciprocating engine. On a sidenote, the ACM also resorts to a turbocompressor and a heat exchanger which resembles an intercooler.

Methods of compressing air at over 100% efficiency are possible using a temperature differential and the ocean.

But unless we are compressing CO2 exhaust from a power plant what’s the point of a gigantic underwater air column?

And if we did
why waste it in an inefficient air motor that has just as limited of a range as a Hydrogen or Early BEV vehicle?
Compressed CO2 would have more value in industry than blowing a car.

The only advantage of an air car is free air conditioning, maybe nice in Solcal but not fun up north.

I may be wrong, but if you have a way of either efficiently absorbing and replacing the heat during compression and decompression, or a way of efficiently insulating the heat in under compression so it's there when you decompress, then that should raise efficiency.

It's when you compress the air, lose the heat after and not during compression, then decompress the air without letting it heat up in some way or form during decompression, that's when pneumatics are inefficient.