Prius Sales Tank Even With Higher Gas Prices

I think you like the idea.

It is a curious one and some issues such as running the lights and a/c when the car is just running off air. Perhaps an uprated electrical system is an option or perhaps led headlights to reduce power consumption.

I'm looking forward to when they make their way to my local Peugeot dealer. I still like their 3008 diesel hybrid but there are other nicer cars out there for the money.

 

I'm enamored by the idea

Electric hybrids were conceived of 100 years ago but electronics had to catch up (along with a lot of Toyota ingenuity) to make them practical. In the case of pressure hybrids materials improvements has done the same and I suspect has an optimistic path forward. That at least seems clear for the tank. I am less sure about the high pressure plumbing and motors.

 

There is a big difference in the energy released when decompressing gas and decompressing liquid. Compressing gas stores far more energy but it can also do a lot more damage if containment fails.

 

..... A lot of ingenuity in deed, but I give a big nod to a certain ingenious (Dr. Severinsky) Russian imagrant too - who had to spend 6 years and big bucks defending his hybrid parents against Toyota:
The Hybrid Inventor Who Sued Toyota – And Won | Autopia | WIRED
... just sayin' - It ain't easy going against the #1 auto giant, and successfully eating their lunch right in front of them.

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The air hybrid is indeed facinating...but if its anything like nat gas the US version may require more cost. In the case of nat gas, in EU you can convert a car for ~$500-1000 to nat gas, but here we want min. ~$6000 for a special HP tank, so you're talking $7000+ for the same conversion here.

 

No it isn't. It could be improved with a smaller engine that eats less gasoline. It could be made from aluminum to reduce weight to ~2500 pounds. It could have a proper teardrop shape & wheel covers to reduce drag to 0.20. (I could go on and on but I won't. Lots of internet articles cover ways to make cars use less energy.)

No it looks like a Toyota Echo with a trunk. The rearseats don't fold down. Blech.

Technically the MPG king was and still is the Honda Insight (1999-2006). It not only scored 62 mpg on the highway test (55 combined) but also carried the badge as "greenest car you can buy" according to the American Council for an Energy Efficient Economy (greenercars.org). Even the Civic Natural Gas was not as clean (it ranked #2).

I'm glad you like your prius. I like my prius too. But I don't delude myself into thinking it's the best or "flawless" or king. There are/were other cars that looked better, scored higher MPG, and of course there are many ways my car could be improved (aluminum, better aerodynamics, better canyon carving, more road feel, etc).

 

How many times have you been told that the 2-seater Insight was ULEV and the EPA tests were modified circa ~ 2008 ?

 

Erm in some parts of Europe you can convert a car (read that as old carburetor car) for $500, namely anywhere in Eastern Europe where standards and more importantly enforcement vary. The simple systems for carburetor or single point injection are cheaper but such vehicles are now few and far between and usually quite old.

I was quoted about £1,800/$3,000 to convert the Prius to lpg as it needed multipoint lpg injectors etc. The circular lpg tank would fit where the spare sits and you have the choice of petrol or lpg. Because of the extra weight it was recommended to uprate the rear suspension which would have added more cost.

Convert your petrol-powered vehicle to run on Autogas LPG | Autogas

Are you sure $6,000 is correct? What is different between the tank or is it that it has to be registered and because of low volumes sold the extra cost is passed on?

Environmental benefits of running a vehicle on Autogas LPG | Autogas interesting to see the emission reductions.

 

Energy loss would depend on how good the thermal insulation is, how quickly the energy is used after compressing it, and environmental factors. There are many variables at play.

As you probably know, the sooner the compressed energy is used, the less energy would be lost as heat.

I was wondering if the refrigeration effect of releasing the pressure could be used to cool the passenger cabin, but I'm fairly sure this would be impractical.

 

The discussion was with regards to thermodynamics. Carnot cycle stuff.

 

Actually, the max pressure of the tank is not a factor. When calculating a thermodynamic cycle what I really need is three of the four location points on the thermo graph chart. (I'm old fashioned, I'm use to plotting cycles.). In this situation the energy inefficiency is the area enclosed and those location points are not identified in your question directly. A set of pressures and temperatures for at least three points in the cycle is needed.

For example, if the tank is fully insulated and suffers no temperature loss, it should be close to 100% efficient. It is acting like a big spring in this situation. If the tank is completely charged in hot air on a hot day and then cools to morning ambient before discharging, then the area gets big and the losses are significant.

What I do know is ANY energy storage device of reasonable efficiency (battery, HP air, flywheel) can be engineered to make for much more efficient autos.

 

Well, as long as I am putting my thermodynamic ignorance on display, please explain why the drop in temperature inside the container is not part of a Carnot cycle

 

Actually, using a HP air tank as an energy storage medium is trying to avoid being part of any thermodynamic cycle, Carnot or otherwise. So any thermal losses in this application are pure energy losses. Now a cyclic temperature change in this energy storage setup can be shown on a Carnot plot of Pressure vs. Volume. Think of it this way:

1) Empty HP air tank is pumped up to 500 psi. The tank heats up to 200 degrees. (This a seat of the pants calculation, not an accurate one.)
2) Overnight tank cools to 75 degrees. Pressure lowers to 400 psi. (Useless heat loss.)
3) You only get 400 psi of work out for the 500 psi of work put in.
4) The rest of the work went into heating the planet.

That is a cycle, but not a Carnot cycle where the useless heat loss is designed to be (close) to zero. So any area enclosed on a Carnot like plot is useless energy loss.

 

FPL,

Starting from your point that tank PV losses and loss to the environment can be close to nil, and assuming a serial hybrid configuration using a diesel engine operating @ 45% efficiency, P/M with 2.5% losses each way and a gearing that loses 3%, I calculate 41.4% of each gallon's energy reaches the wheels.

Since diesel's energy content is ~ 11% higher than petrol, I calculate
15.348636 kWh to the wheels per gallon of diesel.
Assuming 200 Wh/mile, that works out to almost 77 MPG (us)

Sound about right for a target ?

 

I don't see how you got the 41.5% with the losses presented, but that is minor. The overall calculations work out sensibly.

 

45% thermo efficiency for best in class diesel car engine

2.5 + 2.5 + 3.0 percent losses in the drivetrain, so

0.45*0.92 = 41.4% tank to wheels

 

Does this link better explain how this air car works?

Peugeot 2008 Hybrid Air prototype review | Auto Express

Not being educated in such matters I am probably wrong but it appears to be more hydraulic than just compressed air. The main tank holds compressed nitrogen and oil and pushes it through the motor to a lower pressure tank, or that's how I read it. I'd imagine nitrogen is more stable and the oil helps keep pressure stable in various temperatures?

"Central to the HYbrid Air's powertrain is a compressed air tank, entirely self contained, which can hold 20 litres of nitrogen and oil at a pressure of 220 bar. By discharging this tank and forcing the oil through a hydraulically actuated motor which spins the front wheels."

 

Got it.

 

That answers two questions I had:
1) An accumulator is a standard name for a tank holding both compressed air and liquid in the same tank. There may or may not be a piston or separator (e.g. bladder) between the air and liquid.
2) The real engineering challenge is for a real high efficiency method of converting expanding air into rotational motion. Using an intermediate liquid makes the size and efficiency of this conversion occur in a lot smaller space compared to using air. The liquid can be optimized for temperature range, lubrication, and viscosity. All the issues with moisture in the compressed air is totally eliminated with this approach.

Now the issue is cost effectiveness. Given the EU cost of fuel, this should take off.

 

...closer to $12000 for my minivan (I have VW-badged Dodge Caravan disucssed in the PM article):
How to Convert Your Car to Natural Gas - CNG Conversion - Popular Mechanics

In the USA, gaso ICE is our cheap case, everything else is $5-10k more, right?

ICE gasoline $BASE
ICE Hybrid +$5000
CNG ICE (Civic GTX) +$8000
CNG Conv +$8000
Diesel (Cruze) +$8000