Diesel-electric cars...

[beef_bourito]

i don't remember where i read it but it said turbines were more efficient. and with planes you're using thrust instead of shaft power so that might play an important role in the efficiency. the problem with pston engines it that you have to accelerate the piston down, then decelerate it, then accelerate it up, then decelerate it. all those accelerations (both positive and negative) take energy, with a turbine engine you only accelerate it in one direction. although i don't know how efficient they are at transferring gasses moving in one direction into shaft rotation.

another alternative is a quasiturbine, just for the hell of it to make it sound cool and to try something else. if i'm going to make something radical, might as well make it really radical as long as it works. but i would just use a diesel engine to accomplish it.

[Alastor187]

Turbines are more efficient than IC engines, they can commonly have efficiency approaching 40%. Some of the more cutting edge turbine technology is closer to 60% efficiency.

The biggest problem with automotive applications is the response time of the turbine is comparatively slow. So there is significant delay between when the driver pushes the "gas-pedal" and the engine delivers more power, and vice-versa.

Similar to an IC engine a turbine is best suited to operation at a constant speed.

[GreyGoose006]

wasnt there a turbine powered buick or something a while ago.
i remember i saw something on something like that. it was a concept car i think.
how would an automotive turbine work anyway?
what would happen to all the hot exhaust gasses?

[Alastor187]

Originally Posted by GreyGoose006

wasnt there a turbine powered buick or something a while ago.
i remember i saw something on something like that. it was a concept car i think.
how would an automotive turbine work anyway?
what would happen to all the hot exhaust gasses?

I would guess they are exhausted in a similar manner as with an IC engine.

Keep in mind that it is not the exhaust gases that would propel the car, that is unique to “jet engines”. Instead the turbine spins a shaft that is mechanically linked to the wheels.

There are probably better pictures out there, but here is a cross-sectioned gas turbine used in the M1A1 Abrams tank.

http://tanxheaven.com/m1agt1500/AGT1500_ex%20view.jpg

[Moppie]

Rover made a turbine powered version of the old P6.
It worked, very well, had only one forward gear, and top speed of well over 100mph. Considerably faster than the orginal V8 powered car. Even got better fuel economy.
Just two down sides, the engine was not very responsive, and when it went it WENT!.
And the the heat generated was terriable. They had to duck it out the top of the hood, and haze would often obscure the drivers view.
Ducting it out the back of the car caused problems for anyone stopped behind it, or even walking behind it.

There is a company in the states that makes limited production Turbine powered bikes.
They have big problems with the exhaust melting the bumper of anyone who stops to close to the back of the bike.

[Steel]

You know. I bet a good use for that waste heat caused by a turbine motor would be to power a stirling engine... Wham bam, extra efficiency right there. Kinda tight on time, i'll extropolate later.

[beef_bourito]

or you could do something much simpler, get a heat exchanger between the exhaust and the intake. turbines like hot air so it would bot cool the exhaust and heat the intake.

by the way, the turbine bike you're talking about is the Y2K, it's got a 300hp turbine engine and does 0-222mph in just over 14 seconds.

[UncleBob]

Originally Posted by beef_bourito

by the way, the turbine bike you're talking about is the Y2K, it's got a 300hp turbine engine and does 0-222mph in just over 14 seconds.

yes....and the Y2K gets horrible mileage too

4-6 mpg

http://www.popularmechanics.com/auto...e/1302876.html

my wimpy 250HP bike gets mid 40's

[beef_bourito]

true but that's a 300+hp engine that's being used completely differently. i'd only look for about 70-100 depending on how much i'd need to charge those batteries. the thing is that you don't need to accelerate the gas engine with a generator-electric motor setup so you waste less fuel.

[GreyGoose006]

how can it get such bad mileage.
if it came out of a helicopter, it would have to run for a LONG time.
helicopters cant be carrying tons of gas with them.

[UncleBob]

can't speak for helicoptors, but most jet planes rate them by gallons per mile instead of the other way around

[curtis73]

Its true that turbine's are more efficient in how they extract BTUs from the fuel, but not how they transmit BTUs into HP. The exhaust from a car accounts for about 20% of the BTUs of the combusted fuel. In a turbine, it accounts for nearly 75%. It all depends on what you do with the BTUs released by the turbine.

If you use the exhaust (like a jet engine) you're using most of the BTUs. Not only are you using the spinning shaft, you are using the thrust of the expanding gasses. If you are simply using the shaft torque (like you would in a helicopter or a car), its very inefficient. All that heat is wasted out the exhaust unused.

[curtis73]

I'm pretty excited about hydrogen-electric fuel cells. I don't know tons about them, but its an electric "generator" that makes an electric potential by putting hydrogen ions near a permeable membrane. The only real emission is water and hydrogen, and (provided the hydrogen is harvested from the surface instead of from crude oil) still makes zero net emissions.

They aren't overly efficient right now, but they have the potential to be... but even if they aren't, its a basically free fuel that already exists in our atmosphere. If we don't extract any energy from it the first time, its still there for us to do it again with little or no consequence.

I'm also very excited about biofuels. When you burn fossil fuels, you're digging up HCs from underground, burning them, and putting them in the atmosphere. That is seriously upsetting the balance. Combine that with deforestation and you have nothing to "scrub" that junk out. Biofuels make HC out of existing water and CO2 already above the surface and in the atmosphere. So the only things that we put into the atmosphere are things that the plants we grew already took out of it. We would have to have enough plant life to scrub out everything we put into the atmosphere.

Recent studies by the ARB and EPA have pointed to the fact that if we had entirely fleets of biofuel vehicles (in specific biodiesel and ethanol) then the increased NOx emissions (from the fact that ethanol requires higher compression and diesel already has high compression) would not be as much of a greenhouse threat. Basically, we've filled the air with so much junk that now we have to be super careful about what we put in it. If we hadn't messed it up, NOx would be a relatively harmless set of gasses.

I don't see how anyone can ignore the fact that we're bringing up billions of barrels of HC from underground, burning it, and putting it in the atmosphere... and then we try to make cleaner ways of burning it??? I say stop burning it and use the biofuels already in existence in the air.

[Steel]

The only problem with hydrogen is that it's VERY costly (money and energy) to extract it, and it's very difficult to store. The most efficient way to get hydrogen is to crack it from the oil in the ground, or from methane gas, but that kinda defeats the purpose, no? To extract hydrogen from water takes a LOT of energy because a lot of it is lost (its only about 50-70% efficiency to electrolyze water with electricity, and that doesn't take into account the inefficiency of making the electrical power in the first place, as we discussed before).
On top of that, hydrogen is also a losing battle when it comes to storage. Any material is basically a sieve to hydrogen, because it is the smallest atom and quite simply passes through the walls of the container with relative ease. Not to mention I wouldnt want a tank filled with liquid hydrogen pressured at 3000psi. A way around this is using hydrides, metals that absorb hydrogen and can store it easily, but that's still being developed.

I'm with you all the way with the biofuels, however. I feel that that is the best option for future energy needs for the world. If room temperature superconductors are finally discovered, the whole world with revolutionize (well that, and feasible nuclear fusion reactors). Even relatively poor countries could have more than enough energy to support themselves and advance. Heck, with fusion reactors and RTSC's the world could be completely electrically based.

[KiwiBacon]

Originally Posted by curtis73

The problem with converting all of your engine's power to electricity is that its INCREDIBLY inefficient. As much as 80% gets lost to heat, light, and sound energies.

The engine itself is only about 87% efficient at getting the energy from the fuel, and then the generator only effectively turns a small fraction of that into electricity

Locomotives use that system mostly because they have to, but its incredibly wasteful. If you were to impliment this in cars you would end up burning many times more fuel to get the same output at the wheels.

Your conversion efficiencies are way out. There's no engine that can deliver 87% effciency.

A very good diesel can get almost 40% of the fuels energy into output at the crank.
An electric generator efficiency depends on the type, but you can do better than 2/3rds.

Electric motors can do upwards of 95%.

But the weight and cost are the biggest problems for a passenger car.
For big trucks, you won't beat the efficiency of a mechanical transmission.