The big tripples thread got me thinking... Gas Turbines...

Ok, not a direct drive gas turbine vehicle, but as Jaguar is playing with on the C-X75 concept (Link to site) I'd like to discuss the possibility of a gas turbine powered electric car. Using a small turbine as a genset in order to power a vehicle and still use regenerative braking and other energy recovery technology. What do you think? What fuels? I'm thinking CNG/propane/butane/hydrogen for extra clean burn and all that crap. LOL Electric motors in or at each wheel? Unlimited traction control, torque instantly and torque vectoring. It would be pretty cool.

Ok, what do you guys think?

It sounds awesome... in 45 years.

singleslammer wrote: It sounds awesome... in 45 years.

LOL

Why not today? Wouldn't even really need a huge turbine, just one or 2 smaller ones used to spin a genset and a battery backup/storage. Generator kicks on when energy getting low.

it comes down to the energy density of the fuel, and being able to harvest that most effectively. Id hazard a guess that most singular systems are relatively inefficient by themselves, with regards to losses from combustion heat and friction. Moving that energy through a second system may add extra losses given the same amount of energy input. So if you lose 10% energy from the heat of combustion and friction losses in the combustion engine, and another 8% from friction in the generator (just tossing out wild guess numbers there), its only a benefit if an internal combustion engine and transmission of similar power outputs loses more than 18% overall.

Now theres something to be said for energy harvesting efficiency when youre able to maintain the most efficient state of the combusting device (i.e. maintaining the most economical RPM in a 4 stroke engine, or the best combination of rotational speed and fuel usage in a turbine) over a longer operating time. A normal 4 stroke engine is most efficient at a particular RPM, but is often operating at some other speed while speeding up or slowing down, therefore producing less energy per quantity of fuel used vs maintaining that peak RPM constantly. Having a system that maintains that RPM constantly may be more efficient, but my guess is the additional cost of the electricity generating system, electric motors, and electricity metering system would be cost prohibitive, NTM energy density of batteries is still pretty archaic. Theyre heavy and big. You may lose additional efficiency gained simply from weight alone.

Lots of factors

OK, how do we get around those problems?

My assumption has always been that it only makes sense if you can make it really big and heavy and you're moving at a fairly constant speed for really long periods of time. So it works great in a train or on a ship, but once you try to shrink it down to car-size and put it in stop and go traffic, not so much. I thought I heard about someone trying to do that with a semi, though. Perhaps MAN over in Europe?

Conquest351 wrote: OK, how do we get around those problems?

Volvo did a turbine hybrid a decade ago.

Chrysler did a turbine production car 4.5 decades ago.

And Ford was working on turbine heavy trucks 4 decades ago.

This isn't new.

the #1 problem, buy a very, very wide margin is cost. If you can make a 60hp gas turbine at all for $1000, then the rest of the issues become worth while trying to solve. Especially a $1000 gas turbine that you can make in volumes of even 100k a year.

When you get near that hurdle, then we can talk about the efficiency, emissions, durability cold performance, and how to use it.

In reply to alfadriver:

That sounds like the sort of thing manufacturing technology can/will sort out at some point.

I just want a turbine/electric Unimog, and I don't know why, exactly.

ransom wrote: In reply to alfadriver: That sounds like the sort of thing manufacturing technology can/will sort out at some point. I just want a turbine/electric Unimog, and I don't know why, exactly.

Why would you think that? Gas turbines have been made for a LOOONG time, and if the cost of them can a significantly cheaper to make, airlines would be all over that.

Alas, 40 years after trying, the cost of making single crystal blades is still incredibly expensvie and slow.

If the carrot is big enough, there's more than enough reasons why it would happen. There's not a conspiricy against the gas turbine.

BUT, if you think it's really possible, get into it, and solve the problem. There's plenty of money in it if you can do it.

In reply to ransom:

You don't need a reason other than that sounds BAD-ASS!

In reply to Conquest351:

My reasoning has more to do with the way the industry works and the fact that building a turbine, see above, is very expensive right now. Hence the 45 years.

alfadriver wrote:

ransom wrote: In reply to alfadriver: That sounds like the sort of thing manufacturing technology can/will sort out at some point. I just want a turbine/electric Unimog, and I don't know why, exactly.

Why would you think that? Gas turbines have been made for a LOOONG time, and if the cost of them can a significantly cheaper to make, airlines would be all over that. Alas, 40 years after trying, the cost of making single crystal blades is still incredibly expensvie and slow. If the carrot is big enough, there's more than enough reasons why it would happen. There's not a conspiricy against the gas turbine. BUT, if you think it's really possible, get into it, and solve the problem. There's plenty of money in it if you can do it.

I know a bit about the single crystal thing. My company dabbles in that.

So, the thing with turbines is that they are crazy crazy efficient... hen they're gigantic. We size our best turbines for the rotor to not be supersonic at 60hz/50hz. Making them small gives you a tremendous disadvantage in terms of power and efficiency. I promise, this isn't one of those "if only they developed it more" types of things. If you think otherwise, OP, build some and try them out. There are tons of parts that have to be made with very tight tolerances, and the efficiency for tine itty bitty turbines is naturally going to be tough to deal with.

Why not a small turbo diesel? Runs at a constant speed, drive the genset when needed, far less critical clearances, etc, and adapting known, cheap technology. Batteries still a problem, though.

You guys are probably right, and obviously WAY more informed about the particular issues of turbines.

I didn't meant that nobody's trying or if they just looked at the problem harder it'd be done next year. I was thinking about the general march of materials progress and thinking that it's "the sort of thing" which sometimes ends up being solved by advances from unrelated research.

cwh wrote: Why not a small turbo diesel? Runs at a constant speed, drive the genset when needed, far less critical clearances, etc, and adapting known, cheap technology. Batteries still a problem, though.

Locomotives run diesel/generator setups without batteries, but the engines run all the time and vary engine speed to go faster or slower. Still, I think a small turbo diesel running a generator would be a very efficient setup, I would buy one. Heck I have thought about trying to make one in a small car, maybe one day.

There was a prototype GM EV-1 series hybrid with a gas turbine driving a generator.

Wikipedia link

cwh wrote: Why not a small turbo diesel? Runs at a constant speed, drive the genset when needed, far less critical clearances, etc, and adapting known, cheap technology. Batteries still a problem, though.

I'm sure the reason is cost as well, there.

How much more of a benefit would you get with a diesel, and would it be worth the extra cost of a diesel? No question, it could be a ton more efficeint. How many years of ownership would it take to offset the price?

Say a 45mpg TDI vs a 60mpg TDI-Hybrid- or even call it 70. Neither use a lot of fuel. So it would take a lot of time and miles to pay off.

Even now, people are reporting 100mpg with plug in hybrids. How much more would it be with diesel? 150? At that mileage, you are not using a lot of fuel in the first place.

For heavy trucks, busses, and trains- it makes a whole lot more sense, since most of the cost is gas in your business, and miles per year can be in to 100-300k range.

technicaly, a hybrid PZEV diesel is fairly straight forward.

It's a great idea, you can do it today, it just costs money.

In-wheel motors are great for packaging but send unsprung weight through the roof. Central motors make packaging more difficult but save a lot of weight and give no increase in unsprung weight. The CX-75 uses individual motors mounted inboard with axles going to the wheels, this is sort of in-between the two.

For fuel you can burn whatever's convenient. Hydrogen is a PITA to contain. Butane, proopane and CNG could work but they're fossil fuels, boring . Ethanol and biodiesel are options, maybe even WVO?

Oh and BTW, while the CX-75 concept uses micro-turbines, the production version will use a heavily boosted gas I4. So I don't see why a turbo-diesel couldn't work too.

alfadriver wrote:

cwh wrote: Why not a small turbo diesel? Runs at a constant speed, drive the genset when needed, far less critical clearances, etc, and adapting known, cheap technology. Batteries still a problem, though.

I'm sure the reason is cost as well, there. How much more of a benefit would you get with a diesel, and would it be worth the extra cost of a diesel? No question, it could be a ton more efficeint. How many years of ownership would it take to offset the price? Say a 45mpg TDI vs a 60mpg TDI-Hybrid- or even call it 70. Neither use a lot of fuel. So it would take a lot of time and miles to pay off. Even now, people are reporting 100mpg with plug in hybrids. How much more would it be with diesel? 150? At that mileage, you are not using a lot of fuel in the first place. For heavy trucks, busses, and trains- it makes a whole lot more sense, since most of the cost is gas in your business, and miles per year can be in to 100-300k range. technicaly, a hybrid PZEV diesel is fairly straight forward.

www.caradvice.com.au/80408/2011-peugeot-3008-hybrid4-worlds-first-diesel-hybrid/ 3.1L/100km = 76 MPG but the big benefit here is the CO2 levels, sub 100g/km is impressive...

In reply to Raze:

No question the numbers you get are really good. But is it worh it?

When gas gets to $10-20/gal, it may very well be. Hovering where it is now... eh.

And compared to gas- how much cost/gal delta plus mileage delta is needed to pay for it?

Granted, there will always be the technophiles out there who will get it for the sake of getting it. But the general public more buys with their pocketbook. Be it Europe or the US.

Conquest351,

I remember Volvo built a concept car that is pretty close to what you described. It must have 10 to 15 years ago. You might see what you can find out about it.

The current state of thermodynamics and materials means for a huge amount of work and money you'll end up with something that gets lousy mileage.

If you want to do it just 'cause, look into surpluse APUs (Auxillary Power Units.) That's exactly what you need all done up already.

When the turbine was incorporated into the helicopter, it solved all kinds of problems and became the norm. But helicopters are maintained by trained, specialist technicians, not the high school student at Jiffy Lube. I think a major barrier is the scaleability of such a power source to accomodate a wide range of climates and service intervals.

If you have ever heard a turbine-powered car start up at a cruise, you will agree that we should be working on the problem. I want one!

Every time I see "tripples," I think "nipples."