Pusher/generator trailer idea.

[Isaac Zackary]

So I'm interested in getting an EV, especially a Leaf, or maybe convert my 1972 Beetle. Although, yes, the range of the Leaf is more than enough to meet my daily needs there's always that desire to be able to take it further out of town.

So this just popped into my head, what about a non-petrol range extending trailer. I know there's been bio-diesel ideas. But I was thinking more along the lines of a liquid nitrogen or stirling engine trailer.

I'm just throwing this out there to see what you think.

[Isaac Zackary]

I don't think that a pusher or generator trailer has to have the power output of a full sized car engine. Most cars use an average of about 15 to 20hp to drive down the road. So if I charged up and took off with a 20hp trailer that might make the vehicle have practically a limitless range. Now I could also go with less, like 10hp. That would basically double the range. It would mean I'd be using around 10hp average from the electric drive train instead of 20hp average. And if I run out of electricity then the 10 or 20hp could be used to limp my way to a nearby place where I could charge.

I have a couple ideas. One would be to make a Hampson-Linde cycle air liquifier or two. One to liquify air and another to take boiled off nitrogen and liquify it so as to have pure liquid nitrogen. Then I'd have to get a large dwark flask for storing it. They make 55L models for under $1000. Then of course a pump that can work at cryogenic temps, and a large Gask motor or two. They make a 9hp unit that costs around $1500. So I'm thinking that for under $5000 I could have a little trailer that runs off of liquid nitrogen and gets me twice the range in an EV like the Leaf.

But then what if I run out of liquid nitrogen. So that's why I was thinking of the stirling engine. I could make the stirling engine run off of liquid nitrogen, or any heat/cold sorce, like propane, bio-diesel. etc. Of course I'd have to completely fabricate the engine. I'm thiniking a 4 cylinder alpha cycle stirling engine that drives a swashplate.

[Astro]

For a generator trailer rather than a pusher you could use just about any motor you like. The RPM of the motor doesn't need to match the cars speed or require a gearbox to achieve the desired ratio.
So why not use a motor with a good power to weight ratio?

If you want to try something a bit different how about a jet turbine electrical generator?
Has a good power to weight ratio.
Scales to any size.
Can be made to run on just about any fuel.
Diesel (including bio-diesel)
Kerosene
Gasoline
Ethanol
Natural Gas
CNG
LPG
Bio-Gas / Methane
So refuelling whilst on a long journey wouldn't be difficult.

Did a quick search and found this one from Bladon Jets but there are probably many more.
12kW output.
Output options, 230v AC , 120v AC or 48V DC.


Actually you probably wouldn't even need a trailer, this could easily be lifted in and out of the car as required. Maybe even mount it where the old exhaust muffler was and have it generate some thrust as well as electricity.

The 134,000 nominal RPM does seem amazing, at least it should be well outside the human hearing range.

[oldtamiyaphile]

Originally Posted by Astro

Did a quick search and found this one from Bladon Jets but there are probably many more.
12kW output.
Output options, 230v AC , 120v AC or 48V DC.

How much? Last I checked those micro turbines weren't cheap.

But yes, just add them to the car:

Bladon Jets | Jaguar C-X75 Concept Case Study

Jaguar are going to build it, but without the jets:

http://www.topgear.com/uk/car-news/j...ial-2011-05-06

Perhaps these turbines are not quite production ready then? I mean a supercar doesn't have to be Toyota Yaris practical. Mediocre reliabilty, short service intervals and expensive bills are all part of the supercar experience, so if Jaguar can't make it work here, I'm not sure if I'd be doing it just yet.

It does seem like a great way to build a DIY EV with unlimited range.

[Astro]

They didn't mention a price but they keep mentioning a lower total cost of ownership than a diesel genset.
As this would include the fuel savings and the reduced maintenance. It is difficult to say how much more expensive the initial purchase price would be.
As they quote lower total cost of ownership and not a lower purchase cost i would say it would be more expensive than a similar sized diesel genset. But by how much?

The good thing about DIY EV it allows us to choose a range extender to suit our wallet.
The original post was talking about $5000 for a nitrogen set up.
Further Googling gives a possible figure of around $500/kW for a micro gas turbine.
Difficult to get an exact figure as the manufacturers don't list prices.
So a 10HP (7.35kW) equivalent could cost around $3500.
With a limited market and purchasing only one unit i would expect to double that figure.
So more expensive but not overly so.
Then the advantages of the gas turbine start to kick in and make it a little more attractive.
Fuel options, simplicity, power to weight, size, etc.
And don't forget the grin from being able to say you run the same engine as the Bat Mobile.

[Piotrsko]

Uh....... most of the batmobiles I've seen (5 out of 12) run either a 352 or 460 with one 429 variant

[P-hack]

Generally small turbines are not real efficient, nor are non-cogeneration turbines (where they have another use for the waste heat). I'm real sceptical about any inferred efficiency of the turbine unit, especially if "total costs of ownership" is based on the expected long runtime of the turbine vs replacing the ICE an arbitrary number of times.

I don't see notrogen as an efficient energy storage (or convenient) for that matter, any figures on cost of compression and efficiency @ extraction?

The only thing that comes to mind for best efficiency and some effort at compactness is a free piston regenerative (as in heat) stirling with linear alternator, and still that will have series losses to contend with (but minimal mechanical losses).

[Isaac Zackary]

Thanks for all the great input!

I'd love to do a turbine setup. The problem is that yes, small turbines tend to be very inefficient. They are also loud. The beauty of an electric is the noise reduction. Part of the reason I'm not up for an ICE piston engine is the same reason, because they are loud. If I do end up getting a Leaf I also would want to keep the thing a bit of a secret. Imagine if I went by a police, especially with a tail pipe sniffer, in a Leaf and he hears the Leaf go "WWWWEEEEEEEEAAAAAAAARRRRRROOOOOOOOOOOOOOMMMMMMMMM !!!!!!" as it goes by. Not that I want to break the law, which is why a zero emissions vehicle might give best with a zero emissions LN set up.

Ya, the LN set up would be a bit inefficient. I think the best case scenario would be 25% from plug to wheel. But this would be used only a few times a year, not daily.

But then again, these are just concepts. Who knows, maybe a small turbine could be made well enough to be the better option. But for now I think it's more feasible to just rent a car on those occasions.

[Isaac Zackary]

Wait a minute! Maybe you turbine promotors are right! Bladon Jet Study

[P-hack]

Every time they mention the word "efficient" it is not in comparison to a diesel, just sitting there by itself. You'd think if it were something to be proud of they would give a relative figure. It isn't much of a "study", and any clues as to actual efficiency are missing.