High Efficiency APU

[fake mccoy]

Hello,

I'm looking for a high efficiency Aux Power Unit. I'm actually
building a electric car, and want some way to recharge besides plugging
in. I'd like to go with a microturbine/turbine for both space and
efficiency concerns. I'm looking for anything over 30 kW of power,
with efficiency being my main concern. Gas stations havent started
stocking Jet-A, so I guess you can add that to the list of
requirements.

I'll probably be using my own alternator/generator, a secondary 40kW
unit, but I couldnt complain too much if the unit came with one.

Any sort of links at all would be really useful. You guys are really
the only domain I know of that might be able to help with something
like this. Even links to other good message boards would be great. I
really appreciate it!

Thanks mates,
McCoy.

[[email protected]]

Assuming that your interest in some kind of fuel efficiency why not
consider one of the small Wankels? They can be had in the power range
you are looking for and are far more fuel efficient than a turbine.
Weight and size is not that much different either.

http://www.rotary-xr40.com/rotary3.htm

There are also Wankel powered aircraft APU's available, but the price
is steep.
==========
Leon McAtee

[[email protected]]

Unfortunately, neither Wankel or small turbines are very efficient.
Best bet currently is a diesel, but they are not especially light.
tom

[Tim Ward]

"fake mccoy" > wrote in message
oups.com...
> Hello,
>
> I'm looking for a high efficiency Aux Power Unit. I'm actually
> building a electric car, and want some way to recharge besides plugging
> in. I'd like to go with a microturbine/turbine for both space and
> efficiency concerns. I'm looking for anything over 30 kW of power,
> with efficiency being my main concern. Gas stations havent started
> stocking Jet-A, so I guess you can add that to the list of
> requirements.
>
> I'll probably be using my own alternator/generator, a secondary 40kW
> unit, but I couldnt complain too much if the unit came with one.
>
> Any sort of links at all would be really useful. You guys are really
> the only domain I know of that might be able to help with something
> like this. Even links to other good message boards would be great. I
> really appreciate it!
>
> Thanks mates,
> McCoy.

At 30 KW, the Capstone turbine would fit your bill.
Only one moving part, can be set up for diesel or natural gas.
Pricey, though.
http://www.microturbine.com/

Tim Ward

[Richard Riley]

Capstone hides their fuel specific pretty well, but you can tease it
out. .57 lb/hp/hr. Very good for a small turbine with a single stage
compressor - but even an awful 4 stroke piston engine should be about
..45. A serious stratified charge engine can get down around .33. I
think the record is about .25.

The Capstone uses some very clever air bearings, but they won't stand
up to any gyroscopic force. Put them in an airplane and try to turn,
you'll crash the bearings.

[Ian Stirling]

Richard Riley > wrote:
> Capstone hides their fuel specific pretty well, but you can tease it
> out. .57 lb/hp/hr. Very good for a small turbine with a single stage
> compressor - but even an awful 4 stroke piston engine should be about
> .45. A serious stratified charge engine can get down around .33. I
> think the record is about .25.
>
> The Capstone uses some very clever air bearings, but they won't stand
> up to any gyroscopic force. Put them in an airplane and try to turn,
> you'll crash the bearings.

The OP does explicitly say that this is for use to recharge an electric
vehicle instead of plugging into the mains, so that won't be an issue.

However, if I was making an electric vehicle with an APU, I'd certainly
want it to be able to run 'direct', too.
Even the best batteries only put out what, 75% of the charge put into
them.

Running direct means that you can in principle get 25% better mileage
out of the same amount of fuel, save some wear and tear on the
batteries, and not have to stop so often.

[Tim Ward]

"Ian Stirling" > wrote in message
...
> Richard Riley > wrote:
> > Capstone hides their fuel specific pretty well, but you can tease it
> > out. .57 lb/hp/hr. Very good for a small turbine with a single stage
> > compressor - but even an awful 4 stroke piston engine should be about
> > .45. A serious stratified charge engine can get down around .33. I
> > think the record is about .25.
> >
> > The Capstone uses some very clever air bearings, but they won't stand
> > up to any gyroscopic force. Put them in an airplane and try to turn,
> > you'll crash the bearings.
>
> The OP does explicitly say that this is for use to recharge an electric
> vehicle instead of plugging into the mains, so that won't be an issue.
>
> However, if I was making an electric vehicle with an APU, I'd certainly
> want it to be able to run 'direct', too.
> Even the best batteries only put out what, 75% of the charge put into
> them.
>
> Running direct means that you can in principle get 25% better mileage
> out of the same amount of fuel, save some wear and tear on the
> batteries, and not have to stop so often.

Lead-acid puts out about 75%, Lithium can go as high as 95%.
Capstone has already installed them in buses, so ground vehicle apps aren't
ground-breaking.

[Ian Stirling]

Tim Ward > wrote:
>
> "Ian Stirling" > wrote in message
> ...
>> Richard Riley > wrote:
<snip>
>> However, if I was making an electric vehicle with an APU, I'd certainly
>> want it to be able to run 'direct', too.
>> Even the best batteries only put out what, 75% of the charge put into
>> them.
>>
>> Running direct means that you can in principle get 25% better mileage
>> out of the same amount of fuel, save some wear and tear on the
>> batteries, and not have to stop so often.
>
> Lead-acid puts out about 75%, Lithium can go as high as 95%.

Well - there will be some losses in the converter - even if it's a
couple of percent either way, that's close to 10% power loss.
I diddn't know that lithium was that high.

> Capstone has already installed them in buses, so ground vehicle apps aren't
> ground-breaking.

Unless it's an electric earthmover :)
(I have seen one, but it was marketed for use by 5-8 year olds)