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Friday, 19 November 2010


Hybrid cars are a sort of half-way house between old-fashioned twentieth-century petrol cars, and proper electric cars with batteries.

We can't quite have the latter, of course, because the batteries aren't up to it yet (see my post on electric aeroplanes of a few weeks ago).

All the hybrid cars I have seen, though, use a conventional reciprocating engine to drive their alternators.   This is very silly - reciprocating engines are inefficient and unreliable.  They have one single advantage: they respond rapidly when you blip the throttle.  You need that if they are directly connected to the power-train, as in the old-fashioned cars I just mentioned.  But that advantage is completely pointless in a hybrid, in which the battery accommodates sudden changes in load.  For a hybrid you need a simple reliable engine that runs at constant speed and more-or-less constant power.

The picture is of a Garrett GTP 30-67 gas turbine.  It's about half a meter long and generates about 25 Kw of power.  That sort of engine would be perfect for a hybrid car.

Go build one, World...


Rhys Jones said...

Jaguar are already on to it

Adrian Bowyer said...

Great! (I said the blog was under-researched...)

Alasdair said...

And another link - Bladon Jets are collaborating with Jaguar (at our expense):

(actually, I think the TSB is one of the more sane ways of financing research, but that's another story)

As far as I can understand, it's difficult to get the highest of efficiencies in a small turbine, since you need minimal compressor and rotor clearances.

But I'm sure someone will figure it out.

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