[LINK] Compressed Air Hybrids [WAS plug-in-hybrid-vehicles and grids]

David Boxall david.boxall at hunterlink.net.au
Mon Sep 7 16:38:43 AEST 2009

On Mon, 07 Sep 2009 at 15:52:15 +1000 Karl Auer wrote:
> ... it seems to me that compressing air as a means of storing energy
> must be one of the worst methods ever thought of. Compressing air heats
> it; heat is easily lost. Pressure vessels are tricky at the best of
> times, but the pressure needed to move a *car* would be terrifying.
The energy stored in a hybrid's battery is no joke either. Ever 
accidentally put a spanner across the terminals of a car battery? It's 
enough to vapourise (parts of) the spanner and the battery! Add to that 
the toxic chemicals involved, plus the sheer weight of the batteries, 
and consequences of an accident are potentially severe.

In stop-start driving, the energy isn't stored for long, so heat loss 
isn't the issue it might otherwise be. The air tanks are carbon fibre, 
which is light and fails (in an accident, for example) by tearing. 
There's no explosion, as there can be with batteries in that situation.

With no batteries or secondary electric drive train, compressed air 
hybrids are lighter than battery-electric, which makes for greater 
efficiency. The electro-hydraulic gear that replaces the cam train in 
compressed air hybrids (so the engine can be programmed to act in both 
internal combustion and compressor modes) also offers intriguing 
potential for tuning and optimising the combustion cycle.

Transport will reply on liquid fuels for the foreseeable future, at 
least for longer distances. Those fuels may not be fossil, but we'll 
need to make the best of them. The potential of a fully-programmable 
combustion cycle is intriguing indeed.
David Boxall                    |  When a distinguished but elderly
                                |  scientist states that something is
http://david.boxall.name        |  possible, he is almost certainly
                                |  right. When he states that
                                |  something is impossible, he is
                                |  very probably wrong.
                                                   --Arthur C. Clarke

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