> Tony Smith wrote:
> >>> Compare the
> >>> cost of that new hybrid with the cost /difference/ between
> >>>       
> >> the gas my
> >>     
> >>> old civic will use compared to the new hybrid. [...]
> >>>       
> >> I remember a while back one of the presenters at the local SAE 
> >> chapter meeting mentioned that storing the braking energy as 
> >> compressed air achieves up to 70% efficiency, compared to only 20% 
> >> for batteries. I do not recall the reason why hybrids are 
> still using 
> >> batteries. Safety? Difficult to achieve smooth acceleration?
> >>
> >> Best regards,
> >>
> >> Vitaliy
> >>     
> >
> >
> > Energy density.
> >
> > Battery don't hold much power, but bottles of air contain even less.
> >
> > Tony
> >
> >   
> I looked into compressed air as well, for storing household 
> energy. The pressures must be incredibly high before 
> compressed air becomes useful, but once the pressures are 
> high, air works wonders. For example, it is the ONLY way to 
> start large diesels (as in marine vessels). But to be useful 
> in the storage of energy, it seems to generate a lot of 
> useless heat when compressing, and cold when decompressing 
> (sounds like old Volkswagen air conditioner, doesn't it..?).
> 
> Years ago, as a young engineer from TI, I was sent to monitor 
> some TI seismic equipment on board seaborne seismic vessels. 
> The schemes used a method of generating explosions called an 
> "AIR GUN".
> It was a high-pressure air cable attached to a gadget that 
> was capable of releasing a HUGE bubble of air quickly, which 
> caused a shock wave that hammered the rock in the ocean 
> floor. These high pressures were generated by stout 
> three-stage , water-cooled air compressors on board the 
> seismic boat. The amount of energy released  with the bubble 
> was remarkable; fish within 200' were killed by the shock wave.
> 
> For me in 2002, the idea was to build a house in the western 
> desert of the US, self-sufficient, with wind generator and 
> batteries for light storage, and use compressed air for 
> long-term storage. For safety, the compressed air tanks had 
> to be buried deeply underground. The reason is that in the US 
> Western desert, wind speeds are high for several months of 
> the year, then low for several months, and excess wind power 
> would run compressors to store excess power. I think it is 
> feasible for a house, but NOT feasible for a vehicle, because
> (1) an accident could result in a disastrous explosion, and 
> (2) extra weight would be needed to make the tanks strong 
> enough to withstand 2000psi+..


Compressed air has a lot of power but not much energy, high volts but low
amps, you might say.

Can you claim the fishing method as environmentally friendly?

They is/was a company making flywheels to store energy for houses, you dug a
hole & dropped it in there.  They were targetting them at businesses to use
as back up power, replacing petrol generators & UPS batteries.

Fairly safe, if the flywheel exploded, well, it's in a hole in the ground.
They were in a low pressure (maybe a vacuum) container with magnetic
bearing, so 'self discharge' was low.  Not a bad idea if you can get it to
work.  Would last a long time too, not much to wear out.

Tony

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