Horace we can't be right, or the whole thing would have to be a gross scam. This serious looking resource here:
http://www.efcf.com/reports/E14.pdf seems to agree reasonably with Wikipedia's 12kWh: "At 20°C a 300 Liter tank filled with air at 300 bar carries 51 MJ of energy." That's 51000 kW s / 3 600 = 14.2 kW h I guess we'll both have to brush up our thermodynamics :/ But we are not the only ones to get it wrong, according to the above paper's abstract: "the claimed performance has been questioned by car manufacturers and automobile expert. Basically, when referred to ambient conditions, the relatively low energy content of the compressed air in a tank of acceptable volume is claimed to be insufficient to move even small cars over meaningful distances. On the other hand, another air car developer claims to have driven 184 km on one 300 Liter filled with air at initially 300 bar pressure" I just saw Robin's explanation for the discrepancy (heat taken from ambient air during expansion, which produces cold air as is well know), it makes sense to me. It's quite remarkable that 9 kWh out of the 12 seem to be provided by the environment! It would also mean that the car's range could be considerably reduced in very cold weather. It might also give insight into how the fuel (gasoline, whatever) is used in highway mode... maybe it simply heats up the expanding air to get more energy out of it? Michel ----- Original Message ----- From: "Horace Heffner" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Friday, January 11, 2008 10:09 PM Subject: Re: [Vo]:Re: Photos of Guy Negre's compressed air car on CNET News.com > > On Jan 11, 2008, at 7:56 AM, Michel Jullian wrote: > >> I understood the sentence as referring to some pneumatic version of >> regenerative braking, but >> admittedly it was unclear. >> >> What amazes me with this compressed air energy storage thing is that it is >> so dead simple, isn't >> there a catch somewhere? >> >> Let's see how much energy they store in their 300 litres at 300 >> atmospheres, it's P*V isn't it? >> >> P*V= 300*10^5Pa * 0.3m^3 =~ 10^7 J = 10^7 W.s = 10^4 kW.s > > Yes - I get 9.12x10^6 W s = 9.12x10^3 kW s = 2.53 kWh. > >> >> Mmmm... only about 10000/3600 =~ 3 kWh???? >> >> Which is wrong, me or Jed's beloved Wikipedia? http:// >> en.wikipedia.org/wiki/Compressed_air_vehicle : >> "300 litre air at 300 bar only amounts to about 12kWh (the equivalent of >> 1.4 litre (0.37 >> gallons) of >> gasoline)" > > > The above should be 0.075 gallons of gasoline., or 0.28 liters. > > >> Probably me, the maths must be more complicated than P*V... correction >> welcome. > > > Looks to me like you have it right and Wiki has it wrong. > > >> >> Michel >> >> ----- Original Message ----- >> From: "Jed Rothwell" <[EMAIL PROTECTED]> >> To: <vortex-l@eskimo.com>; <vortex-l@eskimo.com> >> Sent: Thursday, January 10, 2008 3:57 PM >> Subject: Re: [Vo]:Photos of Guy Negre's compressed air car on CNET News.com >> >> >>> A Cnet report: >>> >>>> Fill'er up: >>>> http://www.news.com/2300-11389_3-6225395-4.html?tag=ne.gall.pg >>> >>> This one says: >>> >>> "Here's where you fill 'er up with compressed air. The air drives the >>> pistons in the engine, >>> and >>> the engine returns the favor by recompressing air for later use." >>> >>> A perpetual motion machine! >>> >>> These reporters are such idiots. >>> >>> - Jed >>> >> >> > > > > Horace Heffner > http://www.mtaonline.net/~hheffner/ > > >
