The Electric Car
in [Design]
|
From: MooseFET on 12 Aug 2007 10:26 On Aug 12, 2:07 am, JosephKK <joseph_barr...(a)sbcglobal.net> wrote: > MooseFET kensm...(a)rahul.net posted to sci.electronics.design: > > > > > On Aug 8, 7:37 am, Gary Tait <classic...(a)yahoo.com> wrote: > >> Guy Macon <http://www.guymacon.com/> wrote > >> innews:W8GdnQS9I_ZqOSXbRVn_vw(a)giganews.com: > > >> > You will never see pneumatics in a bulldozer, and you will > >> > never see hydraulics in a machine that puts CDs into CD > >> > cases. Having worked as a design engineer for both Parker > >> > Hydraulics and SMC Pnuematics, I don't see either of them > >> > cutting into the other's business. > > >> FWIW, I have seens both pnuematics and hyraulics on the same > >> systems before. > >> Pnuematics used for quick low power actuating (guiding product); > >> the plumbing and controls are a bit simpler, hydraulics for the > >> bull work; orbit motors and a hydraulic lift. > > > It is a question of storing energy that was at issue not of taking > > it from place to place. In a car the tranfer of power is well > > handled by the mechanical transmission. > > > For energy storage in a hydraulic system, hydro-pneumatic > > accumulators > > are the most commonly used accumulators. The energy is stored by > > compressing the gas in the accumulator. This is the path the US > > EPA took on this: > > >http://www.epa.gov/otaq/technology/420f04019.pdf > > The elastic bag in hydro-pneumatic accumulators accounts for about > half of the stored energy. Surprised me when i did the calcs. Yes that surprises me too. It still will store a lot of energy per pound in the air part. Compressed air has a lot of nice qualities for this sort of purpose.
From: Don Lancaster on 12 Aug 2007 11:48 MooseFET wrote: > > Yes that surprises me too. It still will store a lot of energy per > pound in the air part. Compressed air has a lot of nice qualities for > this sort of purpose. > Nope. Energy per pound storage is trivial compared to alternatives. Energy per pound is also totally meaningless for terrestrial auto aps. Start with any thermo book and read example problem #1 on isothermal versus lossy air compression. Hard to reach 15 watthours per liter and 60 percent efficiency. -- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don(a)tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com
From: MooseFET on 12 Aug 2007 12:21 On Aug 12, 8:48 am, Don Lancaster <d...(a)tinaja.com> wrote: > MooseFET wrote: > > > Yes that surprises me too. It still will store a lot of energy per > > pound in the air part. Compressed air has a lot of nice qualities for > > this sort of purpose. > > Nope. > Energy per pound storage is trivial compared to alternatives. I assume you have a number to back this up. Remember it is energy per pound. > > Energy per pound is also totally meaningless for terrestrial auto aps. You are wrong here. The problem with the lead acid battery is its weight not its size. > Start with any thermo book and read example problem #1 on isothermal > versus lossy air compression. > > Hard to reach 15 watthours per liter and 60 percent efficiency. ... and yet the hydraulic hybrid autos seem to be using it to store the energy http://www.theautochannel.com/news/2006/08/14/018529.html
From: Guy Macon on 12 Aug 2007 13:02 Don Lancaster wrote: > >MooseFET wrote: >> >> Yes that surprises me too. It still will store a lot of energy per >> pound in the air part. Compressed air has a lot of nice qualities for >> this sort of purpose. > >Nope. >Energy per pound storage is trivial compared to alternatives. > >Energy per pound is also totally meaningless for terrestrial auto aps. > >Start with any thermo book and read example problem #1 on isothermal >versus lossy air compression. > >Hard to reach 15 watthours per liter and 60 percent efficiency. Don is right. I have designed many pneumatic systems with energy storage. Storing enough to bring a bunch of pneumatic actuators to a safe position on power loss is easy. Storing enough to be a practical energy source for a car? Not at all practical. Not only that, but it would make an excellent bomb just waiting to go off in a crash. -- Guy Macon <http://www.guymacon.com/>
From: Guy Macon on 12 Aug 2007 13:12
MooseFET wrote: >.. and yet the hydraulic hybrid autos seem to be using it to store the >energy >http://www.theautochannel.com/news/2006/08/14/018529.html Storing the energy of braking to a stop so as to give it back when you accelerate requires a lot less energy storage than storing enough energy to replace the engine. It's well worth doing in the case of a delivery truck, but it isn't a practical replacement for an electric car. -- Guy Macon <http://www.guymacon.com/> |