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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / September 2005Chemically Regenerative Braking?
Regenerative braking is touted as one of the energy-saving advantages of hybrid/electric vehicles. Without going into the merits of that claim, I'd like to ask if there might be any way for the regenerative braking idea to work for regular combustion-powered vehicles (without resorting to flywheels). In other words, is there any way for energy recuperated from braking to be used to regenerate chemical fuel in a reasonably efficient way? > Regenerative braking is touted as one of the energy-saving advantages > of hybrid/electric vehicles. Without going into the merits of that [quoted text clipped - 4 lines] > In other words, is there any way for energy recuperated from braking to > be used to regenerate chemical fuel in a reasonably efficient way? Doesn't this pretty much describe the battery operation in an electric or hybrid car? I can't imagine any other method that wouldn't be impossibly complex compared to a chemical battery. Maybe a regenerative fuel cell? Don't make things any more complex than they need to be. --Damon >>Regenerative braking is touted as one of the energy-saving advantages >>of hybrid/electric vehicles. Without going into the merits of that [quoted text clipped - 13 lines] > > --Damon Don't know much about fuel cells, but are they reversible, like a motor-generator? In rec.autos.tech Don Stauffer <stauffer@usfamily.net> wrote: > Don't know much about fuel cells, but are they reversible, like a > motor-generator? A typical fuel cell takes hydrogen and combines it with oxygen from the air, producing water and electricity. Reversing the process is simple, it's called electrolysis. The problem is how do you store the hydrogen (the oxygen you can throw away because it's in the atmosphere already at about 20% concentration). Compressing hydrogen takes equipment that is too heavy and bulky and expensive to put in a typical car. There are other ways of storing hydrogen but they all have some type of overhead cost that makes them impractical. A battery, as many drawbacks as it has, is still far better for recovering energy created by regenerative braking. Even a supercap or a flywheel would suffice if the amount of regenerative braking energy is limited. > In rec.autos.tech Don Stauffer <stauffer@usfamily.net> wrote: > >>Don't know much about fuel cells, but are they reversible, like a >>motor-generator? we have reversible fuel cells available at http://www.green-trust.org/2005/09/award-winning-fuel-cell-kit.html for educational purposes.  SignatureSteve Spence Dir., Green Trust, http://www.green-trust.org Contributing Editor, http://www.off-grid.net http://www.rebelwolf.com/essn.html >> In rec.autos.tech Don Stauffer <stauffer@usfamily.net> wrote: >> [quoted text clipped - 4 lines] > http://www.green-trust.org/2005/09/award-winning-fuel-cell-kit.html > for educational purposes. Then regenerative braking on a fuel cell car should work. > In other words, is there any way for energy recuperated from braking to > be used to regenerate chemical fuel in a reasonably efficient way? I recall something about using hydraulic accumulators. It would be much simpler. Best, Dan. SignatureAdd one for email > > In other words, is there any way for energy recuperated from braking to > > be used to regenerate chemical fuel in a reasonably efficient way? > > I recall something about using hydraulic accumulators. It would be much > simpler. Sure, that's a possibility. How about a ratcheting spring? There are ways. The actual usage determined more by about density, packaging, reliability and cost. A battery and electric motor are pretty useful. >>>In other words, is there any way for energy recuperated from braking to >>>be used to regenerate chemical fuel in a reasonably efficient way? [quoted text clipped - 5 lines] > ways. The actual usage determined more by about density, packaging, > reliability and cost. A battery and electric motor are pretty useful. An air motor/compressor and compressed air tank would also work. However, the problem with either this or the hydraulic accumulator is that the total amount of stored energy is limited by the volume and weight of the accumulator or pressurized air tank. Maybe enough to save energy from single traffic light stop and feed it back in to recover most of it when starting, however. That should help milage in an urban cycle. >>>> In other words, is there any way for energy recuperated from braking to >>>> be used to regenerate chemical fuel in a reasonably efficient way? [quoted text clipped - 5 lines] >> ways. The actual usage determined more by about density, packaging, >> reliability and cost. A battery and electric motor are pretty useful. But the topic was not HEV. > An air motor/compressor and compressed air tank would also work. > However, the problem with either this or the hydraulic accumulator is [quoted text clipped - 3 lines] > most of it when starting, however. That should help milage in an urban > cycle. Sure. That is exactly what was meant. Hybrid vehicles are some other animal. Best, Dan. SignatureAdd one for email > Regenerative braking is touted as one of the energy-saving advantages > of hybrid/electric vehicles. Without going into the merits of that [quoted text clipped - 4 lines] > In other words, is there any way for energy recuperated from braking to > be used to regenerate chemical fuel in a reasonably efficient way? The only method I know where regenerative breaking could be used in a non-electric propulsion vehicle is to use a flywheel. The engine spins up a flywheel which is then used in the drive train to power the wheels, through a suitable clutch system. During breaking the flywheel is spun up from the breaking effort. The engine will have to add the rest though. Signature******************************************************************** Paul E. Bennett ....................<email://peb@amleth.demon.co.uk> Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/> Mob: +44 (0)7811-639972 Tel: +44 (0)1235-811095 Going Forth Safely ....EBA. http://www.electric-boat-association.org.uk/ ******************************************************************** >Regenerative braking is touted as one of the energy-saving advantages >of hybrid/electric vehicles. Without going into the merits of that [quoted text clipped - 4 lines] >In other words, is there any way for energy recuperated from braking to >be used to regenerate chemical fuel in a reasonably efficient way? Yes if you count energy store in a battery as "chemincal fuel". If not, i don't think of any method. Theorically, you could break with a power generator and use electricity to electrolyze water, keeping hydrogen as a secondary fuel for the engine, but this would be costly and inefficient. "Chemically-Regenerative Braking" sounds like marketing hype for battery recharging by the motor/generator. It's easy to do; a relay or two switch the armature from being fed by the power source to feeding the power source, and can be controlled by zero-throttle setting or light brake pressure. Hydraulic accumulators and compressing air have fatal flaws: very heavy, very inefficient. Both generate considerable heat, which comes right out of the energy being recovered. Diesel-electric locomotives have used dynamic braking for years. The motors become generators, and the electricity produced is run through heating grids in the roof of the machine and fans blow away the heat. They don't have batteries big enough to store the energy. Dan > In other words, is there any way for energy recuperated from braking to > be used to regenerate chemical fuel in a reasonably efficient way? There could be reversible fuel cells, certainly. The simplest chemical reversible situation is still the lead/lead sulfate/sulfuric acid storage battery. > Regenerative braking is touted as one of the energy-saving advantages > of hybrid/electric vehicles. Without going into the merits of that [quoted text clipped - 4 lines] > In other words, is there any way for energy recuperated from braking to > be used to regenerate chemical fuel in a reasonably efficient way? Compress air. SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ Quidquid latine dictum sit, altum viditur. (Whatever is said in Latin sounds profound.) >>Regenerative braking is touted as one of the energy-saving advantages >>of hybrid/electric vehicles. Without going into the merits of that [quoted text clipped - 6 lines] > > Compress air. Paul.... check your equations, there :-) Compressing air is AT MOST 50% efficient. Old PV=NRT bites you in the butt- when you compress a gas the temperature of the gas increases. Unless you USE the compressed gas BEFORE it cools back down to ambient tempreature, you're throwing away over 1/2 the energy you put into the compressor as heat that leaks out of the gas storage reservoir. |
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