I have reported before that almost 20 years ago I visited MDI in France, who were supposed to release an air-powered car. I checked their physics and came to the conclusion that without heat exchanger, their efficiency would be horrible and the air engine would freeze up. That is exactly what several news reporters have said once they took a slightly longer test run than just a loop in the parking lot. Physics is quite clear about the efficiency of compressing and expanding a gas like air. You invest a *lot* of power in the compression and get a *lot* of heat out at that moment. As Lee would say: heat is the indicator of (in)efficiency. Only if you are able to either store or feed that heat back in during expansion, can you get a decent efficiency. Since MDI did not design that in, their cars were doomed to be wasteful and since the compressed air storage has so low energy density, their range was short. There really was not a whole lot of difference compared to running batteries, though in theory the weight could be less and the absence of lead or acid or other dangerous materials was a benefit, but the lower efficiency made it a non-starter. There are niches where air powered vehicles were used, think mine corridors where no dangerous goods, sparks or combustion was a big benefit for the operation underground. Today we would use an AC (brushless) drive to avoid the sparks and achieve better efficiency.
Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of EVDL Administrator via EV Sent: Saturday, October 01, 2016 4:51 PM To: [email protected] Subject: Re: [EVDL] Compressed Air On 30 Sep 2016 at 19:44, Michael Ross via EV wrote: > Can we discuss compressed air a a storage medium that can spin > electric motors in autos and trucks? Maybe, but I don't see how air can power a motor. We've had posts on compressed air cars before - check the archive - but those aren't EVs. See Wikipedia for a decent article on compressed air cars that explains why they've never made the big time despite nearly a century of tinkering witih the concept. The problems are low efficiency and an energy density by volume that's worse than lead batteries. > Certain elements can be reformatted to higher energy states and then > reacted to power EV's. Isn't this how batteries work? > There is a particular reaction that could be used to store energy from > sustainable, but temporally irregular energy sources. It is a very > simple reaction, readily available ingredients are found everywhere for > little cost. And that is ... ??? > Technology exists to store the energy and release it, that is > sufficiently efficient (since there is no alternative other than to > waste solar and wind energy when it is inconveniently timed efficiency > becomes less concerning) As I understand it, batteries are the gold standard for efficiency in this. Between 20% and 80% SOC, lead batteries are close to 100% efficient. I'd guess that other types have similar ranges with similar efficiency. Air compressed in undergound mines has been used for utility load leveling. The programs so far have required natural gas input to warm the cold released air. Their efficiency looks decent if you ignore the gas input. However, one source I read put the actual efficiency for air storage at 25- 45%. Pumped hydro is much more common and supposedly runs 60-85% efficiency, though I admit I find that hard to believe too. The island of El Hierro is now generating almost all of their electricity with wind, and storing it with pumped hydro. > compressed air could do this, but I would really prefer it was a > compressed reactive gas not just nitrogen and some other lesser > components. Can you explain why? > If this particular gas was used, an additional use is possible, we > could use to power EVs. What gas are you talking about? It almost seems as if you're avoiding naming it. Why all the mystery? David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
