I'm not a physicist, and college physics was too many years ago, so maybe I have no business commenting on this. However, I'm somewhat sympathetic with the idea that maybe it's possible to harvest some energy from a roadway.
What is regenerative braking but the process ot retrieving and saving kinetic energy that we'd normally dissipate as heat? So IF (IF!) it can be shown that a roadway is significantly heated by the flexing of the asphalt or other surfacing material under the force of passing traffic, then it would appear that there's some energy there to be grabbed rather than wasted, no? (I have not seen this evidence, have you?) A few other thoughts here, in no particular order: I'm not sure these are of any value, but ... Is this one of those ideas that works great in the lab, but is too expensive and has too meager a return to bother scaling up? Some ideas are too risky for investors to back them. That's where government investment can move science ahead. There are perils in this, but some developments would never have happened without politicians. For example, if JFK hadn't said "let's go to the moon," would we have integrated circuits today? Would you be using this computer? Wouldn't it be tempting for the engineer designing such a road to make it more flexible to harvest more energy? Wouldn't that then increase the losses from passing vehicles? (Someone mentioned "like driving on sand." Exactly.) You might think of this as a road use tax, paid for in the extra energy the vehicles use compared to a conventional road. Hidden taxes like that can be sorely tempting for some politicians. :-\ Someone mentioned the piezo generators used in disposable butane lighters. Obviously they're generating a pretty respectable voltage because they can produce an arc to strike the gas. The piezo generators I know better are the ones used for decades in ceramic and crystal (Rochelle salt) microphones and phonograph pickups. These have a much higher voltage output than their dynamic counterparts - on the order of 10^3. A typical moving magnet phono cartridge will have an output of perhaps 3-10mv into a 47k load when playing a 5 cm/sec velocity 1000 Hz recorded tone. A crystal cartridge will produce something closer to 2-4 volts, easily enough to directly drive a Hi-Z audio power output tube such as a 50C5 or 50L6. (As a youngling, I had a one- lunger phono of exactly that design.) This is just from the feeble vibration of a stylus in a vinyl groove. But they require a high load impedance, on the order of several hundred k ohms. Any useful load for a "piezo roadway" would be between a fraction of an ohm and a few ohms (yes? no?), so some kind of conversion would be necessary. The devil is in the details! My intutive reaction -- and we all know how much THAT'S worth -- to this proposal is that it's kind of PITS (Pie in the Sky). This opinion I pulled from the air (or maybe from somewhere less exposed to sunshine) suggests that the piezo roadway idea will prove to be practical for energy prices many times higher than our current extractive energy prices. I suppose it would be safer to invest the same sums in proven sources -- PV, wind, and so on. But then there's that Apollo program that gave us modern electronics to think about ... As I say, this is all strictly from the gut, so feel free to trash my ideas. 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)
