>From the article: "An efficiency of 97.4 percent was achieved for the inductive power transmission at a coil distance of 13 cm. The transmitted power reaches up to 22 kW."
I doubt that the two achievements coincide, I mean that they probably were able to push 22kW across an inductive link (at much greater loss than the claimed 2.6%) and the claimed efficiency is only for the inductive power transmission, so just the coil-to-coil energy transfer (2.6% lost of the EM field) and does not take into account any electronics or conversion losses on the two ends. It is not the system efficiency, it is a component or actually a "module" efficiency and likely at relatively low power. In a transformer you can also find such optimums, where the inherent "magnetisation losses" are relatively low compared to the total power that you are pushing through, but before the I2R losses become significant enough to claim the majority of the losses... It is a research lab result, not a practical application result. Please note that there are plenty real-life EV-charging wireless stations in daily use! Since at least a year a commercial bus line in The Netherlands is running an EV bus with wireless charging at the end stop where the bus is parked for several minutes each trip and it receives enough charge to make the next trip, so it can be in continuous service each day without relying on just night time charging and a huge battery... I hope that we will get the figures from these practical applications, because those say more than the research lab numbers, even though it is good to know that efficiency *can* be pushed very high. NOTE that even conductive charging can have several percent of loss. It is not uncommon to see the charging voltage of a 120V outlet drop from 120 to 110V and even if I plug in 2 feet away from the service panel, the voltage at the end of my 100 ft charging cord drops by about 5V so that alone is approx 4% of losses in just the cord. As always, YMMV. Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of Lee Hart via EV Sent: Sunday, June 08, 2014 1:32 PM To: Peter C. Thompson; Electric Vehicle Discussion List Subject: Re: [EVDL] EVLN: Greenfield, MA's dicey drunk freakazoids unplugging EVs Peter C. Thompson via EV wrote: > BTW, I finally found a press release from someone other than Qualcomm > Halo - claiming 97.4% efficiency. I'll believe it when I see it. It's essentially impossible to build a *transformer* that's 97.4% efficient at this power level -- let alone the conversion losses in the electronics, and the inevitable losses in the air gap between sending and receiving coils. -- All children are born as engineers. Watch them at play. They're not just playing; they're building and learning. They are engineering. Then we get them in school and spend years squashing it out of them. -- Geoffrey Orsak, Southern Methodist University dean of engineering -- Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use 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 For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
