Path: ...!local-3.nntp.ord.giganews.com!Xl.tags.giganews.com!local-1.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Sun, 02 Jun 2024 17:51:12 +0000 From: john larkin Newsgroups: sci.electronics.design Subject: Re: A couple of problems with EV charging roads? Date: Sun, 02 Jun 2024 10:51:11 -0700 Message-ID: References: User-Agent: ForteAgent/8.00.32.1272 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 57 X-Trace: sv3-Ewqe1GwsZnjQ9LTSlOoAEskjxeL5cB5tlCUvCJvicmciVrQ9EPHOcdhLuVu2acczpsCmQtTCwo/4C+R!DMg41hzIUaVzd/v5OG+6rt6kGXdG6ghX6HeAkRN6KkaZ3YFUWgRkqttRYgd9LA0MppLognH6QtHp!O27sFw== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 3671 On Sun, 2 Jun 2024 12:32:25 -0500, Crash Gordon wrote: >I've seen a couple of articles about roads with embedded inductive >charging for EVs. And there are a couple of issues that seem to me to >make these roads unfeasible. (I'm not even going to get into any of the >financial side) > >My qualifications: I have a few decades experience in circuit design >and have had the word "Engineer" in my job title at several different >employers, but never went to college. So I have a lot of >"wisdom-through-experience" but there are a lot of holes in my basic >knowledge -- I tend to know a lot about the things I know, but nothing >at all about other closely related things. So I am quite willing to >accept that there's stuff going on here I simply don't understand. Feel >free to educate me. Moving along... > > >First: Inductive charging is basically building a transformer where the >primary is in one device (in this case, the road surface) and the >secondary is in a different device (here, an EV). Ordinarily when we >design transformers, we take great care to maximize the coupling between >the primary and secondary because loose coupling is responsible for much >of the loss in transferred power. > >But in charging an EV there is necessarily going to be a considerable >air gap between the primary and the secondary. Although we can optimize >in other areas to account for this somewhat, it seems to me that there's >going to be a lot of energy lost here, mostly as heat radiated into the air. > >Second: In order to transfer significant energy, there's going to have >to be some significant coupling of magnetic fields between the EV and >the road. Wouldn't this be a source of substantial drag? Effectively >the car would be driving "uphill" the whole time it's charging. > I'd expect that drag to be small. But if the car drops down a coil, to be closer to the roadway, air drag will increase. > >My thought is that if we're going to be shoveling huge amounts of >electricity into a road surface, we could use it more efficiently by >building a giant linear actuator with the EV as the moving part. > > >Opinions? It's a silly idea. The cost would be incredible. And we're eliminating power plants and working towards rotating blackouts already. Imagine adding a megawatt per mile of road. Resonant coils can couple fairly well, even with an air gap. I think some electric busses charge that way. Efficiency will be low. Some of the transmitted energy will heat the soil and rerod and car parts. And melt snow!