The Electric Car
in [Design]
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From: Eeyore on 2 Aug 2007 11:53 Nobody wrote: > On Wed, 01 Aug 2007 20:18:45 +0100, Eeyore wrote: > > > I drove a Peugeot 1.9 turbo diesel as long ago as 1988. It was pretty brisk. Performance seem to > > be less of an issue with diesels these days although they don't rev as fast. > > They do take a bit of getting used to. If you're used to petrol, it takes > quite a while to get into the habit of changing up earlier (when your > subconscious is convinced that the engine would splutter). And modern engines don't splutter !
From: Eeyore on 2 Aug 2007 11:57 default wrote: > One alternative to a different class of electrical service might be > super caps Have you any idea how poor the energy density of even super caps is compared to batteries ? Graham
From: default on 2 Aug 2007 12:34 On Thu, 02 Aug 2007 16:57:31 +0100, Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > >default wrote: > >> One alternative to a different class of electrical service might be >> super caps > >Have you any idea how poor the energy density of even super caps is compared to >batteries ? > >Graham No. The point I was making was the idea of an interim storage system just to bypass the need for three phase power or super high amperage service, long runs of high current wire etc. Vacuum flywheel? No reason to expect practical solutions yet - new technology takes time and demand, practical takes time. I don't think the Tesla Roadster is practical, but I'm glad it is there. Now what about my diesel hybrid motorcycle? -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =----
From: Nobody on 2 Aug 2007 12:34 On Thu, 02 Aug 2007 16:52:15 +0100, Eeyore wrote: >> >> On the highway, the engine gets connected directly to the wheels. >> >> This takes the sosses of the electric machines out of the picture. >> > >> > What losses ? Electric motors are highly efficient. >> >> Any motor inefficiencies are doubled (the generator likely has similar >> losses to the motor), and added to any losses in the power electronics >> (which may increase when running at full power continuously; e.g. >> a MOSFET's R[DS(on)] increases with temperature). > > It seems to just argued against using any electric motors at all. Not at all. Motors are a lot more efficient than an ICE. But if you're using an ICE as the power source, you're not comparing motor efficiency against ICE efficiency, but an electric generator->conversion->motor drivetrain against a mechanical drivetrain. It may still win, either in absolute or relative terms (i.e. whether or not you take into account the ability to run the ICE at optimum speed/load). But for now, the issue is whether it wins by enough to overcome the inertia of sticking with the "safe" option. >> >> It also allows the engine and both motors to be used for passing power. >> > >> > At the cost and complexity of requiring a transmission. I just don't see any sense in it. >> >> Mechanical transmission is what they're familiar with. Current hybrids >> largely try to tweak existing technology rather than starting with a >> clean slate. > > Which is why the advantage they offer is so poor. > > Do wake up. You seem to be looking at it from an "ideal world" perspective, i.e. considering the technology on its merits alone. I don't think that's a particularly meaningful perspective. None of the major car makers are going to abandon ICE technology soon, so they will be looking to "dual-purpose" as much of their existing technology and infrastructure as possible. If you design an engine purely for a serial hybrid, the result isn't going to look anything like a normal car engine. The same applies to much of the rest of the car: wheels designed for embedded motors won't look like those designed for an axle. Cooling for an engine whose power doesn't vary with speed is a different problem than for one which relies upon forward motion for the airflow. And so on. A ground-up redesign involves a lot of cost and a lot of risk. Even if it's successful, you end up competing with yourself, as gains in one technology don't easily transfer to the other. I just don't see any major car maker betting their future on electric vehicles right now. Development will be incremental, and entirely subordinate to the constraints of their conventional production lines.
From: Eeyore on 2 Aug 2007 14:06
Nobody wrote: > Eeyore wrote: > > >> >> On the highway, the engine gets connected directly to the wheels. > >> >> This takes the sosses of the electric machines out of the picture. > >> > > >> > What losses ? Electric motors are highly efficient. > >> > >> Any motor inefficiencies are doubled (the generator likely has similar > >> losses to the motor), and added to any losses in the power electronics > >> (which may increase when running at full power continuously; e.g. > >> a MOSFET's R[DS(on)] increases with temperature). > > > > It seems to just argued against using any electric motors at all. > > Not at all. Motors are a lot more efficient than an ICE. But if you're > using an ICE as the power source, you're not comparing motor efficiency > against ICE efficiency, but an electric generator->conversion->motor > drivetrain against a mechanical drivetrain. And if the ICE is operating in its most efficient regime in its generator application (which it will be) all those losses will still outperform an ICE driving the wheels directly. Plus, pure electric traction easily lends itself to the most effective and easily implemented regenerative braking, and traction control etc etc.. Graham |