On 5/14/2015 11:21 AM, Ben Goren via EV wrote (in part):
No way is that station going to have a 20 MW feed from the grid...that's about 5% - 20% of the output of a utility-scale generating unit. And even the utilities themselves would have problems running such a facility because of the sharply peaking nature of the load.
Ummm, No. You guys are not electric utility guys, and you need a little reality check from one. Except for some small utilities, a 20MW load is really no big deal. A bit much for most residential distribution lines, but not a big deal otherwise. The distribution line that feeds my house is 12KV (phase to phase on the 3 phase or about 6.9KV from each phase to neutral). As I recall during peak loads it runs about 300 amps per phase or about 2MW per phase. This i an OLD distribution line. My electric utility is running considerably higher voltage for distribution in newer construction areas. BTW, for reasonably modern utility generating stations, a small one might be 250MW, and a large one in the 750 to 1,000 MW (or in some cases larger). So your 5 - 20% figure is WAY off.
But if, on average over the course of a day including times when all slots are empty, the station only "sees" one or two stalls in use at a time...well, a megawatt utility connection is still pretty freakin' huge -- 1 kV @ 1 kA, or however you want to balance the two -- but much more manageable.
A megawatt connection is going to be a the local distribution voltage which depending on the utility and how old it is, will likely be no less than 12KV and could be as much at 66KV. That's only about 15 - 80 amps (and yea, I'm simplifying it by giving a number as if it was single phase - it would actually be 3 phase and I'm too tired to do the math in my head right now).
Everything I've heard from the utilities is that charging even large numbers of EVs is not a real problem.
-- 73 ------------------------------------- Jim Walls - K6CCC j...@k6ccc.org _______________________________________________ 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)
