07-07-2021, 11:41 AM
(This post was last modified: 07-07-2021, 11:47 AM by Tony Griffiths.)
I did a couple of longish runs recently. Home to Bristol to home via Birmingham; 540 miles without stopping for fuel and still with 240 miles of range left. Then, home to Heathrow via Rubgy and home; 335 miles all both runs with just one stop for fuel and enough remaining for a further 690 miles or so. Our knock-about grot-box for local running needs just one ten-minute stop every six weeks to fill up. When electric cars can beat those figures I might buy one. But, there is a snag and some brutal facts to face, as this chap pointed out in the paper the other day. "There currently around 20,000 public charging points in Britain, with another 20,000 private ones - and the SMMT reckons we'll need around 2.3 million by 2030. Only 2.26 million to go - and I make that about 4,750 per week (allowing for holidays). Good luck with that, Greenies!
Now, what about these magic “ultra-rapid" chargers that "can charge cars in a matter of minutes". Sounds exciting, but, why are there are so few of them? Here's the reason: take the tiny, useless Renault Zoe - battery 52kWhr, 400-Volt lithium - and do some rough calculations on the current / voltage needed to put 80% of nominal charge into it in five minutes. Feel free to check my working: plugged into a 3-phase, 440-Volt supply that’s over 100 Amps - but how many homes have a 3-phase supply? virtually none. Use the domestic 220-Volt single-phase supply and it rises to over 220 Amps - but the typical house breaker trips at 65 Amps - so, that’s a non-starter. Something EV manufacturers hide about rapid-charge stations is that the battery gets very hot - and a quarter megawatt of heat is not easy to dissipate. The Nernst equation says that heat kills cycle life (above ~40C, about 2x per 10C).. You can rapid charge often for convenience, but doing so will kill the battery sooner rather than later. Perhaps an undisclosed EV financial warranty liability?
Of course, Motorway service stations and ordinary filling stations have a 3-phase supply, but what if they fit twenty ultra-rapid chargers? With all in use, that's about 2,000 Amps, with two lots of cabling to split the load into something manageable, with each of the three cores (plus earth) being 630 sq. mm. in cross-sectional area, and each core 38 mm in dia. So, maybe the services on the M25, and groups of local garages can club together and buy their own power station driven by a nuclear sub-type reactor from Rolls-Royce? Twenty chargers in one service area on a packed M25 - not really enough is it, so, let’s go to forty and install five stations so equipped. Operating simultaneously that’s 0.25MW x 200 = 50 Megawatts of power. That’s a lot of electricity – enough to power 25,000 homes - just for five charging stations operating at full capacity (on the M25 alone). The grid can barely service current requirements – so where will we find 10s of gigawatts of extra power to recharge a 100% EV fleet? Compare this to a petrol filling station, which is essentially just a big underground tank and a pump. The power is conveniently stored in liquid form, so it's much easier and cheaper to handle and deliver. Without some major breakthroughs, all-electric national vehicle fleets are just as much of a fantasy as the rest of the green package of climate “solutions”. "
Now, what about these magic “ultra-rapid" chargers that "can charge cars in a matter of minutes". Sounds exciting, but, why are there are so few of them? Here's the reason: take the tiny, useless Renault Zoe - battery 52kWhr, 400-Volt lithium - and do some rough calculations on the current / voltage needed to put 80% of nominal charge into it in five minutes. Feel free to check my working: plugged into a 3-phase, 440-Volt supply that’s over 100 Amps - but how many homes have a 3-phase supply? virtually none. Use the domestic 220-Volt single-phase supply and it rises to over 220 Amps - but the typical house breaker trips at 65 Amps - so, that’s a non-starter. Something EV manufacturers hide about rapid-charge stations is that the battery gets very hot - and a quarter megawatt of heat is not easy to dissipate. The Nernst equation says that heat kills cycle life (above ~40C, about 2x per 10C).. You can rapid charge often for convenience, but doing so will kill the battery sooner rather than later. Perhaps an undisclosed EV financial warranty liability?
Of course, Motorway service stations and ordinary filling stations have a 3-phase supply, but what if they fit twenty ultra-rapid chargers? With all in use, that's about 2,000 Amps, with two lots of cabling to split the load into something manageable, with each of the three cores (plus earth) being 630 sq. mm. in cross-sectional area, and each core 38 mm in dia. So, maybe the services on the M25, and groups of local garages can club together and buy their own power station driven by a nuclear sub-type reactor from Rolls-Royce? Twenty chargers in one service area on a packed M25 - not really enough is it, so, let’s go to forty and install five stations so equipped. Operating simultaneously that’s 0.25MW x 200 = 50 Megawatts of power. That’s a lot of electricity – enough to power 25,000 homes - just for five charging stations operating at full capacity (on the M25 alone). The grid can barely service current requirements – so where will we find 10s of gigawatts of extra power to recharge a 100% EV fleet? Compare this to a petrol filling station, which is essentially just a big underground tank and a pump. The power is conveniently stored in liquid form, so it's much easier and cheaper to handle and deliver. Without some major breakthroughs, all-electric national vehicle fleets are just as much of a fantasy as the rest of the green package of climate “solutions”. "
(07-07-2021, 10:38 AM)Chris KC Wrote: And of course how 'green' it is depends on how the electricity is generated. Norway = hydro electric = full marks. Eastern Europe = coal fired = <gulp>Not to worry, in 2020 the Chinese built over 50 new coal-fired power stations and plan many more. India, Indonesia and many other countries - backed by Chinese money - also plan an expansion of cheap, coal-fired energy.