On Saturday, June 16, 2018 at 6:03:27 AM UTC-7, Martin Gregorie wrote:
On Fri, 15 Jun 2018 18:54:18 -0700, moshe.braner wrote:

On Friday, June 15, 2018 at 5:23:14 PM UTC-4, Martin Gregorie wrote:
On Fri, 15 Jun 2018 11:54:26 -0700, Steve Koerner wrote:

On Friday, June 15, 2018 at 10:39:26 AM UTC-7,
wrote:
On Friday, June 15, 2018 at 12:18:30 PM UTC-4, Steve Koerner wrote:
Go ask your electrical utility for a price quote on that sort of
connection...

Well Moshe, when the supercapacitors become workable in cars, why
wouldn't they also become workable for buffering at the filling
station? Megawatt connections won't be the issue.

You'd need a heck of a lot of those supercapacitors. The reason
they are being talked about in cars is to provide acceleration or
regeneration for a few seconds, a small amount of energy relative to
what's stored in the main battery. Sort of like a now-old-hat
"hybrid"
car uses the battery for short-term acceleration and regeneration
while the gasoline tank stores most of the energy. The supercaps
have a much lower energy storage density, and much higher price per
energy unit, relative to batteries. Also, at a "filling station"
you'd want to allow one car to fill-er-up after the other, not much
time for buffering. So you'd still need megawatts of supply.
That's actually perhaps economically feasible at a dedicated filling
station, but not at home.

Makes sense. I've not looked at numbers. It's fun to read the
tidbits in Gliding International about carbon nanotube materials and
super dense battery technology -- even if it's mostly fictional and
none of it will come to light. Numbers just spoil the fun. I'd
rather continue to contemplate supercapacitors that will be tiny and
cheap and hold enormous energy.

A very quick bit of playing with numbers (service station with 18
chargers, assuming that each recharge was the equivalent of a tankful
of petrol, 60 litres, and charging averages one full charge sold per
charger each hour over a 10 hour day) looked like an equivalent
electric charge point would need a continuous power input of around 0.1
MW.

Assumptions:
- 60 litres is a full tank: that's roughly what my Focus takes.
- The standard energy content of a litre petrol is 10 KWh.
- The number of pumps matches my local supermarket.
- The average fill rate of one tankful per pump per hour is a guess
based on how full the service station is at various times combined
with a guestimate that the average stop for a full tank of gas is
10-12 minutes.


--
Martin | martin at Gregorie | gregorie dot org

Martin: check your numbers. 60 liter * 10 KWH/l * 18 pumps * 10 hours =
108,000 KWH, or about 10,000 KWH per hour, i.e., 10 megawatts (if
supplied over those same 10 hours).

Yep. I forgot to convert KWh to MWh. I was having a slow day.

And one tankful per pump per hour is very slow for a gasoline filling
station,

Sure. Based on my usual timing, a fill seems to take around 10 min if you
include queuing at the til - pay at the pump has only just appeared at my
usual service station and I haven't yet got my head around how long it
takes now. But, it would seem unlikely that a pump could deal with more
than 20 cars an hour, but average over a whole day the throughput has to
be less when you consider that for much of the time maybe only 25% of the
pumps are in use.

although fairly fast for
battery charging with current non-vaporware batteries.

Agreed.

The actual
filling of a tank takes about 1/18 of an hour, so that flow rate of fuel
into your tank is 10 megawatts! Yes, it's hard to beat fossil fuels in
energy density.

Yes, exactly so. Another point is that building the generation capacity
to replace the refineries producing petrol and diesel and adding the
cabling to get that power to the charging stations is going to take quite
a lot of time and money. That process will be slow and expensive enough
here in a physically small country, so I wonder how long and expensive it
will be in a place as big as the USA. Have the people planning your
carbonless future thought about that? I don't think ours have.


--
Martin | martin at
Gregorie | gregorie dot org

I've watched them build the Tesla charging station near my home. The power service looks like a small power substation. I think they only have 10 charging stations, supposed to be able to get a Tesla to something like 80% in 30 minutes.

Tesla also proposed, and began to build, battery swap stations for their cars. I'm not sure it was every made operational. The Tesla batteries are underneath and apparently quickly swappable - not slide out, but put on a lift and R&R with some special equipment. One problem you will run into is the battery pack you get might have 5000 cycles on it, vs. yours with only 500..

Another problem with mass conversion to electric cars: the public believes the electricity comes out of trees or something. In fact in most of the US, fossil fuels (coal or diesel) are used to generate the power. Many of these plants are turbines, and are not as thermally efficient as a modern car engine. Hydro power is pretty much fully developed (as much as the public will stand anyway) and there hasn't been a nuclear plant built in decades. Solar may be an answer, but it requires energy storage systems that are not currently in place. Fusion IS the answer, but someone has yet to crack that nut.