Re: Couple of Fundamental Electric Vehicle Questions
- From: "Rob Dekker" <rob@xxxxxxxxxxx>
- Date: Sat, 24 May 2008 15:21:04 -0700
"Bill Ghrist" <notmyname@xxxxxxxxxxxx> wrote in message news:9n%Vj.1074$lQ1.319@xxxxxxxxxxx
wdoe999@xxxxxxxxx wrote:.....
Here are a few ball park calculations. these are not intended to be extremely precise, but I think they represent a fair picture.
Assumptions:
Energy consumption for an electric vehicle is about 2.5 mile per kWhr.
Cost of electricity is about $0.10 per kWhr.
Gas mileage is about 25 miles per gallon and gas costs about $3.50 per gallon.
Total miles driven in the US by passenger cars is 1.7 10^12 miles per year
(http://www.bts.gov/publications/national_transportation_statistics/html/table_01_32.html).
US electrical generating capacity is about 900,000 MW, and peak demand is about 760,000 MW
(http://www.eia.doe.gov/cneaf/electricity/epa/epat3p2.html).
Total generation is about 4 10^9 MWhr per year, which would translate to an average demand of about 450 MW
(http://www.eia.doe.gov/cneaf/electricity/epa/epat1p1.html).
Thanks for finding these numbers !
Use an average of 2.5 mile per kWhr, for 1.7 trillion miles that passenger cars drive, then we need 680 GWhr per year, or an average
of 77 GW.
At average current demand of 450 GW, that is only a 17 % increase in average load on the grid.
The grid and baseload generation can probably handle that today if most of these vehicles get charged at night.
If we would want to build this 77 GW extra baseload, this could be done by building 40 large 2 GW nuclear plants, or some 300 small
250MW solar thermal plants (like the one that's build in Arizona right now). Of course, could do this with distributed PV (like
California's 2 GW million solar roof initiative) or any other electrical generation resource for that matter.
The total (investment) cost of these would be anywhere between $ 100 billion - $ 300 billion in 2008 dollars.
Since this is spread out over many years (not all cars turn EV overnight), that seems rather modest, and seems the least of our
problems right now.
Here is the much bigger problem :
For a full electric passenger vehicle fleet, the 77 GW power that we need will actually go into charging batteries !
Image how much the batteries will cost ? Anyone dare to try a back-of-the envelope calculation ?
After this, we still would need fuel for the 1.3 trillion miles that trucks and other vehicles drive each year too. And these big
trucks use a lot more energy per mile..
P.S. Where did you get the 2.5 miles per kWh from ?
Nighttime demand is about 40% of peak daytime demand (i.e., about 300,000 MW)
(http://www.ecoworld.com/blog/2008/02/06/solels-solar-thermal/).
Given the above, the fuel cost for an electric automobile is about $0.04 per mile and that of a gasoline powered automobile is
about $0.14 per mile. If you drive 10,000 miles per year, you would be paying $1,000 more for gasoline than for electricity.
The big unknown is battery cost. Right now, there is no battery technology available that would provide sufficient range to allow
all automobiles to be totally electric, as opposed to plug-in hybrids (which use both electricity and gasoline most of the time)
or extended range electrical autos (such as the proposed GM Volt, which uses only electricity for a limited number of miles, then
has a gasoline engine to recharge the battery for extended range). If we would ever get to the point of having all electric
vehicles, that would presuppose advances in battery or fuel cell technology which make costs impossible to predict at this time.
GM seems to agree with you. Batteries are the problem.
They are not bringing the Volt into production yet, because "the batteries are not included".
I find that rather upsetting, especially since the first line of hybrids should not even need much of a battery to obtain great fuel
economy. And neither does the Volt.
Instead, it could use an ultra-capacitor (of a few hundred kJ) to handle (fierce) accelleration and regenerative braking, and a very
modest ICE/generator (maybe 50hp) to overcome rolling and air drag losses. The Volt already has that (although not the
ultracapacitor).
Such cars can still be equipped with strong (300hp) electric motors for very sporty accelleration and almost complete regenerative
braking, using the ultracapacitor.
Overall 50 MPG is proven with this concept, probably could increase even further when the concept is better optimized.
Here is a concept car :
http://www.pmlflightlink.com/archive/news_mini.html
Battery can be then added (for full EV drive) when battery technology progresses (less expensive and less mass).
When do we start ?
If an electric vehicle costs, for example, $10,000 more than a gas powered one, you would reach break-even after 10 years (at
1,000 mile per year, and not considering the finance costs for the additional $10k).
If all of our current passenger car travel were to be done with electric vehicles (at 2.5 mile per kWhr), it would use about 680
10^9 kWhr of electrical energy per year. If we assume that recharging would occur overnight, for eight hours per night, that
would result in an increased average demand of about 240,000 MW.
Ideally, that increased demand could be covered by the difference between daytime demand and nighttime demand, so no new
generating capacity would be needed. It is unlikely, however, that this would be the case. For one thing, it is not likely that
the actual peak increase in demand could be averaged out that perfectly. For another thing, right now nighttime demand is
supplied by the generators with the lowest operating cost (nuclear, for example), while higher daytime demand requires the use of
generators with higher operating costs (gas turbines, for example). Increasing the nighttime load so much would increase the
average cost of electricity, so new plants would probably be built for economic reasons.
Bottom line (for generating capacity) is that the increased demand is in the ball park of what is available now at night, but it
is not really possible to predict what the increased peak demand might be and what that might mean in terms of added generating
capacity.
.
- References:
- Couple of Fundamental Electric Vehicle Questions
- From: wdoe999
- Re: Couple of Fundamental Electric Vehicle Questions
- From: Bill Ghrist
- Couple of Fundamental Electric Vehicle Questions
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