[SGVLUG] Off-topic - for Tom - plug-in car that can power yourhouse

[Dustin Laurence]

On Thu, Apr 12, 2007 at 06:35:53PM -0700, Emerson, Tom (*IC) wrote:

> I think this calls for some back-of-the-napkin calculations...
> 
> > -----Original Message----- Of Dustin Laurence
> > 
> > It would be even cooler if Tom's Prius were new enough to be 
> > a plug-in candidate, so he'd be motivated to do the 
> > conversion and then show us. What's $10,000 when the planet's 
> > at stake?  :-)
> 
> Hmmm... As much as I'd like to agree with you and your "smiley",
> something doesn't add up here...
> 
> The buyback for a $10k add-on would (naturally) be $10k of gasoline NOT
> purchased over the lifetime of the vehicle.

You misunderstand--I was suggesting you'd get *no* repayment whatsoever,
buyback time infinite.  But you'd feel great about losing $10,000
because you'd be single-handedly saving the planet. :-)

> Now, for the discussion at hand: the site talks about "selling" the
> excess energy in your vehicle as a "profit center" for joe average.
> Unfortunately, this doesn't take into account that if you sell off this
> "excess" energy, your MPG rating drops back down to 50mpg since you stop
> getting the benefit of using it to push your car around.

That depends on your driving patterns.  It makes the most sense for
a car that isn't a daily driver or, perhaps, for someone who has a short
commute (the Prius' forte anyway) and can plug in at work).  If you have
to generate on-board all the power you sell to the grid, then it
probably doesn't make sense.  More importantly, it probably emits more
carbon and pollutants, as a car can't carry around the kind of emissions
controls a plant can (but it all depends on whether you'd be buying,
say, wind power or coal power, so it might go any which way depending on
where your utility gets it's power).

But there are many two-car families with one garaged during the day, and
I think that is where this could possibly make sense.  There is a bunch
of storage capacity going unused, why not use it?

I'd like to see someone do the calculation taking into account any
shortened battery life from the extra charge/discharge cycles; if it
shortens the life, as I suspect, you'd have to make enough back to pay
for the earlier battery replacement.

> BUT... Why bother going to this much trouble?  If the "deal" is to buy
> low/sell high by storing electricity in a battery for about 12 hours,
> why not just skip the part about having wheels on it?.  Or to put it as
> is often seen on slashdot:
> 
>    1) buy "cheap" electricity during off-peak hours
>    2) charge a battery with it
>    3) ??? [or in this case, "wait 12 hours"]
>    4) sell back "expensive" stored electricity
>    5) profit!
> 
> Unfortunately, this will only work if nobody else does this.  If
> "everybody" were to put a car-sized battery in their garage, "buy" cheap
> electricity off-peak, and "sell" it during peak, eventually the
> "off-peak" demand will reach or exceed the "peak" demand...

Obviously, this is for market conditions as they exist now.  There is a
price imbalance, thus a potential profit.  If enough people serve that
demand, naturally the price imbalance will decrease.

> rate.  If, in addition to that, you "buy" 1kw per hour off-peak and
> "sell" it all back, you'll be making 12*$0.15/day, or $1.80/day, or
> $54/month.  If your electric bill is less than that, your making a
> profit.  Of course, you do need to figure in the initial cost and
> depreciation of a battery capable of storing 12kwh -- if your "bill" is
> $50/month, it may take longer than you'd like to "pay off" this purchase
> with only $4/month to show for it...

My guess is that this won't pay for the storage, otherwise it would pay
Edison to do the same thing on a massive scale.  But perhaps I'm wrong
for some reason.

> OK, it's time for me to head for the meeting -- expect this discussion
> to continue at BC tonight...

Oddly enough, that didn't happen.

Dustin

-- 
    "Intolerance?  The *truth* is intolerant." -- le Faux

The small binary attachment on every message I send is my PGP digital
signature, not a virus.  If you don't know what that is, you can ignore it.
If you do, my keyserver is pgp.mit.edu.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
Url : http://www.sgvlug.net/pipermail/sgvlug/attachments/20070413/3d702a53/attachment.bin