Hybrid Car – More Fun with Less Gas

what would a similar system scaled down to average home cost? - Page 2

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Posted by vaughn on July 29, 2010, 8:47 pm

Like I said, different folks, different assumptions.  I do notice I forgot to
figure in the round-trip efficiency of the battery.  When you put 1 kWh into a
battery, you unfortunately do not get 1 kWh.  I usually se 80% used as an
assumption.  Don't know if that includes inverter and other system losses.

With daily cycles?

Fair enough, but even those assumptions have problems.  At the end of life
(whatever that is) you no longer have a battery with the original capacity,
because the battery capacity slowly decreases over its lifetime.  So you can't
really use the full factory nameplate capacity as a lifetime figure when doing
your cost calculations.

Yes, but the article was more about storage for time-shifting to take advantage
of excess capacity and to get around peak hour pricing.  My point is that
battery energy storage is not free, it can actually be quite expensive.


OK, I was mostly talking about the battery portion of the expense.  I came up
with 15 cents per kWh, while your working assumption is 11 cents, so we agree
that battery storage is neither free nor cheap.  Last month, I paid just under
11 cents/kWh for my grid power (all inclusive).  It would make no sense to pay
11 cents/kWh to store power that costs me 11 cents.kWh.

Thanks for a good response!


Posted by wmbjkREMOVE on July 29, 2010, 10:17 pm

On Thu, 29 Jul 2010 16:47:56 -0400, "vaughn"

Yup. One guy I'm thinking of had the most messed up arrangement
imaginable. It didn't look like it was possible that it ever got fully
charged, and yet it had been functioning that way for over 5 years
then, and another year since. I'm thinking that the daily discharges
were always shallow though, and for sure they're shallow now with full
charges most days. The bank may only be a fraction of its original
capacity, but it's still doing the job.

That's supposed to be taken into account when purchasing. But the
longer the projected life span, the less likely that the use will be
as expected. About the only thing that's stayed the same with my place
over the last 15 years is that the energy use keeps changing. :-)  3
different radio-phone setups over the years, 3 different Internet
delivery methods, 2 different TVs, 3 different time-shifting setups,
daily computer use was originally 1 machine for 1 hour, now it's 3
machines for a total of 15 hours, etc.

Disregarding the battery thing for a moment, the only sense would be
if you wanted to make a "green" statement and a good long-term
investment. Plug your zip, monthly bill, and the name of your power
company into this
You might want to change the default $ to reflect your local costs
and/or your DIY skills. Retail is supposedly $ here according to
local news reports. I did it for my place just for fun - called it $0
per month and $ per watt. It came up with $K investment, 9 year
breakeven and nearly 300% return.

Right back at ya'.


Posted by ghio on August 3, 2010, 1:15 pm

On Jul 30, 5:28am, wmbjkREM...@citlink.net wrote:

A good description of a daylight only system.

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