On Wed, 8 Dec 2010 14:06:17 -0000, "BartC" wrote:

The best use of Economy 7 would probably be to use it to charge up
batteries overnight, and then use the batteries to supply power as and
when required during the day. Unfortunately, while such an
installation is perfectly possible, the capital cost would be pretty
horrendous, and I doubt you would recoup the cost in saved electric
bills over the lifetime of the installation.

It would have to be a pretty big battery, to deliver several thousand watts
over 16 hours or so. Perhaps you can convert the garage into one giant
battery.

Not *that* big. A normal car battery will store around 1kWH. So the
number of car batteries needed will be the same as the number of units
of electricity you want to store per day. Obviously in practice you
would use much higher capacity cells - but it gives you an idea of the
sort of size involved. I bet you could fit quite a few car batteries
into a small garden shed.

It would probably be the most cost-effective to buy (or make) open
cells with removable plates (such as "fish tank" style batteries), and
to clean the tanks (cells) and reform the plates yourself as the cells
lose capacity. Maintainance will then be a very low cost. Otherwise
you will have the major capital outlay of buying a new set of
batteries every 4 or 5 years.

Off-peak electricity might be best used to pump water uphill, then use that
to drive a hydro-electric unit. But there are a few problems with domestic
use (such as having a big enough hill in the garden).

And the storage volume needed would be a tad more than for batteries!

--
Cynic