[Hidden-tech] Backup power

[Robert Heller]

At Sat, 20 Jan 2007 15:51:00 -0500 Jean Graef <jean.graef at montague.com> wrote:

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> The recent winds and ice have made us think again about backup power
> for both our computers and household appliances. I still remember one
> spring when the power was out for 3 days.
> 
> We have battery backup on all our computers, but the longest any of
> them last is a half hour and the manufacturer wasn't any help for a
> whole office/house.

The UPS systems commonly used for (home/office) computers are designed
for either short power loses and/or to provide time to do a 'clean'
shutdown.  Not really meant for long term functioning during a power
failure.

Data centers that need to be up 24/7 no matter what use completely
different technology, generally a diesel generator is the ultimate backup
power.  Ditto for hospitals and the like.

> 
> Does anyone have any ideas about how to get backup power for 3 - 4
> days without using a generator?

How much power are you talking about? 

A typical household has electrical service of 220V at up to 100A, or
something like 220*100 VA, or 22KVA.  4 days is 4*24 hours = 96 hours. 
22KVA for 96 hours yields 2112KVAHr, or a seriously large amount of
battery storage.  Now the 22KVA service allows for heavy appliances,
such as washing machines, dryers, stoves/ovens, hot-water heaters, etc. 
I will assume that you what you want is 'essential' 'service': the
computers, lights, small appliances and that you plan to skip things
like laundry or massive feast/baking projects during a 3-4 day power
outage, so what you need to do first is figure out what that amounts
to, in terms of power requirements.

A *large* pile of deep-cycle batteries and a (large) DC-AC inverter is
possible. 2112KVAHr is a huge pile of batteries, though. You would need
a way to charge the batteries as well -- this could include solar
(photo-voltaic) or a windmill.  A fuel cell system is also possible (I
believe GE makes fuel cells that 'burn' propane or natural gas). 
Neither are particularly cheap (once you add up all of the pieces). A
generator is probably the most cost effective way to keep your
household running for several days during a power failure.
It is possible to get a *diesel* generator and burn bio-diesel (this is
a little more environmentally friendly).  

> 
> Jean
> -----------------------------------------------
> Jean Graef
> The Montague Institute
> www.montague.com
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