[Hidden-tech] Backup power

[Bruce G. Hooke]

Lots of good information has been posted so far on this issue. As someone
who has lived "off the grid" and whose father recently installed solar
panels in part to deal with the issue you are looking at, here are a few
thoughts:

1. To last long off the grid without spending tons of money you first need
to focus on reducing your load. In your case, this can partially be handled
by considering which electrical devices are essential and which you can do
without during a power outage. Getting high-efficiency appliances also
helps. There are special high-efficiency refrigerators that are made for off
the grid homes, but it may not make financial sense to go that far. Look
particularly carefully at anything that uses electricity to generate heat
(beyond stuff like a toaster that is only used for a few minutes a day).
Generating heat with electricity takes a LOT of electricity. So, switch to a
gas stove and a gas dryer (or don't use the dryer in a power outage) and if
you have electrical baseboard heaters you are going to have major problems
trying to support them off the grid. The cleanest way to segregate what gets
power and what doesn't in a power outage is to split up the circuits in the
house based on essential versus non-essential, but this is expensive to do.


2. Having done step 1 you are in a better position for step 2. I haven't
done the math, but solar systems designed for off the grid homes clearly
need to have enough battery storage to last through a few cloudy days, so it
does not seem totally out of the question to do this all with batteries.
That said, to last more than a couple of days you do start to need some sort
of outside power source. Three likely candidates are wind, solar and
small-scale hydro. If you have a good site for small-scale hydro that is by
far the best option, but good sites are rare. Wind and solar both have
pluses and minuses but in the end solar is probably the easier way to go for
most people. The added plus of any of these is that they also generate power
when the power grid is not down. The down side is, of course, that
installing any of them is a much bigger investment than installing a basic
generator...

- Bruce

-----Original Message-----
From: hidden-discuss-bounces at lists.hidden-tech.net
[mailto:hidden-discuss-bounces at lists.hidden-tech.net] On Behalf Of Robert
Heller
Sent: Monday, January 22, 2007 11:51 AM
To: Jean Graef
Cc: Hidden-discuss at lists.hidden-tech.net
Subject: Re: [Hidden-tech] Backup power

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

> 
> MIME-Version: 1.0
> 
>    ** The author of this post was a Good Dobee.
>    ** You too can help the group
>    ** Fill out the survey/skills inventory in the member's area.
>    ** If you did, we all thank you.
> 
> 
> 
> 
> 
> 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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Robert Heller             -- 978-544-6933
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