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re: system sizing
28 mar 2000
dr. rich komp writes from his off-grid house in maine:
>1. if one is off the grid, the battery sizing has to be for the extreme
>case (how many days [or weeks] are you planning on lasting until the sun
>comes out again?) here in jonesport we have been known to have over 40
>days of fog in a row.
wow. what did you do when that happened?
>2. more batteries may be cheaper (and certainly less hassle) than a
>backup fossil fuel generator, as a solution to problem #1.
altho the tiny backup (honda?) might also make heat, possibly useful
in solar heated houses during 40-day cloudy spells :-) i'm trying to
think of other ways to make backup heat, as if fossil fuels were already
too expensive or polluting to burn. just ordered an oxygen sensor to
turn on a blower when o2 gets low in an in-vessel composting furnace
experiment, using wood shavings and poop from my neighbor's 3 horses.
i have in mind measuring humidity too, and increasing the heat output
as needed by increasing moisture content, with a sump pump and sprinkler
over the compost. altho compost also makes c02...
then again, there's trash. this week's pa greenworks gazette says that
we pay $10 billion per year to dispose of it, and "5 million homes could
be heated for 200 years with the wood and paper thrown away in the us
each year," so 1 billion homes could be heated (and electrified with
steam engines) for 1 year with our yearly trash output! incredible.
i called 'em (800-334-3190, www.dep.state.pa.us) to ask where they got
that estimate, and they say they will call back in a few weeks...
>3. a system that is shut off because the batteries are full is 0%
>efficient at that moment.
maine seems in the lead with grid-tie regs, apres lord's musketeers.
can you bank power there? deliver excess energy in summer and use more
than you make in the winter, with no money changing hands?
>4. going to 24 volts makes a lot of sense nowadays for medium size
>systems (200 watts or more) with the good inexpensive inverters
>available. i still like the idea of having lots of the lights, tv,
>stereo, etc hooked directly to the batteries without any inverter, in
>case the inverter quits or something; so i usually tap the system in the
>middle for two 12 volt legs. 48 volts should be reserved for really big
>systems.
two inverters might deliver the same reliability with less fuss.
having worked as an ee, i keep thinking that electronics is one
thing that can easily get better and cheaper, given the demand.
>hope this helps, or at least entertains the group.
sure. thanks for your thoughts. i'll take that as an ok
to post your email...
nick
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