On Wed, 14 Dec 2005 15:02:56 -0800, "RST Engineering"
wrote:

After much thought and ponderance, I've come to the conclusion that to
electrify the hangar using Pacific Gas & Electricity (PG&E -- Pigs, Goats,
and Elephants) isn't clever. By the time you get them to hang a meter
($5k), trench from the power pole to the end of the row of hangars, conduit
romex to 35 hangars at a cost somewhere around $50k ($1500 per hangar), and
then pay the monthly electric bill, you could buy a hell of a wind/solar
system and perch it on the (flat) hangar roof.

Before I flail about gathering data, has anybody on these ngs actually
installed a design whereby a hefty solar panel charges a hefty battery to
run a hefty inverter? It doesn't have to be absolutely "clean" sinewave
power as all we are running are fluorescent shop lights (about 400 watts
worth), every now and again a small compressor, a small drill press, a small
grinder, but none of these last few at the same time.

My hit on it is that a 2 kW inverter would be more than enough to handle the
AC side of it, and a bank of 12 volt truck batteries would work for the DC
side of it, but there are the problems of parallelling large batteries, how
to combine the outputs of solar cells and wind generators, and a reasonable
source for all this stuff.

There are issues around protecting the solar cells from hail, which we do
get from time to time, battery acidic gases inside a hangar where a very
expensive lump of aluminum is sitting for months on end, sizing the solar
cell and wind generators, and other considerations along these lines.

Comments appreciated.


Jim


Jim,

As one who lives "off-the-grid" in eastern Maine, (and for similar reasons,
I might add -- excess costs to run power here), perhaps I can be of some
assistance. We use both wind and solar to power our home, and also have a
backup generator. The problems of coordinating all these things has been
solved with readily available technology. As has all of the other issues
you mentioned.

In order to make an intelligent decision and design an economical system,
your very first step has to be to estimate your electricity usage as
accurately as possible. In addition to adding up your daily consumption in
kWh or amp-hours, you also have to consider peak loads. And, especially
since you may be using a compressor, you will also have to consider the
startup surge -- with a compressor this may be five to ten times the
running amps. That information should be decipherable from the motor face
plate.

The next step is to assess your solar resource, and there is information on
the web available for that. Being at an airport, my advice is to forget
about wind. You need to have a wind turbine on a tower high enough to get
out of turbulent air, in order to make it worthwhile. The required height
would encroach upon the FAA mandated clear zones.

I'd be happy to help if you like.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)