Wind/Solar Electrics ???

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.

yes, thats when solar pv starts to look good.


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.

There are 2 main invertor options, sine or modified sine, which is IRL
rectangular wave. IIRC, iron fl ballasts and motors can overheat on
MSW, so all your apps ideally want sine. However MSW is much cheaper,
and there are workarounds. Fl lights can be run at just slightly
reduced power, or heatsinks added to the ballasts, etc. Electronic
ballast lights would run happily on 150v dc. Motor driven tools would
be fine as is unless youre running them to where they already get
seriously hot, ie heavy use. There are ways round it if it proves to be
an issue.


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.

ok, first with those powers it would make more sense to run your
battery back at apx 150v (assuming you want 110v ac) and use a simple
chopper to produce the ac. Your output will then have unregulated
V_peak and regulated constant rms. That should work for all your loads.

You should add a parallel diode across each battery cell, so that one
cell going down has little effect on system performance, and enables
everything to continue running. Ditto with the panels, there its
particularly important to have a diode across every panel when youre
running them at HT.

This avoids parallelling batteries (not that thats needed anyway), plus
reduces cost of invertor and wiring. Also it means you can supply 150v
dc to mains CFL bulbs, electronic ballasted fl lights, and anything
else that rectifies the mains, again cutting down on system cost and
improving reliability. Use a different plug/socket type for the dc
supply.

One way to shave 10-20% off power consumption would be to up your
supply frequency slightly, this would work nicely with magentic ballast
lights and brushed motors, but not induction motors. FWIW brushed
motors can run on dc anyway - but not @ 150v.


Solar pv is cheaper than wind, and has less significantly issues, so
I'd stick to solar.


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,

Battery case is vented to the outside.


sizing the solar
cell and wind generators, and other considerations along these lines.

Comments appreciated.


Jim

alt.solar.photovoltaic is the place to go.

Also dont overlook simple ways to cut cost. A minimal cost reflector
outside a window can be used to increase daylight levels, and delay
lighting dwitch on until later in the day, thus reducing system cost.
And of course a switchbank for your lighting will enable you to use the
lights only where theyre wanted at the time. No sense lighting the
whole place up bright when youre only working in one area.

And dont forget batteries dont last forever, you need to account for
future replacement. Beating your PG&E costs should not be difficult, as
long as its designed competently.


NT