🚀 go-pugleaf

 
In article <CvqJ41.Lr@cdthq.uucp>, 
Gary Heston (gary@cdthq.uucp) writes:
>In article <498@solar.win.net> jstanley@solar.win.net (John A. Stanley) writes:
>
>>My electrical power comes from 2000 peak watts of photovoltaic
>>panels and a 1000 watt wind generator on an 84' tilt-up tower. I
>>also get most of my domestic hot water and heating energy from five
>>solar thermal panels that heat the water in a 350 gallon insulated
>>tank in the basement. Propane provides supplemental heat, cooking
>>fuel, and backup electrical power.
>
>Would you mind describing this a little further, and possibly giving
>some numbers on typical performance and costs, your typical gain from
>the photovoltaic panels, typical consumption, hours of runtime on
>the Onan generator, and such? 

Seeing as how I just today moved into the house for the first time,
I don't have any numbers to throw at you. We've also had problems
with the instrumentation (Cruising Equipment meters have proven to
be total garbage; they keep going catatonic.) The reconditioned
industrial NiCd batteries have also proven to have much less than
stellar performance. So... once I switch over to lead-acids
(which will require a heating system in the battery box) and change
over to a computer-automated logging system for the
instrumentation, I can come up with some real numbers... like in 6
months or so. 

The entire construction of the house was primarily powered by the
sun (diesel fuel powered the rammed earth block machine, and the
Onan powered the compressor for the nail gun so that the Trace
could power all the saws.) Last winter they got the Whisper 1000
(wind generator) up and running. It is located about a quarter mile
from the house out in the back 40, where it is on high ground and
wide open to the N, NE, and NW; perfect for those howling winter
winds. The unit puts out 240v three phase AC. That means all that
power flows through a cheap piece of 10ga wire with only 2% line
loss. It is stepped down and rectified at the power panel in the
garage. 

The Onan is meant as a back-up only. The system should have
sufficient sun and/or wind energy to meet all my needs. So why did I
sink so much money into a generator that won't see much use?
Because when I *do* need it, it will work; ya get what ya pay for.
Also, cheap engines don't take too kindly to being converted to
propane: gasoline provides top-end lubrication, propane doesn't.
The Onan was designed to be run on propane, and therefore runs
cleaner and more reliably (no old gas fouling up the carb.) 

Heat is in Wirsbo tubing embedded in the slab. This system simply
heats up the floor. There are different zones with separate
thermostats. This works marvelously with solar heat because the
water in the system need not be any hotter that 110 deg. F. There
is at the moment no heat in the small upstairs (~400 sq. ft.), but
it is open to the downstairs in the center of the house, so the
heat should rise up there. Warm air from the attached greenhouse
can also be brought into the house for additional warmth. 

While the foundation has an R value of about 35, the slab is
completely uninsulated. That means that the slab has a tendency to
remain at ground temp when there is no heat on. This is a primary
source of cooling in the summer. And actually, last winter when
there was only plastic on the windows and no heating system, the
house remained at 35-40 degrees in sub-zero weather. The wood
burning fireplace insert would raise the temp about 15 degrees in
several hours. Keep in mind that this is a 3000 sq. ft. house.

Fresh air can be brought into the house through a huge concrete
air plenum buried 10' underground. This system cools air in summer
and warms it in winter. 

Costs? Obscenely expensive and twice what I had originally planned
on. I have nothing more to say about this. 

>Did you look into, or whoever designed your system, using a DC 
>generator that could directly charge your batteries, instead of
>making AC and feeding it into a charger? That would be far more
>efficient, and is the way one UPS manufacturer does it.

You'd then have a generator that can do nothing but charge the
batteries. Can you say expensive boat anchor? There's a very good
reason that my system is common: flexibility. I can disconnect my
generator from the 4kw Trace inverter, switch it on, and presto! I
have an additional 4kw of power at my disposal. Some folks downsize
their system and use the generator to do laundry and other energy
intensive tasks while charging up a smaller battery bank for powering
lights, electronics, and refrigeration. Another problem: when my
Onan is charging the batteries it's also powering the whole house.
Try *that* with a low voltage dc generator; do you realize what
kind of current you'd have to generate to do both tasks? Do you
realize how humongous the windings would have to be? You'd have a
bloody fortune in copper in such a generator. If you're willing to
shut down your entire electrical system so that you can charge
your batteries, then go for it. Me? My generator will come on
automatically when the bank drops to a particular voltage, and
I'll never even know it. The switch between inverter power and
generator power is completely seamless. 

Homebrew types will sometimes rig up an old lawnmower engine to an
old car alternator for battery charging, but my system is rather
large with a 24v battery bank, not 12v. Your idea may be more
efficient, but it sure is impractical, if not downright unworkable
in a large system.

--
John A. Stanley                    jstanley@solar.win.net