Wind/Solar Electrics ???

wmbjk wrote:

I take that to mean that you won't be providing any examples of sine
wave inverters with stepless waveforms. What a shocker.

Wayne

Take it to mean that you can't prove that true sine wave inverters don't
exist.

Modified Square Wave inverters = True

Modified Sine Wave inverters = False

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)

In alt.solar.photovoltaic Steve Spence wrote:
I believe "stepped sine wave" to be an oxymoron.

I (obviously) don't agree with that. Gotta call it something. It's not a
sine wave, but if you squint at the oscilloscope a little, it looks more
like a sine wave than a square wave.

UPS (uninterruptable power supply) isn't so wrong, as from the computer's
POV, the power never was interrupted.

Ah, from a particular Point of View... if that's the criterion, then the
square/modified/lumpy/sine wave is a sine wave for most applications.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

philkryder wrote:
Steve - How many equal "steps" are necessary for the MSW inverter to be
a sufficiently close approximation to a "rotary" sine wave?


That depends on what you are driving. A laser printer requires closer
representation than a computer. The manufacturer of a particular load
could tell you that information. The old test of whether something was
sine or some version of square was a lamp dimmer. On a square wave unit
the light goes full bright. We have a touch lamp that will not change
state on MSW, but will on generator.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

On Mon, 19 Dec 2005 23:51:48 -0800, philkryder wrote:

Steve - How many equal "steps" are necessary for the MSW inverter to be
a sufficiently close approximation to a "rotary" sine wave?

It depends how you count "steps". I once worked with an inverter that
used two, count'em, two, output transformers, each driven by a plain
vanilla square wave, but they were in series, and the regulation
took place by controlling the phase of the two square waves - 120
times a second, the two secondaries flipped from "buck" to "boost".
The output waveform was essentially a positive pulse, then zero, then
a negative pulse, then zero, then another positive pulse, and so on.

It ran everything we plugged into it, even an induction motor bench
grinder. Lamps are trivial, and series motors, like a hand drill,
don't care.

We didn't plug a computer into it, however, or anything with an SMPS,
so I guess my recommendation would be to check the spec on what it
is you're plugging into it.

Good Luck!
Rich

It seems as though we are trying to build a cathedral foundation to hold an
outhouse. It isn't like I'm LIVING in the hangar, nor am I there working
all day every day. Sure, lights when you are elbow deep inside an engine
are nice, but hardly bleeding edge solar design. What? Ten fluorescent
fixtures with 80 watts of bulbs each? A drop cord with another 20 watt
fluorescent bulb? Perhaps a hand drill twice a day WHEN you are working in
the hangar?

As to the compressor, drill press, grinder etc., a gas generator for the few
times a month you need them is quite in order and certainly less expensive
in both the short and long term than gearing up for 100% solar for the
peaks. And, if you design the system correctly, letting the gas generator
run for an hour every time you fire up and letting the batteries take a full
charge from an inexpensive battery charger can add to the output of the
solar system.

I've done a little digging and it seems that Great Plains has the best
pricing on solar panels. Harbor Freight has a little better pricing, but I
need something that I can reliably get month in and month out (I'm the
guinea pig for about 50 hangars) and I can never rely on Harbor Freight to
have what I need when I need it.

My best guess after doing a little educated digging is that I can come up
with a system I can live with for a little over 1 AMU.

(For those of you not on the aviation newsgroups, an AMU is a measure of
money used to disguise the true cost of airplane ownership from other ...
ummm ... family members who might think that clothes, food, and other
nonessentials take priority over flying. 1 AMU = $1000US.)


Jim

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.

On Tue, 20 Dec 2005 10:29:12 -0800, RST Engineering (jw) wrote:

My best guess after doing a little educated digging is that I can come
up with a system I can live with for a little over 1 AMU.

(For those of you not on the aviation newsgroups, an AMU is a measure of
money used to disguise the true cost of airplane ownership from other
... ummm ... family members who might think that clothes, food, and
other nonessentials take priority over flying. 1 AMU = $1000US.)


"Aircraft Monetary Unit?"

I've heard that a boat is a hole in the water lined with wood, into
which one pours money. ;-)

Do airplane people have a similar saying? I have only a little bit of
experience with airplanes - I logged 4 hours in a Cessna 150 before the
local flight school got shut down because of fuel considerations, and
I've sat in a DC-9 simulator, and had a simulated airplane ride where
I drove, but I've never gotten into any of the cameraderie, like one
would do as a skydiver.

Yeah, that's it - the best experiences I've ever had with airplanes
has been either abusing them or jumping out of them. ;-P

But, do airplane guys use the term "money hole" like boat and house
owners?

You can't "pour" anything _up_, you know, albeit I have heard that
humans were created by water to transport itself uphill. ;-)

Cheers!
Rich

Rich Grise wrote:

You can't "pour" anything _up_, you know, albeit I have heard that
humans were created by water to transport itself uphill. ;-)

How about suck, as in "an airplane is a rather small hole in the sky made
of aluminum or cloth and wood that sucks the money right out of the owner?"

--
Peter

Rich Grise wrote:

But, do airplane guys use the term "money hole" like boat and house
owners?



We drill expensive holes in the sky

Boring $100 holes in the sky ... going fifty miles for a $100 hamburger ...
standing in front of a fan tearing up $100 bills ... dozens more.

Jim


"Rich Grise" wrote in message
news
I've heard that a boat is a hole in the water lined with wood, into
which one pours money. ;-)

Do airplane people have a similar saying?