Wind/Solar Electrics ???

[RST Engineering]

Plonk!

Jim

 

[Rich Grise]

A chirped-frequency, nanosecond-wide, random-amplitude pulse train is
a modified sine wave.

John

;-)

Thanks!
Rich

 

[[email protected]]

A chirped-frequency, nanosecond-wide, random-amplitude pulse train is
a modified sine wave.

I will accept that definition as offered.
Does that preclude having any other valid definitions?

 

[Steve Spence]

I would prefer "stepped sine wave". But I can accept the term "modified
sine wave" as marketing speak that has been on lots of UPS boxes for 20
years. (UPS itself being inaccurate for a standby power source.)

I believe "stepped sine wave" to be an oxymoron. UPS (uninterruptable
power supply) isn't so wrong, as from the computer's POV, the power
never was interrupted. Of course, we know the difference between
"online" and "backup".

 

[philkryder]

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

 

[Roger]

With a small solar panel to keep the continuous load going, not a bad way to
go.

I recently talked to a guy down in Florida, where the sun is more
direct and shows up much more often than here in Michigan. He said a
decent solar powered system to run a medium size (what's medium size?)
house was about $20,000 for the installation.

You can plan on replacing lead acid batteries about every 3 years or
so. Nickel Metal Hydride (NiMH) are about the same, except the car
manufacturers are claiming much longer life using computer controlled
charging. Time will tell.

Solar panels are still darned expensive. Using a mix of solar and
wind you charge different banks with solid state regulators and
switches.

The inverter only needs to be sized large enough to handle the
expected load. As long as you are not running electronics the wave
form is not much of a problem...except... for radio interference. Some
switching supplies (which are very efficient) are very noisy.

You can get one whale of a nice liquid cooled Honda Generator that
runs quiet and will supply enough juice to run a good size house
continuously. I have a 9,500 Watt continuous generator that will
power our whole house on about a gallon an hour. Maybe a tad less. It
burns way less than the little 4400 watt portable I used to have and
it is *much* quieter. Unfortunately I spend $1,200 and it's not a
quiet Honda. OTOH fortunately I purchased it from Lowe's a couple of
weeks after the Y2K fiasco. People had cleaned them out and were then
returning the "unused" generators. They finally said "No more". Some
of those "unused" generators looked like they'd been sitting out in
salt spray for a couple of months. Mine was more than 50% off and it
was still in the box. It was one of the few that they hadn't sold.
They had a lot of them cheap for a few months. The one store here in
town must have had 50 or more although most of them weren't 9500 watt
units.

Currently Home Depot has some 15KW "home generators" complete with
transfer switch that will do an automatic transfer, as well as
exercising once a week. They'll run on Gas, Natural Gas, or LP gas
and come in a small enclosure that looks like a whole house air
conditioner. I'd like to try one of those, but my wife says I spent
more than enough on what we have and we can drag that heavy cable out
to the generator shed for a lot less than $2,200 <)

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Jim

Roger

 

[Roger]

I've had my reservations about RG ever since they endorsed those
piezoelectric washing-machine tablets.

More than anything though, CE/UL-approved grid-connect inverters (ok
AND EU subsidies, especially in Germany) are helping to increase cell
and panel manufacturing capacity. Which is essential to driving down

There have been several "breakthroughs" that could *potentially* cut
the cost of the solar cells to less than half of current and at the
same time increase the efficiency by a substantial margin.

There were a lot of weasel words in the press release so ... who
knows. IF, how soon, and how much.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

 

[George Ghio]

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

 

[Ron Rosenfeld]

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)

 

[[email protected]]

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.

 

[Steve Spence]

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.

 

[Rich Grise]

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

 

[RST Engineering \(jw\)]

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

 

[Rich Grise]

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

 

[Peter R.]

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?"

 

[Ray Andraka]

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

We drill expensive holes in the sky

 

[RST Engineering \(jw\)]

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

 

[Ron Rosenfeld]

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?

It's not a matter of building a cathedral foundation, but rather trying to
design the least expensive foundation.

But I guess if you're going to light 35 hangars with ten fluorescent
fixtures that are on for a few minutes each day, you won't need much.

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.

Very reasonable, and what I would suggest depending on how much the surge
is. Of course, that means you'll have to have wiring so that those items
will plug directly into the generator, rather than going through the
inverter.

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.

It is extremely inefficient to bring the batteries up to full charge using
the gas generator. Batteries charge more slowly as they approach full
charge. Better get a reliable generator, then.

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.

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

 

[daestrom]

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

Careful. Even true 'rotary' generators don't always put out a true sine
wave.

Even the very, very large commercial generators used in power plants, don't
put out a 'pure' sine wave. The number of stator slots and rotor geometry
cause a small amount of harmonics. The exact connections of windings is
often used to help improve the fundamental and minimize some of the higher
harmonics (6th, 9th and 11th are some of the more troubling ones).

After it passes through several transformers, getting to the substation,
most of the harmonics have been filtered out by the characteristics of the
transformers.

So the question, as usual, boils down to 'how good, is good enough?'

daestrom

 

[[email protected]]

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?

An Airplane is a large mobile fan into which the owner is obliged to
throw handfuls of money (to watch it blow away).

David Johnson