Wind/Solar Electrics ???

When a lie becomes industry-accepted terminology then the industry is in deep shit.

Yes Mildred there really are true sine wave inverters that are not just a sq. wave with many, many steps.

Do your own f****ng search.

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

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".

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

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

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)

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)

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.

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

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

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

"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

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?"

We drill expensive holes in the sky

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.

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.

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.

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.

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.

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

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

Modified Semantic Wave is correct.

examples of sine

shocker.

wave inverters don't

We previously went through this crap with CD players. The sampling frequency was chosen to be 44.1 kHz, well beyond the range of human hearing. No filtering would be needed.

Except for one thing...when they played the CD back unfiltered, people would find their tweeters melting for some weird reason....44.1kHz! at huge powers!

Out came the drawing board and complex analogue (and expensive) filters were designed until one day some smart engineer discovered they could double the freq. in a computer and put out 88.2 kHz sampling noise and use a less efficient and less expensive filter.

Well, the audio hype that came out then was "2 times oversampling" followed by 4x, 8x, 16x & 32x "oversampling". Shister and ignorant marketing people explained this as "reading the CD 16 times repeatedly and eliminating the digital errors" "You can eliminate scratches with this"

In reality the "oversampling" technique was the development of a digital filter that made the analogue filter into a simple capacitor to eliminate the sampling noise.

Any square wave can be filtered enough to produce a pure sine wave. The trick is the cost. Huge core inductors and capacitors to handle and smooth out big quantities of power cost money to design and money to produce. Not to mention the sheer weight of the beasts.

Multistep waveforms can be filtered much easier. This is analogous the "oversampling" technique used in CD players of years past. Digital filtering is much easier and cheaper than the equivalent analogue filtering. It's not like an inverter, these days, doesn't have a computer chip inside then anyway.

How little distortion do you need anyway? Most of it can be accomplished inside the computer and then just amplified to useful power levels. At a cost, of course, and a marketing tool for more money...always.

the MSW inverter to be

sine wave?

put out a true sine

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