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#51
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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 |
#52
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Wind/Solar Electrics ???
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) |
#53
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Wind/Solar Electrics ???
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 |
#54
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Wind/Solar Electrics ???
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 |
#55
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Wind/Solar Electrics ???
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 |
#56
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Wind/Solar Electrics ???
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. |
#57
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Wind/Solar Electrics ???
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 |
#58
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Wind/Solar Electrics ???
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 |
#59
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Wind/Solar Electrics ???
Rich Grise wrote:
But, do airplane guys use the term "money hole" like boat and house owners? We drill expensive holes in the sky |
#60
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Wind/Solar Electrics ???
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? |
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