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BushWhacker
Junior Member
Canada
339 Posts |
 Posted - 09/04/2008 : 03:58:28
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I just watched a show on planting some off shore windmills in the north sea (near Holland) and it got the wheels of my mind spinning. I hope to set up a battery shack (shed) near my next house.
Here is the question (and I hope Ghurd reads this), If I want to run a combination of 110V AC (mostly) and 12V DC (lighting and fans, perhaps a water pump) am I better off running the inverter in the battery shack (say, 50 feet from the house) or running the 12V to the house to feed the inverter? What distance is the trade off point for an equal AC vs DC load using 2 gage welding cable? 4 gage?
You know, line loss and voltage stuff? Remember I am the electrically challenged member of Gotwind.
Cheers!
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein
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ghurd
Junior Member
USA
337 Posts |
Posted - 09/04/2008 : 15:04:52
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"Mostly AC" means keep the inverter near the batteries.
12VDC, #2 for 50' is going to get some significant losses at 400W.
120VAC, #14 is plenty for 1800W.
The DC wilre will still need to be fairly large and expensive.
Pick power efficient DC items. CFL lights. Etc.
Does the water pump really need to pump 3GPM, or is 1.5GPM enough? Stuff like that.
Look for better ways to do the same thing. An example would be a fan. Google "5000% more efficient box fan".
I made a couple, and they move about the same air with 12V 5W, as the 110V 20" box fan on medium using over 100W.
A problem. Inverters use power being on and not doing anything. Saw a 300W one a guy bought at a flea market that pulled almost 1A doing nothing. Fine in the car, but it would take a lot of solar watts to make up for a nights worth of waste. He bought a better one.
So do you leave it on 24/7, or run back and forth to turn it on and off all day?
Some larger (750W and up) fancier inverters have load sensing and shut themselves down if there is no load. They tend to need 50W to turn back on (an 11W CFL won't do it).
Some have wired remote abilities. The remotes can be crazy expensive.
Some on ebay (US) now have a after-market orange wire that is a wired remote hack-job. It works.
And someone here is working on a simple wireless remote controlled inverter.
I told him many people would find it useful.
He needs to get some pics and post it. HINT HINT HINT to him.
Here is a chart with 12V and 120V.
http://www.nwes.com/Wire%20Loss%20Tables.htm
G-
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BushWhacker
Junior Member
Canada
339 Posts |
Posted - 10/04/2008 : 04:05:26
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Hi Ghurd;
Thanks for the reply... I think... or maybe you are just trying to make my head hurt. ;-) I think I'll just hire an electrician to figure out the electrickery stuff out. I have one that I can trust although he is not familiar with home brew systems.
Can I get your take on these Outback inverters?(edited to add) 2K 12 volt.
http://preview.tinyurl.com/4gen43
The things I like are you can gang them for 220 volt and they are pure sine wave. Now say I decide to add a 3rd inverter, can I add a third or do I need a fourth because of the infrequent 220 volt demands?
As for the fan thing I have opted to use 4" computer fans that draw .44 amps @ 12 volts. To quiet them down I am running two @ 7.5 volts in series. By my calculations ... carry the 9... add 7... times, who cares... I come up with 3.3 watts + losses due to the fancy wall wart. please correct me if I am wrong! I am opting for low speed (hence quiet)and compact.
Thanks,
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein |
Edited by - BushWhacker on 10/04/2008 04:07:48 |
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ghurd
Junior Member
USA
337 Posts |
Posted - 10/04/2008 : 17:23:47
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Outback is good stuff.
Link won't work for me. I'm not up on much of the Outback stuff. Not sure if they can be ganged past 2.
Other than that... Dang! That'll take a big RE system.
220VAC is for big loads. (US and Canada)
2000W 12V, (80% eff inverter) means pulling 210A out of the batteries.
If the system is that big, consider going to 48V. (skip past 24V)
If the system is not that big, leave the 220VAC loads on-grid.
If the system is not that big, yet, but will be, consider MSW instead of pure sine. And a 750 to 1.7KW inverter?
Take the very large pile of left over inverter money and make the RE system bigger.
I don't have a pure sine inverter any more. Run 2 laptops from a $35 400W Vector. Run a digital temperature controlled solder station from a $25 175W vector. Etc.
I know 100's of off-grid local people, and can only think of 2 pure sine inverters. One guy has more money than brains (called a mail order place and said "Sell me the best one you have" which got him an Exceltech 1100W), and the other guy bought one for a fancy $300 cordless razor (125W Wagen).
Electricians won't understand much of this stuff, at least the ones I know don't.
This is more EE.
G-
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speo
Junior Member
Canada
120 Posts |
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It got the wheels spinnig...
