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Old 02-19-2013, 11:28 PM
 
Location: Naptowne, Alaska
15,596 posts, read 34,556,906 times
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I am in the market for an antique ice box for our cabin if anyone comes across one of those! We normally use a cooler to keep things cold in the summer, but an old icebox would be a nice feature.

We cook on the woodstove fall winter and spring, and use the firepit in the summer months.

Have candles with reflectors and a propane lamp for lighting. As little as we use the cabin we don't need the high dollar items.
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Old 02-21-2013, 08:33 AM
 
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DC - Thanks for your insight on RV appliances. Personally, I never had any of those issues for the weeks straight I have used them.... But that doesn't diminish your comments and thoughts on the subject one iota.

But then again, I wasn't full timing or expecting typical residential service out of them either - and you shouldn't expect that type of service living off grid (Can't have your cake and eat it too) I love a microwave, but running one off a generator and most invereters stink, just as an example.
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Old 02-25-2013, 08:31 PM
 
Location: Texas
5,070 posts, read 8,767,266 times
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Here is an article I just came across...
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Old 02-26-2013, 03:53 PM
 
4,718 posts, read 8,694,070 times
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Interesting article - so make sure you got the windturbine and your neighbor does not... In the areas where the wind is constant, why wouldn't you take advantage of it regardless? (as long as the ROI works out - which right now it barely does)

I see the very large wind turbines and wind farms all over the upper mid-west states. Seems to be working out well -- farmers still have most of their land to grow or raise animals and the wind turbines are spinning...
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Old 02-26-2013, 08:28 PM
 
Location: Palmer
2,518 posts, read 5,872,902 times
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I noticed today that the sun was putting out noticeable heat. I had to open my window...got too warm. And it's still February.
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Old 02-27-2013, 12:17 PM
 
287 posts, read 483,717 times
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Wind farms and you and your neighbor having a wind turbine are quite different. It's hard to take an article dealing with wind farms and applying it to you wanting to put up a turbine for your home.

I don't take much stock in articles that claim you can't make it work when it already does...
Wind -- West Texas, Coastal Breezes Blow Power to Greater San Antonio

As with any government owned alternative energy source... if anyone in San Antonio wants power from the wind farm, it will be more expensive... kinda the "see, alternative energy isn't cheap" kick in the teeth.

If we could get big business out of the government, we would stand a chance...

Research "Earthships"... I'm not talking about the building method - I'm talking about the "self contained, self sufficient" way they exist. Completely off-grid and completely self contained, no outside utilities what so ever.

But you could never build that where building codes exist - they don't want you to be self contained - they want EVERYONE to have utility bills, and if they had their way - we would.
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Old 02-27-2013, 03:26 PM
Status: "King of the World" (set 15 days ago)
 
Location: Itinerant
5,188 posts, read 3,747,109 times
Reputation: 4061
Quote:
Originally Posted by dcbrewmeister View Post
With ANY off-grid setup, you would be a LOT better off finding appliances that are 12, 24, 36, 48 volt (according to whatever your system will be).
I'm going to cut this right here...

Because the answer is it depends.

Firstly with low voltage for the same power you have high current, high current means heavier gauge wire, you're not going to run a lighting loop on a 12, or 24V system on 12-2 Romex, well you could, but it also could result in a house fire depending on the overall load. The length of travel can also become a problem in high current systems (say a 1000W washing machine) where if the run is 5' for a 12V machine (using power transmission rated ampacity) you could use 2 gauge cabling, for 24V you would need 5 gauge, for 48V you would need 8 gauge, and for 110V you would need 12 gauge (i.e. 12-2 Romex). So that 5' run would cost roughly $70 for 2 gauge, and $3 for Romex.

Oh about the run, at 12V there's a 1.1% drop in voltage in 5' (11.8 terminal voltage on 2 gauge Cu) for 110V it's 0.01%. If you used 12-2 Romex for the same run at 12V you'd get 9.8V terminal, so you'd be burning 172W in the wire using 5' of 12-2 Romex to distribute to that washing machine, as it stands using the rated ampacity gauge you're still burning 17W in the wire. This BTW isn't something many people think about, I've seen some people running a full wiring loop for their homes using 14-2 (which is code in many places) for 12V lighting, I don't stay in those places at night when it's dark.

Secondly strangely 12V or 24V or 48V equipment can be more expensive overall than the price of a 110V equivalent and it's inverter, and the additional power cost of the inverter itself and required upsizing if necessary of the off grid power system. This is especially pertinent if you already have a bunch of electrical gear you want to keep. We had this, and even though previously we were on-grid, we were efficient, so the TV (37" OLED) for instance has a total draw of 40W, but it's a 110V TV. Same TV in 24V was 50% more expensive go figure, economy of scale one expects.

Thirdly you're going to lose some power anyway, it's not wise to be entirely off grid and electrically dependent without some form of almost guaranteed power, which means a generator. Almost all commercially available generators are 110V/220V so you're going to lose some in the charger for your batteries anyway. The question is whether the power lost in generation, and distribution is what you consider fair in comparison to other costs.

Finally of course there's choice, far more choice in electrical appliances at 110V than 12/24/48V and you might find that the overall power consumption from a 110V appliance is lower than the alternative 12/24/48V it depends on the appliance. Now in general I would say that a LV identical electronic device would have better efficiency, but, not necessarily electrical equipment. Motors for instance are more efficient at higher voltages (higher EMF, means more torque for the same windings).

So for the most part, when you take EVERYTHING together, the answer is strongly dependent on what the person is trying to achieve, and making sure that everything is included. Wiring in LV DC systems can easily become cost prohibitive if your overall current draw is high. Here's a real world example, we wired our entire house in 12-2 and 12-3 Romex, for around $200. Our Battery interconnections and runs to the 24V Inverter cost $400, the longest length of battery cable is 4'. Now if the DC is being used at point of source, it's no big deal, but if you want some form of typical home wiring, then you need to do your math and work out what is most cost effective.

There's a reason we use 110V AC, and the arguments held between Tesla, Westinghouse, and Edison resulted in going for higher voltage AC transmission than lower voltage DC transmission still are pertinent on the micro scale. You're going to have losses, the choice that needs to be made is are they in the wiring, or in the inverter, AND which of these losses is less, and which is more affordable taking into account the losses projected.
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Old 03-02-2013, 11:06 AM
 
287 posts, read 483,717 times
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That's the reason it's easier to design a house to be off-grid then it is to convert an older one... the high draw appliances can be put closer to your power source eliminating long runs.

Wire Size Tables

And DC appliances are more costly due to low sales volumes and limited markets to buy them... if you could buy them at Best Buy or Sears - they would be cheap(er).

And if you are going to experience losses anyway - why increase it by running everything off an inverter?

Anyone who has the desire to go off-grid has to be honest with themselves on what they expect or want and/or are willing to live with and without. You need to talk with several people who are off-grid - and ideally have different style systems (inverters, gas or DC appliances) - before you even start...
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Old 03-02-2013, 01:56 PM
Status: "King of the World" (set 15 days ago)
 
Location: Itinerant
5,188 posts, read 3,747,109 times
Reputation: 4061
Quote:
Originally Posted by dcbrewmeister View Post
That's the reason it's easier to design a house to be off-grid then it is to convert an older one... the high draw appliances can be put closer to your power source eliminating long runs.

Wire Size Tables
But what's a long run? Is it 5', 10', 50', 100'? More pertinently if you have a short run, then the power hungry appliances you have need to be within short range of your battery array, thus presumably this means in the kitchen (or immediately above/below it) and/or near your well. So this would mean that the well is within say 5' of the kitchen, and then the kitchen and well within 5' of the batteries, but then there's storage tanks and pressure pumps too, which also need to be within 5' of the kitchen/well and batteries. Now that little 10' diameter sphere is starting to get pretty crowded, and we haven't even gotten to the workshop. Oh and I'll point out that the run length is the length of wire, not the physical proximity, the fridge could be in contact with the batteries but with a 100' wire circuit it might as well be 100' away (I know most people get this, but, for those that don't).

Your table only covers up to 50 amps and for 5% loss. This means you have at best 95% system efficiency before you even hit any equipment. An inverter running at peak efficiency (20-30% peak output) can have an efficiency of 96% (saving 1% from your wiring chart) doesn't sound like much but if we're picking the fly ***** out of the pepper... It also leaves you the option to use commercial 110v equipment. Now agreed 96% is about as high an efficiency as you're going to get from an inverter, it could be much lower, however it can be much lower with LV DC too, if you're running a lot of current through too narrow a gauge wire, and it's just burning up the insulation.

Quote:
Originally Posted by dcbrewmeister View Post
And DC appliances are more costly due to low sales volumes and limited markets to buy them... if you could buy them at Best Buy or Sears - they would be cheap(er).
But they're not, and they are more expensive. If wishes were fishes.

Quote:
Originally Posted by dcbrewmeister View Post
And if you are going to experience losses anyway - why increase it by running everything off an inverter?
From your wiring chart, you're not increasing your losses necessarily, if you have an inverter running at peak efficiency and it's efficient then 96% of your battery power (subtracting maybe 0.01% or so for wire loss) becomes 110V AC, which is more efficient than a 5% loss from your wiring guide. Your guide also only goes to 50A, at 12V this is only ~600W which sounds like a lot until you consider well pumps, laundry equipment, microwaves, hell even a hairdryer.

One thing you fail to mention on "why increase it" is convenience, but it's not determined that you are increasing your losses anyway, that's system dependent, put LV DC in the wrong application and you can have far greater losses than even an inefficient inverter system. However screw everything else, you cannot deny that going to Sam's/Walmart/Fred Meyers/Best Buy picking up some newfangled gizmo, taking it home and plugging it in with no concern about compatibility and then having it work is worth a lot, it's certainly worth the possible 1-2% lower efficiency than theoretically peak efficiency DC.

Quote:
Originally Posted by dcbrewmeister View Post
Anyone who has the desire to go off-grid has to be honest with themselves on what they expect or want and/or are willing to live with and without. You need to talk with several people who are off-grid - and ideally have different style systems (inverters, gas or DC appliances) - before you even start...
Agreed, which is why I said you need to do the math, what can you afford building out an inverter end-2-end system with the cash you have available including costs of appliances you'd be using if you don't already own them. Do the same with the DC system including all end-2-end costs including the cost of appliances you'd be using if you don't already own them. If you need to upsize or downsize based on power consumption and/or cost then redo the math. Most important calculation is to figure out how much peak power you really need (and no it's not the figure you might use from grid tied, with everything on at the same time, and the tumble dryer running). We use a MAXIMUM of 8kW/h per DAY, and that's with all my electronics being used daily for around 5-6 hours which probably accounts for half or more of that.

My point is, that often people will say "oh don't waste time on an inverter, because they cost money, and are inefficient." without considering the added costs and efficiency limitations of going pure LV DC (and as I've mentioned I've seen LV DC systems wired with 14-2 Romex because the self-installer didn't take into account the increased current flow), that cabling costs are going to be a couple of orders of magnitude higher, that common appliances are going to be up twice the retail price when they can be found (this is AK, not the lower 48, there may be a 50% surcharge or more for shipping too). There's also the convenience factor of just plugging something in, and having it work, while the homeowner might be able to do this with their 12/24/48V power supplied equipment, what about family, friends, guests who want to plug in and charge their 110V laptop, phone, etc.?

LV DC can work very well with low draw circuits (high efficiency lighting for example) or at point of use, but when you're considering higher draw distribution circuits of 300-400W and over then its not so cut and dried. There's the other doozy mistake I've seen people make with appliances, where they're running a DC loop, and putting a 500W truck inverter off of it to power a TV/DVD any possible savings in power consumption you might think you might have made on using LV DC just went up in smoke on that inverter, not to mention the fire hazard (these are often the 14-2 Romex guys). These are all things that need to be thoroughly thought through before making any decisions on whether LV DC will work for you, or whether you should just go with 110V AC and an inverter.
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Old 03-02-2013, 02:38 PM
 
Location: Naptowne, Alaska
15,596 posts, read 34,556,906 times
Reputation: 14657
So to make a long story short (because I'm no electrician) one should not use typical 110 wiring (12-2 or 14-2 Romex) to run a 12 volt system?

I've been kicking around wiring our somewhat remote cabin, but not yet sure if I should wire to run off a generator, or a battery bank/inverter. Or wire to run 12 volt lighting much like a motorhome or boat might be. (heck maybe motorhomes are more than 12 volt I don't know, I've never owned or worked on one)

We don't need much. Currently have a portable propane lantern that lights the entire cabin up. But it would be nice to have porch lights or bedroom lights now that we are preparing to sheet interior walls. Might be better just to use stand alone battery powered single lights in each room?
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