wind and solar energy

[dcbrewmeister]

RV's are 12v.

And if you use LED's, most draw 0.25 - 0.5 amps so romex shouldn't be a problem.

[dcbrewmeister]

Originally Posted by Gungnir

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.



But they're not, and they are more expensive. If wishes were fishes.



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.



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.

Who said anything about 5 feet? No one except you.

And who runs their well pump off romex? Only someone who wants a fire. So again, who said anything about everything had to be within 5 feet?

You type a lot of stuff in your responses and, dare I say, overfill it with facts and figures. If you want to run EVERYTHING off inverters - that's your prerogative... but there are other options, and they aren't nearly as expensive as you make them out to be. Considering a DC CF light will last years over a standard bulb in the first place - you can take that into account when buying it. With your system - it has to be over built - just to run the inverters and account for the losses... meaning more money just to build it...

[Dakster]

This is turning into a which oil is the best oil to use in my car thread....

I would not convert my on grid house to 12v anymore than I would convert every light/appliance in my RV to 110v. Everything has its place and the limitations that go along with it. There has to be a reason cars run on 12v and on grid houses run 110v.

Although just throw a wrench into the works, I remember awhile back that there was a push to up a cars voltage to 24v, but that obviously hasn't happened.

IMHO, on grid house use on grid 110v appliances. Off grid house where you primary power generation/storage will be DC based use those. Certain things you can get both ways which is why power converters/inverters are made...