I have a cabin in my backyard that has been wired to the 110V grid. I want to remove the feed cable and install solar panels.
Rather than re-wire for 12V, is there amy technical problem with using the existing in-wall 110V wiring?
Of course, for safety, sockets and lighti fistures will need to be replaced with 12V versions, or at least relabelled.
Mark Fisher
Depends whether or not you mind if your shed burns down.
The current flow in the wires for a fixed power load will be roughly 10x larger when running at low voltage 12v compared to 110v. The resistive heat dissipation in the wires I^2R will be 100x more.
A 100W lamp at 110v draws less than an amp, at 12v it draws 8A.
I would do the sums again *very* carefully for solar power if I were you. It generally is not at all economic if you are already on grid. How many Ah of batteries needed and what panels & charge controller.
Most times it is a lot cheaper to hump a heavy battery around and charge it at home than to charge it in situ by solar (or wind) power.
Provided you don't exceed the total current rating it might be OK. But remember to use a low voltage automotive fuse in the circuit to protect against accidental short circuits causing red hot cables.
I saw a very nasty fan heater failure at the weekend - one of those oscillating ones and the power cable failed by stress fracture on the wrong side of the thermal cutout protection. It was a filled plastic chassis construction and well alight when the owner found it.
Regards, Martin Brown
Hmm... maybe I should consider gas lamps and a Sterling engine.
Mark Fisher
Wouldn't running Natural Gas through the Romex be just as problematic ??
Just asking.
;-)
Leave wiring and fixtures as is and install an inverter
Sounds fine to me. If someone plugged a 120v appliance into the 12v outlet, nothing dramatic would happen. You'll of course have fuses or breakers somewhere anyhow.
John
I can't imagine you'll be producing much more than 20 amps per circuit so it should work OK. I'd use a breaker panel (or fuses) to limit the current to an acceptable level. I'm assuming you will 'buffer' with a deep cycle LA battery, right?
Personally I'd replace the connectors/fixtures with 12V ones, for no other reason other than you'd be able to control polarity and anything plugged in won't accidentally be plugged into a 120 V circuit.
-- I'm never going to grow up.
That may not be any better than solar.
You should take Martin's point: the wiring is rated for _current_, by dropping the voltage by a factor of 10 you're reducing the available power at the socket by a factor of 10, also. If you're willing to live with that, you'll do fine -- one way to reduce the cost of solar is to reduce your power consumption.
-- http://www.wescottdesign.com
If you are not technically competent to judge the suitability of a bit of wire you are not technically competent to judge the suitability and cost vs benefit of grid vs any other form of power generation.
My advice would be to leave the grid connection and wiring intact because he will almost certainly want to use them in the future.
Batteries alone cost more than the amount of electricity at grid prices they can charge and discharge in their lifetime.
NOOOO! Any and all AC appliances with transformers may burn up with 12VDC applied. AC motors likewise will cause high (fault) currents. The odd 120V light bulb won't explode your fuses, though.
It may be appealing to consider an auto-style 12V battery for energy storage, but it's NOT a 'natural' solar-electric component. It makes no sense to modify a dwelling in favor of 12VDC. Heck, what ARE the refrigerator options with only 12V available? Or electric blanket?
AFAIUI, RVs typically have 12V systems, including lighting, fans and water pumps. Fridges, heaters and such like are propane powered but require 12V for the controllers. It might make sense if your dwelling _is_ an RV.
RV/trailer 'fridges are called 3-way; they'll run off 120VAC, 12VDC, or propane. They use the "ammonia cycle," where heating causes cooling. There are two heating elements and a little propane burner.
But if _all_ you have is 12V, I wonder if Peltier would be worth looking into?
Cheers! Rich
?
Makes no sense to change out the wiring of an existing mains powered dwelling. Inverters are now part and parcel with solar cells, in fact one manufacturer has gone so far as to create a distributed inverter technology that is built into the panels, if not the cells themselves, and is parallelable. The vast majority of the market is geared towards powering the dwelling load and off loading the excess onto the mains only for the periods of adequate insolation - with no battery backup or storage of any kind used or contemplated. Since 12V rquires 10x the current and therefore 10x cross-sectional area and volume of copper- this would be what is called an unacceptable carbon footprint and unsustainable approach to using solar. It is important the OP find a solar PV inverter, one that incorporates MPP tracking as a minimum, and not just any old inverter.
You could replace the duplex sockets with the 220v ones that have the 90 degree prongs. Not many plugable 220v appliances here in the US.
Cheers
Hmm, lets see.... Air conditioner, clothes dryer, stove, dust collector, cabinet saw, air compressor...
...arc welder!
Not yet. Bandsaw first. ;-)
There aren't many reasons to be off grid.
1) there is no grid available. 2) you derive some personal non-economic benefit, well being, "hey look what I can do", from being off grid.You can live in a tent...but unless you are willing to dramatically decrease your needs for energy, there is no economically feasible solar system, today. No, the schemes whereby you transfer the cost to ME thru government subsidy or force the utility to buy electricity at inflated rates raising MY bill don't count. I don't want to pay for your system!
The current you can get thru the wiring is the rating on the breaker. So you get 1/10th the power. Unless your peak load on the circuit was less than 1/10th the rating, you're gonna have a problem. See "living in a tent" above.
You don't want to put 12VDC on 110VAC wiring. Plug in a device with a transformer and sparks will fly. Polarity is important. Lotsa devices have non-polarized plugs. Call up the local electrical inspector. If he's on his toes, he won't let you do it.
I can hear the villagers lighting torches to come after me. "No that can never happen", "I won't tell the inspector", "he has no jurisdiction", "I'll never have any visitors who might compromise the system"...Use common sense. Stuff happens.
Put separate 12V wiring in the place, or use an inverter and the existing AC wiring.
Go visit newsgroups that address these issues for details, but... Use more than 12V for your DC storage system into the inverter.
Here's how you talk yourself out of the project. These are round numbers, but the message is the same.
Turn on everything you want to power simultaneously and spend some quality time with the utility meter. You need at least that much peak power plus any additional for motor starting peaks etc.
Measure consumption over an average day in the season when you use the most energy. Multiply that by how many consecutive cloudy days you want to survive. Times some efficiency factor. That's how big your batteries need to be.
Google for insolation charts for where you live. That'll tell you how much solar energy you can expect to get from a typical winter day. Divide that by 10 for the efficiencies of the solar system and charging system and and and... Divide that number into the average daily energy requirement to see how many square meters of panel you need.
A popular number is 1KW/square meter. Depending on the efficiency of the panels and other system components you can afford, you're looking at 10% of that on a sunny summer day with no buildings or trees to block any of it. But averaged over the day, it's a lot less. And in winter it can be near zero depending on where you live.
Add up the installed cost of all that stuff.
Bottom line is that solar power is a fool's errand. There's no way it can pencil out on an individual basis with current technology. Unless you can get someone else to pay for it...that would be me...and I object to my tax dollars fueling your errand.
Wiring is the least of your worries. Find a different hobby...like convincing the tree-huggers that we need to get some nukes on line BEFORE we kill off all the trees.
There are refrigerators that get their power directly form Liquid Propane "bottle gas".
Yea 3 way RV fridges, AC, DC & LP gas. I believe they use an Ammonia refrigerant.
Cheers
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