Secretly off grid
 

okay. so after extensive research into NC and Federal laws, apparently in order to have a solar panel on my roof, my private property, furthermore using the sun which only God owns, i must use a grid tie inverter. I must have a Federal approved grid tie inverter that has a Kill switch so that the power company can turn my solar array off at will... I don't like this one bit.

So, being that i am fairly new to the PV thing, i am relying on your foundation of knowledge...

I want to comply with the law so that they wont complain, but i want to hack the system so that i can be off grid when i choose, not when the state chooses... im PV dumb, but not electrical dumb...

Also i want to convert my entire house, including appliances, to DC. I understand that the inverter takes care of the DC to AC conversion, but like i said, i want to be completely off grid, and DC uses less power, so i will need a smaller PV source...

So a Rectifier in all appliances is in order, or just one for the entire house?

How would i be able to achieve all this?

Doh!!!

The reason i post this thread is because, i dont know where to start. maybe you all pioneered this thread before. but im bad with PV lingo, and i honestly dont know where to start...

what appliances do you currently have that use electricity? Completely DC is possible but usually involves using gas/wood/propane/... for the major appliances. I highly doubt you would come close to saving any money by going 100% DC just throw a couple of extra panels on the roof to deal with any losses during the conversion.

I don't know the requirements in your area but it should be possible to get a grid tied with battery bank setup that will disconnect your house from the grid when the power goes out or the utility wants to but will leave you drawing from the batteries so the house stays running.

It's just a question of money. How many KWH a month do you currently use?

It sounds like there are big holes in your source knolage, a big reason for using AC is that high voltage AC tends to be safer then high voltage DC, low voltage DC is both expensive an wasteful because of the line loss so any system that has low voltage DC tends to keep those runs as short as possible, as in less then 10 feet, less then 5 feet is even better! also PV panels produce DC electricity so you don't need a rectifier at all, also if your lines are under 30v (24v battery bank, but please do not take my word on this part) then I don't think the electrical code is very strict at all, but your cost in wire sky rockets and your cost in low voltage DC appliances sky rockets, to the point where the only way you could ever save any money is if you are building a cabin out in the middle of no where, where it would cost you $10,000 to bring in the power lines.

As for the disconnects, your AC inverter has to be designed to now allow it to back feed in to the grid when the grid is down, this is so you do not kill line men.
Your system also is required to have a service disconnect that is out side of your house so if your house is on fire the fire department can turn it off, preventing firemen from being electrocuted and dying, this is not a remote disconnect that is located at the secret underground government center, this is on the outside of your house that is used to prevent death of those who are trying to keep your house from burning to the ground, if you have an issue with this please post large signs at the ends of your drive way so all firemen showing up at your house know that they should let your house burn instead of risking their lives.


If you fallow the electrical code, you should end up with a system that is safe for everyone, will save you money and that the only way to turn it off is to be standing out side of your house in plain sight, turning off a large switch that you could then turn back on.

thanks for the clarification... i tend to be a little on the paranoid side when it comes to the gov't...

i was unclear as to whether or not the cut off was big brothers way to control me. im glad it is for the safety of others. in that case i am all for safety. if being safe helps me save money, then safety is paramount...


And at my peak usage:
utility says roughly 45kw avg a day.

this can be cut down, and im averaging for a particularly hot summer, which saw 3 weeks straight 100*f plus temps in july...

this is my first year in this house, so its tough to tell what the normal usage is. i haven't done much to increase efficiency yet, so my average can be cut drastically.
i have CFL's
i have a Timer on my bedroom tv center
I have a smart powerstrip on my living room tv center.
i have room darkening blinds, and curtains.
and my clothes washer is energy star @ $13/yr
i just upgraded my rear sliding glass door, to Energy Star french doors.

its a work in progress...

Could you elaborate please?

-AC_Hacker

I'm assuming that's 45 kwh/day? if so that's a lot to try and cover via solar. It's doable but you had better be rich. First step is to figure out where all of that power is going and reduce the usage. Get something like a kilowatt meter and start recording power usage on all of your 110V devices.

I'm assuming your house is all electric with that level of usage so check the temperature coming out of the hotwater tank. It can probably be turned down a lot.

AC takes a lot of power and will require a serious off grid system. If you are going to keep using it I'd recommend looking into a grid tied system sized appropriately so that during the sunny winter months you can build up a credit with the utility and then draw that down during the summer with the AC.

Also going with a grid tied system you can spend less to get it up and running since it is not necessary to have storage. The downside is you only have power when the grid has power but you can always add storage later.

I forget what the exact reasons were for AC being safer, I just remember it from my old electrical text book that I read 15 years ago but I seem to remember that it's easier to brake an arc in AC then it is in DC.
It's also easier to work with because you can use transformers with AC, a lot of switching power supplies require AC, induction motors require AC, and there is such a small demand for DC appliances that they tend to cost more and you have a smaller selection.
Going through my parents shed I found a box of 32v light bulbs from when we lived off grid, boxes of other low voltage DC appliances, all out dated and less efficient then pretty much anything that you can get new.

i just know that an inverter wastes current to produce AC...
DC cant be that dangerous... my phone hasnt blown up on me, but if i touch an AC outlet, i get fried... ive put my tongue on a 9v battery, got a little tingle, yet it can power a flashlight for hours. ive always thought of DC being more efficient... if it wasnt, then why doesnt RVers use an inverter for their appliances, including a stove... All DC appliances on a RV or Boat. Why? AC wastes too much power in its inversion from DC.

Yes there is power loss in the inverter. That being said, do you know how much batteries will cost? Enough batteries to run lights for a house for the night, much less an AC unit? Can you get DC AC units? I imagine not.

Off the grid is cool and I'd do it if I were a bazillionaire, but alas I'm not. Honestly an off the grid system would probably cost 1/2 as much as my house.

I know a fellow who recently built an off the grid house for a rich guy. The guy wanted spray foam for insulation entirely. It cost $60K for insulation alone. I don't know what the power get up cost but I was told that the cost of the insulation was nothing in comparison.

DC at low voltages is less dangerous however it loses a lot when you try to send it long distances. A 12V system would lose a lot of it's energy with regular 14/2 wiring on a long run so you go with thicker wires. The copper costs alone eventually make it cheaper to switch to a higher voltage system. That's why on most whole house systems you see 36V or 48V. touch your tongue to the leads of a 48V battery bank and you're dead.

You do waste power converting to AC but it's trivial to deal with cost wise compared to going 100% DC. The major reason boats and RV's are all DC is because they have to have a DC battery on them and then it saves them money to not do an inverter to make 110V for a few lights and fans. I don't know of any RV that tries to run more then that off of the 12V system. All appliances are gas and things like the AC and microwave work off of an inverter and usually only when a generator is running.

Some of the most efficient solar electric systems you can install use micro inverters on the back of the solar panels to convert the low voltage DC to high voltage AC, the higher the voltage the less line loss you have and the smaller the wire has to be, and with AC power you can use a transformer to bump the voltage up even higher to go longer distances, like is done with high tension power lines, there are losses in transformers too but there is greater losses in low voltage wiring.
RV's use DC wiring because, like has already been stated, it's cheap and RV's are small so the wire runs are short, but the light at the far end of the RV is going to be dimmer then the light close to the battery.
My electric car runs off 48v DC and if you touch the two ends of the pack with bare hands it will not kill you but you will feel it and you can get burned if you are not careful, I'd like to have 72v in my car but that is boardering on what can kill you.

It's not the voltage that can kill you but the high amperage thats unsafe

I will echo the earlier post that suggests you focus on reducing consumption first. 45 kWh/day is a LOT of solar, and a lot of $$$. It's almost always easier and cheaper to reduce that load than it is to increase production.

Limits To Growth
 

PaleMelanesian speaks the truth! But if you really consider where we are in the grand scheme of things, 'almost always' may not belong in that sentence any more.


This is a prediction graph generated by a computer in the early 70's. It is from a book called 'Limits To Growth'.

The book has attracted a legion of critics and deniers since it was printed. But the irony of it all is that we are pretty much on track, regarding it's predictions.

It takes a bit of study to soak it all in.

-AC_Hacker

great chart AC. They don't chart education which I would suggest might change the results for industrial and service output forecasts. ever the optimist.

@d3vi1d06
To go back to your original post. Why go to an all DC household? Why not have a separate part of the house DC. Low voltage DC is perfect for LED lighting. Yet AC offers all the benefits of mass produced highly efficient appliances, esp. fridges.
How do you control DC though. I can't help you there. You mentioned rectifiers. Anybody? It's a question I share. Can you run a 3volt/.5 amp device on a 12 volt/1200 amp battery or do you have to damp it down and how?
** btw. you've been in the house for a bit, what is your daily electric consumption? I can't believe it would be 45kwh.
** S-F Batteries aren't that expensive. A modest 1kw system can run on 6 L16 batteries and that, I would think, would power a households' lights and tv/internet/computers. Maybe even an AC fridge off an inverter. You might want to double it and run your heat and (if nec.) well pumps. That's $5 to 7K diy?
DC to AC inverters are up to 97% efficient now. If you have 3.6 kw daily input off a 1kw system and you lose 100 watts it's not a big deal.
** Ryland:that just made me laugh. Hands across the waters.
Also, old news? AC current alternates. So apparently there's a 1/10 millionth of a second pause between alternations. And, I've heard, the human brain sends muscle response signals at 1/100 millionths of a second. Hence, you can pull your contact (ie. drop the live wire) by sending a signal to your muscle and with AC, message received. DC just overwhelms the signal paths and you can't let go. With sufficient amperage the last thought you will have will be, "oh, so that's what my eyeballs boiling in my skull smells like." :D

JumboCarbonitefootprintious ?
 

If you are really using "roughly 45kw avg a day", that comes out to 1350 kWh a month!

That's like you are continuously burning 1,875 watts, 24 hours a day, 7 days a week..

Please tell me what kind of appliances you have plugged in, to burn power at that rate.