Solar Forum Trolls of The Energy Industry.

[Nifty]

If the batteries were cheaper and/or we didn't have super reliable power here, I'd consider going off the grid.

My biggest problem / concern with being grid tied is that once the grid goes down, so do your solar panels. A grid-tied inverter requires power from the utility in order for it to be "on".

I've been discussing some interesting ideas with a few engineering buddies of mine to find ways to do the following if the grid goes down:

1) Automatic switch to disconnect from the grid
2) Turn on backup power from a generator or small bank of batteries to get the inverter running
3) Once the inverter is up and running, feed a small amount of power back into the backup power system to keep the whole system functioning (at least until the sun goes down).

 

[sunsaver]

I don't know much about grid-tied systems, but i know they make tranfer switches which will automatically switch you to a generator or battery bank. If you just want to run the invertor off the panels, i would think that you would have to disconnect from the grid, which is down and would ground you out. Once the physical connection from the grid is broken, you should be able to use power from one of your panels to supply whatever control signal is nessesary. I would imagine there is a normally open relay that is powered by the grid to prevent you from being connected when it is down. If it needs 120vac, you could get a cheapo inverter and tie it into one of the panels at the combiner box. Well, your panels are probably 24volt, so you might need a slightly more expensive model. Even if you did this, your lights would be out at night. If you switch to 2watt LED lights, you could light your whole house with one battery and a cheap invertor. Youd still need a transfer switch, and it wouldn't hurt to have dedicated lines for emegency lighting. It's an interesting problem. Got panels, but the lights could still go out. Wish i could be more help.

 

[Nifty]

Right, the only feasible solution right now is to buy and install a completely separate inverter where I'd need to disconnect from the grid and bypass the existing inverter and route power to the regular (non-grid tied) inverter.

Of course, I'd only really need this in the event that the power was going down for more than a day or so. If there really was a serious emergency where power was going to be out for weeks, I'd probably pull a couple panels of the roof, wire them in parallel, and feed the power into a couple car batteries in series, then run my mini 12 volt inverter off of the car battery.

Note to self: When the Apocalypse happens and I'm going to move forward with the plan above, make sure to get the help of the neighborhood electrician so you don't kill yourself!

 

[offgridgirl]

It's really nice to finally meet other people who live off-grid, or who are going solar. There are some forums out there, i wont name names, whose sole mission is to divert people who want to go off-grid, and steer them back unto the grid.

What type of fridge did you get offgridgirl? how can you run it on so few batteries?

I tried to find other off grid people on some of the "solar" sites and I got blasted for our batteries. Sure...I'm sure they want to sell me their batteries. Our batteries work great.

I got a Frigidaire which is so much cheaper than a sun frost or something similar. We figured it would be less expensive to get a real refrigerator and upgrade our system if we needed to. So far we are good...but we are looking into more panels to give us a little more juice on the cloudy days....just in case.

Our house is a berm home and is about 1100 sq. ft. We designed our home knowing we would be off grid. To get electric up to our house would have cost about $20,000. We started with a propane fireplace for heat, a propane stove, refrigerator, GE clothes dryer, washer and gas water heater. We have since changed out the fireplace for a wood burning stove and a back up wall heater, and changed the propane refrigerator for my new electric refrigerator....yay it has a self defrost. We are looking into a solar water heating system.

My husband designed our system with no prior knowledge and although we have made some changes he did a pretty awesome job. Everything works really well The batteries are doing great. We don't ever run them down. Hubby checks the water in them each month and that's it. We call our home "an experiment" since my husband and I have never done anything like this. It is awesome to be able to be away from the grid and live normal.


If anyone is interested I posted a weekly story from us finding our land, building our home, and my hubby designing our system. It's a long story with lots of pictures. I started posting 3 years ago.
http://www.city-data.com/forum/tennessee/359683-going-off-grid-east-tennessee.html

 

[sunsaver]

Wow! That's so cool. I did my own system, but i have an extensive background in electronics and electrical wiring. Im impressed that your man did it himself. I sort of think of my home as an expirement too. I'm dragging this creaky, 100 year old house into the 21st century kicking and screaming. My next goal is some sort of ac. Im burning up. I want to do geothermal. Ive got a pump, ac coil, a squirll cage blower. I think im going to put my exchanger vertical, so i can dig the hole or holes with an auger. I have alot of fruit, nut, and berry bushes packed in like sardines, can't get a backhoe in here.

Well im definitely going to read your whole story!

 

[Denim Deb]

I'd like to go off grid, but hubby won't go for it. He thought about doing a tie in, then he talked to someone, and found our electric bills would actually be higher than they are now! So, why bother?

 

[animalfarm]

We have wind and solar.

You can have grid tie with batteries. The grid supplies a small % of the load being used at all times. If the grid goes down, the system simply runs off the batteries. You must make sure you don't have too large a load that will drain the batteries quickly. You can also have grid tied, batteries and a back up generator. The inverter controller handles all of this. You just program it.

The generator can be set to be primary or secondary back up (grid is the other). You can change this at will by pressing a few buttons. You can cut the grid off completely at any time or pretty much have any configuration you want.

We have the dryer and hot water tank on hydro. Everything else is on solar wind with all of the above options. We also have on demand propane hot water for everyday use and shut down the electric hot water tank during the summer. In winter, an outdoor boiler/heater heats the water for the electric tank and we switch from on demand to that.

We have one dedicated plug for hydro in each room separate from the off grid/hybrid system. We can go completely off grid (as soon as we get all the kinks worked out) or be a hybrid system with the grid as back up along with our generator.

 

[Nifty]

Interesting! What is the make / model of your inverter?

One thing I'm still not wrapping my head around with your setup: If the grid goes down in the middle of the day, are your solar panels still providing power to the inverter and then to the house? Does your system auto-disconnect from the grid before kicking on?

My buddy works for PG&E (utility out here) and said that they require that inverters shut off when the grid is down because they don't want 4 Kw + being fed into the grid when their guys are up working on the lines that are suppose to be "dead".

So, I'm guessing any system that is grid tied and has batteries, etc. would legally have to disconnect from the grid if the grid goes down to protect the linemen.

 

[Nifty]

BTW, all this solar talk made me realize I'm 14 days away from my 1 year solar anniversary! Instead of hijacking this thread some more I updated my thread here: http://www.sufficientself.com/forum/viewtopic.php?pid=256162#p256162

 

[sunsaver]

I've been following your stuff. You have a very nice rig. Alot of people have ng or propane back-up generators with automatic transfer switches, electronic ignition etc. I've only got two panels, and my back-up generator was made in china, has to be cranked by hand, and can't get any compression during an ice storm.

Now it won't crank at all. I think the electronic timing is broke. Good luck finding that circuit board from china! I want to take out the generator part, ditch the gas engine, and make a wind turbine for it. I've got a gearbox from an old troy-built tiller that should be robust enough and close enough ratio, but i don't have the room for a big enough turbine to crank it. it's 2700 watts. Not much wind here either, but it would probably work great during thunderstorms!