Basis for my micro-grid power system.

The beginnings of my micro-grid AC power system that will run on a combination of batteries and solar panels. This is an Accurate Tools AT2000P Pure Sine Wave Inverter as the master inverter, and then one of the 300 watt grid tie inverters. These are all from China but made to USA specifications. There is a seller on Ebay by the name of "dmssg" out of Michigan who I don't know personally, but is offering great bargains on these things. A micro grid system generally requires a master inverter that can initiate power in the entire power grid, then the power production gets boosted by other power sources, which feed into it through the grid tie inverters that are placed at different points in the grid. If the entire solar/wind production system is only going to be feeding into the power company grid, then you do not run the primary sine wave inverter off the batteries, but run the grid tie inverters off the solar panels directly, then plug them into the system which goes to the main power company grid, thus reducing your power bills or even possibly giving you a monthly check for surplus power after the add for the power you buy while using more than you produce, then reduce your bill by the amount of power that you can feed back into the system, as measured by a variant of your regular power company meter like you would see on the side of a house.

Category:

Howto & Style

Tags:

• micro-grid power system
• solar
• wind power
• Wind Power

[davidtwillis]

I am thinking about doing something similar, however I want to use the micro grid tie inverters to feed back into the grid while the grid is on (but have a battery bank charged also). Then if the power goes out, I could shut off the grid, and plug in my master inverter to turn on the micro grid tie inverters.

What I would like to know, is if there is a way to divert power to charge the batteries, or into some other useful place if the grid inverters are producing more than is being used.

[8digitPDX]

@davidtwillis yeah, although I have removed the GTI from my system for now. One very reliable way of accomplishing this is a simple bypass switch. You wire the GTI in line between the panels and the charge controller, with switches to selectively bypass the GTI or charge controller depending on what you want to do. I can make a diagram of this to explain it.

[davidtwillis]

@davidtwillis

The only ones I can find are outback, and xantrex.

[davidtwillis]

@8digitPDX

I have been searching for something to do this. However it seems like it would actually be cheaper to just buy a grid-tie inverter, and run it while the grid is up. then if the grid goes down, shut the grid off, and have a separate charge controller with, and inverter to run the house with a off grid setup.

If you could point me to an inexpensive inverter that will run as grid-tie (around 2kw), then switch over to off grid when the grid goes down, that would be great.

[8digitPDX]

@davidtwillis It definitely pays to shop around with the solar equipment. The big firms operate on very generous profit margins then downtalk the cheaper stuff, which seems to work quite well in my experience. The cheaper stuff has vastly improved in just the last two to five years. I will probably be getting into the business since just on my own I secured some pretty good wholesale arrangements with suppliers.

[davidtwillis]

@8digitPDX

Yes, they can, but the conventional inverter is expensive, and is not modular like these new ones are. I love the Idea of being able to just keep adding on as I go, and don't have to fork out $3k for an inverter just to get started with a 100W panel. I may just try hooking up my little 600 watt inverter to a battery, then plug my 250w grid tie (with a 100w panel) into it, and run a 100 watt light bulb off of it and see how it goes.... worst case I am out $200.

[8digitPDX]

@davidtwillis Some new style panels are set up that way, each having its own GTI, they are nicknamed "AC solar panels" which are specifically for grid tie only applications. What you are trying to accomplish though would actually mainly be done through a conventional current technology charge controller, not the newer stuff. There are larger commercial charge controllers which handle all of that internally.

[davidtwillis]

So then the question arises, what happens when I am producing 2kw of power, but my house is only using 1kw? I would like for that to spill over and start charging my batteries, however it doesn't make sense to have my battery charger charging when I am using 3kw, and my solar panels are only producing 2kw.

[davidtwillis]

@8digitPDX

Thanks, I will take a look at your later videos. But I don't think I explained myself very well. I want to have about 10 200 watt solar panels, each plugged into a 250w micro grid-tie inverter. I am not sure how I will keep my batteries charged yet, but it might just be a charger plugged into the 110 power. I will just keep this setup until I have a power outage in the grid. At that point I will disconnect the grid, and plug in my master inverter (to activate my micro)

[8digitPDX]

@davidtwillis If your panels produce more power than the grid tie inverter would use, for example, 350 watts in full sunlight, but your GTI is a 300 watt, then you can put the GTI inline between your panel connection and your charge controller. It should bleed off its 300 watts then leave the remaining 50 to keep the batteries topped off. That does not work though if the GTI uses more power than the panels make. You would still have to manually unplug the GTI to charge 12v+

[8digitPDX]

@davidtwillis The grid tie inverters will automatically stop feeding into the grid if the grid power is off or unplugged, so you can leave one wired into your system and when it is not plugged into a regular grid outlet, all that gets used up is a little power running the LED light which says it is not feeding the grid. Higher end units will have a built in switch. I just leave mine disconnected when not in use.