Which inverters can be used with this system?

Re: Which inverters can be used with this system?

The system would be a PV/Wind system that uses the grid as the support AC power for a battery bank (instead of a normal diesel/gasoline generator). This would be similar to a "battery back-up system" except for the fact that the batteries are used as first choice power supply, until their voltage drops below a certain level, and then the grid will kick-in to supply power to the house and charge the batteries. The concept is to use the minimum minimum amount of electricity from the grid (if at all). I hope this is clear.

I'm sorry if this was discussed and I missed it, but the bold part of this makes no sense to me. Why have the grid charge the batteries here? So let's say the sun is shining brightly (wind is blowing), the battery voltage has dropped below the pre-set level, the inverter has flipped to grid power and is powering the house and charging the batteries, and the PV/Wind system is, what? Sitting idle?

If your goal is minimum grid power use, I'd think you'd want the battery charge to come from the PV/Wind once the batteries are below the voltage preset, and then you wait (using grid power) until the renewable energy source brings their voltage back up to full. So no grid charge of the batteries at all. Charging batteries from the grid is likely to result in more net grid power use (due to battery inefficiency), not less.

Re: Which inverters can be used with this system?

i mentioned the magnum before and he didn,t seem interested. The magnum can pass power thru from the grid for battery charging or to pass power thru to your service panel. The way I am setting mine up with using a forktruck battery. I figure if I don,t need power from grid all I need to do is throw the breaker. With the http://www.interlockkit.com/ use of a generator interlock kit I can either use grid power or inverter power. :Dsolarvic:D

Re: Which inverters can be used with this system?

Here is a link to our forum sponser. You can download a manual and read it. The pae models suport ac coupleing http://www.solar-electric.com/maensiwainac.html
. I wishI had the pae model but I got a good buy on the one I got used,. solarvic

Re: Which inverters can be used with this system?

ggunn,

The way I see it, the point is to use the grid support to maximize use of the solar power while minimizing the stress on the batteries (and the size of the battery bank).

So imagine a solar power array and a suitably-sized battery bank for that array. If purely off-grid, with no grid support, you must have average daily loads that are small enough not to draw the batteries down too deeply.

With the grid-support system, you can have the same sized array and battery bank but larger average daily loads on the system, because you know that you can set the system to switch to grid-support at, say, a 20% depth-of-discharge, or whatever else you want in order to preserve the batteries.

So consequently, you might be able to put a larger daily load on the grid-supported solar system without stressing the batteries, thus increasing the kwh average load the system is able to carry, relative to the off-grid only system. For instance, while the off-grid system might be done charging by 11:00 a.m. on a typical sunny day, the grid-supported system might have a heavier load connected to it and consequently continue charging the batteries longer into the afternoon. So there's more power being generated by the solar system in the grid-supported situation. The fact that it will flip to grid early on cloudy days might offset this gain if cloudy days are the norm, but shouldn't do so otherwise.

So the OP's idea makes sense, given his desires and situation relative to the availability of grid-tie. It's not about whether the charge is coming from the grid or the charge controller, it's about how efficiently the system could be used while still prolonging battery life.

Another thing: even if the above considerations where somehow irrelevant, I can't see how it would make no difference whether or not you charge from grid, if you have the option of passing through grid power directly and charging from the array. Charging from grid forces you to lose power due to the battery inefficiencies and AC/DC conversion losses, even when you normally have the option not to (because you could pass the grid straight through). Charging from the charge controller also involves those losses, but there's no option not to in this case -- it's the only way.

So unless you have unreliable power or want to load-shift like BB suggested above, I can't see how it would make sense to charge batteries from the grid. But I can see how it would make sense to charge them from the solar array if the goal is to maximize efficiency.

Re: Which inverters can be used with this system?

BB. wrote: »

...
Off grid inverters, even with fairly accurate frequency standards will still make clocks and timers that use line frequency as a reference, almost useless because the time will drift way too much:

• 24 hours per day * 60 min/hour * 60 seconds per min * 0.1% (0.001) clock error = 86.4 seconds per day drift

-Bill

And I wish they would fix this. It's NOT hard to use a TV colorburst crystal (3MHz) and get a stable clock out of it. And that's in every TV sold, and cost is in the pennies.