suggestions for adding grid tie to existing Off grid system

denlow1

Have been operating off grid for many years, but now have a chance to grid tie. Primary reason is to be able to run air conditioning without having to resort to the generator. Here is a summary of my current system and am looking for suggestions / tips on what to upgrade or to be aware of to allow the grid tie.

3.22kw PV panels controlled by 2 FlexMax charge controllers (1.46kw into FM60 and 1.76kw into FM80) (no MATE system)

Trace PS2524 invertor with generator control module and  remote controller

8 L16 RE batteries (24 volt: 2 parallel strings of 4 ea)

Kohler 14 RESA propane generator

small Windseeker wind turbine

Will I need to upgrade to a hybrid invertor such as the Outback Power FX-R Renewable Hybrid?

Thanks for input.

Dave Angelini

Only need to change inverters if you intend to sell power.
The plus I see is it could increase your property value having utility.
The minus is the expense to connect and possible building department/utility requirements.

If you are running a genset for air-conditioning you really should look into mini-splits. I have over 100 offgrid clients doing that. Many do not even need a genset depending where they live. I am happy to be one of them

denlow1

Dave

Thanks for your insight. I am not real concerned with selling power as we are just "squeaking by" as is.

We do have a mini-split in our bedroom (a 110 volt unit) but even it seems to draw so many amps it causes the generator to auto start due to the amp draw. The rest of the home is cooled (relative term ) with an evap cooler. This past summer was much too warm here in NW Arizona to be of much help.

Dave Angelini

For a split to work well and cool the whole house offgrid, it needs to be the best model available.
 If you look at LG, Panasonic, Fugitsu or mitsu, they all have 3 or more models in the 12,000 btu range. The most expensive is what you want. It will have SEER ratings of 25+. Many use the 9,000 btu models offgrid and they can easily get over 30 Seer. You need to run a split from 220 vac to get these numbers.

An array that faces south east to start the cooling early and a south west array to run late when cooling. They run all the time when you need it and can use as little 300 watts at night keeping the place at 77 or so. 

We were at 100f alot with wildfire smoke and had no problem running 24/7 for a month.  It seemed like a year. Man did this year suck or what? Can't wait until New Years to kiss it goodbye

I would lose the 24v inverter, go 48vdc with the Schneider CSW 4048 or the small Outback Radian. Your batteries will be much happier. Good Luck! 

Dave Angelini

Yea, get a Radian and it will talk with your Flex mppts. Serious improvement to be able to see a 24 hour graph of how and when you use power.
All of the nice things about the old inverters lasting forever. They did not network with your power system and that is a major shortcoming for many. I get thank-you's all of the time on that one.

Above is a full charge and then EQ graphically displayed.

Photowhit

denlow1 said:

Thanks for your insight. I am not real concerned with selling power as we are just "squeaking by" as is. 

It's a good time to remember that off grid systems have much more losses than the grid. Because you must reach full charge and lose all the 'extra wattage' several times a week.  Array's for the same amount of energy used will be more than 2x the size for the same energy used. I would encourage you to 'bank your energy' with the grid and use the batteries as backup. Do a full cycle, every month for battery health. Bring down to 50-60% and recharge.

If you can do this without allowing your energy use to grow too much, you should be better off with your energy budget, on a grid tied system. Your FLA batteries 'suck energy' with losses, as well as your inverter changing DC to AC. If you have both the grid and a battery system you will save a minimum of 25% wattage drawing from the grid rather than the battery system BEFORE considering the energy lost when you reach absorb and later float.

I'd be glad for others to jump in if they feel I'm wrong, I've lived off grid only, have huge losses as I sized my system to run air conditioning. I don't own a generator.

denlow1 said:

Trace PS2524 invertor with generator control module and  remote controller

8 L16 RE batteries (24 volt: 2 parallel strings of 4 ea)

Nice to see you are currently running 2 parallel strings of batteries for your 24 volt system. It will be a great time to replace your 24 volt inverter with a 48 volt one. Wish I could address hybrid inverters, but no experience with them.

Photowhit

A couple more thoughts.

Since you intend to be grid tied, is your solar array on your roof? If it needs to be inspected, it will likely need to meet new NEC codes to shut down series connected panels 'within' the array if they reach 80 volt threshold. I think this only applies to roofs/buildings as residents, but speak to your local AHJ.

Moving to a 48 volt system voltage, will allow double the array sizing with the charge controller you have now. So it will allow easier expansion.

denlow1

Photowhit, Thanks for your comment and thoughts. I am still considering going 48 volt. Currently my only DC loads are the evap cooler with a 24volt DC "squirrel cage" motor and a stepped down 12volt DC cell phone booster. Everything else is 120 v AC MSW from the Trace inverter. PS my PV array is not on the roof, it is a ground mount.

Photowhit

Of course all your AC loads become 24volt DC loads right now.

denlow1

Photowhit, of course you are correct, all are 24v loads (indirectly). I was only thinking out loud that I would have to deal with my 24 volt DC cooler motor and cell phone booster if I change from a  24v to 48v system.

Photowhit

Perhaps the evaporative cooler won't be needed as much with air conditioning...lol.

Guessing you are somewhere dry... In 2003 I decided I 'needed' air conditioning. When solar panels were $5 a watt, The whole process was Buy a lot good for solar, build a tiny home/cabin with 6" thick walls, so I could do minimal air conditioning so I could sleep 8 hours with a 1000 watts of array(purchased in 2004 for $4 a watt delivered). Missouri is usually pretty humid in the summer.

denlow1

Photowhit, Am at 4200' elevation in NW Arizona.....yes very dry. The evap cooler works great with RH< 30% and temps below 100 F. This past summer, though, was brutal with 43 days reaching over 100 degrees and extreme drought....6.75" annual rain when our normal average is around 14"!!