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freds avatar image
freds asked

Semi Off Grid Implementation

I am trying to help my cousin out who has a farm out in the boonies here in the USA and want’s to install a solar system and I am trying to kick around some idea’s to help him.

I very much welcome feedback and criticism on this idea!!!

I did look at the power passthrough but from my reading:

  1. It gives mains power priority and only supplements when main power feed is not enough. No solar/battery first mode.
  2. No idea if it can pass more power than the inverter rating?

He has lots of building that he could install solar panels on and use micro-inverters to feed power back through the existing wiring.

However with micro-inverters I believe that he is required to be grid-tied or hooked up downstream of the inverter?

I have also been viewing a number of YouTube videos on how grid-tied is not the way to go due to the contractual side, technical design requirements, access requirements for inspections and in some cases additional liability insurance which can wipe out your savings.

Plus you have to go thru the process all over again if/when you make changes.

Given that his farmhouse and facilities are fairly old having to re-engineer everything would likely be cost prohibitive to bring up to code…

Note: I have seem some farm based YouTubers keeping their solar totally separate from their existing electrical system for these reasons.

I have come across a couple of meter mounted devices that do not require redoing your main electrical panel.

Basically you get your power company to remove the meter, insert the device and reattach the meter.

The first device is ConnectDER which is cheap way to add an EV outlet or plumb in the output of your Grid Tied inverter (after jumping through all the Grid Tied legal hoops).

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The link for this is:

https://connectder.com/

The second class of device is meter mounted power transfer switch for emergency generators which I think is more useful for our desired goal.

This device gives generator priority (so you test it); so anytime it has generator input it switches off the feed from the power company, totally isolating you from the grid at the power meter...


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https://www.generlink.com/generlink.html

The limitation on this device is that it can only handle 10KW of power. (Note in extremely cold weather his average load might be more then 10KW to keep the livestock water tanks from freezing).

The internal transfer switch is non-shorting with a Break before Make functionality. So there will be a brief power interruption on each power cycle.

But hey with some NodeRed automation it has lots of possibilities for solar/battery priority to consume minimal grid power.

Plus all you have to do is tell the power company that this UL approved device (your mileage may vary depending on your power company) and as far as they know you are only installing it for emergencies and hey it’s dirt simple for their employees to install!!!!

With NodeRed you can monitor:

  1. Battery state
  2. Current power consumption
  3. Current and predicted solar production.

Control states:

  1. Monitor inverter output, when it reaches a set maximum value. Turn the inverter output off to revert to the grid as your power source.
  2. When inverter is off due to excess AC power draw monitor the power being consumed from the grid, when there is no longer an overload situation for X minutes. Turn the inverter output on and stop using grid power. (Note as a safety measure the GenerLink will not allow transfer to the generator input if drawing more than 50 amps of power from your power company). There are numerous IOT power monitors that you can use with NodeRed to monitor the grid power consumption.
  3. Monitor battery state. If low, turn the inverter output off to revert to the grid as your power source.
  4. When battery state is low, look at a combination of solar predictions and current battery state to turn the inverter output on and stop using grid power. Optionally add a bit of charging from the grid to make sure they will be topped off the next day.

This offers a number of advantages in that you can start small and then scale everything up by adding more solar, inverters (up to the 10KW limit) and batteries.

Again I very much welcome feedback and criticism on this idea!!!

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3 Answers
Michelle Konzack avatar image
Michelle Konzack answered ·

Hmmm, to avoid explidoding costs, I would suggest to install the MultiPlus in the Main Power line and make sure ut does not feed-in which is anyway the default.


The I would use one GTI plus Solarpanels on each building which us more efficient and has lesser power loss.


Be aware to respect the 1:1 rule.


Since you probably need more Power, you can add more solarpanels using the RS 45/200 (11,2kWp each)


This systen should significant reduce the energy bill and csn keep the farm alive if the Grid fail.


However, you sayed he need already 10kW inverter outout to keep the water from freezing. Thus mean, he will need very tough batteries. In Europe with 1,70€/l Diesel an appropriated GenSet is more expensive then a SOPzS Battery with 200kWh... while in the USA the fuel is cheap


Hence he woukd need Quattros...

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freds avatar image
freds answered ·

Ok this is a farm with pumps, welders, heat lamps, water heaters, etc. Most of the time except for extreme cold spells the power usage is relatively low.

The 10KW figure is just a guess and just happens to be the capability of the meter mounted power transfer switch; but during birthing season the ultimate load could be a multiple of that figure.

If we feed the entire farm with a MultiPlus so that we could use grid tied inverters for the solar panels, wouldn't we have to size it for what the ultimate load would be? I.E. no way to revert to the grid because of the grid tied inverters for the solar panels?

The battery backup is not really for disasters but to make maximum use of solar production and draw as little from the grid as possible.

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Michelle Konzack avatar image Michelle Konzack commented ·
I do not know, what kind of Winter you have but I am in Estonia at 59° Latitude and 100% Off-the-Grid with my 4ha Organic Farm (I have also lifestocj), but with sikarenergy only, i would need around 10kWp to get only in the middle 1kWh a day, hence I would beed a solar power plant of 120kWp. This is why I have some 2000W and 700W windmill here.


But are talking about 10kW load, mean 240kWh a day?


I think, you will run into problems with solarenergy...


...and the climat is changeing.


This summer (!) I had to run a GenSet to have enough energy! From August to now, we have horribele weather like couds, rain and very little wind. I got from Wind and Solar only 7,5kWh in August and 6,2kWh in September a day.


I hope, you can cope with such situation.


Oh, I have currently 4x 24V/735Ah, hence 70,5kWh of SOPzS Batteries, but I need to upgrade to 8x 24V/915Ah hence 175hWh otherwise it will be very hard to survive.


Oh, the new Batteries cost the same as if I would request a Grid connection, 29.000€ including BMVs and Balancer, but with energy prices up to 67¢/kWh, Abo, energy transfer tax and eco tax I prefer to stay Off-the-Grid

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freds avatar image
freds answered ·

Ok from the first response I can use a multiplus Inverter with solar panels on different building back feeding power via microinverters to charge the batteries?

I am looking to support 10K of power via USA 120V/240V split phase power. So I am assuming 2 Multiplus 120V inverters, however the 120V is only 3000VA and the 5000VA is only available in 230V?

Does the solar microinverters have to be 120V or 230V?


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Michelle Konzack avatar image Michelle Konzack commented ·

No, this will not work.

You need two identical 120V Inverters or the 2x120V version.


However, with 3000VA and 5000VA you can not provide 10kW to the second building.


You would need at least

1) 4 Multiplus 48/3000 (and then you run the System on the absolut limit)

or

2) better 4 Mutipus 48/5000 (where each support up to 4kW @25C).

or

3) 2 Multiplus 48/8000 (12kW) which could be the cheapest and easiest solution



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