Safely grid tying solar system....

So some of you may have seen my solar generator partial build in the build section.  

The more I think about it, I'd like to start getting some return on the investment as soon as I can- at least as much as I can.

Which mean I need to somehow tie the system into the grid.

But I'm not sure what the most effective way to do that is.

as a reminder, so far I have just two major components- a large enough pure sine wave inverter to power a fridge and some other basic things, plus just barely enough battery back up to run that for a day or two (getting sun is REALLY easy in Ponce).

What I don't have are the solar panels to charge it.  So I have an opportunity.

The current plan is to get 300W of solar panel, to feed the system I made.  But it appears that I can set it up that those 300W feed a micro inverter which will also feed the house system.  And even perhaps I can use the battery storage to feed that...  

I'm just not sure what the correct way of doing that is.

The KISS system appears to be- get the small inverter, grid tie it, and then use a charger to keep the batteries topped off.  If the power goes out, un-plug the solar panels from inverter, plug into charge controller, and then run the extension cords to the small generator I made.  Not all that elegant, but it would work.

Any other ideas?  Given the time that I needed to make the system, it kinda seems that the base inverter won't be able to be tied into the grid system....

Since your post mentions "Safely" the first thing you need to do is see what requirements your local distribution company has for tying onto their grid. Up here systems under 10 kW aren't a big deal to go through the approval process to get a Net-metered connection and the costs of that process are eaten by the utility rather than the generator (you). They will lay out what anti-islanding features and approvals your inverters need to have and any other requirements that need to be met to keep their linesman's safe. 

I don't think 300W of solar panel is going to be worth the trouble of doing this properly, if that is the size you are looking at for now I would just have a separate system to play around with and learn on not tied into the grid.

Adam

I'll have to look into that specifically- but assume a small system- less than 1000W of solar panels- and micro grid set ups I've seen just plug into the wall for the 1200W systems I can find.  I know all of those require the grid to be up and active to run....

I've never done a micro system, but I have done several large systems.

Electric companies and code enforcement officials are really ticky about these. They absolutely do not want grid components live when they are thought to be powered down.  It would shock me if they permitted you to do this in a"grassroots way".

As a minimum you will have to have a net metering setup and a disconnect.  You can't get this without assistance from the power company and proper permits from code enforcement.  Requirements vary by location.

Talk to you local power provider.

This https://www.amazon.com/dp/B07D41S7CK/?coliid=IFQ8P74J7ODZ8&colid=1X7ULYR6Z5GHI&psc=1&ref_=lv_ov_lig_dp_it may be a solution.

That keeps the solar system separate from the grid system, allows me to run some stuff with solar power, and still have grid back up if needed.  Better than trying directly tie the system in....

SVreX said:

It would shock me if they permitted you to do this in a"grassroots way".

 

Actually, I think it would be more likely to shock an employee at the electric company. 

In reply to SVreX :

I'm not asking about the Grassroots Method- I just want to use the small amount of solar I have that is used as an emergency generator for some nominal loads.  So that it's not just sitting there not doing anything.  The latter is what happens to gas generators.  Might as well get some use out of this small set up, and at least try to offset some of the costs in real time.

I don't expect to pay for itself, but given the actual frequency of outtages, it's not going to be used a lot.

The grassroots way is to take apart an uninteruptable power supply that has a decent size battery inside and wire your solar directly to charge the battery.  The inverter part doesn't care where the power is coming from, the battery doesn't care which charger is charging it, the battery charger part will just charge less if the solar is working. Plug in your stuff and call it done.

In reply to alfadriver :

Thats fine, but you are still gonna have to work with the power company to tie to their grid.  They will have very specific requirements, and they may be costly.

We have a big, clearly labeled knife switch on the outside of our building to isolate the solar. I forget how many panels are on the roof here, but memory says it's something like 36kW.

I work for an electric utility. If you are going to tie into the grid they tell you how you have to do it.

Why not pick a very constant 250ish watt draw and then power it 100% with solar and battery? Ie separate a circuit from the grid.

Maybe the fridge is perfect. It runs from solar during the day, (while surplus solar charges batteries), battery at night, and then the fridge power never hits your bill.

In reply to Robbie :

that's the top consideration.  

I've looked in to this, even when I was wanting to do something like, 3-5 panels just to try and cut costs and even help out a lil bit.

Gotta go through the utility company that handles your electric and they'll have/tell you everything you'll need to do.

oldopelguy said:

The grassroots way is to take apart an uninteruptable power supply that has a decent size battery inside and wire your solar directly to charge the battery.  The inverter part doesn't care where the power is coming from, the battery doesn't care which charger is charging it, the battery charger part will just charge less if the solar is working. Plug in your stuff and call it done.

This. UPS power supplies are constantly being tossed out of hospitals and other healthcare facilities because replacing the lead acids inside voids warranties unless they send them back- and most don't want to deal with the hassle of sending batteries due to EPA regulations.

UPS systems have DC converters for your solar, and already are built to offer inverters. I'd seriously poke around for one, you may be able to easily adapt it to your needs.

GIRTHQUAKE said:

oldopelguy said:

The grassroots way is to take apart an uninteruptable power supply that has a decent size battery inside and wire your solar directly to charge the battery.  The inverter part doesn't care where the power is coming from, the battery doesn't care which charger is charging it, the battery charger part will just charge less if the solar is working. Plug in your stuff and call it done.

This. UPS power supplies are constantly being tossed out of hospitals and other healthcare facilities because replacing the lead acids inside voids warranties unless they send them back- and most don't want to deal with the hassle of sending batteries due to EPA regulations.

UPS systems have DC converters for your solar, and already are built to offer inverters. I'd seriously poke around for one, you may be able to easily adapt it to your needs.

Looking into UPS's, I'm beyond that point to get one.  I have a battery, I have an inverter, and I have a solar charge controller- just need to add the panels.  If I had more time to put it together, I may have done that, but I was not really planning on getting one until the earthquake- which meant I had a week to decide for the shipping cut off date.  And for a UPS system, the lead time was longer, since I would have had to send it to my home, and then ship it down.

Great idea, though. 

All I need is a way to run something off of the system.  For now, I'll see if I can re-package it to fit into a small space, and then just directly power the washing machine off of it- no grid connection.  The other idea is an automatic switch to go between the battery and the grid- where there is still NO feed into the grid at all.  I like this as I can just power the intended machine 100% of the time, which then reduces the work required in an emergency.  But I think I'll wait on that until the next trip in December, as I'll get 6 months of power for just the washing machine data.  

The more I look into those, the more I wished I knew about them before.

The larger UPS's have enough output to run a fridge- but just for 40 min.  It would not be a stretch to add more battery to an existing UPS, nor would it have been hard to add a solar charge controller.  That is already UL safe, so it's already a built in safe switch.  Just need to add the battery and the solar charging, and done.

Oh, well.  Live and learn.