Using Solar Power for home when power company grid is off

[DaveC_Napa]

Hello,I have a SolarEdge 7600 inverter installed 9 months ago, no battery backup.
Here is California there is a lot of talk recently about PG&E turning off the power grid during high fire danger times to reduce the risk of power lines causing fires.
I understand that if the power grid goes down, my solar system shuts off so as to not put power back into the grid.
I have a disconnect switch between my solar system and main power power panel on my house to isolate my solar system from the grid.
Has anyone figured out how to "trick" the SolarEdge inverter to produce power if the grid is off?
If the grid goes down, I would like disconnect from the grid and generate electricity during daytime hours and power important appliances in the house.
This seems like a better option than buying a home generator.
Would hooking up a small gas generator to the power lines trick the Solar Edge inverter into producing power? My concern if doing this is that it may burn up the gas generator if the SolarEdge tries to push surplus power back into generator.
Should I just invest in a batter backup system?

suggestions?

Dave in Napa.

[Mike90250]

The best/easiest thing is a small gasoline or propane generator. Simple, cheap, and 2 - 3 kw will keep the fridge running and a couple lights. but you may need 5 days of fuel. Maybe the easiest is to plan to fill your auto gas tank and siphon from it as needed. Storing and rotating 5ga jugs is difficult to do safely in the city.

[SunEagle]

Hello,I have a SolarEdge 7600 inverter installed 9 months ago, no battery backup.
Here is California there is a lot of talk recently about PG&E turning off the power grid during high fire danger times to reduce the risk of power lines causing fires.
I understand that if the power grid goes down, my solar system shuts off so as to not put power back into the grid.
I have a disconnect switch between my solar system and main power power panel on my house to isolate my solar system from the grid.
Has anyone figured out how to "trick" the SolarEdge inverter to produce power if the grid is off?
If the grid goes down, I would like disconnect from the grid and generate electricity during daytime hours and power important appliances in the house.
This seems like a better option than buying a home generator.
Would hooking up a small gas generator to the power lines trick the Solar Edge inverter into producing power? My concern if doing this is that it may burn up the gas generator if the SolarEdge tries to push surplus power back into generator.
Should I just invest in a batter backup system?

suggestions?

Dave in Napa.

Simple answer is No. A generator will not "trick" a grid tie inverter into working unless the inverter is a hybrid or has the option of generating a small amount with the proper isolation equipment, like the Sunny Boy Secure Power inverter.

If you want an emergency backup power source then what Mike states is the best bang for your buck.

[DaveC_Napa]

OK, thanks for the replies.
A small generator is likely to cost $1k+. It is frustrating to have to generate power with a generator when I have a solar inverter capable of generating power, and in the off mode.

A battery back up system is going to cost a lot more than a small generator, and will not produce as much power.

[PNW_Steve]

Depending on how frequent and how long your power outages are.

For Infrequent, short duration power outages I would recommend a Honda EU-3000is and possibly an extended run kit. The longest I have had to run my Honda was 11 days.

For frequent outages I would look at an 1800 rpm, water cooled diesel generator. I had an 8kw Kubota powered generator that I kick myself for ever letting it go.

[SunEagle]

OK, thanks for the replies.
A small generator is likely to cost $1k+. It is frustrating to have to generate power with a generator when I have a solar inverter capable of generating power, and in the off mode.

A battery back up system is going to cost a lot more than a small generator, and will not produce as much power.

I agree but there are hybrid inverters that will allow a solar pv system to continue to work by diverting it's power to batteries. But a grid tie inverter must disconnect to keep people safe from being electrocuted.

By the way I purchased a 12kw dual fuel generator for about $1100 and it will provide a good bit of power to my home needs should the grid go down.

[peakbagger]

Welcome to the third world where power is not reliable. Pick up a inverter type generator and a transfer switch. If you have a deep well, you may need to switch to variable speed well pump to cut down on surge loads so you do not need to oversize the generator for surge loads.

[Ampster]

...... It is frustrating to have to generate power with a generator when I have a solar inverter capable of generating power, and in the off mode.
.......

The issue is that your inverter was designed to only be capable of delivering power when connected to the grid. The reason grid tie inverters are less expensive than hybrid inverters is they do not contain the electronics that a hybrid inverter has. That electronics usually includes a transfer switch, and other electronics to monitor the house load and rapidly modulate the solar production to match the household loads. Batteries are needed to be able to dump the generation while the solar is being modulated. It is more complex than one initially thinks.

SolarEdge has an add on package that makes one of their grid tie inverters capable of generating power when the grid is down. It has all the above electronics but is not yet available in the US. It does require batteries. The market is growing for the capability you are seeking. Others like Tesla Energy, Sonnen Outback, SolArk and SolarEdge have products but none of them are cheap.

I also suspect the manufacturers of generators will develop that kind of power modulation and coordination of solar capability. Generac recently purchased Neurio which is a device that Tesla Energy uses to do that.. Stay tuned, the next few years will be interesting.

[J.P.M.]

The issue is that your inverter was designed to only be capable of generating power when connected to the grid.

The way I learned it, generators make power. Inverters deliver conditioned power at their output and while doing so, rather than generating power, lose some power from input to output.

[Ampster]

The way I learned it, generators make power. Inverters deliver conditioned power at their output and while doing so, rather than generating power, lose some power from input to output.

You are correct. I changed the term. There are probably a lot of terms that could describe what an inverter does. I am not sure how the discussion is better informed by distinguishing between the simple phrase "generating power' or the verbose, "deliver conditioned power at their output and while doing so, rather than generating power, lose some power from input to output". I do not disagree with what you said, and that is most likely how you learned it. I believe the important issue on a discussion forum is not what you have learned, it is what the Original Poster would like to learn.

Have you anything else to add to the topic that the Original Poster asked, which is, "Using Solar Power for home when power company grid is off".

[foo1bar]

OK, thanks for the replies.
A small generator is likely to cost $1k+. It is frustrating to have to generate power with a generator when I have a solar inverter capable of generating power, and in the off mode.

SolarEge does have their "StorEdge" battery system.
So they have a solution available, but you have to pay for it.
At this point (and probably at any point) I think it's a better financial choice for you to buy a small generator.
Or prepare yourself that you'll be OK with losing power for however long it's likely to be out. Keep the fridge closed, have frozen stuff in a chest freezer that is mostly full (with blocks of ice if not foodstuff), have ice on hand and a cooler, and a cooking method that doesn't require power.

[DaveC_Napa]

The issue is that your inverter was designed to only be capable of delivering power when connected to the grid. The reason grid tie inverters are less expensive than hybrid inverters is they do not contain the electronics that a hybrid inverter has. That electronics usually includes a transfer switch, and other electronics to monitor the house load and rapidly modulate the solar production to match the household loads. Batteries are needed to be able to dump the generation while the solar is being modulated. It is more complex than one initially thinks.

SolarEdge has an add on package that makes one of their grid tie inverters capable of generating power when the grid is down. It has all the above electronics but is not yet available in the US. It does require batteries. The market is growing for the capability you are seeking. Others like Tesla Energy, Sonnen Outback, SolArk and SolarEdge have products but none of them are cheap.

I also suspect the manufacturers of generators will develop that kind of power modulation and coordination of solar capability. Generac recently purchased Neurio which is a device that Tesla Energy uses to do that.. Stay tuned, the next few years will be interesting.

Thank you for the good reply. I understand the point you are making because I have an electrical engineering background.

[Salts]

The answer to your problem is AC Coupling into a battery bank. At the moment, there are some really good deals to be had with SMA Sunny Island inverters, or you can just get an Outback Radian inverter.

So the way this would work is that you would install a generator interlock on your circuit breaker panel. The battery inverter would feed into your circuit breaker panel via the 240 volt breaker on the interlock. When the power goes out, the interlock will force you to turn off the main breaker in order to turn on the breaker that is fed from the battery powered inverter system. Once you turn on that breaker, you activate the battery inverter and it starts making power using energy stored in the batteries. Once power is being made, the grid tied inverter thinks the grid is back up and it starts making power. The battery inverter sees the excess power coming from what it thinks is the grid and uses that power to run the house. If there is too much solar power, it uses the excess to keep the batteries charged, if there isn't enough solar power, it makes up the difference by drawing energy from the batteries and adding that to whatever the solar inverter is making.

That's the easy way to do it and it is what I have done. There is no chance of the grid inverter sending power to the grid because the interlock has isolated the entire house. It works, it is safe, and it is fully functional. Technically, the grid could go down permanently and you could just hum along like nothing was wrong.

Our home has an 8kw grid tied solar array. We use an average of 16 kW of power per day with most of that being used during the day. We use two SMA Sunny Island 6048 inverters tied to a 16.5kW Lithium Ion battery bank.

We don't have fire hazards here, nope.. none at all.. Our grid just sucks. We lose power every time a mean looking cloud floats by. In the past 4 months, we've lost power 7 times for an average of two days each time. Sometimes as long as 5 to 6 days, sometimes as short at 12 hours.

When the grid goes down, I go into the basement, flip a couple of breakers, push a couple buttons, and our own private mini grid comes to life. Within a few minutes, the solar system will also resume making power as if nothing was wrong.

If the fire hazard grid-down thingy becomes a frequent problem, the Sunny Island inverters can be hooked up in a way that causes them to activate on their own. In fact, they're supposed to be so fast at it that you won't even see your lights blink. Everything will continue running as normal and you'd need an alarm of some sort to tell you that the grid even went down. This type of setup requires a bit of a different kind of hookup but its nothing special.. just a bit more expensive as you have to add a critical loads sub-panel and automatic transfer switch.

[Salts]

The other option is to install the Tesla Power Wall. This device must be installed by Tesla certified techs and costs about $8000 or so. It will provide 14kw of power. It's limiting factor is that you can't expand the battery bank unless you buy another power wall and its only a 5kw inverter. I don't know what its surge capacity is.

[Ampster]

I can elaborate on some of the above. With the Outback solution you don't need a transfer switch since it is built into the Radian. However the transfer switch may be part of the AC coupling. The Outback Skybox which I have is similar but it does not yet have AC coupling but that is promised soon. The Tesla Powerall and others are all AC coupled. I think the Powerwall has surge capacity to about 10kWs. Sol Ark is another hybrid inverter that is similarly priced to the Skybox and currently supports AC coupling.

Earlier someone else mentioned the SolarEdge Storedge and that is DC coupled. Right now the only 400 volt battery that works with it is the LG Chem battery which comes in different sizes. If SolarEdge comes out with a conversion box for the US then the OP could convert his existing SolarEdge grid tie inverter to give it Storedge cababilities. I think someone also mentioned that SolarEdge is working on a battery so that you would have an option to the LG Chem.