# Using Grid-tied solar emergency power



## wy_white_wolf (Oct 14, 2004)

May soon be able to some of your grid tied solar when the grid is down without batteries.

From another forum:


> Hello everyone. My name is Greg Smith and I am a technical trainer for SMA America and I wanted to touch base on the original question about a Sunny Boy with a "battery backup" capability.
> 
> The 3000/4000/5000TLUS inverters do indeed have an emergency power switch that will provide 12A to a load(s) when the grid is down and the sun is up, however there are no batteries in this system. It uses the solar energy during the day to provide power to the switch. As we know more about this revolutionary new feature we will pass along the information. ...


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## ET1 SS (Oct 22, 2005)

Wouldn't stand-alone be better?


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## Lisa in WA (Oct 11, 2004)

Our grid tie system first powers all of our house needs then pushes any extra power to the grid. At night or on cloudy days, it pulls from the grid to make up for any power shortfall from the solar panels. In the case where the grid is down, a frequent occurrence in North Idaho, our controller pulls less power from the solar panels.


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## TnAndy (Sep 15, 2005)

*The 3000/4000/5000TLUS inverters do indeed have an emergency power switch that will provide 12A to a load(s) when the grid is down and the sun is up, however there are no batteries in this system. *

Alrighty then ! 

So what happens to the refrigerator motor that's running when a cloud passes over, and the solar input drops below the motor requirement ? Or the freezer motor tries to kick in about the same time, requiring more amps than the shaded panels can supply ? Sounds like a setup for classic "brown out" to me.....

Lights that dim and then brighten are one thing......but under supply of amps to motors is a good way to be replacing burned out motors. I'd be real curious how Sunnyboy's "no batteries required" solves that problem.


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## TnAndy (Sep 15, 2005)

LisaInN.Idaho said:


> In the case where the grid is down, a frequent occurrence in North Idaho, *our controller pulls less power from the solar panels*.


And I'd be interested in the specs on your system, as that last statement doesn't make a lot of sense to me.

A "controller" ( charge controller ? Inverter ? what ? )doesn't "pull" from panels....it's FED whatever the panels produce, assuming there is an electrical load on the consuming end.


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## Jim-mi (May 15, 2002)

Should read "when the grid is down the controller sees No current"

It is an interesting issue, but the vast majority of peoples here on HT have never heard of SMA products . . . Because of the Big price tag.
They seem to think that a truck stop $79.95 inverter is more than adequate.

Totally agree with Andy about playing with fire ----rather the big possibility of damaging critical loads with passing clouds.

And that "12 amp" statement would only be true if you have at least a certain minimum number of modules ..........

AC coupling is the way to go.


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## ET1 SS (Oct 22, 2005)

A system needs to be capable of supplying all needs of your home. The refrigerator, freezer, washer, microwave, interior lighting, and well pump. You only control a few of these things. 

The alternative is that you would need to be aware of your loads and how many amps are being used each time before you start a load of laundry. Or put something in the microwave.

If your system can not handle the entire load of your house, then you are destroying something. Brown-outs are not good.

First a system must be 'rated' for the maximum possible load. Anything less and your looking at possibly burning up a motor somewhere [well, frig, freezer] or spiking your TV, stereo or PC. An under-rated system is harmful to your stuff.

No battery means no power when the grid is down. For me that means at least once a month, often 3 or 4 times each month.

First decide the rating of your system; second decide how many days you may possibly go without sun. So you can determine the size of battery bank you will need. 

Average usable sun-light in the USA is 4 to 6 hours/day year-round [depending on your location]. If you get a storm during those hours then you made no power that day. Two days of mid-day storm means you went two days without making power. Your battery bank needs to be big enough to carry you through stormy days.

Also if you just barely have enough battery, then when you do go those 2 or 3 days, your battery bank will be empty of power. This is called 'cycling' your battery. Cheap batteries can only survive 50 cycles until they die. More expensive batteries may survive 100 cycles. The most expensive batteries may survive 200 cycles before they die.

First decide the rating of your system.
Second determine the size of battery bank.
Then look at panels.


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## Lisa in WA (Oct 11, 2004)

TnAndy said:


> And I'd be interested in the specs on your system, as that last statement doesn't make a lot of sense to me.
> 
> A "controller" ( charge controller ? Inverter ? what ? )doesn't "pull" from panels....it's FED whatever the panels produce, assuming there is an electrical load on the consuming end.


My husband must have posted this last night on my username. He doesn't post often and he usually does it in a hurry.
I haven't a clue about the system other than it worked perfectly the entire time we were off grid and it works perfectly now that we're grid tied.

I assume he knows what he's doing since he's an electrical engineer from MIT and his power system has worked quite well for the past ten years.


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## wy_white_wolf (Oct 14, 2004)

ET1 SS said:


> Wouldn't stand-alone be better?


Depends on your situation and what you want and how much you want to spend.

If you're not prepping for a SHTF situation and live in an area of few blackouts and/or high grid-tie incentives this could be the ideal inverter.

WWW


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## wy_white_wolf (Oct 14, 2004)

TnAndy said:


> *The 3000/4000/5000TLUS inverters do indeed have an emergency power switch that will provide 12A to a load(s) when the grid is down and the sun is up, however there are no batteries in this system. *
> 
> Alrighty then !
> 
> ...


If you're trying to run a frig and a freezer both on a 12A circuit you really deserve what's going to happen. 

As far as running a single motor, if you're worried about browning out from a cloud the problem would easily be solved by installing a computor style UPS on the frig.

This is designed to try and solve the problem of people wanting to have a little power from there grid-tie system when the grid is down. Since they are not yet on the market all the info is not fully availbekl yet. They are on the Japanise market but need redesigned for the US market.

WWW


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## TnAndy (Sep 15, 2005)

Wolf,

People will try to run whatever they can. 

Most of them don't have a clue what a "little bit of power" is....they will use right up to the 12a limit, and, again, my question is: what happens when a cloud passes over, and that little bit of power goes to near zero ? 

If you have a 'wall wart' charging a laptop, and an another charging a cell phone, what happens when the voltage drops too low ? Will the chargers or batteries being charged be damage ? ( I don't know on those, merely asking )

A UPS is a battery backup. If you're gonna have a battery backup, have a real battery backup.....which was my original point.....doesn't seem like you could run a system off line without one. The whole purpose of the grid, or a battery bank, to buffer loads when you have a variable source of power input ( the PV panels ).

And by the way, what forum was that originally posted at ?

Thanks


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## wy_white_wolf (Oct 14, 2004)

Solar Panel Talk

Here's the thread but you may need to be a memeber to see it

SMA Inverters with Emergency backup?


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