NJ Solar - Why can't panels act like generator during the day if power outage happens

[bradykp]

I know it's because they don't want people feeding the grid - but I can have an electrician install something for a generator on the panel to switchover so the power doesn't go out to the grid. Does anyone know why this can't be done with solar? So if i want a defacto generator i basically have to get a battery storage system of some sort - which doesn't seem worth it at all?

[SunEagle]

I know it's because they don't want people feeding the grid - but I can have an electrician install something for a generator on the panel to switchover so the power doesn't go out to the grid. Does anyone know why this can't be done with solar? So if i want a defacto generator i basically have to get a battery storage system of some sort - which doesn't seem worth it at all?

The grid tie inverter that takes the electricity your pv panels are generating and puts it out to the grid is disabled by internal logic if the grid goes down. This is a required safety feature for all grid tie inverters to keep anyone working a the "downed" grid from getting electrocuted.

There are some inverters like the SMA which has a feature that allows you to switch over to a separate circuit and provide 120volt power to a dedicated outlet with up to 1500watts of power directly from the pv panels as long as the sun is providing enough sunlight. This option requires someone to manually turn it on and then back off when the Utility grid comes back up.

Other ways to provide power to a home without going onto the grid is what you have mentioned which requires a quality and approved transfer switch that keeps power from a generator going back onto the grid and hurting someone. Most people that install a solar grid tie system don't install a transfer switch because the grid tie inverter provides this safety feature.

[bradykp]

The grid tie inverter that takes the electricity your pv panels are generating and puts it out to the grid is disabled by internal logic if the grid goes down. This is a required safety feature for all grid tie inverters to keep anyone working a the "downed" grid from getting electrocuted.

There are some inverters like the SMA which has a feature that allows you to switch over to a separate circuit and provide 120volt power to a dedicated outlet with up to 1500watts of power directly from the pv panels as long as the sun is providing enough sunlight. This option requires someone to manually turn it on and then back off when the Utility grid comes back up.

Other ways to provide power to a home without going onto the grid is what you have mentioned which requires a quality and approved transfer switch that keeps power from a generator going back onto the grid and hurting someone. Most people that install a solar grid tie system don't install a transfer switch because the grid tie inverter provides this safety feature.

So basically, I am getting the SMA inverter so I sort of have what I want - but it's limited too 1500w?

[HX_Guy]

Yes, 1500W and 12A.

[bradykp]

i guess that's enough to power a few basic things. a fridge though?

[SunEagle]

i guess that's enough to power a few basic things. a fridge though?

Depends on the amount and type of light you are getting at the time and how much of a power surge that fridge takes to start the compressor.

Usually when the grid goes down for me it is during a storm. Not much sunshine at that time or for hours after so the SMA option would be useless to me.

If I was worried about keeping my fridge running and food cold I would have a generator ready to go.

[bradykp]

good points. we've got aging infrastructure in my neighborhood so we have transformers blow periodically knocking power out locally. especially on hot summer days when everyone has the a/c cranked!

[paul65k]

Let me try and resurrect this thread and ask a related question;

I have a 4.2Kw Grid tied system with enphase micro inverters. Installed in my set-up at home is a Generator transfer switch (Manual) so that I can power my home with a 10K portable generator that I have for emergencies. I like in a VERY hot climate and our outages come year round as a result of being rather isolated and an aging sbustation in our area which is part of the SCE infrastructure and supports only 250 households plus or minus so there is not much of a chance that it will be upgraded anytime soon,

When the power goes out and it's 115 degrees outside I really need the generator to keep the food from spoiling as well as keeping my central AC (16 SEER 3 ton) running.

BTW......the solar is tied into a master "Sub-Panel" which is fed by a separate pedestal mounted single 100A circuit which runs through the generator disconnect and on to the panel with all the breakers for the house and AC unit.

I have tested and the sine wave from my current generator will not trigger the inverters when run-off grid, which is a bad idea anyhow I know and I wouldn't do this but just wondering if there are any solutions or if there might be a potential market here for some sort of limited "Limp along" mode for grid tied system in the event of a power outage at some point in the future?? The issue I see is that even if you can isolate the grid for safety reasons if you back feed to the generator you could have disastrous consequences........wondering what those of you that know more about this stuff might think??

PS....the last couple of times I have had to use the generator due to a power outage I have turned off the solar feed breakers to make sure that they didn't inavertently try to energize prior to flipping the transfer switch and energizing the genny.

Thoughts??

[paul65k]

Ttt

[Mike90250]

If your generator is stable enough (most non-inverter generators are not) to allow the micro-inverters to sync up, it's possible, AS LONG as there is no way for the loads to drop off and allow the micro-inverters to push power into your generator. That will make it really unhappy, and likely damage it as the micro-inverters won't trip offline till 270V or so. So you might be able to power up a few to share the load, but surely not all the load.

This assumes the transfer switch is in the right location to allow this to all safely work without powering the grid feed lines.

[paul65k]

If your generator is stable enough (most non-inverter generators are not) to allow the micro-inverters to sync up, it's possible, AS LONG as there is no way for the loads to drop off and allow the micro-inverters to push power into your generator. That will make it really unhappy, and likely damage it as the micro-inverters won't trip offline till 270V or so. So you might be able to power up a few to share the load, but surely not all the load.

This assumes the transfer switch is in the right location to allow this to all safely work without powering the grid feed lines.

Thanks...that's related to my question but not actually what I was asking I think.

1. I was asking is.....would there be a market to develop a product that could SAFELY energize the system via a non-grid source that would allow it to operate in some limited fashion as long as it is totally isolated from the grid until such time as the power is restored (stable again).....even if the technology isn't available today.

2. I completely understand the danger of using the system with the possibility of back feeding the generator(s) so no go at this time....again looking for a solution and/or is this an opportunity (is there a large enough market if the technology becomes available).

3. My transfer switch IS installed properly and does completely isolate the grid from the possibility of back feeding (thanks for asking)

[inetdog]

Thanks...that's related to my question but not actually what I was asking I think.

1. I was asking is.....would there be a market to develop a product that could SAFELY energize the system via a non-grid source that would allow it to operate in some limited fashion as long as it is totally isolated from the grid until such time as the power is restored (stable again).....even if the technology isn't available today.

2. I completely understand the danger of using the system with the possibility of back feeding the generator(s) so no go at this time....again looking for a solution and/or is this an opportunity (is there a large enough market if the technology becomes available).

3. My transfer switch IS installed properly and does completely isolate the grid from the possibility of back feeding (thanks for asking)

There are such systems, and they are called hybrid systems, and you will find lots of discussions of them in existing forum threads. They have batteries and also can synchronize to the grid when it is present.
Trying to build such a system without using batteries is possible, but very limited in usefulness since the power you are using would be daytime only and would go away every time a cloud passed by.

Hybrid systems (from manufacturers like SMA and Schneider) cost significantly more than either a pure GTI system or a pure off-grid system.

A few of them are also designed work with and support a generator, while they are running off either stored energy or current PV production.

[paul65k]

There are such systems, and they are called hybrid systems, and you will find lots of discussions of them in existing forum threads. They have batteries and also can synchronize to the grid when it is present.
Trying to build such a system without using batteries is possible, but very limited in usefulness since the power you are using would be daytime only and would go away every time a cloud passed by.

Hybrid systems (from manufacturers like SMA and Schneider) cost significantly more than either a pure GTI system or a pure off-grid system.

A few of them are also designed work with and support a generator, while they are running off either stored energy or current PV production.

Thanks.........so maybe there is a market for a small battery system to only act as a buffer during daylight hours and when a generator is running without the high cost of installing a battery bank (read very expensive) that can maintain during non-daylight hours.......strictly a mechanism to PV power to augment generator power during daylight hours...........certainly not an elegant solution but why not have a mechanism to harness the power at least during daylight hours if there is an interruption to the grid supplied power???

[paul65k]

At a minimum it could be a great marketing gimmick for some company to differentiate (or try to differentiate) themselves in a crowded and noisy world of PV.........just trying to think outside the box a little.

[Wy_White_Wolf]

i guess that's enough to power a few basic things. a fridge though?

SMA doesn't recommend motors to be run on this. If the solar wattage produced drops below what is needed by the motor (brown out) it could easily be damaged. Then you not only have no power but no frig when it does come back on.

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