Possible to Island a Grid Tied Solar Array ?

[SG-1]

Installer says I get two receptacles with a total of 4000W where ever I like & they work during an outage.

Will discuss this with them later:
I can probably pull the DC directly off the array for any inverter powered or DC devices. Maybe place a dedicated inverter & manual transfer switch at the well controls.

 

[paulengr]

Considering adding a solar array & would like to be able to island during service outages. Is this an option ?

Yes but it’s extra cost because the inverter has to have sync/paralleling capability and you need a transfer switch with closed transition since you must remain offline (open circuit) in an outage then transition back via closed transition on sync.

 

[ggunn]

Installer says I get two receptacles with a total of 4000W where ever I like & they work during an outage.

Will discuss this with them later:
I can probably pull the DC directly off the array for any inverter powered or DC devices. Maybe place a dedicated inverter & manual transfer switch at the well controls.

Sounds like two SMA Sunny Boy inverters with their, oh, I forget what they call them, their emergency power outlets. The caveat there is that you can get that full 4kW only if your array is well lit, and if you try to pull more than it can give it shuts down.

 

[analog8484]

None of this is manufacturer approved, so kiss your battery warranty goodbye.

This is a common misconception. There is no automatic voiding of warranty legally allowed for third-party add-on/replacement component in the US per Magnuson-Moss Warranty Act. Manufacturers must prove damage directly resulted from third-party add-on/replacement component for warranty claim denial. If there is no such protection the custom car audio industry would have been out of business long ago.

 

[winnie]

Given that batteries are known to have a limited cycle life, it would probably be pretty easy for a car manufacturer to claim that using your car battery to run your house would accelerate the aging of the battery.

 

[analog8484]

Given that batteries are known to have a limited cycle life, it would probably be pretty easy for a car manufacturer to claim that using your car battery to run your house would accelerate the aging of the battery.

Manufacturers can claim lots of things and put "Void If Removed" stickers everywhere but that does not make them legal. Manufacturers must prove damage resulted directly from third-party add-on/replacement components. Otherwise, manufacturers can easily deny warranty claims for any car with a aftermarket stereo receiver or amplifier.

 

[jaggedben]

....

A lot of what we see being installed now is battery backup to a specific circuit(s) refrigerator, living room, bedroom. That’s about it. And the run time is hours. So a major event will stop it unless the solar during the day manages to power the circuits AND charge the batteries.

Basically what I’m seeing installed is a huge UPS..

A well designed system can certainly recharge thhe batteries from solar for many days if the weather and the season are accounted for. In fact, since solar systems are typically designed to offset annual consumption, in the summer they typically produce way more energy each day than the customer uses, plenty to recharge batteries to 100%. We had a client whose service drop got taken out by a falling tree in a fall windstorm. Because the riser was trivally damaged (really just the weatherhead had to be popped back into place), the utility insisted they get a permit and meter release from the city before they would reconnect them, which obviously took some extra time. Fortunately for the client this happened the week after we commissioned their solar+energy storage. They had to watch their usage a bit, but they had uninterrupted power for 5 days while we harangued the city and utility to get the grid connection back. They could have gone longer if necessary.

 

[electrofelon]

Any recommendations on where to source solar components?

For panels, check out sun electronics, sunelec.com. Shipping can be non insignificant so check Craigslist and ebay too.


I have an account at AEE solar and some of their stuff is priced much cheaper than anything you can find in the web. But then some things a basic web search brings up cheaper stuff. Typical I suppose.

 

[SG-1]

Sounds like two SMA Sunny Boy inverters with their, oh, I forget what they call them, their emergency power outlets. The caveat there is that you can get that full 4kW only if your array is well lit, and if you try to pull more than it can give it shuts down.

Thanks, I get that. 4KW would be a little over 25% of the total system KW.

 

[Hv&Lv]

For some reason the 7kW systems seem to be popular around my area.

A well designed system can certainly recharge thhe batteries from solar for many days if the weather and the season are accounted for. In fact, since solar systems are typically designed to offset annual consumption, in the summer they typically produce way more energy each day than the customer uses, plenty to recharge batteries to 100%. We had a client whose service drop got taken out by a falling tree in a fall windstorm. Because the riser was trivally damaged (really just the weatherhead had to be popped back into place), the utility insisted they get a permit and meter release from the city before they would reconnect them, which obviously took some extra time. Fortunately for the client this happened the week after we commissioned their solar+energy storage. They had to watch their usage a bit, but they had uninterrupted power for 5 days while we harangued the city and utility to get the grid connection back. They could have gone longer if necessary.

 

[SG-1]

Yes but it’s extra cost because the inverter has to have sync/paralleling capability and you need a transfer switch with closed transition since you must remain offline (open circuit) in an outage then transition back via closed transition on sync.

Can you explain the need for a closed transition transfer switch. The array must do this every morning, yes ?
What would be wrong with open transition ? Either automatic or manual.

 

[jaggedben]

Yes but it’s extra cost because the inverter has to have sync/paralleling capability and you need a transfer switch with closed transition since you must remain offline (open circuit) in an outage then transition back via closed transition on sync.

There's no real reason you need closed transition type switching. The point, generally, is to make use of available solar energy when the grid is out, particularly if it will be out a long time. Momentary loss of power when the grid comes and goes doesn't defeat that goal. UPS type functionality is a different goal, and can be supplied to a device that needs it with ... a UPS.

 

[macmikeman]

For most people who are using PV on their boat, it makes up a very small part of their energy production. Most of it comes from a gas or diesel-powered generator. If someone is doing hairshirt sailing, only powering lights and really small loads, they can get away with PV. There is just very little room for PV modules on a boat, if you get 2 or 3 you are lucky. That is not powering an electric drive, watermaker, refrigerator/freezer, and other large loads.

Wrong. I can verify around a dozen in just a single sweep of search engine. No fossil fuels onboard , but running water makers , fridges, electrical engines, more.

 

[pv_n00b]

Wrong. I can verify around a dozen in just a single sweep of search engine. No fossil fuels onboard , but running water makers , fridges, electrical engines, more.

How long have you owned your boat? I've had mine for over 20 years and interact with cruisers in real life. No one is powering large loads off of just 2 or 3 300W modules on their bimini. Go Google all you like, get some real-life experience too.

 

[Bjenks]

It can be done, Tesla Powerwall does it, but even then over a period of time the load will disconnect in order to get the batteries back up to a set voltage level. Basically you have to have a way to disconnect from the utility. Then you need another set of inverters or generator that can create a sync voltage to tell the main inverters to keep running. Then you have to manage your load to make sure you don't overload the inverters. Then you need a bleed load such as a water heater, lake or heat resistor to absorb the power you don't use. As you can see it isn't easy and can cost a fortune.

 

[ggunn]

....Then you need a bleed load such as a water heater, lake or heat resistor to absorb the power you don't use. As you can see it isn't easy and can cost a fortune.

Not necessarily. An AC coupled battery inverter can typically munge the frequency on the AC bus to make a PV inverter throttle back or drop off line, depending on how the PV inverter responds to frequency drift, when the battery is full and the usage is less than the PV system production. It's one of the advantages AC coupling has over DC coupling.

 

[winnie]

I presume that a DC coupled inverter _with storage and storage management_ would be smart enough to reduce the PV production when the battery is full and usage is less than production. One can always run the PV panels inefficiently, and I'd consider it a design defect if an hybrid inverter/charge controller is not capable of doing so. You end up paying quite a premium to have energy storage and control, and smart reduction in PV production should be part of what you pay for.

Of course this all goes back to the initial design of the system and the value of 'island' capability. If you have a system that is designed to produce maximum output and only export to the grid, then trying to trick the system into working off grid without a battery is like trying to take the best chicken soup in the world and use it to make coffee.

Mentioned in this thread are the 'sunny boy' secure power outlet feature. This is a cheap way to provide limited 'island' power by the simple expedient of providing far less than the rated power of the complete system. If you try to use more power than the PV system can produce then you are SOL.

-Jon

 

[GoldDigger]

...

Mentioned in this thread are the 'sunny boy' secure power outlet feature. This is a cheap way to provide limited 'island' power by the simple expedient of providing far less than the rated power of the complete system. If you try to use more power than the PV system can produce then you are SOL.

-Jon

...than the PV system can produce instantaneously.
You may also have your loads drop out when a cloud passes by.

 

[winnie]

...than the PV system can produce instantaneously.
You may also have your loads drop out when a cloud passes by.

Exactly.

Poor man's island operation, but probably useful to keep the fridge cold and the phone charged.

Jon

 

[electrofelon]

...than the PV system can produce instantaneously.
You may also have your loads drop out when a cloud passes by.

Exactly.

Poor man's island operation, but probably useful to keep the fridge cold and the phone charged.

Jon

I wonder about using the SMA secure outlet to feed a UPS and then you load? My system has SMAs but I haven't tried the island outlet feature.