No Grid Power = No Solar Power

[thew]

But you would never want it to "throttle back".. if you are producing more than your Battery back up needs it sends the extra to the Grid and makes your meter spin backwards.. Thus you will get credit for your Production when you are not using it all..

I think the context of here is what happens when the grid goes down, and now you are producing a surplus (possibly several kw worth). Assuming your batteries are topped off, you need to shed that extra power somehow. There's a reason off-grid systems often have dump loads, and a smart inverter will be able to throttle or disable your PV system so you don't need to dump it.

My plan is to wait a few years, add some graphene panels and graphene SCs, and go completely off the grid. UCLA is making great progress with their graphene SCs.

"A few years" is easily going to be a few decades, if ever. Get what you can now, if you're ready now, and upgrade later!
=Smidge=

No if your in Off Grid mode you wont likely be making a surplus.. And the system just does not feed the Batteries what it does not need. Yes its very Smart.

The systems are much smarter that you guys seem to be understanding. The Logic in the Inverter and Feed systems Knows when the grid is down.. IT does not Feed the Grid unless it first sees a Sign Wave from the Local Transformer in your Circuit. Then and only then will it try to "Back Feed" the grid.. If it does not sense the Grid sign wave from the transformer.. its just keeps charging the Batteries.. (When the Grid is Live this Inverter runs the other way and Sends the "extra" back to the power Co. )

The Batteries are always feeding there assigned circuits via a Big ass inverter.. All day. every day. The Power Flows from the Battery pack to the Inverters , to the 50 amp service.
The Grid Tie Feeds the AC inverter that will keep the Battery Pack Topped off. Then the Battery pack Feeds the DC inverter system that Feeds the AC 50 AMP service with the Homes important circuits, LEAF etc.. Its a Great system WE have been running since 2008 .

I will soon have a Video up showing the system .. Ill share it here when its done.

P.S this is why you use the Good equipment like Out Back.. They have been at it for a very long time and make great stuff. Also FYI the system has Lightning Shunts installed to on both sides of the Arrays .

 

[thew]

With our two Utilities the PV system is required to automatically shut down if the grid goes down.

I think you may only be reqiured to Disconnect from the Grid.. You can simply shut off the Main to your house and comply with their needs. But you still get to make your own power. Assuming you have some storage.

 

[Smidge204]

And yes the system is set up as suggested above.

So you have a dump load? Whatever power your system generates that you can't store or use goes to heating the great outdoors?

=Smidge=

 

[thew]

And yes the system is set up as suggested above.

So you have a dump load? Whatever power your system generates that you can't store or use goes to heating the great outdoors?

=Smidge=

No Read Above again.. its a Smart system.. We dump nada.. I charge Batteries All day..

 

[QueenBee]

And yes the system is set up as suggested above.

So you have a dump load? Whatever power your system generates that you can't store or use goes to heating the great outdoors?

=Smidge=

You don't need a dump load, or if you had one a dump load that did something useful would be good. Fancy inverters are able to just scale down the amount of power they are inverterting making the solar panels less efficent.


thew, what model are the components in your system?

 

[thew]

They are old by today's standards. Circa 2008...

Ill check .

The new ones are all internet compliant to so you can controll system from a PC anywhere..

And yes the system is set up as suggested above.

So you have a dump load? Whatever power your system generates that you can't store or use goes to heating the great outdoors?

=Smidge=

You don't need a dump load, or if you had one a dump load that did something useful would be good. Fancy inverters are able to just scale down the amount of power they are inverterting making the solar panels less efficent.


thew, what model are the components in your system?

 

[Smidge204]

No Read Above again.. its a Smart system.. We dump nada.. I charge Batteries All day..

That doesn't really sound sustainable... either your PV capacity is relatively small compared to your actual loads, and after multiple days without grid power you will run out of battery power, or your battery capacity is way oversized and after a few days without grid power you'll end up overcharging them. It's quite inconceivable that you manage to balance your average load and average generation day after day after day so you never hit either end.

You don't need a dump load, or if you had one a dump load that did something useful would be good. Fancy inverters are able to just scale down the amount of power they are inverterting making the solar panels less efficent.

That's pretty much what I said, yeah.
=Smidge=

 

[thew]

No Read Above again.. its a Smart system.. We dump nada.. I charge Batteries All day..

That doesn't really sound sustainable... either your PV capacity is relatively small compared to your actual loads, and after multiple days without grid power you will run out of battery power, or your battery capacity is way oversized and after a few days without grid power you'll end up overcharging them. It's quite inconceivable that you manage to balance your average load and average generation day after day after day so you never hit either end.

You don't need a dump load, or if you had one a dump load that did something useful would be good. Fancy inverters are able to just scale down the amount of power they are inverterting making the solar panels less efficent.

That's pretty much what I said, yeah.
=Smidge=

So your assuming the Sun has Burnt out in your summation ?
And that some how the Computer Logic has failed in the Inverters..?

Also Considering our system has been up since 2008 doing just that. There is not to much to balance here.. You cant pull more out of the Box than is put in. In this case we have a 50amp service powered by our Back up Battery pack.. WE don't need to balance anything.. The system charges the Batteries with SUN... or Grid. Or Both.

 

[Smidge204]

So your assuming the Sun has Burnt out in your summation ?
Also Considering our system has been up since 2008 doing just that. There is not to much to balance here.. You cant pull more out of the Box than is put in. In this case we have a 50amp service powered by our Back up Battery pack.. WE don't need to balance anything.. The system charges the Batteries with SUN... or Grid. Or Both.

Right. My question is when you DON'T have the grid, which is the theme of this thread.

If you have the grid up and connected, any surplus or deficit is absorbed by that. Easy-peasy.

What happens if you lose grid power for, say, two or three weeks straight?
=Smidge=

 

[RegGuheert]

What happens if you lose grid power for, say, two or three weeks straight?

The charge controller simply moves to a different point on the curve of the PV panels, thereby producing less, or no, electricity. So the PV panels become less efficient and they heat up a bit more than normal.

 

[Smidge204]

What happens if you lose grid power for, say, two or three weeks straight?

The charge controller simply moves to a different point on the curve of the PV panels, thereby producing less, or no, electricity. So the PV panels become less efficient and they heat up a bit more than normal.

Yes, that's one way to do it. The other, perhaps more old-fashioned way is to turn on a dump load (eg resistive heater) that just consumes the excess power.

But thew says he doesn't have a dump load, and that his panels are never throttled/turned off, so I'm curious about the specifics.
=Smidge=

 

[thew]

So your assuming the Sun has Burnt out in your summation ?
Also Considering our system has been up since 2008 doing just that. There is not to much to balance here.. You cant pull more out of the Box than is put in. In this case we have a 50amp service powered by our Back up Battery pack.. WE don't need to balance anything.. The system charges the Batteries with SUN... or Grid. Or Both.

Right. My question is when you DON'T have the grid, which is the theme of this thread.

If you have the grid up and connected, any surplus or deficit is absorbed by that. Easy-peasy.

What happens if you lose grid power for, say, two or three weeks straight?
=Smidge=

ok..
During the Night when the sun is asleep we pull all our power off our Batteries, during the Day the sun comes back up and charges the batteries.. Yes we could run the washer and dryer all day and night long and pull more power out of the Pack then it has.. It would then shut off.. Leaving us until the Day time for the Sun to come back up and start charging the Batteries and Powering the Inverters for the home. In the Case of Armageddon. with no grid at all, we would simply adjust our usage for the big things in the house like the LEAF, and the Washer Dryer to run during PEAK Solar Activity time. Then at night try not to use anything except the essentials.. TV, Fridge, Internet. Office Computers Etc..

So far we have run the system for about 6 days in this mode. But you must first tell the Wife to Not Wash all the Laundry at night!!!..

 

[davewill]

... In the Case of Armageddon. with no grid at all, we would simply adjust our usage for the big things in the house like the LEAF, and the Washer Dryer to run during PEAK Solar Activity time. Then at night try not to use anything except the essentials.. TV, Fridge, Internet. Office Computers Etc..

So far we have run the system for about 6 days in this mode. But you must first tell the Wife to Not Wash all the Laundry at night!!!..

And if the batteries get full because you are so good at conserving? That's what Smidge204 is getting at. Your system has to have a way to stop charging the batts when they are full, the grid is down and the sun's still shining. You have to do one of the following:

1. Shut down the panels entirely until the battery level drops enough to start charging again. (It puts extra cycles on the battery, but doable if the system doesn't run in the off-grid mode very much).
2. Throttle the inverter output to match what you're currently drawing.
3. Dump the excess generation into a dump load.

You just keep answering that it never comes up, but the system has to be able to do one of those things when the battery gets full and there's no grid to dump to.

 

[thew]

... In the Case of Armageddon. with no grid at all, we would simply adjust our usage for the big things in the house like the LEAF, and the Washer Dryer to run during PEAK Solar Activity time. Then at night try not to use anything except the essentials.. TV, Fridge, Internet. Office Computers Etc..

So far we have run the system for about 6 days in this mode. But you must first tell the Wife to Not Wash all the Laundry at night!!!..

And if the batteries get full because you are so good at conserving? That's what Smidge204 is getting at. Your system has to have a way to stop charging the batts when they are full, the grid is down and the sun's still shining. You have to do one of the following:

1. Shut down the panels entirely until the battery level drops enough to start charging again. (It puts extra cycles on the battery, but doable if the system doesn't run in the off-grid mode very much).
2. Throttle the inverter output to match what you're currently drawing.
3. Dump the excess generation into a dump load.

You just keep answering that it never comes up, but the system has to be able to do one of those things when the battery gets full and there's no grid to dump to.

Its already answered the Inverters are Smart. They don't Produce what is not Needed. That was the answer from the start!.

 

[davewill]

Its already answered the Inverters are Smart. They don't Produce what is not Needed. That was the answer from the start!.

RegGuheert was saying that but you seemed to be contradicting him. Anyway, I figured it was a misunderstanding, so I decided to rephrase for Smidge. Glad it worked.

 

[thew]

Also, you must keep in mind that the Array itself is constantly being tuned to max output, Or Sleep mode.. In the Case of a Full bank of batteries, when off Grid.. (Not Likely) The Array itself will put itself to sleep. If the inverter wants more juice it will draw that from the Array and the Array will wake back up and tune itself to max output across the entire array.

Its all of the Logic that is the answer to your questions. The system is designed to generate what is needed at any given moment to Fill the Batteries, or Back feed the grid.. It really never would have an opportunity to sit with a Full battery during an Off Grid moment for very long where it would be at full.. Something is always drawing off the Batteries.. Regardless the System knows how much it wants and then allows it to happen. It does not just make extra voltage and dump in in the ground.. It simply does not make what it cannot use..

If The grid is down and the Batteries are full and all the systems in the house are off.. No Fridge no computers nada.. Then the system would put the Array to sleep in the middle of the bright sunshine and produce nothing..

 

[thew]

What happens if you lose grid power for, say, two or three weeks straight?

The charge controller simply moves to a different point on the curve of the PV panels, thereby producing less, or no, electricity. So the PV panels become less efficient and they heat up a bit more than normal.

Yup, that pretty much sums it up..

 

[AndyH]

I don't care how many solar panels are on the grid - I want to know how many people will be able to keep their food from rotting in the refrigerator next time a superstorm rolls through. And that's the point of the thread, I think...

If that is what you want to know then you need to include all the people who have fossil fuel generators as backup. Much cheaper to buy a ICE generator and convert it to natural gas. Still has maintenance costs though.

No I don't, because I'm not talking about generators. One does not automatically require the other.

 

[thew]

I don't care how many solar panels are on the grid - I want to know how many people will be able to keep their food from rotting in the refrigerator next time a superstorm rolls through. And that's the point of the thread, I think...

If that is what you want to know then you need to include all the people who have fossil fuel generators as backup. Much cheaper to buy a ICE generator and convert it to natural gas. Still has maintenance costs though.

No I don't, because I'm not talking about generators. One does not automatically require the other.

I thought the Point was No Grid no Power..

 

[AndyH]

Seriously, grid-tied folks!

An off-grid system and a grid-tied with backup are very similar, but adding storage requires a battery and a charge controller.

Off-grid:

PV -> Charge Controller -+-> Battery
                         |---> Inverter --> AC Load

Grid Tied

PV -> MPPT/Inverter <-+-> Grid
                      | --> AC Load

Grid Tied with Backup

PV -+-> Charge Controller -+-> Battery
    |---> MPPT/------------+-Inverter <-+-> AC Load
                                        +<--> Grid

(Ok, that's not entirely accurate from the grid to the battery charger. The key 'black box' points are that electricity from the PV can charge the battery and flow to the grid. Overnight, the battery can charge from the grid. When the grid drops, the inverter disconnects from the grid but can still still power designated circuits from the battery.)

The interface between the panels and the battery is a charge controller. That's the component that either (old tech) pulse-width modulates the electrons from the PV into the battery or (new tech) uses maximum power point tracking. Either way, the charge controller is a smart three-stage charger (for a flooded lead acid battery) that'll properly charge the battery without overcharging. When the battery is full and there is no load, the panels are disconnected from the battery.

In off-grid mode (or when the grid's down) during the day, energy flows from the panels to the charge controller to the inverter to the loads in the house. Either the battery or the inverter will accept energy. Electrons may not 'always' flow into the battery and back out during the day. The inverter doesn't have to match supply and demand because of the battery buffer. If the PV system is supplying 2KW, the battery is full, and there are 2KW of loads (ignoring losses, etc.) then electrons flow PV -> charge controller -> inverter -> load. Add more load, and the battery and PV are supplying the inverter in parallel. When loads decrease, excess energy from the PV recharges the battery. When the loads are gone and the battery is full, the system shuts down.

The grid-tied operation is just like your systems - PV in, inverter, grid synchronization, anti-islanding, etc. are all there.

Dump loads are generally not used in PV only systems, unless one regularly has a full battery. One can divert PV to, say, a water heating element, when the battery is full. It's not efficient but it allow the system to keep harvesting. A wind system (and I believe microhydro) will always have a dump load - often first the water heater and then a bunch of really big resisters.

http://www.homepower.com/articles/ask-experts-solar-energy-wasted
http://www.homepower.com/articles/sizing-grid-tied-pv-system-battery-backup
http://www.homepower.com/articles/ask-experts-adding-backup

Finally, this is not the kind of project that most grid-tied PV installers have experience with. You will need to find an installer who is expert in battery-based systems.