grid tie inverter in blackout

[greenHouse]

Not sure I agree with all of that. Sulfation is a real concern. I agree if you are deeply discharging batteries below 70% capacity the sulfation and shedding of plate is accelerated. It happens with FLA Gel, and AGM. With FLA it is measurable. What I do agree with you if the batteries are going to be used for Float Service Emergency Power, AGM is the good route to go, but for different reasons than you suggested. I would never use a Gel battery for anything other than Fire Alarm Panels or Emergency Egress Lighting.

Starved electrolyte batteries are less prone to sulfation, but it really does happen. Because of concerns about excessive recombination, gassing and subsequent loss of life, it's my understanding that AGM batteries sulfate more in practice than they should in theory.

With that said if a battery is used in everyday Cycle Service (20 to 30% DOD daily) like an Off-Grid application, then there is no better bang for the buck than a good quality FLA battery. Even a mid grade FLA will outlive (cycle life) any high end AGM (like Concord) or Gel for that matter. AGM has its place but really is a Nich Application Product to justify the added cost per $/Kwh capacity.

Well ... this is the "Solar panel systems on the grid" forum, so I wasn't even considering the "off-grid" scenario. You're absolutely right -- for off-grid applications, or environments where power outages are frequent, such as developing nations or small Caribbean islands ...

How are you figuring that? If you use AGM's you can get efficiency up into the 80% range because AGM charge efficiency is in the 95% range, vs FLA in the low 80's. You would also have to use MPPT controllers and keep line losses to 2% or less from panels to input of inveter. Once you take all the losses from input end at the panels to the utilization device hanging out on the end of the inverter wiring more like 66 to 68% best case. If someone is ignorant enough to use PWM controllers 50% is best case. But I do agree efficiency is a real down and why Off-Grid should never be used unless there is no other options.

Ignoring the fact that I own a business that makes equipment capable of measuring end-to-end efficiency, with DCPV systems there are more conversion steps and often just plain more wire. They are also intermediate between ACPV / detached microinverter systems and high voltage string inverter for shade tolerance and panel mis-match.

You are wrong about FLA charge efficiency - they are very close to AGMs in "float" (on-grid ...) service, and where I see a lot of inefficiency is with the opposite of what I write up top about AGMs. Because FLAs are more tolerant of over-charging, they tend to be overcharged more. Gassing reduces charge cycle efficiency and FLA-based systems tend to be configured more towards "will gas" because the alternative is "will get sulfated". FWIW, since float service batteries are almost only ever given some kind of "daily topping off charge" the cycle efficiency doesn't apply. On account of they aren't being cycled ...

What I really have a problem with is the foolishness of Hybrid Systems. I refuse to give advice to anyone or take on such a job as it is unethical IMO. If you have commercial power, and demand emergency power, then the right answer is a conventional grid tied system with a Whole House Generator using either NG or LPG as the fuel source. Using a hybid battery system is just plain foolish IMO. It still requires a generator on top of very expensive batteries which are not used and a much more expensive inverter, higher installation cost, and very limited amount of power. Why on earth folks do that is beyond me especially if the live in Air Conditioning country. When there is an extended outage I could careless about lights and keeping my milk cold, I want my Air Conditioner and everything on in the house like nothing ever happened. Only way you can do that is with a Whole House Generator and I can have it for 1/2 the cost of those that go hybrid and have to suffer with limited power. That is just nucking futz. So when someone demands it, I refuse the work and send them to someone else who will take their money and waste it.

For suburban use, outside of hurricane or other severe weather areas, where power outages are very few and very far between, totally agree. I was sold on hybrid systems at a time when there was a lot of talk about energy shortages and the possibility of rolling blackouts. Developments in Demand Response have all but silenced talk about rolling blackouts. The massive deployment of wind resources (18% of current real-time generation right this moment) hasn't hurt either. Within that environment, and not living on the Gulf Coast -- hybrid systems are a waste of money. For an area like the Gulf Coast, there's no guarantee you'll have natural gas for that generator of yours. I think going with batteries is the only solution if you live in an area prone to hurricanes or whatever.

[Sunking]

I did not realize it was that extreme!
How much of that is directly due to the oxygen-hydrogen recombination and how much to other construction features including starved electrolyte?
( I have a copy of the Battery Bible, but have not waded through it yet.)

It has to do with the batteries internal resistance. AGM has very low impedance compared to a like size FLA battery. Thus when charging a FLA you are loosing efficiency from heat losses from current flowing through higher resistance. Since AGM is lower resistance you have less heat losses while charging.

[Sunking]

You are wrong about FLA charge efficiency - they are very close to AGMs in "float"

Me don't think so, neither do the scientist and engineers who design/build/test batteries. FLA batteries have higher internal resistance than AGM for a given size and application. It is the higher resistance where FLA losses efficiency. As for gassing it would be a huge mistake to set Absorb voltage set point to higher than the gassing voltage of the battery. Equalization is the only one set point that should used for FLA batteries. VRLA on the other hand are set to above gassing voltage as a practice.

For suburban use, outside of hurricane or other severe weather areas, where power outages are very few and very far between, totally agree. I was sold on hybrid systems at a time when there was a lot of talk about energy shortages and the possibility of rolling blackouts. Developments in Demand Response have all but silenced talk about rolling blackouts. The massive deployment of wind resources (18% of current real-time generation right this moment) hasn't hurt either. Within that environment, and not living on the Gulf Coast -- hybrid systems are a waste of money. For an area like the Gulf Coast, there's no guarantee you'll have natural gas for that generator of yours. I think going with batteries is the only solution if you live in an area prone to hurricanes or whatever.

Well if I was in a hurricane prone area I would do two things. Forget about solar because solar panels are not likely to survive the wind, and no battery can survive a flood. Second thing I would do is have LPG fueled genny so I do not have a utility supplied NG to be interrupted. Besides you still need a generator for both hybrid and off-grid systems.

[ButchDeal]

Well if I was in a hurricane prone area I would do two things. Forget about solar because solar panels are not likely to survive the wind, and no battery can survive a flood. Second thing I would do is have LPG fueled genny so I do not have a utility supplied NG to be interrupted. Besides you still need a generator for both hybrid and off-grid systems.

So the generator is going to survive a flood?
Why would a bimodal (hybrid) system need a generator?
You have the grid for regular use and the system should be sized optimally for the emergency load.

[SunEagle]

So the generator is going to survive a flood?
Why would a bimodal (hybrid) system need a generator?
You have the grid for regular use and the system should be sized optimally for the emergency load.

The problem is that if the grid goes down for a while and the sun don't come out you will need a generator to charge the batteries. Think of it as a necessary but hopefully little used tool in your system.

[Sunking]

So the generator is going to survive a flood?
Why would a bimodal (hybrid) system need a generator?
You have the grid for regular use and the system should be sized optimally for the emergency load.

Well a genny has a much better chance of surviving a hurricane mounted on a elevated pad than panels on your roof. Not to metion those so called bimodal systems are limited to very low power around noon time. My genny if still around will run my air conditioner, lights, and fridge all night long while I watch you with a gun in my hands.

[ButchDeal]

The problem is that if the grid goes down for a while and the sun don't come out you will need a generator to charge the batteries. Think of it as a necessary but hopefully little used tool in your system.

Today is mostly cloudy and already have 10kWh.
It was VERY overcast yesterday at my place (dark clouds) and still produced 7kWh solar.
Monday was mostly sunny and generated 20kWh.
If we ever get heavy thunderstorms in WV for a week straight, I think I can figure something out, of course there would be massive flooding of the Potomac river if that ever happened washing away Washington DC...

Snow on the other hand with our record snowfall and record cold temps (but NOT a single power outage, strangely) did cut my power production on a few days to near 0. Six days in a row from 1/22 to 1/27. Had I lost power during that time I would have cleaned off the panels.

http://pvoutput.org/list.jsp?p=0&id=31117&sid=28507&v=3&o=date&d=desc

[ButchDeal]

Well a genny has a much better chance of surviving a hurricane mounted on a elevated pad than panels on your roof. Not to mention those so called bimodal systems are limited to very low power around noon time. My genny if still around will run my air conditioner, lights, and fridge all night long while I watch you with a gun in my hands.

What do you mean very low power. The bimodal inverter I have is rated at 3kW output. I don't have near that on the emergency panel. My Fridge and freezer will have power though I don't plan to be standing in front of them all night with the door open either.

I understand that with a generator you can get inverter + generator power which I can always add to my system should I acquire a generator.

"If still around" and fuel still around and not contaminated.
be careful scavenging for fuel for that genny as there may be others watching with rifles, not smart to be out gunned or out ranged.

[Sunking]

What do you mean very low power. The bimodal inverter I have is rated at 4kW output.

So you claim 4 Kw when the grid is down?

Care to share that info with us Pros as we would like to know who makes such a product.

[ButchDeal]

So you claim 4 Kw when the grid is down?

Care to share that info with us Pros as we would like to know who makes such a product.

sorry typo 3kW. OutBack Flexpower One with GTFX3048 inverter.
though there is also a Flexpower two rated at 6kW.

[Sunking]

sorry typo 3kW. OutBack Flexpower One with GTFX3048 inverter.
though there is also a Flexpower two rated at 6kW.

That is battery power. Any hybrid system requires a genny.

[SunEagle]

Today is mostly cloudy and already have 10kWh.
It was VERY overcast yesterday at my place (dark clouds) and still produced 7kWh solar.
Monday was mostly sunny and generated 20kWh.
If we ever get heavy thunderstorms in WV for a week straight, I think I can figure something out, of course there would be massive flooding of the Potomac river if that ever happened washing away Washington DC...

Snow on the other hand with our record snowfall and record cold temps (but NOT a single power outage, strangely) did cut my power production on a few days to near 0. Six days in a row from 1/22 to 1/27. Had I lost power during that time I would have cleaned off the panels.

http://pvoutput.org/list.jsp?p=0&id=...&o=date&d=desc

It is not just about getting some power from panels but enough amps to charge the batteries. A generator will provide the right amount what ever the weather is. You may think you have enough power being generated but even if I had a system like yours I would still have a genny in my tool box.

[ButchDeal]

That is battery power. Any hybrid system requires a genny.

You claimed it would have significant power drop at noon, assuming full (or any) sun otherwise why specify noon, how is this batter power. In mine yes as I only chose to install 3kW so max power is derated from that but the fact is it can provide more power at noon than midnight given the integrated FM80 CC in the FlexPower One system. My system doesn't need 3kW and was sized as such.


This constant claim that a Bimodal requires a gen. Is counter productive and short sighted to the needs of the majority of home owners. I agree that having a Bimodal power your entire house the same without grid as with is absolutely crazy without generator. But if home owner is NOT looking for A/C or electric range, microwave etc use during outage and just wants a limited set like well pump and fridge and cell phone, it is a fit.

[ButchDeal]

It is not just about getting some power from panels but enough amps to charge the batteries. A generator will provide the right amount what ever the weather is. You may think you have enough power being generated but even if I had a system like yours I would still have a genny in my tool box.

The FM80 can easily get enough to the DC bus.

That would be your choice.
My concern is with the claim that "all bimodal systems need gennys". I don't think most suburban or even rural home owners do NEED a genny. I know many people that bought generators and they have a hard time using them: old fuel, bad plugs, never maintained, lack of fuel, too much load
Not claiming that a bimodal doesn't need maintenance but something like mine maintains AGM batteries and gives warnings when they are getting old etc. which is simpler than a genny with ethanol fuel that has been sitting for 6 to 12 ( or 24) months. It is just an added cost / complexity that is not needed and not wanted.
In the north east power outages happen often from ice on lines, storm tree falls etc. I live about 2 hours from DC in WV, Big storm get lots of support in bigger neighborhoods and closer into DC while I sit for 2 days in nice weather waiting for line techs to get around to fixing the lines that run 1.5 mile through fields to the small neighborhood. This happens maybe once a year then probably 20 to 30 times a year power goes out for 1 to 3 hours. I often don't even notice these any more.

[Sunking]

I know many people that bought generators and they have a hard time using them: old fuel, bad plugs, never maintained, lack of fuel, too much load

That is because you and your neighbors are stuck in a box. Pad mounted emergency generators do not use gasoline or Briggs and Straton Lawn mower engines that you buy at Wally World and throw into your trunk. They use LPG, Natural Gas or diesel which does not go bad and use 4 to 8 cylinder commercial grade engines like you would find in a tractor or heavy equipment made to outlive you.