differing types of invertes question

elesaver

There are grid-tied and off-grid inverters. Since the newer inverter technology allows use of a battery bank option with a grid-tied inverter, then isn't it a good idea to have a grid-tied inverter even though it is primarily being used for off grid only? Options are always good but perhaps not here?

Cariboocoot

Re: differing types of invertes question

elesaver wrote: »

There are grid-tied and off-grid inverters. Since the newer inverter technology allows use of a battery bank option with a grid-tied inverter, then isn't it a good idea to have a grid-tied inverter even though it is primarily being used for off grid only? Options are always good but perhaps not here?

There are three types:

1). Grid-tie inverter. No batteries involved and batteries can not be used. PV goes direct to AC system.

2). Off-grid inverter. Requires batteries and can not sell back to grid.

3). Hybrid inverter. Basically and off-grid inverter (requires batteries to function) that can sell back to grid or sync with a generator. Can provide the functions of a GTI but also give power back-up when the grid goes down.

There is no GTI that can have batteries added later as far as I know.

Why by an inverter that has capabilities you won't ever use?
If you buy a hybrid inverter you have the added expense of batteries and charge controller over a standard grid-tie system. if your outages are infrequent and short-lived you will have made a large capital investment in equipment you don't really need. The batteries will die over time whether used or not.

elesaver

Re: differing types of invertes question

"Why by an inverter that has capabilities you won't ever use?
If you buy a hybrid inverter you have the added expense of batteries and charge controller over a standard grid-tie system. if your outages are infrequent and short-lived you will have made a large capital investment in equipment you don't really need. The batteries will die over time whether used or not."

I fully understand this rationale. But, what about the opposite situation? The goal is to be off grid but would there be instances where this may not continue to be possible? I'm just trying to cover all the bases, so the speak.

Cariboocoot

Re: differing types of invertes question

elesaver wrote: »

I fully understand this rationale. But, what about the opposite situation? The goal is to be off grid but would there be instances where this may not continue to be possible? I'm just trying to cover all the bases, so the speak.

I don't know: would there? How likely is it that the grid would come to where the off-grid install is now?

At my cabin: zero chance. No one is going to run power lines across miles of public and private land to power half a dozen part-time homes.

However if you feel the grid might be installed one day there's more than one option. You could use the grid with an off-grid inverter-charger; the utility power acting as a sort of generator. You could switch over to a GT inverter when the time comes, as you'd be laying out a fair amount of money for the installation anyway. Or you could start out with a hybrid inverter and be "ready to go" as it were, providing the utility will allow back-feeding.

It all depends on present circumstances and the unpredictable changes in the future.

Mountain Don

Re: differing types of invertes question

elesaver wrote: »

I fully understand this rationale. But, what about the opposite situation? The goal is to be off grid but would there be instances where this may not continue to be possible?

I'm trying to imagine what would cause that, other than a conscious decision by the off grid system owner. Is there some other scenario you have in mind?

elesaver

Re: differing types of invertes question

I guess the "boiled down question" is whether or not a hybrid grid tie could be used in a fully off grid situation or are they designed for emergency only off grid use and the use of one for full time power would be harder on the inverter itself?

verdigo

Re: differing types of invertes question

I built my system primarily as a back-up with batteries. The thought of it just sitting there doing nothing while the grid is available was hard to swallow so I opted for a grid interactive inverter that decreases the electric bill as long as the batteries are topped up. As far as straight up grid tied goes for me there would have been a lot of aggravation to look at all of those solar panels doing nothing during an outage.

Although a generator is a much cheaper back-up option for short outages I feel pretty good about my investment. In today's world you never know what a day will bring.

elesaver

Re: differing types of invertes question

After some diligent searching, I have found that the hybrid type of inverters are not recommended for off-grid use. This doesn't mean they CAN'T be used, but they are not recommended. There ya' have it! Thanks all. You are the best!

inetdog

Re: differing types of invertes question

elesaver wrote: »

After some diligent searching, I have found that the hybrid type of inverters are not recommended for off-grid use. This doesn't mean they CAN'T be used, but they are not recommended. There ya' have it! Thanks all. You are the best!

Please do not overgeneralize. When you are off grid and have to rely on a generator for occasional charging and for large loads like doing the wash or cooking a big dinned with electricity, a hybrid system with what is called "generator support" mode (not just autostart!), as found in some Xantrex models, can make the difference between a good experience and a bad one.
If you do not have that scale of power need, then the added expense of a hybrid system is generally not justified for truly off-grid.
Often a grid tie system and a separate UPS system and generator, without any permanent link to your solar PV, may be the most economical when you want to have standby power in the mix.

Cariboocoot

Re: differing types of invertes question

elesaver wrote: »

After some diligent searching, I have found that the hybrid type of inverters are not recommended for off-grid use. This doesn't mean they CAN'T be used, but they are not recommended. There ya' have it! Thanks all. You are the best!

This is incorrect. Quite a number of off-grid systems use inverters like the XW or Radian or GTVFX without any issues.

You may be getting confused with utilizing back-up UPS systems as off-grid inverters which often does not work (depending on the UPS in question).

vtmaps

Re: differing types of invertes question

elesaver wrote: »

I guess the "boiled down question" is whether or not a hybrid grid tie could be used in a fully off grid situation or are they designed for emergency only off grid use and the use of one for full time power would be harder on the inverter itself?

As the others have mentioned, that is not correct. If you learn about AC and DC coupling, you will have a better understanding of these inverters.

Suppose you want to run a 2500 watt AC load and you have a 4000 watt off-grid inverter and a 2000 watt generator. Your battery bank cannot sustain the load without help from the generator. The sun is behind clouds. Here are three ways to manage the situation: (in the examples, there are no inefficiency losses)

DC coupling:
The generator runs through a stand-alone battery charger to push 2000 watts of DC onto the battery bus.
The off-grid inverter draws 2500 watts from the battery bus.
The sun, through the charge controller, is contributing only 100 watts to the battery bus.
The batteries contribute 400 watts to the battery bus.

Note: all loads and power sources are combined at the battery bus.

AC coupling with two inverters:
The generator output contributes 2000 watts to the AC bus.
The load pulls 2500 watts from the AC bus.
The sun, through a grid-tie inverter, contributes 100 watts to the AC bus.
The batteries, through a hybrid inverter, contribute 400 watts to the AC bus.

Note: all loads and power sources are combined at the AC bus. This can be very tricky... all sources must have their AC waveforms synchronized. One source must be the 'master' to which the others synchronize. There must be a way for the hybrid inverter to tell the grid-tie inverter to stop making power if the battery is charged and there is no load.

Combinations:
You can mix AC and DC coupling. In the above AC coupling example, the sun could make its contribution through a charge controller directly to the battery, but let the hybrid inverter and the generator be combined on the AC bus.

Generally, AC coupling is more efficient. DC coupling is more robust and you can mix and match power sources and loads that do not need to communicate or synchronize.

--vtMaps

mike95490

Re: differing types of invertes question

elesaver wrote: »

After some diligent searching, I have found that the hybrid type of inverters are not recommended for off-grid use. This doesn't mean they CAN'T be used, but they are not recommended. There ya' have it! Thanks all. You are the best!

I guess it depends on what hybrid inverter means to you. My XW6048 is a hybrid and this is the first I've heard this.