Fooling a grid-tie inverter to provide power without grid.

[Tecnodave]

Grid tie inverters do not produce less......they run at full all the time, the grid is a huge power dump, it can suck up megawatts, along as there is enough transformer and wire capability to transport it to where it is needed

 

[Tecnodave]

That is what is built into approved hybrids such as the MagnaSine PAE series, you do not need any outside software or equipment to do this

 

[solar8484]

That is what is built into approved hybrids such as the MagnaSine PAE series, you do not need any outside software or equipment to do this

PAE uses frequency shift to turn off GTI which is not usable for everyone. Many devices and appliances do not work properly with frequency shifted power.

 

[newbostonconst]

PAE uses frequency shift to turn off GTI which is not usable for everyone. Many devices and appliances do not work properly with frequency shifted power.

Can you give an example of such devices? I have been doing frequency shifting for a couple years and never had a problem.

 

[Tecnodave]

Solar8484,

not true.....when the voltage rises due to the grid tie excess power the off grid inverter will reduce its output to shutdown when the mini grid is at a voltage high enough , this alone should cause the GT units to shut down

I haven’t said it because I do not want unskilled to try this, I’m using a MagnaSine MS4024AE.......NOT PAE which is an off grid inverter and I do use Morningstar GT inverters, it does work but the AE not being a grid tie capable unit cannot bump its frequency up to shrug off the microinverters. So I do a workaround when I’m using my welder which pushes the MagnaSine real hard, When my welder pauses I switch on a big dump load which will eat all the power from the GTI,s....it’s really skitsy as I use 4 Morningstar units for an extra 2000 watts which with the 4000 from the MagnaSine off grid unit easily powers my Miller welder

 

[Tecnodave]

If I didn’t do the load dump the output of the MagnaSine will shut down causing the MStar units to drop out, now I have to wait 5 minutes for GT restart

 

[solar8484]

Can you give an example of such devices? I have been doing frequency shifting for a couple years and never had a problem.

Peopled have found problem with various UPS, smart controls (e.g. Insteon), clocks, etc.

 

[solar8484]

Solar8484,

not true.....when the voltage rises due to the grid tie excess power the off grid inverter will reduce its output to shutdown when the mini grid is at a voltage high enough , this alone should cause the GT units to shut down

I haven’t said it because I do not want unskilled to try this, I’m using a MagnaSine MS4024AE.......NOT PAE which is an off grid inverter and I do use Morningstar GT inverters, it does work but the AE not being a grid tie capable unit cannot bump its frequency up to shrug off the microinverters. So I do a workaround when I’m using my welder which pushes the MagnaSine real hard, When my welder pauses I switch on a big dump load which will eat all the power from the GTI,s....it’s really skitsy as I use 4 Morningstar units for an extra 2000 watts which with the 4000 from the MagnaSine off grid unit easily powers my Miller welder

Of course the inverter can shutdown to turn off GTI but that cuts off all the loads. I was referring to only turning off GTI while still providing inverter power to loads.

 

[robby]

This post has touched on a topic I had not even thought of before. I am in the process of putting in Panels and a Sol-Ark 12K inverter and 10KW of Batteries. I don't plan on selling power back to the grid because they pay almost nothing for it. So what exactly happens at lets say 2PM and the batteries are fully charged and the house is not consuming as much power as the panels can produce? I just assumed the Inverter throttled back the load seen by the panels. Am I missing something?

 

[Tecnodave]

Power switch! or breaker for the GT, I use the GT inverters very rarely as my MagnaSine can handle all my loads with few exceptions and that is very rare.

 

[Tecnodave]

Robby,

correct, if you are not in grid tie mode once your batteries are full the off grid inverter(charge controller) powers down to a “float mode” which powers all the devices that are on and just “Tickles” the battery. This is for non-lithium batteries. Lithium batteries do not like to be charged when full and many BMS,s will terminate charging once the battery is fully charged but this does not account for system load, in my opinion this is a weakness of Lithium. Often late in the day my FLA banks will be “topped off” but my charge controllers will still be putting out considerable power to run my system and my diversion controller which uses excess power to heat my water so even when my batteries are full I am still using a kilowatt or so running things and heating water, I’d rather not have to run from my batteries when I have enough solar to heat my water >1200 watts

EDITED for clarity....I’m assuming you are using an all in one, I do not, I have inverters and charge controllers, they are not combined as in an all in one inverter/charger/charge controller

 

[sunshine]

Grid-tied inverters are "current sources".

Thanks,,, good reply.
There are so many older redundant inverters being given away at the moment this would be a question asked by many.

Edit....after a few minutes thought.... There is really no need to consider this option of using 10yr old ex-grid tie inverters when the latest, regional approved, 12/240v 1500w inverters are $200

 

[robby]

Robby,

correct, if you are not in grid tie mode once your batteries are full the off grid inverter(charge controller) powers down to a “float mode” which powers all the devices that are on and just “Tickles” the battery. This is for non-lithium batteries. Lithium batteries do not like to be charged when full and many BMS,s will terminate charging once the battery is fully charged but this does not account for system load, in my opinion this is a weakness of Lithium. Often late in the day my FLA banks will be “topped off” but my charge controllers will still be putting out considerable power to run my system and my diversion controller which uses excess power to heat my water so even when my batteries are full I am still using a kilowatt or so running things and heating water, I’d rather not have to run from my batteries when I have enough solar to heat my water >1200 watts

EDITED for clarity....I’m assuming you are using an all in one, I do not, I have inverters and charge controllers, they are not combined as in an all in one inverter/charger/charge controller

Dave
I will be using a Sol-Ark 12K which is a Hyrbid Inverter and it will be Grid Tied.
There is an option in the settings Menu for how much power you want to send back to the Grid, they state that you can set it to Zero and nothing will be sent back.

My batteries will be discharging daily from probably 6pm until 10pm if things go as planned. This will get me past the peak charge usage hours and then at about 20% capacity they will cut off and I will be using the Grid from roughly 10pm until 10am the next day. The unit is all in one and has a breaker for hooking up a dump load.
I was thinking of using it for my hot water heater but I am not sure of the logistics of this as it is a single element heater that draws nearly 4KW when running. I may change the element to a lower power but it all depends on how well the system works and if I really do have a bunch of excess power.

For now I was planning on leaving it on the non critical panel as we only turn it on at about 10 pm before everyone is going to shower and then switch it off at 12am just before going to bed. The remaining hot water is good enough to carry us through the morning routine before we head to work. Since I am now living in the Caribbean having hot water for a shower is not a big deal. On some hot summer days I do not even bother switching it on as the straight tap water is not very cold.


Rob

 

[Tecnodave]

Rob,

you are going past my experience, I’m off grid and old school American engineer, I did a career in electrical here in the USA , I know American made equipment, I do not like off shore electronics especially so I don’t have any, well not much, I use MidNite Classic charge controllers as they are the most programmable and capable out there ( Washington State), my Exeltech inverter, has the best MTBF rating of any inverter, (Texas) all my stuff is industrial quality, MagnaSine MS4024AE, Low frequency Inverter, huge motor running capability that none of the Chinese high frequency inverters are capable of, RollsSurette FLA batteries, I’ve had Chinese, had it go up in smoke, no support, etc. I really don’t use the offshore stuff for these reasons.....no support....limited functionality....poor design.....consumer product

But.....with knowing not much about your equipment, you should do diversion at midday when grid power is cheapest, run on solar all day, Turn off diversion before grid hi rate surcharge kicks in. then switch to stand alone when those rates go through the roof, go back to grid power when the rates fall. Basically do power hungry when power is cheap. It is very hard to run from batteries if cheap grid is available. And invest in a bit more battery, not to sell, its for that unseen storm, or grid outage, they will get worst, Texas and California are examples of what is to come. Out here on the left coast our power provider shuts down the grid during windstorms to keep from burning the state down in a wind storm.
If I understand what you are saying turn on water heater at 10p.m. , is this after the high rates fall? Are you on grid at this point....if you are thinking of running the water heater on the inverter, not a good idea...it would be less expensive to do it during high solar production time.

david

Edit....after rereading there are some words in there that I did not say.....blame Apple they have this neat feature called appleautobutchermyspelling, it’s really incredible, it can’t remember engineering terminology but can remember appleautobutchermyspelling.

 

[Tecnodave]

My system is quite different, I divert power at dawn to a water heater element, when water is warm (not hot) morning shower , I shut off diversion and charge batteries from early till about 2-3 pm by then all charged up then I start diverting the excess power to 24 volt heating elements for the hot water, by 5 pm water is hot, batteries are full, I’m still powering from sun at this point. I have a wake up bank looking at the morning sun, a midday bank looking at solar noon and top off bank looking at setting sun, almost everything I have is dc but I gotta have my Carver Stereo, the Exeltech inverter happily runs the Carver with NO EMI/RFI, the bigger inverter is powered up only when I need big power.....but then again why do they call me tecno......it’s all automatically controlled with many system data inputs, if it’s storming, I skip that morning water heat up, the batteries are more important...etc

 

[newbostonconst]

A hybrid inverter is the only safe answer, they are UL listed to work safely.... Other options talked about are not safe... Signing off from this thread, to much confusion and guessing...

 

[svetz]

To expand on what @newbostonconst said, if you have a grid-tied system and you'd like to be able to get power out of it when the grid is offline you want a system that can safely manage it. Yes, youtube has other ways, but from the prior description as to what's happening, hopefully it's evident that they're more interested in hits than safety.

The only proven solutions I know of are DC or AC coupling (e.g., Outback, Powerwall, Schneider) or if you have Enphase, their Ensemble solution. If you're just starting from scratch, then the new hybrid inverters (e.g., Sol-Ark, Skybox) or Ensemble are the best starting places.

All these systems have specific rules for how many panels they can safely manage during a grid outage (e.g., Best practice for PV to energy storage system (ESS) ratio in Ensemble system design).

 

[solar8484]

This post has touched on a topic I had not even thought of before. I am in the process of putting in Panels and a Sol-Ark 12K inverter and 10KW of Batteries. I don't plan on selling power back to the grid because they pay almost nothing for it. So what exactly happens at lets say 2PM and the batteries are fully charged and the house is not consuming as much power as the panels can produce? I just assumed the Inverter throttled back the load seen by the panels. Am I missing something?

Sol-Ark appears to use switch for GTI control which I explained previously so it's different from typical hybrid inverters that use frequency shift to turn off GTI. Assuming you properly configure the AC coupling settings in Sol-Ark then you don't need to worry about excess GTI power when batteries are full. Basically, Sol-Ark monitors the battery bank SOC and when it's near full it will turn off GTI via the built-in switch to GTI and continue to power loads from the battery bank. When SOC is low enough then the GTI switch will turn on again. I personally like the switch method of GTI control so I don't have to worry about potential problems with frequency shifted power with the devices/appliances I have now or purchase in the future. In general, few electronic devices/appliances are designed and tested to work properly with power frequency outside of the normal grid frequency range.

 

[robby]

Normally I like to play around with DIY stuff but in the case of Solar it becomes a bit too risky due to possible fires and electrocution from the PV array. When your playing with 400VDC with 10amps behind it there are no good scenarios involving with getting shocked.

I some how get the feeling that a lot of older PV equipment limitations are being applied to newer inverters.
If an inverter has a modern MPPT it should be able to get max power out of the panels when needed but also move the tracking point to use much lower voltages when the load on the inverter is low. When I was researching the SMA Sunny Boy I did not see any mention of things blowing up if you did not feed excess power back into the Grid or a Dump load! This thread contains a lot of very confusing information.

 

[solar8484]

Normally I like to play around with DIY stuff but in the case of Solar it becomes a bit too risky due to possible fires and electrocution from the PV array. When your playing with 400VDC with 10amps behind it there are no good scenarios involving with getting shocked.

I some how get the feeling that a lot of older PV equipment limitations are being applied to newer inverters.
If an inverter has a modern MPPT it should be able to get max power out of the panels when needed but also move the tracking point to use much lower voltages when the load on the inverter is low. When I was researching the SMA Sunny Boy I did not see any mention of things blowing up if you did not feed excess power back into the Grid or a Dump load! This thread contains a lot of very confusing information.

Yeah, it can be confusing. If using DC coupling (the inverter is doing direct DC/AC conversion from solar panels) then it can directly control how much is produced based on configuration settings regardless of MPPT or not.