What's all this On-Grid, Off-Grid, Hybrid stuff all about. Solar systems demystified.

[Crossy]

So, I've been asked on a number of occasions to clarify the various types of solar inverters and what they can do.

 

Here's my Idiot's Guide.

 

Off Grid

So the classical solar installation would be a simple Off-Grid system. The panels charge the batteries and the batteries run the house. The grid is not involved anywhere although some users might install a generator type transfer switch so they can switch to grid or a generator if the batteries are dead.

 

This system has the issue that the maximum load can never be greater then the inverter maximum output.

 

 

On Grid or Grid-tie

By far the most common system here in Thailand, it also happens to be the cheapest as there are no batteries involved. The inverter supplies power to the network whilst the sun shines, it is synchronised to the grid and so offsets the consumption from the grid.

 

A plus of doing this is if you need more power than the solar is supplying it simply draws that extra energy from the grid in a totally seamless manner.

 

On the negative side is that, because there are no batteries, if the mains goes off so does your local power even if the sun is beaming down.

 

If you generate more power than your local loads are using then the excess is exported to the grid. The old disc-type meters happily run backwards during export saving up the energy for you to use later. This "net-metering" is technically illegal and if the meter reader sees the meter going backwards you will likely get a "no reverse" meter installed. 

 

If you already have an electronic meter these don't go backwards, indeed they might actually bill you for any power you export!

 

In order to mitigate any export issues many on-grid inverters have a zero-export function so the inverter exactly matches what the load is using. Of course any extra power available from your panels is simply wasted.

 

 

 

Off-Grid Hybrid

In order to offset the disadvantages of an off-grid system the off-grid hybrid adds a mains powered battery charger into the mix. This allows the mains to top up the batteries or "help" the solar if the sun is feeling tired.

 

Most have a "bypass" which allows the load to operate directly off the grid if necessary.

 

These hybrids usually have several modes available depending upon how you want it to behave. The usual setting would be "Solar First" whereby the load draws power from the solar most of the time, if there's not enough solar then the extra comes from the batteries and if there's still not enough (batteries discharged) then the remainder comes from the mains.

 

Of course, so long as you have solar and/or juice in the batteries you never actually end up in the dark even if the grid is off.

 

Like the simple off-grid system this unit still has the issue that the maximum load can never be greater then the inverter maximum output.

 

 

On-Grid Hybrid

The on-grid hybrid is really the ultimate system combining all the advantages of off-grid (never in the dark) with the advantages of on-grid (no limit on power available if the grid is on).

 

Again there are many modes to choose from the usual one would be "Self Usage". The inverter attempts to keep your grid current at zero where it can. If there's excess solar it charges the batteries, if there's not enough solar energy is pulled from the batteries to keep your grid consumption at zero.

 

Most also have an "Essential Power" output which gives UPS like functionality when the mains is off to keep your important stuff (lights, TV, PC etc.) running when the grid is down.

 

Like the on-grid systems these inverters can export to the grid if the batteries are full and you are making more than you are using. The same caveats regarding net-metering apply of course.

 

 

 

 

 

[Crossy]

We have an on-grid hybrid, a Sofar HYD 5000 ES https://www.sofarsolar.com/product-detail/481/HYD 5000-ES

 

I've tried to illustrate it going about its business with the diagram below, the base plots are real world data from our system. 

 

A. Night time, zero solar, the batteries are discharging and meeting some of the night load (battery discharge is limited to 500W, I'm being nice to them).

 

B. The sun is waking up, so solar output increases, batteries are still discharging at 500W. We are still importing power from the grid although this is decreasing.

 

C. Solar matches the domestic load, grid energy is zero, the balance of the solar output is charging the batteries.

 

D. The batteries are fully charged (it was a sunny morning) so excess solar is now exporting to the grid (Grid Power goes negative).

 

E. An NBBC (Nasty Big Black Cloud) arrives and begins to dump its contents.

 

F. Solar output plunges as the storm continues, batteries are discharging at the 500W limit but that combined with the remaining solar isn't sufficient so power is imported from the grid.

 

G. Night again, zero solar, the batteries are discharging and meeting some of the night load.

 

 

[ExpatOilWorker]

Excellent and very informative write up.

I am still trying to get my head around #3 off-grid hybrid. At first glance it doesn't make sense at all. It is a hybrid system and it IS connected to the grid, so why the off-grid name?

This was the source of much confusion for me, but it is just a bad name of an otherwise good system.

A much better name would be "grid supported hybrid", but I guess we better stick with off grid hybrid for now.

[JBChiangRai]

@Crossy, on your Sofar inverter am I right in saying that in a PEA power cut you only get power on the Essential Power (UPS) Circuit?

 

Can you slave multiple inverters together?

[UKJASE]

good work crossy.  an interesting subject that i feel i should learn more about..........

 

we live in hua hin (often sunny), have a 4 bedroom villa with no trees around (so plenty of sun falls onto the roof) and have an average electric bill of 2000 / month (we dont use AC much).  We are connected to the grid through a 3 phase system, that feeds our small moo baan.

 

which system would be best for us and how much would it cost?

 

how many years of usage do you think it would take before we recouped our initial investment?

 

do systems go wrong much, and therefore need a lot of fixing?

 

we have had some cheap solar lights in the garden for a year or two and i have been impressed with their reliability and power 

 

great topic mate - and thanks in advance if you can offer any guidance

[Crossy]

  On 8/20/2021 at 2:05 AM, JBChiangRai said:

@Crossy, on your Sofar inverter am I right in saying that in a PEA power cut you only get power on the Essential Power (UPS) Circuit?

 

Can you slave multiple inverters together?

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Yes, you are correct, if the mains is off then you only get power from the UPS output, and it's limited to 3kW.

 

On the grid side there's no problem having as many inverters as you like in parallel, but going over 10kW may invoke the wrath of PEA. On the UPS side I did ask Sofar support about parallel operation but never got a satisfactory response, I will remind them, their man (Forest) is pretty good.

 

The Huawei units that @Thaifish has may be able to support full power on the UPS side as it seems they have a separate switching unit, have a look at his thread.

[mistral53]

  On 8/20/2021 at 2:20 AM, UKJASE said:

good work crossy.  an interesting subject that i feel i should learn more about..........

 

we live in hua hin (often sunny), have a 4 bedroom villa with no trees around (so plenty of sun falls onto the roof) and have an average electric bill of 2000 / month (we dont use AC much).  We are connected to the grid through a 3 phase system, that feeds our small moo baan.

 

which system would be best for us and how much would it cost?

 

how many years of usage do you think it would take before we recouped our initial investment?

 

do systems go wrong much, and therefore need a lot of fixing?

 

we have had some cheap solar lights in the garden for a year or two and i have been impressed with their reliability and power 

 

great topic mate - and thanks in advance if you can offer any guidance

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Don't bother - with the little power you use, the payoff is quite long. If you however want to help reducing green house gases, every little thing helps!

 

One thing most installers fail to tell their customers is that after installing solar, the consumption will go up. Another important part is the actual vs. theoretical yield is worlds apart - during the hot period of the year, the output is easily 30 to 50 percent lower due to clouds and rainy days. And comes the dry season with lower temps, the yield jumps - the reverse of what we need since we run AC's a lot

 

BTW - you are lucky to live in H-H, we have 3 installers here, good competition gives great prices.

 

 

[Peterphuket]

  On 8/20/2021 at 2:41 AM, mistral53 said:

Don't bother - with the little power you use, the payoff is quite long. If you however want to help reducing green house gases, every little thing helps!

 

One thing most installers fail to tell their customers is that after installing solar, the consumption will go up. Another important part is the actual vs. theoretical yield is worlds apart - during the hot period of the year, the output is easily 30 to 50 percent lower due to clouds and rainy days. And comes the dry season with lower temps, the yield jumps - the reverse of what we need since we run AC's a lot

 

BTW - you are lucky to live in H-H, we have 3 installers here, good competition gives great prices.

 

 

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Very nice explanation Crossy, I self have a hybrid system but my experience about HH is not as you described.

From the 3 installers I contact was there one who never answer, the second let me come to his shop while nobody stay there, and the third gives me a quotation but when I let him know I like to buy the batteries by myself, I never get an answer anymore.

That's why I decided to do it myself, with satisfactorily with one exception, the wi-fi plugs are impossible to get configured.

And as mentioned before about aftersales service....don't ask MUST.

[driver52]

  On 8/20/2021 at 2:20 AM, UKJASE said:

have an average electric bill of 2000 / month

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I think that's quite a lot, suppose it depends on the size of your family lol

how many kWh do you use each month? is it say an electric shower that uses most of the power? try solar hot water in that case?

why do you have 3 phase? I removed a 3 phase system in France, I think they're crazy in this day and age....

Up the Boro!! ????

[Crossy]

  On 8/20/2021 at 4:06 AM, driver52 said:

why do you have 3 phase? I removed a 3 phase system in France, I think they're crazy in this day and age....

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Oddly enough I wish we'd installed 3-phase. We don't need it for our load, we are quite happy on a single-phase 15/45 meter, but because the most common kind of grid failure (at least for us) is loss of one phase (and it's always the one we are on). With a 3-phase supply there are often still 2 good phases to use and if you have an automatic phase selector then you probably wouldn't even notice.

 

Our place in Delhi had 3-phase, next to the TV were 3 outlets, one on each phase. Select the "best" phase for the TV to work properly.

[Peterphuket]

  On 8/20/2021 at 4:13 AM, Crossy said:

 

Oddly enough I wish we'd installed 3-phase. We don't need it for our load, we are quite happy on a single-phase 15/45 meter, but because the most common kind of grid failure (at least for us) is loss of one phase (and it's always the one we are on). With a 3-phase supply there are often still 2 good phases to use and if you have an automatic phase selector then you probably wouldn't even notice.

 

Our place in Delhi had 3-phase, next to the TV were 3 outlets, one on each phase. Select the "best" phase for the TV to work properly.

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Yes, I'm in the same situation, induction cooking 6kW, Electric Boiler 70 ltr, Micro wave/oven combination 2 kWh. etc etc, but 1 phase.

I remember when i come here where I live now, I ask for 3 phase but the electricity company was not willing to help me.

[driver52]

  On 8/20/2021 at 4:13 AM, Crossy said:

With a 3-phase supply there are often still 2 good phases to use and if you have an automatic phase selector then you probably wouldn't even notice.

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yeah interesting but like here for example, you'd be paying 3 times the monthly standing order for starters!

I'd rather put that money into batteries, etc

It's also interesting to hear what is important to folks if your supply goes down. TV is a brainwashing medium for me most of the time ???? PC is pretty boring without internet, I'd rather do some exercise like going out on my bike and can always make a cuppa with a gas cooker lol

[driver52]

  On 8/20/2021 at 4:17 AM, Peterphuket said:

induction cooking 6kW

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that's a good example, bonkers to me! my whole supply is 6kVa and I can run a kettle, a microwave and a halogen set top cooker simultaneously without the system tripping! Disclaimer: not in Thailand lol

[Crossy]

  On 8/20/2021 at 4:21 AM, driver52 said:

PC is pretty boring without internet, I'd rather do some exercise like going out on my bike and can always make a cuppa with a gas cooker lol

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Our internet remains up unless there's a huge blackout (it's never gone off due to power failure) and we have a mobile data connection as a backup too.

 

Invariably when the power goes off it's bucketing down, so going for a bike ride would be a somewhat moist experience.

[driver52]

  On 8/20/2021 at 4:25 AM, Crossy said:

Invariably when the power goes off it's bucketing down, so going for a bike ride would be a somewhat moist experience

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Brucie bonus, you get exercise and a wash at the same time! ????

[Crossy]

  On 8/20/2021 at 4:28 AM, driver52 said:

Brucie bonus, you get exercise and a wash at the same time! ????

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Looking at the state of the car after rain I'd end up even dirtier.

[tinot]

This is great. Were looking to get off grid ourselves and I had no idea where to start.

I seen a place selling PVCs at our local market but they seemed to be for water pumps when I was trying to ask about powering the home etc in my broken Thai.

Anyone aware of a one stop shop online for purchasing said supplies and more importantly getting  advice about whats right? We have every known device to man eating up power and AC is pretty much on most of the time so bills are big. Complete noob!

TIA

[Crossy]

  On 6/18/2022 at 3:18 AM, tinot said:

This is great. Were looking to get off grid ourselves and I had no idea where to start.

I seen a place selling PVCs at our local market but they seemed to be for water pumps when I was trying to ask about powering the home etc in my broken Thai.

Anyone aware of a one stop shop online for purchasing said supplies and more importantly getting  advice about whats right? We have every known device to man eating up power and AC is pretty much on most of the time so bills are big. Complete noob!

TIA

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Why not start a separate thread?

 

Tell us what you want to do, offset your power bill or go totally off grid (maybe with grid backup).

 

Do a rough power budget, what you want to power, also your rough energy consumption, you can get the latter off your power bill.

 

It's not really rocket science if you are a competent DIYer or you could go with a contractor (add $$$).

[KhunLA]

I'm expecting to be 'off grid' - cost wise, but for < ฿50 a month to stay conx w/PEA, it really doesn't make sense to be 'technically' off grid.  Simply conx doesn't mean you have to use.

 

With hybrid system, you get to control import, export, battery use/charging.  If your inverter or other part of your system has an oops, nice to have something to hold you over till sorted.

 

That diesel genny that has been idle for over a year, might not be cooperative when needed.  Then again, if you have way more money to play with than myself, and your solar generator is fully charge, well done.   Or your EV has V2L capabilities, just break out those extension cords.

[tinot]

  On 6/18/2022 at 3:34 AM, Crossy said:

 

Why not start a separate thread?

 

Tell us what you want to do, offset your power bill or go totally off grid (maybe with grid backup).

 

Do a rough power budget, what you want to power, also your rough energy consumption, you can get the latter off your power bill.

 

It's not really rocket science if you are a competent DIYer or you could go with a contractor (add $$$).

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Will have to do that.

 

Who's good (contractor wise - National)?

[Pink7]

  On 6/18/2022 at 3:34 AM, Crossy said:

totally off grid (maybe with grid backup)

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You have any good alternatives than the typical hybrid inverters as off grid backup?

 

Pink

[Elik]

There is fifth way to have solar, where you install small off grid system in the same house that you have a grid, and then have a switch where you can choose to draw from solar or from grid.

 

I see an automatic switch on Lazard’s (ATS Automatic Dual Power Transfer Switch 2P ) that will automatically switch when the batteries turn off.

 

Amorn solar has a battery kit for 19000 THB, get a second panel your out 25 k, and earning 2 kWh pr day, so you looking at a pay back time of about 2500 days. Not too bad, and you have a little emergency power in case of power out.

 

I do have a couple of questions I hope the forum can answer

 

Does the switch legally count as a off-grid system??

I have a small UPS so I won’t get interrupted during the switch, but can a UPS handle if the sinus waves from the grid don’t match with the ups sinus.??

 

 

[Crossy]

  On 10/20/2022 at 9:20 AM, Elik said:

 

I do have a couple of questions I hope the forum can answer

 

Does the switch legally count as a off-grid system??

I have a small UPS so I won’t get interrupted during the switch, but can a UPS handle if the sinus waves from the grid don’t match with the ups sinus.??

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I suggest you start a separate thread to discuss this situation.

 

But generally, what you are proposing will work just fine.

[Greenside]

Very good explanation Crossy.  Thanks as ever ????

We're just at the point of having a contractor supply and install a Hybrid system sufficient to offset our monthly bills (three phase: around 3,500 bht) and provide charging of a (they told me today) soon-to-arrive MG4.  From the prices I've seen so far it looks like about an 8 year payback (depending on future electricity prices) although I hope that if the job is done properly the value of the house will improve and provide some compensation.

Planning to visit one of the two Fully Charged Live Shows when I'm over in England this April/May.  If the events are anywhere as good as their YouTube channels it will be very interesting.

[Encid]

Does anyone have a link to the list of PEA-approved inverters?

[Crossy]

  On 4/23/2023 at 11:48 AM, Encid said:

Does anyone have a link to the list of PEA-approved inverters?

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Have a search of the PEA website.

 

This is a fairly recent version: -

 

PEA-Inverter-list-ครั้งที่-5-2565.pdfFetching info...

 

[Ben Zioner]

  On 8/20/2021 at 4:13 AM, Crossy said:

Our place in Delhi had 3-phase, next to the TV were 3 outlets, one on each phase. Select the "best" phase for the TV to work properly.

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Imagine the wiring... Great thread BTW. Had a visit  from PEA yesterday; they want  me to go  ON grid with a generator. While my requirements match On grid hybrid.

 

And I am  3 phase, current bill  is 10k.

[Muhendis]

  On 10/20/2022 at 9:20 AM, Elik said:

There is fifth way to have solar, where you install small off grid system in the same house that you have a grid, and then have a switch where you can choose to draw from solar or from grid.

 

I see an automatic switch on Lazard’s (ATS Automatic Dual Power Transfer Switch 2P ) that will automatically switch when the batteries turn off.

 

Amorn solar has a battery kit for 19000 THB, get a second panel your out 25 k, and earning 2 kWh pr day, so you looking at a pay back time of about 2500 days. Not too bad, and you have a little emergency power in case of power out.

 

I do have a couple of questions I hope the forum can answer

 

Does the switch legally count as a off-grid system??

I have a small UPS so I won’t get interrupted during the switch, but can a UPS handle if the sinus waves from the grid don’t match with the ups sinus.??

 

 

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I would clasify that as not a fifth way but the very first way.

You have solar panels and an inverter and an ATS but that system only wortks during sunlight hours.

If you want you can add charge controllers and batteries so you can have stored solar electric for night time use.

 

All other systems are based on this and quite neatly put into a single box which is wrongly, in my opinion, called an inverter.

Variations on this "inverter" are quite popular with a grid connection which does away with the ATS and can even alow feedback into the grid which PEA will stop you doing if they find out.

[Muhendis]

  On 8/17/2022 at 9:21 AM, Pink7 said:

You have any good alternatives than the typical hybrid inverters as off grid backup?

 

Pink

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Sorry to jump in here.

The alternative is easy and plentiful.

• you could get a low frequency inverter* which runs off a 48v DC supply..
• Solar charge controlers and batteries to give you your 48v supply.

* An inverter in this instance is a device which creates a mains AC voltage from a lower DC voltage.

[Encid]

Solar Power related terminology