Planning an off-grid hybrid solar system

[Encid]

24 minutes ago, Muhendis said:

Note there is only 1 MPPT input per inverter so paralleling needs to be done with a combiner. 

BUT

The East and West arrays could produce 7.82kw each which is above the spec. of 6kw per inverter.

Do you think I should reduce the number of panels on the east and west arrays?

Am I really likely to get 100% efficiency in power production from those arrays?

 

Is it possible to combine panels from different directional arrays on a single string?

Please excuse me from asking this question if it seems naïve to some but I am new to this and am learning... 

[Encid]

15 minutes ago, Crossy said:

 

Oops!

I missed that... 

[JBChiangRai]

11 minutes ago, Encid said:

Do you think I should reduce the number of panels on the east and west arrays?

Am I really likely to get 100% efficiency in power production from those arrays?

 

 

You won't get 100% efficiency, I have 21.6Kw in panels and 18Kw in inverters, I could hit 17Kw maximum power at installation but 20 months later I'm down to 15Kw (It's been like that for about a year).

[Crossy]

19 minutes ago, Encid said:

Is it possible to combine panels from different directional arrays on a single string?

 

You could put 9 panels in series east and 9 panels series west then combine those groups in parallel on one MPPT.

 

So long as the strings themselves are the same length you can parallel on one MPPT.

 

I would start out as marking up your drawing with the "ideal" panel combinations then work out how to achieve something similar practically.

 

Note that the inverters don't all have to have identical panels. There's nothing to stop you having a 9S2P on one inverter and a 6S on another if that's how your roof works best ????  

[Encid]

50 minutes ago, JBChiangRai said:

I definitely wouldn't go Hybrid again.

Currently we have a (reversible) spinning disk meter so having GTI's is possible and, like you, we could use AC all day long to keep the house cool by using the peak solar generating window and reducing solar curtailment.

But... we want the security of having the whole-of-house UPS functionality, hence going down the hybrid route.

 

Daily fluctuating voltages and brownouts from the PEA grid are a common occurrence in our part of Thailand.

And... every time there is a large thunderstorm with frequent lightning in our vicinity, the grid is shut down completely for a few hours... sometimes longer.

 

Ideally I would like a system that could unofficially perform net-metering (using the PEA grid to "bank our energy" for later use), but also need a battery backup (with minimal cycling of batteries to prolong their operating life).

 

Is it possible to combine hybrid inverters with a grid-tied inverter?

[JBChiangRai]

Just now, Encid said:

Currently we have a (reversible) spinning disk meter so having GTI's is possible and, like you, we could use AC all day long to keep the house cool by using the peak solar generating window and reducing solar curtailment.

But... we want the security of having the whole-of-house UPS functionality, hence going down the hybrid route.

 

Daily fluctuating voltages and brownouts from the PEA grid are a common occurrence in our part of Thailand.

And... every time there is a large thunderstorm with frequent lightning in our vicinity, the grid is shut down completely for a few hours... sometimes longer.

 

Ideally I would like a system that could unofficially perform net-metering (using the PEA grid to "bank our energy" for later use, but also need a battery backup (with minimal cycling of batteries to prolong their operating life).

 

Is it possible to combine hybrid inverters with a grid-tied inverter?

Yes, that is exactly what I have done.

[Encid]

10 minutes ago, JBChiangRai said:

Yes, that is exactly what I have done.

Do you have a diagram of how yours is configured that you could share?

[JBChiangRai]

21 minutes ago, Encid said:

Do you have a diagram of how yours is configured that you could share?

I don't have a diagram, but I will explain it.

 

I have 3 MUST 6Kw Grid-Tied inverters with 7.2Kw of PV on each, these connect direct to PEA.

 

I have 3 of MUST 5.5Kw Hybrid inverters (with parallel cables) with no PV but 28.8KwHrs of LifePo4 batteries attached (48v), the inverters are set to UPS mode and to charge the batteries when needed from their internal chargers direct from PEA.  The Hybrid inverters have their inputs connected to PEA and their outputs connected (through an Automatic Voltage Regulator AVR) to the house's Distribution panels (one upstairs and one downstairs).

 

The Hybrid inverters run in bypass mode with PEA power available and just connect the inputs to the outputs automatically, in the event we lose PEA power, they immediately kick-in to generate upto 16.5Kw of power to the house and when the power comes back again they switch to bypass mode and recharge the batteries.  Unless you hear them kick-in, you can't tell when we have a power cut.

 

Initially I thought I could do it all with the 3 Hybrid inverters, but I found the export function to be really poor, they would export one at a time, no more than 1 Kw, and after 15 minutes of one inverter exporting with it's fans running noisily, the next one would start and the prior one would stop.  So I had 22Kw of panels mostly being wasted, that's when I added the Grid-Tied inverters.

 

My Grid-Tied inverters are naturally cooled without fans, so in normal use the whole installation is silent, when we have a power cut, the Hybrid inverters are noisy as the fans kick in.

 

I had to add the AVR because we have a lift between floors and in the evening as my neighbours were running their air conditioning, the voltage would drop to a level that the lift would error and fail.

 

The room I have the inverters and batteries in is air conditioned 24/7, it serves multiple purposes, it's the power room, it's a wine cellar and it contains my computer servers.

 

We are probably generating around 1,800 to 2,000 KwHr's a month and mostly out PEA bill is about 100-200 baht.

 

[Encid]

23 minutes ago, JBChiangRai said:

We are probably generating around 1,800 to 2,000 KwHr's a month and mostly out PEA bill is about 100-200 baht.

That sounds very much like the sort of system I want. 

 

At our current energy inefficient house in Najomtien we are consuming 1,500 to 1,800 kWh per month and our PEA bill is around 8,000-9,000 baht.

With the new build the house(s) will be considerably more energy efficient, however we will have more occupants so personal energy consumption will be higher.

 

29 minutes ago, JBChiangRai said:

My Grid-Tied inverters are naturally cooled without fans, so in normal use the whole installation is silent, when we have a power cut, the Hybrid inverters are noisy as the fans kick in.

MUST hybrid inverters do have a reputation for being noisy when the fans are operating.

 

30 minutes ago, JBChiangRai said:

The room I have the inverters and batteries in is air conditioned 24/7, it serves multiple purposes, it's the power room, it's a wine cellar and it contains my computer servers.

I plan on doing something similar. 

 

15 minutes ago, JBChiangRai said:

Initially I thought I could do it all with the 3 Hybrid inverters, but I found the export function to be really poor, they would export one at a time, no more than 1 Kw, and after 15 minutes of one inverter exporting with it's fans running noisily, the next one would start and the prior one would stop.  So I had 22Kw of panels mostly being wasted, that's when I added the Grid-Tied inverters.

@Bandersnatch have you ever tried exporting with your Growatts?

[Bandersnatch]

6 hours ago, Encid said:

@Bandersnatch have you ever tried exporting with your Growatts?

The Growatts are hybrid off-grid  - can take power from the grid but cannot send it back.

 

When I found out that 5kW was the maximum size for the solar rooftop feed-in program if you had single phase I decided to go the self consumption route.

 

I told PEA I was fitting solar and asked them to replace my temporary meter with a "solar meter" that could not turn backwards - they didn't.

 

The meter they fitted didn't turn at all as I was running on solar and the meter reader reported it broken. I went to PEA and they asked to inspect my system. Nobody from Surin PEA could understand my system so the Korat Solar team came down and a did a second inspection and signed off my system. I asked again for a meter that didn't turn backwards but it wasn't fitted. 

 

The fifth time my meter was reported broken I had a meeting with the Manager of the meter team who said my solar was turning the meter backwards and it was breaking the meter. I did try and explain that if the meter was turning backwards why was the meter reading always the same. After my solar system was inspected for the third time it was agreed that my meter would be replaced with one that would not turn backwards and a sign would be put on it for the meter reader saying that I had solar and that the meter was not broken - that was over a year ago - still waiting.

 

 

 

 

[Crossy]

@Bandersnatch are you running panels 2P on any of your PV inputs?

 

The spec. doesn't seem to indicate a maximum PV input current, just voltage and power ???? 

[Pink7]

3 minutes ago, Crossy said:

@Bandersnatch are you running panels 2P on any of your PV inputs?

 

The spec. doesn't seem to indicate a maximum PV input current, just voltage and power ???? 

Growatt used to be max 18A but later upgraded to 21A with new firmware.

 

Pink

[Crossy]

10 minutes ago, Pink7 said:

Growatt used to be max 18A but later upgraded to 21A with new firmware.

 

Pink

 

Is that actually quoted anywhere? The spec. seems silent ???? 

[Encid]

9 minutes ago, Crossy said:

 

Is that actually quoted anywhere? The spec. seems silent ???? 

The user manual shows 22A (see page 38).

 

Growatt SPF 3500-5000 ES User Manual.pdf

[Crossy]

5 minutes ago, Encid said:

The user manual shows 22A (see page 38).

 

Cheers. It's knowing where to look ???? 

[Encid]

22 minutes ago, Crossy said:

 

Cheers. It's knowing where to look ???? 

I would have expected to see it on the datasheet too as that is the logical place for specifications.

Maybe Chinese logic is different to ours? 

 

@Crossy How is your system configured?

You have 1 x Sofar 6kW GTI and 1 x Sofar 5kW Grid-tie hybrid correct?

Does it work in a similar fashion to JBChiagRai's system? 

[Crossy]

The 6kW GTI has 2 x 10S strings of 330W panels.

The 5kW hybrid has 2 x 6S strings of 340W panels (room for another 3 panels per string).

 

Right now, the batteries are full (11kWh ish) by about 1PM then we blast up to 8kW into the grid (all the village fans go faster).

 

Leaving alone for now, unless our friends at PEA come along with electronic meters.

 

 

[Dazkkk]

I’d thought about such a setup for wifes Thai family and I’m very interested in this thread. 
 

I have an EV here in UK and just had a quote for £30k for 16 Solar Edge 370 watt panels, 2 Solar Edge 10 KWH Batteries, Solar Edge Inverter and an Emlite 1-PH meter.
I get cheap electric for 4 hours nightly via Octopus Energy, which goes to power the car’s battery (68kwh), with the arrays filling the 2 batteries for use in the house or exporting to the National Grid. 

Still shopping around for other quotes as the price is too high. 
Did a quick calculation on power costs for the car which has done 35k miles in 18 months and just electric costs work out at 1 pence per mile compared to my diesel car which is horrendous at the moment because of high fuel prices. 

[Encid]

With all the recent comments on other topics in this forum I might have to ask for a topic title change to "Planning an on-grid hybrid solar system" 

 

Is it possible to install an on-grid hybrid inverter, but not an ESS immediately?

 

Just thinking... if we retain our existing spinning disk meter we could use the PEA grid as our storage bank for excess power generated during the day, and claim it back during non solar producing hours. Of course we'd have to monitor it closely to ensure that our meter didn't go back into the black!

 

I'm thinking of such an arrangement for our guest house... use the car port roof as the panels supports and install a GTI.

 

Later (6-18 months) when we build our main house we would definitely need extra panels, inverters, and an ESS.

 

So maybe I should be looking at a two stage install?

Would it be difficult to link such a setup, with panels and inverters being physically 50m apart?

 

If at any time the PEA decided to replace our meter with a digital meter, the ESS would then be required.

 

Thoughts?

[Crossy]

20 minutes ago, Encid said:

Is it possible to install an on-grid hybrid inverter, but not an ESS immediately?

 

Yes, but you need to ensure your hybrid will do on-grid with no battery.

 

There's plethora of hybrids described as "on/off grid", you need to carefully peruse the documentation to see exactly what they can (and can't) do.

 

[Muhendis]

For ESS you might like to look at NeFe storage cells.

They are not cheap but the chemistry is good for 30 years or more.

Focus on the TLC. It may put you off

The price is good but only over an extended period'

I like it, but I'm old.

[JBChiangRai]

Does anyone have first hand experience of a hybrid inverter that will export all its surplus energy to the grid?

 

My recommendations are :-

Design your roof for solar and not solar for the roof

Go Grid-Tied without ESS

Install a small solar system from an approved supplier with a feed-in meter, because at some point in the future, we are all going to be on digital meters. 

Install a larger grid-tied system yourself when the dust has settled

Finally, use a grid-tied inverter that you can tweak the settings on *

Use an Automatic Voltage Regulator

 

* if you can tweak the settings, it can't be PEA approved, the MUST dedicated Grid-Tied inverter is approved and the settings are behind a password which they cannot give you (PM me for the password).

 

Grid-Tied systems work by matching the frequency of PEA, then increasing their voltage to pump power out to the grid.  My experience is the grid doesn't like taking the power, at a pre-set voltage grid-tied inverters go into an error mode, wait and restart.  If you can increase that voltage then you can export more power.  If your neighbours on the same transformer & same phase use a lot of power, you won't have a problem, they will soak up your power.  For that reason, I would go 3 phase too.

[JAS21]

Ours does … Sofar Hybrid ES5000 ….can set the export value to what you want …ie between 0 and I guess 5kWs

 

You do need a battery with this model …not sure how small you can get away with though. 

[JBChiangRai]

Just now, JAS21 said:

Ours does … Sofar Hybrid ES5000 ….can set the export value to what you want …ie between 0 and I guess 5kWhs …

Can you set the cut-off voltage? that's the key number on a large GT solar system.

[Crossy]

1 minute ago, JBChiangRai said:

Can you set the cut-off voltage? that's the key number on a large GT solar system.

 

We have the same inverter. It's also one of the few grid-tie hybrids that are on the "approved" list.

 

Those parameters are "hidden" and (rightly) not readily accessible to the regular user. However, the relevant information is (like pretty much everything) available on the net if you know where to look.

[Encid]

OK so taking on board all the really helpful comments and suggestions so far, I have decided to do a small install on the guest house carport roof first.

 

We will change the roof design to be a south-facing steel roof at an angle of 15° so no special supports will be needed for the PV panels.

 

The system I am thinking of will consist of the following:

 

1 x Sofar HYD 5000 ES on-grid hybrid inverter (5kW) (PEA approved list)

2 x LVTopsun LV48100 5kWh batteries or maybe a single 10kWh battery

2 x 10S strings of 340W panels (total 6.8kWp)

 

The Sofar user manual tells me for PV parameters that max DC power for a single MPPT is 3000W so do I have too many panels in my plan?

The Sofar datasheet states that max PV array is 6.65kWp.

 

Should I reduce the number of panels by 2 or should I upgrade the inverter to the HYD 6000 ES (6kW) model where max DC power for a single MPPT is 3500W?

 

Or am I missing something?

 

I am giving serious consideration to install the system from an approved supplier... with the future in mind.

[Crossy]

You're only slightly over the max power, provided you are well within the voltage maximum you will be fine as your array will never get to rated power anyway.

 

Do verify that your packs will talk to the Sofar inverter.

 

[Encid]

9 minutes ago, Crossy said:

Do verify that your packs will talk to the Sofar inverter.

Will do. 

I selected LVTOPSUN because that's what JAS21 has with a similar inverter and they are very cost competitive.

 

 

If anyone has other battery recommendations I'd be happy to hear from you.

[Crossy]

@JAS21 has a pack that definitely works.

 

We are using Seplos BMS's but their packs are not cheap, they do sell kits of a box plus BMS ready for you to install Eve cells from your favourite Chinese seller.

 

[JAS21]

58 minutes ago, Encid said:

Will do. 

I selected LVTOPSUN because that's what JAS21 has with a similar inverter and they are very cost competitive.

 

 

If anyone has other battery recommendations I'd be happy to hear from you.

Be careful with the LV48100… there are variations ….