Good day i am a new member of this forum. My name is Derek my professional qualification is a electrical engineer, but got into Peacan farming in the Upington area for the last 8 years.I need some advice from expert solar installers. I do have a very knowledgeable electrician but he admitts that solar and dc systems is not his strong suit.I am deciding on which system to install hence seeking advice either 5kw or 8kw system. My power consumption from the farm house is very moderate varies between 680kwh to 760kwh monthly. The farm irrigation pumps and general consumption is covered by a 80kva diesel generator. The way i see it( and it is here were the solar boffins come in) the efficiency of  the inverter drives the efficiency of a solar panel system because inverters convert Direct Current (DC) (as produced by the solar panels), into Alternating Current (AC) (as used by the grid). This leads me to wonder what effect over-sizing or under-sizing an inverter will have on overall system efficiency. A solar system’s inverter functions optimally within a predetermined operational ‘window’ (usually laid out in the inverter’s specifications). As the power input from the system’s solar panels goes up and down, the inverter’s ability to efficiently convert it from DC electricity to AC electricity differs. As long as the input from the panels falls with in the range of the window, the inverter can be considered to be operating optimally. Regardless of the output of the solar panels, the power output will be cut-off (‘clipped’) by the inverter so that it does not exceed the inverter’s rated capacity. Inverter under-sizing – sometimes referred to as ‘overclocking’ – has actually become a common and widely accepted practice in Australia where my brother currently resides. I have 4 aircons that is kept in check by 3 energy regulators in the db board. My peak power consumption at any given time does not exceed 4600 watts. Inverter fridge freezer combo 140watts( no starup current LRA=0), lights 160watts Tv, repeater for internet, 1 x Solar geysers, 1 x Gas stove.

My specs below: (What do you think) 

1) 5kva Sunsynk or Deye inverter.

2) 1 x 10/8 Freedom Won batteries.

3) 10 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W

Thanks in advance.

Have a great weekend.

Regards.

Derek

 

 

 

Those panels are not the right match for the 5kW SunSynk. Their current is too high and you will experience “clipping” which will result in less than optimal power production. You need panels which match as close as possible to the MPPT current specification. 

11 minutes ago, PowerUser said:

Those panels are not the right match for the 5kW SunSynk. Their current is too high and you will experience “clipping” which will result in less than optimal power production. You need panels which match as close as possible to the MPPT current specification. 

Thanks @PowerUser just a question will it not be better to have clipping at peak hours but you would have more energy available earlier in the morning and later in the evening, more energy balance during 8 hours. Below a graph that i googled that explain my way of thinking.

Thanks for your feedback this is why i need to ask the questions

 

I would go for an 8kw inverter, 5kw limits you .

 

1 hour ago, Derek3 said:

Thanks @PowerUser just a question will it not be better to have clipping at peak hours but you would have more energy available earlier in the morning and later in the evening, more energy balance during 8 hours. Below a graph that i googled that explain my way of thinking.

Thanks for your feedback this is why i need to ask the questions

 

I think that's right. @PowerUser is correct that you are over paneled but this will have the affect that you describe, and will mean that you get better production on overcast days.

I have a 4.6 kW inverter, the same battery as you propose, and about 4kW of panels. My consumption is lower than yours. On a sunny day I would have maybe 4kWh excess (that I could sell back). Your consumption is higher, but you have 50% more PV. You want to move as many loads as possible to the daylight hours so that you can just tick over on the battery at night.

This brings us to 5 v 8 debate. If the sum of your backed up loads exceeds 5kW at any time, the inverter will trip. So 8kW gives you more headroom for short-live peaks in consumption, and you'll still be in the range of what your battery will tolerate. I know you said 4.6, but if you move loads around then you may go over that. Also we had a problem in our house when, in quick succession, the dishwasher would be turned on, followed by the microwave, the kettle and the toaster, This exceeds the 4.6 kw limit. Only briefly, but for long enough.

This is a change I would make if I were starting over - a higher rated inverter. Most times that 4.6 is enough, and we have learned to live with it, but the 8 would be really nice.

1 hour ago, Derek3 said:

Thanks @PowerUser just a question will it not be better to have clipping at peak hours but you would have more energy available earlier in the morning and later in the evening, more energy balance during 8 hours. Below a graph that i googled that explain my way of thinking.

Thanks for your feedback this is why i need to ask the questions

 

You will in any case be experiencing clipping and overclocking due to putting 6kW of panels on a 5kW AC output inverter. Call it an earlier ramp-up but a loss of 17% of peak power. Not 100% true because DC battery charging output is still possible, but just run with this thought for now.  

Beyond that, the Canadian solar panel's operating current is just too high, 17A, compared to the the 5kW inverter's 13A current limit, such that you're losing further, upwards of 23% of additional generation potential. Maths just thumbsucked to give the idea.

If you're sticking to a 5kW, best to go with a panel with Imp around the 13A mark, and at a higher operating Voltage. If you want an earlier ramp-up, maybe consider just using an East-West panel layout, where you can expect 15% overall loss but spread of generation through out the day.

Better still would be to choose an 8kW inverter, that is not just a tight fit like the 5kW, but gives you room to grow your loads, have greater over-panelling for Winter, better surge capacity, and that is not just better matched to the Canadian Solar panels, but also a better match to the 10/8 FreedomWon batteries.

Basically with a 5kW Deye in that setup you're investing in panel and battery capabilities that you can never use.

Edited April 1, 20231 yr by GreenFields

1 hour ago, Derek3 said:

Thanks @PowerUser just a question will it not be better to have clipping at peak hours but you would have more energy available earlier in the morning and later in the evening, more energy balance during 8 hours. Below a graph that i googled that explain my way of thinking.

Thanks for your feedback this is why i need to ask the questions

 

That curve doesn’t show what is in the x and y axis. Do you have a source for the full article, which explains the exact mechanism to get more energy with over specking the Amps?

@Bobster. @GreenFieldsVery happy i asked the questions i have decided to upgrade then to 8kw Sunsynk inverter thanks for your expert advice and your time. Also thanks to @Nicholas Strachanand @PowerUser for their valuable inputs.

New specs then:

 

1) 8kva Sunsynk inverter.

2) 1 x 10/8 Freedom Won Lfp battery.

3) 10 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W.

Now guys do you know of reputable installers Upington side. Coc a must for insurance purposes.

Just as a side note is the communication protocols between Sunsynk and Freedom Won bms satisfactory.

Edited April 1, 20231 yr by Derek3
Spelling mistake

Simplistic view from a mechanical engineer with lots of time on hand.

My usage profile not very different to yours and I am very comfortable with a 5kVA inverter, 8 x 540W panels and the FW lite 10/8. In fact most often I cruise through the afternoon with very little requirement for production. The other benefit you have in the NC is that your PV potential is probable 30% higher than mine here in East London. In the summer months I can run in addition to my base load of 300 - 500W, a pool pump and 2 x 12 000BTU non-inverter aircons without drawing from grid.

Specific technical advise is aplenty in the other posts.

20 minutes ago, Derek3 said:

@Bobster. @GreenFieldsVery happy i asked the questions i have decided to upgrade then to 8kw Sunsynk inverter thanks for your expert advice and your time. Also thanks to @Nicholas Strachanand @PowerUser for their valuable inputs.

New specs then:

 

1) 8kva Sunsynk inverter.

2) 1 x 10/8 Freedom Won Lfp battery.

3) 10 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W.

Now guys do you know of reputable installers Upington side. Coc a must for insurance purposes.

Just as a side note is the communication protocols between Sunsynk and Freedom Won bms satisfactory.

I started with a 5 kw one and changed to an 8kw.Best decision I ever made.

2 hours ago, Derek3 said:

@Bobster. @GreenFieldsVery happy i asked the questions i have decided to upgrade then to 8kw Sunsynk inverter thanks for your expert advice and your time. Also thanks to @Nicholas Strachanand @PowerUser for their valuable inputs.

New specs then:

 

1) 8kva Sunsynk inverter.

2) 1 x 10/8 Freedom Won Lfp battery.

3) 10 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W.

Now guys do you know of reputable installers Upington side. Coc a must for insurance purposes.

Just as a side note is the communication protocols between Sunsynk and Freedom Won bms satisfactory.

Get an opinion about the fans on the sunsynk. I have a Goodwe which is nearly silent, so you can have it in your house, close to the front room.

2 hours ago, Bobster. said:

Get an opinion about the fans on the sunsynk. I have a Goodwe which is nearly silent, so you can have it in your house, close to the front room.

Will do thanks @Bobster. tell me what model Goodwe do i look at obviously the 8kw as discussed. Googled this model but i see on the spec sheet only 50amp charge/ discharge surely this model inverter won't be adequate for charging/discharging the FW 10/8 battery. Maybe i have the incorrect inverter model.

Goodwe EHB Single Phase Hybrid inverter 8600/10000kva

4 hours ago, Derek3 said:

Will do thanks @Bobster. tell me what model Goodwe do i look at obviously the 8kw as discussed. Googled this model but i see on the spec sheet only 50amp charge/ discharge surely this model inverter won't be adequate for charging/discharging the FW 10/8 battery. Maybe i have the incorrect inverter model.

Goodwe EHB Single Phase Hybrid inverter 8600/10000kva

Mine is an ES, and that range tops out at 4.6kW. I had a look on the Goodwe web site, and if I'm reading things correctly then the EHBs are designed for higher voltage batteries. The ES is designed for 50v batteries. 

With the higher voltage batteries you need less current for the same power, and so can use skinnier cables.

The Freedom Won Lite range are 50v (ish), so I don't think that inverter and that battery will live happily together.

The Sunsynk is not silent, and there's been some discussion here about the noise. Some don't mind it. I think it depends on location. Not everybody is like me with the inverter in the house, near the living area. 

Edited April 1, 20231 yr by Bobster.

Afternoon all you good people out there on the best forum ever. Just throw a eye and see if you agree with my thinking. I need to get this right spending my farm profits here working out to a pretty penny. 😬After inputs from 2 installers in my area and done some calculations myself i came up with the following specs. I have decided seeing that i am going with the Sunsynk 8kw inverter i will increase my solar output to 7200w 12 x 600w 3S2P config/ Mppt Controller. Due to the constant higher temps in Upington area the derating factor will approx be 0.38% per degree C above 25 degrees hence the reason the extra 2 panels.

The new planned installation:

 

1) 8kw Sunsynk inverter.

2) 1 x 10/8 Freedom Won Lfp battery.

3) 12 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W.

Thanks in advance. 

Derek

5 minutes ago, Derek3 said:

Afternoon all you good people out there on the best forum ever. Just throw a eye and see if you agree with my thinking. I need to get this right spending my farm profits here working out to a pretty penny. 😬After inputs from 2 installers in my area and done some calculations myself i came up with the following specs. I have decided seeing that i am going with the Sunsynk 8kw inverter i will increase my solar output to 7200w 12 x 600w 3S2P config/ Mppt Controller. Due to the constant higher temps in Upington area the derating factor will approx be 0.38% per degree C above 25 degrees hence the reason the extra 2 panels.

The new planned installation:

 

1) 8kw Sunsynk inverter.

2) 1 x 10/8 Freedom Won Lfp battery.

3) 12 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W.

Thanks in advance. 

Derek

Just a question. You only going to use 3S on the Sunsynk? per MPPT. 

1 minute ago, Scorp007 said:

Just a question. You only going to use 3S on the Sunsynk? per MPPT. 

The plan is 2 x 3 panels in series then the 2 strings in parallel per Mppt that was the suggestion from both installers @Scorp007 do you feel it is the best configuration look i am not clued up on solar installations hence the reason i need professional advice😅 

3S would be below the start up voltage. MPPT would never turn on.

Why not 6s per MPPT? For max efficiency, you want the highest voltage you can get.

EDIT: In fact, looking at that datasheet, unless I had 2 very distinct lighting angles I needed to catch, I would go for 1 string of 11. And have the other MPPT for future expansion.

Edited April 2, 20231 yr by JustinSchoeman

22 minutes ago, Derek3 said:

The new planned installation:

 

1) 8kw Sunsynk inverter.

2) 1 x 10/8 Freedom Won Lfp battery.

3) 12 x Canadian Super high Power Mono Perc Hiku7 Evo2 Solar Panel - 600W.

Thanks in advance. 

Derek

Its always nice to say "mine is bigger than yours", BUT...

You said your consumption from the FARM HOUSE averages out at 25kWh/day and the heavy equipment runs off a generator.

So what is your plan with the 7200W panels, lets say in winter you'll get minimum 4 X 7200 = 28 800kWh and in summer minimum 5 times 7200 = 36kWh (figures based on JHB, not sure if Upington, ( 8 SAI if you know, you know) , will get more than that)..The 4 and 5 multiplies are based on forum averages, a good indicator.

In effect, if you don't plan to use that "extra" power and you're not feeding back into the grid, its wasted... You have over-speced your setup.

Your other option is to go with a 5kW, 6000W panels and an extra battery...What is more important to you, backup power (battery) or plenty power during the day??

Decision time!

 

Edited April 2, 20231 yr by FixAMess

1 hour ago, JustinSchoeman said:

3S would be below the start up voltage. MPPT would never turn on.

Why not 6s per MPPT? For max efficiency, you want the highest voltage you can get.

EDIT: In fact, looking at that datasheet, unless I had 2 very distinct lighting angles I needed to catch, I would go for 1 string of 11. And have the other MPPT for future expansion.

Although series is the way to go I personally will not run the risk of connecting 11 in series. Without looking and as I remember these panels have a Voc of around 43-44V. The Vmp is fine but one must look at Voc. I guess Upington can get pretty cold in winter? 

1 hour ago, FixAMess said:

Its always nice to say, mine is bigger than yours BUT...

You said your consumption from the FARM HOUSE averages out at 25kWh/day and the heavy equipment runs off a generator.

So what is your plan with the 7200W panels, lets say in winter you'll get minimum 4 X 7200 = 28 800kWh and in summer minimum 5 times 7200 = 36kWh (figures based on JHB, not sure if Upington, ( 8 SAI if you know, you know) , will get more than that)..

In effect, if you don't plan to use that "extra" power and you're not feeding back into the grid, its wasted... You have overspecced your setup.

Your other option is to go with a 5kW, 6000W panels and an extra battery...What is more important to you, backup power (battery) or plenty power during the day??

Decision time!

 

You are here to fix my mess🤣 sorry just had to, so ok there is method in my madness i am in the process of building a packing station next to the farm house and i will need good lighting inside 10 x High Bay led's @ 200w/ lights so extra 2kw during daytime. For future expansion it makes sense then to have capacity during daytime( work hours) so i will stick to 7.2 kw solar and use battery capacity for night consumption. @JustinSchoeman right i hear you will then do configuration of 6S at 34.9v/ panel 209.4v/ Mppt

2 minutes ago, Derek3 said:

You are here to fix my mess🤣 sorry just had to, so ok there is method in my madness i am in the process of building a packing station next to the farm house and i will need good lighting inside 10 x High Bay led's @ 200w/ lights so extra 2kw during daytime. For future expansion it makes sense then to have capacity during daytime( work hours) so i will stick to 7.2 kw solar and use battery capacity for night consumption. @JustinSchoeman right i hear you will then do configuration of 6S at 34.9v/ panel 209.4v/ Mppt

As you need day time light for packing why don't you consider the cheap side of PV namely solar panels and go to 10.4kW. This will help in winter and on the odd cloudy day. 

Good evening to all. Had a busy few days with work and getting quotes from installers. I decided to go with Valsa as my sole solar installer. The branch of Valsa situated in Montague Gardens CT. Total change of setup as previously anticipated.

1) 8kw Deye inverter.

2) 16 x LONGI-575-B solar panels.

3) Ground Mount system 4 panels east facing ,8 North facing 4 West facing, 1 string of 8 panels in series/ Mppt < 400v/ string

4) 2 x FW 10/8 Lfp battery

Thanks to all will keep you updated. Have a good evening.

 

 

 

Is there any particular reason for having some panels facing East and West? (Space constraints seem unlikely on a farm in in Upington...😀)

If not, consider making all face North.  The graphs below show the difference (30 degree tilt assumed) - essentially the same in summer, 28% more in winter.

Given that it is ground mount, also consider adjustable mounts with a "summer" tilt of say 10 degrees and a winter tilt of say 45 degrees.  That would give you an additional 10% in winter and 16% in summer.

 

 

Now you made me go and google "solar insolence"

12 hours ago, Derek3 said:

3) Ground Mount system 4 panels east facing ,8 North facing 4 West facing, 1 string of 8 panels in series/ Mppt < 400v/ string

Huh? This seems to see you have the 4 East and 4 West panels in series?  That sounds like a remarkably bad idea.