Setting up solar installation

[pierrecha]

The 5 strings of 7 panels were a test run (perhaps overzealous) - I intend to return to my original set-up of 2 strings of 9 panels for one inverter, and 2 strings of 10 panels for the other inverter. (Each would be a little less than the 2*10A outlined in the user manual [would be 2*9.26A for each array]).

The cable running from my inverters to the pv arrays are already underground and thus limit access to the children and animals, and I have isolation switches at both the arrays and by the inverters.

I will buy the appropriate cabling for the batteries - however I have a question regarding the appropriate circuit breaker: does the example in the link below seem appropriate to you? (battery circuit breaker)

The inverter is placed in the garage (where it is much cooler than anywhere else in the house) despite the southern temperatures outside [I am in the South of France].

I have a question regarding the battery set-up: I am intending to have both my inverters put to use with the array set-up described above. Do I arrange 4 12V 200Ah batteries for each inverter, or do I arrange a total of 8 of those batteries with 2 strings of 4, connected to one inverter, which itself is connected by a second pair of battery cables to the other inverter (and having the inverters connected in "parallel" i.e. connected with the communication cables and set up in the SolarPower application in the "parallel" configuration)?

Hope that what I'm trying to communicate is clear to you - and again, thank-you for your help!

Would these batteries work for my set-up? They seem, at first sight, to fit the description.

Thank-you again!

 

[marconi]

The next lesson. It is expensive to store electricity in a battery. Batteries deteriorate in capacity with the number of charge/discharge cycles and depth of discharge. They also deteriorate if not charged appropriately to their present charge state and type of battery. They also age if kept too warm or charged/discharged very quickly. Good long lasting, slow deteriorating, safe batteries are expensive but a better return on investment than cheaper ones for long term high useage roles. I have only used a good make of batteries - Victron Advanced Gel Matrix - because they are used in a business critical application every hour, every day, all year and need no maintenance and are both quality assured and safe. I have done all the level of investment, return on investment, cost-effectiveness, opportunity cost, pay-back period analysis. You will need to consider the percentage of time you will be using your stored solar energy over a day, a week and a year to gauge how often you need to draw on energy stored in the battery and hence its capacity. In this regard the 'load profile' - how much power plotted against time (day, week, year) is helpful.

Generally speaking the best way to use the off-grid set-up is to use the solar energy as it is generated until you don't need it for doing any work and then to store the surplus but only as much stored as you can reasonably need in reserve until the next spell of sunshine.

Or you could just 'splash the cash' and buy some 'big' batteries of any make and type and see how you get on. In my application we did not have the luxury of doing this.
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Four of those batteries would be an option but before you buy them look at other Gel/AGM brands. Look at the specifications for floating charge life and expected number of cycles of discharge/depth of discharge, and expected life for regular % rate of discharge and manufacturer's guaranteed life and maximum charging current. All the information is given in the specification for the Ultracell. Also read the comments by users of them.

Look at Victron:

12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine - https://www.photonicuniverse.com/en/catalog/full/470-200Ah-12V-Gel-deep-cycle-battery-for-motorhomes-caravans-boats-and-off-grid-power-systems.html

Whatever you buy they need to be deep-cycle (50%) AGM or GEL. Don't buy lorry or car batteries - buy marine batteries.

Sorry a bit rushed - have to go out.


[automerge]1575364665[/automerge]
12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine - https://www.photonicuniverse.com/en/catalog/full/359-24kWh-48V-500Ah-AGM-deep-cycle-battery-bank-with-metal-racking-24-x-2V-batteries.html
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The last for this session - think hard about whether you can cope without electricity for a period of time - for how long? This helps inform the sizing of the battery. Could you rely on a stand--by generator instead during this period of PV & battery being unavailable?

 

[pierrecha]

The next lesson. It is expensive to store electricity in a battery. Batteries deteriorate in capacity with the number of charge/discharge cycles and depth of discharge. They also deteriorate if not charged appropriately to their present charge state and type of battery. They also age if kept too warm or charged/discharged very quickly. Good long lasting, slow deteriorating, safe batteries are expensive but a better return on investment than cheaper ones for long term high useage roles. I have only used a good make of batteries - Victron Advanced Gel Matrix - because they are used in a business critical application every hour, every day, all year and need no maintenance and are both quality assured and safe. I have done all the level of investment, return on investment, cost-effectiveness, opportunity cost, pay-back period analysis. You will need to consider the percentage of time you will be using your stored solar energy over a day, a week and a year to gauge how often you need to draw on energy stored in the battery and hence its capacity. In this regard the 'load profile' - how much power plotted against time (day, week, year) is helpful.

Generally speaking the best way to use the off-grid set-up is to use the solar energy as it is generated until you don't need it for doing any work and then to store the surplus but only as much stored as you can reasonably need in reserve until the next spell of sunshine.

Or you could just 'splash the cash' and buy some 'big' batteries of any make and type and see how you get on. In my application we did not have the luxury of doing this.
[automerge]1575364086[/automerge]
Four of those batteries would be an option but before you buy them look at other Gel/AGM brands. Look at the specifications for floating charge life and expected number of cycles of discharge/depth of discharge, and expected life for regular % rate of discharge and manufacturer's guaranteed life and maximum charging current. All the information is given in the specification for the Ultracell. Also read the comments by users of them.

Look at Victron:

12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine - https://www.photonicuniverse.com/en/catalog/full/470-200Ah-12V-Gel-deep-cycle-battery-for-motorhomes-caravans-boats-and-off-grid-power-systems.html

Whatever you buy they need to be deep-cycle (50%) AGM or GEL. Don't buy lorry or car batteries - buy marine batteries.

Sorry a bit rushed - have to go out.


[automerge]1575364665[/automerge]
12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine - https://www.photonicuniverse.com/en/catalog/full/359-24kWh-48V-500Ah-AGM-deep-cycle-battery-bank-with-metal-racking-24-x-2V-batteries.html
[automerge]1575364995[/automerge]
The last for this session - think hard about whether you can cope without electricity for a period of time - for how long? This helps inform the sizing of the battery. Could you rely on a stand--by generator instead during this period of PV & battery being unavailable?

I am trying as much as possible to become off-grid but if there is no PV or battery available, I was thinking about using the grid, too. However I run into the problem of setting-up the grid to start at the right time i.e. when neither the PV or battery are available, and I don't want anything to return to the grid. In sum, I want to know if the inverter has some sort of charge controller integrated within (perhaps using the SolarPower application?) that would switch to the grid if ever I were to need it?
[I had originally planned for the solar panels to work during the day for my 24H water pump - throughout the summer, for my olive production - and for the grid to start up when the sun is no longer there.]

 

[marconi]

Yes that circuit breaker (150A) is suitable and the one we have used.

You need an insulated spanner of suitable size for the battery bolts:

Insulated Spanners, Sockets and Accessories | Insulated Tools Ltd - https://www.insulatedtools.co.uk/spanners-sockets.html

You need flexible multi-stranded 35mm2 low voltage cable - Here is a French supplier:

Black Hi-Flex 35mm2 cable per meter - EVEA - Kartmasters | Spécialiste du véhicule électrique - https://evea-kartmasters.fr/en/electric-cables/212-black-hi-flex-35mm2-cable-per-meter.html

To make good solid battery connections using 35mm2 cable you will need a special crimping tool:

https://uk.rs-online.com/web/p/crimp-tools/3982270?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_Connectors-_-Connector_Tools_And_Accessories|Crimp_Tools-_-PRODUCT_GROUP&matchtype=&pla-617994355632&gclid=CjwKCAiArJjvBRACEiwA-WiqqwZErgefDvsFTDhOcFp95Kdv5vXMVUqv3c1-UBADJaurPfILbg8ikRoCMbgQAvD_BwE&gclsrc=aw.ds

and a cable lug of the right diameter hole for the battery terminal bolt and entry for the 35mm2 cable:

https://uk.rs-online.com/web/p/crimp-ring-terminals/1225009?cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Connectors-_-Terminals_And_Splices|Crimp_Ring_Terminals-_-PRODUCT_GROUP&matchtype=&pla-394876820878&s_kwcid=AL!7457!3!243856856084!!!g!394876820878!&gclid=CjwKCAiArJjvBRACEiwA-Wiqq0tSLauWi--8vmlLq242sPVfLKBYbRVXS24bANWw4n7htbkT4C0VmxoCS60QAvD_BwE&gclsrc=aw.ds

This is a useful site for some of these items and the terminal boots/covers:

Auto & Marine Electrical Components & Accessories | 12 Volt Planet - https://www.12voltplanet.co.uk/

 

[marconi]

if you look at page 31 of the manual under 'off-grid 1' I have indicated in red the options I think you need to select for the settings in bold black to meet your requirement. It is possible to set up for timed utility charging of the battery using normal rate or perhaps timed off-peak electricity if available. In all cases below the inverter is in the off grid mode which means it is not feeding electricity back into the French electricity network. There is a nice feature whereby if you go over 5kW the utility supply steps in so you might consider only using one hybrid inverter if you only occasionally exceed 5kW or not for long or both: - the item in italics:

PV energy supply priority setting: 1st Load, 2nd Battery
PV power will provide power to the load first and then charge battery. Feed-in to
the grid is not allowed under this mode. At the same time, the grid relay is
connected in Inverter mode. That means the transfer time from inverter mode to
battery mode will be less than 15ms. Besides, it will avoid overload fault because
grid can supply load when connected load is over 5KW.
Battery charging source:
1. PV or Grid: If there is remaining PV power after supporting the loads, it will charge
battery first. Only until PV power is not available, grid will charge battery. (Default)
2. PV only: It is only allow PV power to charge battery.
3. None: It is not allowed to charge battery no matter it’s PV power or grid.
Load supply source:
When PV power is available:
1. 1st PV, 2nd Battery, 3rd Grid (Default)
PV power will provide power to the load first. If it’s not sufficient, battery power will
provide power to the load. When battery power is running out or not available, grid
will back up the load.
2. 1st PV, 2nd Grid, 3rd Battery
PV power will provide power to the load first. If it’s not sufficient, grid will provide
power to the load. If grid is not available at the same time, battery power will back
up.
When PV power is not available:
1. 1st Grid, 2nd Battery
Grid will provide power to the load at first. If grid is not available, battery power will
32
provide power backup.
2. 1st Battery, 2nd Grid (Default)
Battery power will provide power to the load at first. If battery power is running out,
grid will back up the load.
NOTE: This option will become ineffective during AC charging time and the priority
will automatically become 1st Grid and 2nd Battery order. Otherwise, it will cause
battery damage.

 

[pierrecha]

if you look at page 31 of the manual under 'off-grid 1' I have indicated in red the options I think you need to select for the settings in bold black to meet your requirement. It is possible to set up for timed utility charging of the battery using normal rate or perhaps timed off-peak electricity if available. In all cases below the inverter is in the off grid mode which means it is not feeding electricity back into the French electricity network. There is a nice feature whereby if you go over 5kW the utility supply steps in so you might consider only using one hybrid inverter if you only occasionally exceed 5kW or not for long or both: - the item in italics:

PV energy supply priority setting: 1st Load, 2nd Battery
PV power will provide power to the load first and then charge battery. Feed-in to
the grid is not allowed under this mode. At the same time, the grid relay is
connected in Inverter mode. That means the transfer time from inverter mode to
battery mode will be less than 15ms. Besides, it will avoid overload fault because
grid can supply load when connected load is over 5KW.
Battery charging source:
1. PV or Grid: If there is remaining PV power after supporting the loads, it will charge
battery first. Only until PV power is not available, grid will charge battery. (Default)
2. PV only: It is only allow PV power to charge battery.
3. None: It is not allowed to charge battery no matter it’s PV power or grid.
Load supply source:
When PV power is available:
1. 1st PV, 2nd Battery, 3rd Grid (Default)
PV power will provide power to the load first. If it’s not sufficient, battery power will
provide power to the load. When battery power is running out or not available, grid
will back up the load.
2. 1st PV, 2nd Grid, 3rd Battery
PV power will provide power to the load first. If it’s not sufficient, grid will provide
power to the load. If grid is not available at the same time, battery power will back
up.
When PV power is not available:
1. 1st Grid, 2nd Battery
Grid will provide power to the load at first. If grid is not available, battery power will
32
provide power backup.
2. 1st Battery, 2nd Grid (Default)
Battery power will provide power to the load at first. If battery power is running out,
grid will back up the load.
NOTE: This option will become ineffective during AC charging time and the priority
will automatically become 1st Grid and 2nd Battery order. Otherwise, it will cause
battery damage.

I have worked out a diagram showing my intended set-up using your advice - using all 38 panels and both inverters. I hope that it is all in order (and would appreciate any advice you would have to offer, as you have done so well up till now!).

Thank-you again for your ongoing help and expert advice.

 

[marconi]

Briefly:

1. Each HI must have its own battery bank and its own PV array. The two batteries must not be in parallel.
2. The ac outputs from the HI cannot be connected in parallel. Each ac output will need its own consumer unit and earth leakage protection.
3. You need to connect the 230Vac from utility into each inverter to benefit from automatic fall back to utility in thevent of no PV and a flat battery.
4. How long is the cable run between the arrays and the inverter? You only need 16mm2 for very long run otherwise 6mm2 is good enough.
5. All 35mm2 must be short runs.
6. What sets of loads do you have? eg: Home and Farm? in which case each inverter could be dedicated to its own set of loads.
7. 230V ac installation (at HI inpouts and outputs) not yet designed in accordance with French regulations. Need some ac isolators.

A good start though. . Aim for simplicity.

 

[pierrecha]

Briefly:

1. Each HI must have its own battery bank and its own PV array. The two batteries must not be in parallel.
2. The ac outputs from the HI cannot be connected in parallel. Each ac output will need its own consumer unit and earth leakage protection.
3. You need to connect the 230Vac from utility into each inverter to benefit from automatic fall back to utility in thevent of no PV and a flat battery.
4. How long is the cable run between the arrays and the inverter? You only need 16mm2 for very long run otherwise 6mm2 is good enough.
5. All 35mm2 must be short runs.
6. What sets of loads do you have? eg: Home and Farm? in which case each inverter could be dedicated to its own set of loads.
7. 230V ac installation (at HI inpouts and outputs) not yet designed in accordance with French regulations. Need some ac isolators.

A good start though. . Aim for simplicity.

I set up the cabling from the inverters to the panels in 16mm2 - it is an 80m run (160m there and back) - for the sake of learning, what would the appropriate cable thickness have been?

In the SolarPower application, there is the possibility to run two or more inverters "in parallel" - can I still run the inverters this way (with the 2 sets of 4 batteries each connected to their own inverter), with the communication cables and application parameters?

Concerning your 6th question, I was hoping to put both my home and the necessary 'farm' loads together, in the hopes that if something were to go awry with the panels i.e. shade on one string, that the other panels would continue to work and thus the loads would continue to work, too. I fear that that would not be the case if I were to connect loads separately - and not in the "parallel" configuration depicted in the user manual, on page 53.

Thank-you!

 

[marconi]

Mmm - some things for me and you to think more about. No more tonight - I am cooking - but will respond tomorrow. You have not yet confirmed you need 10kW peak independent of utility whatever and whenever and thus two HIs.

With one inverter and utility fallback for over 5kW you would only need one battery bank -and it could be a large one - and both PV arrays could feed into it. You could then have the second HI as a ready use spare in the event of the in-service one failing. Nice and simple and reliable.

16mm2 was a wise choice.

In which region of France are you so I can look it up?

 

[pierrecha]

Mmm - some things for me and you to think more about. No more tonight - I am cooking - but will respond tomorrow. You have not yet confirmed you need 10kW peak independent of utility whatever and whenever and thus two HIs.

With one inverter and utility fallback for over 5kW you would only need one battery bank -and it could be a large one - and both PV arrays could feed into it. You could then have the second HI as a ready use spare in the event of the in-service one failing. Nice and simple and reliable.

16mm2 was a wise choice.

In which region of France are you so I can look it up?

I can confirm, before you leave for your dinner, that I will be needing a little above 8KW at peak and thus both inverters and two battery packs.

I live in Fontvieille, 13990, in the south of France.

Bon appétit!

 

[marconi]

Well, I admit to have missed that the HIs can indeed be connected in parallel and share the same battery but not the same arrays. You will need the paralleling inter connectors mentioned so the HIs work together.

5kW output from each HIs in battery mode requires a current at 48V of 5000/48 = 104A. So, 10kW from one shared battery is a current demand of 208A. The current carrying capacity of 35mm2 cable is 148A constant and 216A short term - say a few minutes. This means 2 His cannot share one pair of cables between them and the battery - you will need separate pairs for each HI to the battery bank and protected by their own circuit breaker. The advantage of separate cables is the voltage drop along them and heat loss in them are reduced.

You need to study the table on page 54 on recommended battery capacity and page 55 for back-up time. A string of four 12V 200Ah is suitable for one HI; you will need two of these strings connected in parallel to make up a 48V 400Ah battery as a minimum.

I keep harping on about it but folk really don't appreciate the risks and harm that can arise from very powerful battery banks. The potential short circuit current of one string is 2000A and fromteo strings in parallel is 4000A - very, very dangerous - there will in an electrical explosion and personal harm if there is a short circuit. The cabling and batteries must be protected well and people kept away. During work on live 48V batteries and cables you should (in industry it is must) wear Class 2 arc and flash protection personal protective equipment (PPE)which includes gauntlets, head and eye protection and clothing. Suitable PPE can be bought from this company - money well spent if you are serious about safety and working with battery banks:

Electric Arc Flash Protection Clothing | Electricity Safety - https://www.thesafetysupplycompany.co.uk/c/4536001/1/electric-arc-flash-protection-clothing.html

I have a procedure approved by our electrical inspector for connecting up battery banks which I can pass to you PM or through the post.

As I said before the 230V ac side has not yet been designed and is not simply the schematic set-up shown in the manual. We have a rule in the forum that we don't do design but we do comment on designs. The reason is that whoever designs is responsible for it in law. You need to employ a French electrician to design the 230Vac side of the installation. So I have gone as far as I intend for the 230V ac side. And I have a personal rule that I don't do an electricians work.

 

[pierrecha]

Well, I admit to have missed that the HIs can indeed be connected in parallel and share the same battery but not the same arrays. You will need the paralleling inter connectors mentioned so the HIs work together.

5kW output from each HIs in battery mode requires a current at 48V of 5000/48 = 104A. So, 10kW from one shared battery is a current demand of 208A. The current carrying capacity of 35mm2 cable is 148A constant and 216A short term - say a few minutes. This means 2 His cannot share one pair of cables between them and the battery - you will need separate pairs for each HI to the battery bank and protected by their own circuit breaker. The advantage of separate cables is the voltage drop along them and heat loss in them are reduced.

You need to study the table on page 54 on recommended battery capacity and page 55 for back-up time. A string of four 12V 200Ah is suitable for one HI; you will need two of these strings connected in parallel to make up a 48V 400Ah battery as a minimum.

I keep harping on about it but folk really don't appreciate the risks and harm that can arise from very powerful battery banks. The potential short circuit current of one string is 2000A and fromteo strings in parallel is 4000A - very, very dangerous - there will in an electrical explosion and personal harm if there is a short circuit. The cabling and batteries must be protected well and people kept away. During work on live 48V batteries and cables you should (in industry it is must) wear Class 2 arc and flash protection personal protective equipment (PPE)which includes gauntlets, head and eye protection and clothing. Suitable PPE can be bought from this company - money well spent if you are serious about safety and working with battery banks:

Electric Arc Flash Protection Clothing | Electricity Safety - https://www.thesafetysupplycompany.co.uk/c/4536001/1/electric-arc-flash-protection-clothing.html

I have a procedure approved by our electrical inspector for connecting up battery banks which I can pass to you PM or through the post.

As I said before the 230V ac side has not yet been designed and is not simply the schematic set-up shown in the manual. We have a rule in the forum that we don't do design but we do comment on designs. The reason is that whoever designs is responsible for it in law. You need to employ a French electrician to design the 230Vac side of the installation. So I have gone as far as I intend for the 230V ac side. And I have a personal rule that I don't do an electricians work.

I appreciate all the advice that you give and would indeed appreciate seeing the procedure you have mentioned - I think by posting it here (rather than in PMs) that more people can benefit from your expertise (and reduce the probability of dangerous/unsafe installations).

The manual refers to a cable thickness of 38mm2 for the batteries but I have trouble finding such cable thickness online (perhaps this is for other countries? the U.S.?)- I see more cables with the 35mm2 you mentioned (which we see more in online shops here in France). I assume, since you put forward this figure, that it is fine to deviate slightly from the manual?

As for the 230V AC side, I appreciate your warning to not assume that the manual has the correct set-up displayed (indeed it seems that much of the manual applies [can apply?] to the U.S.).

Thank-you again for your continuing advice - and I'm sure that many others are learning a great many things too!

 

[marconi]

35mm2 is fine. Don't enclose them and keep the cables 10mm apart for an air gap and don't let the sun shine on them. All the battery-HI cables need to be exactly the same length. The cables need securing out of harms way to avoid damage using cable tray such as :

Galvanised Cable Tray 4 inch (3mts) Length - https://www.tlc-direct.co.uk/Products/CT4.html

with the cables paired to each HI and laid HI1 HI2 as +10mm - 15mm+10mm - so that their electromagnetic fields cancel.


I cannot find any reference to it in the manual other than page 54 which describes one of the interconnect cables as 'current sharing' - but you may find an option when you set up parallel operation using your computer - for the HIs to undertake ac output power sharing in which case your peak power of 8kW would be delivered by 4kW from each inverter - a battery current of 4000/48 = 83A to each HI in battery mode no PV. The current sharing may also apply to battery charging by the two HIs.

I strongly recommend you don't run the inverters at maximum output for long. In my off grid application the inverter is sized to be at least twice the power of the peak steady state load to allow for motor starting current surges and ensure voltage stability.

I use these warning label kits - Amazon Fr may do French versions:

View: https://www.amazon.co.uk/Solar-System-Warning-Label-Set/dp/B00PQJNQOM

 

[pierrecha]

35mm2 is fine. Don't enclose them and keep the cables 10mm apart for an air gap and don't let the sun shine on them. All the battery-HI cables need to be exactly the same length. The cables need securing out of harms way to avoid damage using cable tray such as :

Galvanised Cable Tray 4 inch (3mts) Length - https://www.tlc-direct.co.uk/Products/CT4.html

with the cables paired to each HI and laid HI1 HI2 as +10mm - 15mm+10mm - so that their electromagnetic fields cancel.


I cannot find any reference to it in the manual other than page 54 which describes one of the interconnect cables as 'current sharing' - but you may find an option when you set up parallel operation using your computer - for the HIs to undertake ac output power sharing in which case your peak power of 8kW would be delivered by 4kW from each inverter - a battery current of 4000/48 = 83A to each HI in battery mode no PV. The current sharing may also apply to battery charging by the two HIs.

I strongly recommend you don't run the inverters at maximum output for long. In my off grid application the inverter is sized to be at least twice the power of the peak steady state load to allow for motor starting current surges and ensure voltage stability.

I use these warning label kits - Amazon Fr may do French versions:

View: https://www.amazon.co.uk/Solar-System-Warning-Label-Set/dp/B00PQJNQOM

I have now ordered the (8) batteries and cables necessary for the battery part of the installation - I will update once they've arrived and been connected in case I still have any questions/just to keep you in the loop should you wish!

I have one last question for tonight: I had previously asked if using 16mm2 cable from the inverters to the panels had been a good choice - had I chosen 6mm2 cables, would this have been appropriate too?

Thank-you for your ongoing advice "sessions" - they are so greatly appreciated!

 

[marconi]

6mm2 single core cable has a volt drop of 7.3mV/Amp/metre at 30C ambient.

So 160m carrying 10A would cause a voltage drop between the array and the inverter of 7.3 x 10 x 160 = 11680mV or about 12V

The power wasted in the 6mm2 cable as heat is 12 x 10 = 120Watts. If the peak power output of the array is say 4kW (400 V at 10A) then the fraction of power wasted is 120/4000 = 3%

Over an 8hour day at peak output that is a waste of 8 x 0.12 = 0.96 or 1kWh from 32kWh PV energy

For 16mm2 the voltdrop is 2.8mV/A/m. This volt drop is 4.5V and power loss is 45W and 45/4000 = 1% Similar waste is 8 x 0.045 = 0.36kWh. from 32 kWh PV energy.

One kWh would run your 2kW water pump for 30 minutes.

On hot sunny days, if the cables are raised in temperature as might be expected in Provence, the power wasted will be greater but less so comparatively for 16mm2 than 6mm2.

A one off higher investment for a lifetime passive return which I reckon is worth it since fractions of kWh matter when not that many are generated each day. If you are interested look up Kelvin's Law for economic conductor size:

Economic choice of conductor size - Kelvin's law - https://www.electricaleasy.com/2016/05/economic-choice-of-conductor-size-kelvins-law.html