Equipment combination help

Hi, looking to pick some brains do I don’t mess the solar installation choices up. I’m concerned some installers are just offering what they can and not thinking about how efficient it is.

My daily usage is about 20-25kWh and we are looking to put 16-18 panels on a se facing roof.
I have been quoted - quotes are including panels.
1st quote
Solaredge hdwave 6000
Solaredge optimisers
Givenergy 9.5kWh battery

2nd
Enphase iq7 microinverter
Enphase s metered
Givenergy 9.5kWh battery
Givenergy 3kw ac coupled - do I need this?

3rd
GivEnergy Hybrid 5.0kw Inverter
Giv-Bat Hybrid 9.5kWh battery

Part of my concern is the swap from dc to ac as I’m not sure if it’s happening too much and don’t know what to pick to resolve it. I am also looking for a system that can work in the even if a power cut and batteries are easy to upgrade.

Thanks in advance
Mark

The 3rd option is closest to what I have, although with 2x5.2 batteries rather that the 9.5. I guess the advantage it that it is all one ecosystem and the hybrid inverter will take care of where to put the energy with minimal conversations. It will also provide an emergency backup power supply, if an isolation switch is added to the circuit you want backing up. It looks like battery charge/discharge power has been increase with the latest generation 2 inverters/batteries to 3.6kWs rather than the 2.6kW my gen 1 can do, which would be more helpful in emergencies.

Thanks for the reply,

I am thinking of now going for the following,
16 Trina Vertex Panels 395
Givenergy 5kw Inverter
Givenergy 9.5 kWh Battery

I am told we can have a max of 16 panels with this inverter but I would like to add some optimisers, what would you recommend apart from Tigo as my installers refuses to fit them.

Cheers

Just a thought....

16 panels at 395W is over 6kW, so on a good day (assuming your panels are all in good sunlight), your 5kW inverter would probably go into power limiting, so you would be wasting some power. And you may put extra stress on the inverter by doing this. If it were me I would go for a 6kW or 6.5kW inverter.

Optimisers are really only useful if some of the panels are likely to be in shade, while most of the others are not (you fit them on the shady ones). Yes they do provide a small increase in power from each panel, as well, by optimising the voltage/current, but I suspect the effect is quite minimal. I have Tigo optimisers but that is because both of my arrays have shading issues.

ToothyChris Thanks, but Givenergy don't do a 6 or 6.5 inverter, any suggestions?

Cheers

You only need optimisers if one/some of your solar panels can be shaded while the others are in full sunlight.

If no shading, no need for optimisers.

Personally, I prefer the AC coupled route (i.e. separate inverters for the panels and the batteries), and I was told that, because our batteries are in the garage with an undergound (AC) cable connectiing said garage to the main CU in the house, it was the only way to go anyway. Something about not putting DC cabling underground.
Anywho - it works fine and if the GE inverter has a dippy fit, the solar inverter in the attic continues to supply.

The 5kW Gen 1Hybrid officially does 6.5kW (albeit only 5 to AC and the remaining 1.5kW to charge the battery at the same time)

The 5kW Gen 1 Hybrid unofficially handles 7.6kW (5kW to AC & another 2.6kW to the battery as per Dan's (GE Technical director) feedback/

My 5kW Hybrid is probably the most abused on here has been chugging along fine with 6.1kW of PV and another 2.5kW of "Fake" PV injected into it (so I get to gloat about having 5kW of Battery discharge only when everyone's dual plant setups are all acting up)
This has been working constantly since December 2020 with 0 issues beyond me meddling with local control.

wilfleek Thanks, I am thinking the more panels now the better. So would it be better installing two Givenergy Hybrid 3.6 Get 2 and adding the extra panels, what benefit can this give me in the future or even now?

Cheers

mark8par
I have a Fronius Primo 5kW and I'm looking to get it switched for a Fronius Primo 6, but they are like rocking horse poo at the moment, because they are well respected.

Would probably be OK, although Givenergy software does not work well with multiple battery inverters apparently. They are working on the software so it is said.

Only you know your annual electricity comsumption and so could work out your ROI if you installed more panels, From our own experience, we put the maximum number of panels we could on teh roof (14x395W) and don't regret that. Just wish we had put a little more battery capacity in too, (we have 2 x 5.2s) although, TBH, that would only be of use to us if we were on something like Octopus "go", which we can't be as we don't have a BEV.

Have zero regrets about the installation in honesty, it is saving us a lot and the Octopus agile outgoing tariff makes a fair bit for us.

ToothyChris Problem is I want to be able to monitor from a less apps as possible and make it pretty seamless.

wilfleek our usage is about 7000 per year, what is your usage?

mark8par I am told we can have a max of 16 panels with this inverter ...

The max. number of panels is determined by the Voc of the panel. For a 5kw gen2 inverter the string voltage must be between 150V and 550V. There are 2 strings on the inverter.

The Trina Vertex 395W black has a Voc of 40.8V, so you can have a minimum of 4 panels and a maximum of 13 panels per string, so a total of up to 26 panels.

Rubikcube Bloody hell, so I can have my 18 or 20 panels and one inverter???
Thankyou Thankyou

Rubikcube Can you point me in the direction that states the inverter can have two strings please?

mark8par

https://www.givenergy.co.uk/products#givhy50G2 and download datasheet

mark8par Similar to yours - 7500kWh pa. (average over the past 5 full years)

On datasheet, 2 MPPT Trackers and 1 string per tracker means 2 strings.

Rubikcube would doing this reduce anything or would it work perfectly fine, I would have thought the installer would have known this rather than me having to find out.

Can't seem to find out what the max charge and discharge rate is on the Gen 2 9.5 battery, any ideas?
Cheers

Thanks for everyones help, its really appreciated.

I do have setup 2. 20 panels, 20 micro inverters, AC coupled and 2*8.2 battery.
Always have had Enphase systems and have worked well. The peak generation for me is 5300KWp due to split roof install.
Sometimes I wish I had gone with another manufacturer instead of AC coupled and battery - it is painfully slow to react and have had dodgy inverter failure

mark8par Different panels have different voltages (usually between 30V and 50V), different inverters have different voltages (usually between 400V and 600V). As long as the panels don't exceed the inverter capacity it will be fine. Installers find this difficult, so prefer a rule of thumb ... 8 always works.

9.5 battery has a technical capability of 80A / 4kW.
Gen 2 Hybrid tops out at 3.6kW so that'd be your max charge/discharge limit.

ispookie666 what would you have chosen knowing what you know now?

Thanks

Start with the panels. A large part of the cost is installation, eg scaffolding, rather than the cost of the panels themselves. Best advice is to go for as many panels as will physically fit on your roof - you can't have too many panels. Panels have a life of about 25 years. All panels degrade their output over the years, the best by 8-10% over 25 years, the worst by 30-50%. Consider this when sizing the panels.

Then select an inverter(s) that will handle the panels. Consider two inverters if a single large one would be more expensive. Don't be too quick to rule out optimisers even with no shading. On my installation, 19 panels into a SolarEdge 6kW inverter with optimisers and no shading, in the last month the 'worst' panel produced 41.57 kWh and the 'best' 46.98 kWh. So there is noticeable variation between panels, and I expect this to get worse as the panels age. Inverters have a life about half that of the panels, so expect to replace the PV inverter(s) in 10-15 years.

Lastly, look at battery systems. Bear in mind that the technology is developing quickly (same as electric cars), and that the life of batteries is 10 years (or less if you cycle them hard). Also, over 10 years the battery capacity will degrade to 60%-70% of its 'new' capacity. So you may end up replacing or adding extra batteries within 10 years. Whereas most PV panels will happily work with most PV inverters, batteries tend to be tied to the same manufacturer's inverters, which is an argument for having a separate AC-coupled battery inverter. Consider what wattage you may want/need from your batteries. If/when you change to electric air source heating (2030 approaches!) you are likely to want quite some power for them. You may want/need more than one battery inverter (with each inverter having its own battery(s)) to get the wattage you want - and that is easier with separate AC-coupled battery inverters. It is likely that electric cars' batteries will become used for 'house' storage within a few years (one or two can already), so house batteries as discrete items may disappear.

Lastly, many/ most solar/battery installers give the impression of being failed double-glazing salesmen, and try to sell you what THEY want to sell.

Baychattan Thanks for the reply, yes I am getting the feeling regarding the double glazing sales person lol

Having lived with our setup for a few years now and remain pretty happy with it, although I am not considering if we should add another battery and inverter mainly to increase winter off peak storage and max discharge to cover our heating needs.
While it might seem wasteful to have more potential output from the panels than the inverter can handle in the height of summer, this would likely be more power than you could use (obviously you can export for some cash), the key part of the year to consider is the winter. So maximising the number of panels will help you gather every bit of energy at a time of year when it is scarce.

Rubikcube I put this to the installer, who replied in a nice tone saying “I’m good at this I know what I’m doing, it’s 16 panels”

Probably gone with Victron or Huawei or Tesla. All these have their own issues but Victron would have been my first choice.

Your potential installer sounds very confident, yet is matching Trina Vertex 395W panels with a GivEnergy 5kW hybrid inverter.
Looking at the data sheets for each, the panels have a maximum power point current of 11.62 Amps at 1000 W/m2 solar irradiance, and the GivEnergy inverter has a maximum current per string of 11.0 Amps, so would be overloaded.
There may be a good reason for selecting these panels, potentially due to availability due to the huge demand at the moment.

By using an online PV information system (https://re.jrc.ec.europa.eu/pvg_tools/en/) and entering a roof slope of 30 or 35 degrees and azimuth of -45 degrees for SE direction, on any perfect solar day from April to August there will be a peak solar irradiance of close to or just above 1000 W/m2 for up to 2 hours per day between 10:00 and 12:00 BST.

Assuming absolutely no shading of any panel, with the sun high in the sky for these periods, the peak power output would be 16 x 395 W = 6320 W or 18 x 395 W = 7110 W. Given the solar panels are only around 20% efficient at converting the solar energy in to electricity, the remaining 80% is converted in to heat in the panels. The panels react to the heating effect by reducing the power output by 0.34% per degree C above 25.0 C. The panels may well operate at 45 C or more, which equates to at least 20 * -0.34% reduction = -6.8%. Apply this to the previously calculated figures, and you get 5890 W and 6626 W respectively.
Bear in mind that with an SE facing array your December output will be just 21% of your May/June/July output, hence the advice to max out the number of panels fitted to the limit of what the inverter can cope with in Summer, or even slightly over the limit as the inverter will automatically protect itself by moving the panel power points to non-optimum values.
Only you can know how much, if any shading will occur throughout each day across all the seasons of the year, to then determine if panel optimisers would be worthwhile or not.
My choice when designing my system (due to be installed this September) was not to have panel optimisers, as I do not have any significant shading during the peak generation periods, and would rather not have electronics units under the panels on the roof that typically only come with a 10 year warranty compared with 25 years for the panels. Any scaffolding costs for roof access to replace an optimiser would soon wipe out any small percentage gain in panel output with their use.

Simon_C matching Trina Vertex 395W panels with a GivEnergy 5kW hybrid inverter.

Agreed, not a great combination. I have Westech Perlight Delta 400W panels (Voc=49.5V, Im=9.76A) on my roof because I (and my installer) consider them a good match to the GE inverter.

Simon_C replace an optimiser

There is an Australian guy somewhere on youtube that describes replacing failed optimisers as a "good little earner".

mark8par

You may need more than 3 quotes. A good selection of failed double glazing salespeople can be found at https://mcscertified.com/find-an-installer/

The limit of 16 panels may also be due to the available physical space on the roof. There are MCS requirements regarding the minimum perimeter size of uncovered roof tiles to be used for safe access.
As @hoggy stated earlier, the GivEnergy 5kW hybrid allows up to 6500 W of panel output split across the 2 string inputs.

All panels also degrade as they age, and typically lose 2% in the first year, followed by 0.25% to 0.5% per year depending on the grade of panel.

If you want to push for 18 panels, and the roof space allows:-
The peak output calculation at the end of year 1 for 10:00 to 12:00 BST in June then becomes (((18 x 395) - 2%) - 6.8% temperature coefficient) = 6493 W.

Hi all, would one of you kind people have a look at this spec and give me your thought please?
18 x Longi 400w Black Panels
1 x Givenergy Gen 2 HY 5 Inverter
1 x 9.5kw Givenergy Battery (9.5kw)
1 x Eddie £500
RCD Protected Socket £150

I have mentioned about the off grid (island mode) but they are not so keen on doing it and say its quite a job. Company seems to have some great reviews so im a little lost what to do.

Cheers

In my mind the PV panels appear to be mismatched with the inverter again, in terms of the current at the maximum power point. Assuming this is the exact model being proposed with Impp of 12.87 A, and an inverter maximum of 11.0 A per string input.

https://midsummerwholesale.co.uk/buy/longi-solar/longi-lr5hib-400w

For the same power output from a panel of say 400 Watts, some manufacturers seem to favour lower voltage with higher current, and others the reverse.

As @Rubikcube stated earlier, there are other panels that can provide the 400 W or more but at a lower current.

I have chosen the REC Alpha Pure 410 W with Impp of 9.61 Amps, Vmpp = 42.7 V and Voc = 49.0 V.

Another possibility would be:-
https://midsummerwholesale.co.uk/buy/qcell-solar/qcells-410w-g10-ml
With Impp of 10.76 Amps, Vmpp = 38.11 V and Voc = 45.13 V, though they are physically a little larger, so check available roof space.

Thanks for checking that for me Simon, I have emailed the installer and asked if they can supply the qcell, they have them listed on the website.

Are you an installer btw?

Can you tell me how the difference in current will affect the system, will it make that much difference?

Qcell are not an option but would these be suitable Trina Vertex S 415W All Black Panel?

Thanks

mark8par , no I am not an installer, just did lots of research when choosing my own system to be installed, and my day job involves selecting compatible electrical components for building controls systems with boilers, chillers, fans along with associated sensors, energy metering and wiring.

What I have learnt about solar PV inverters, is that the PV inputs on them have automatic power point tracking capability which normally adjusts the resistive load seen by the panels in order to operate at them at the maximum power combination of voltage and current.
That is until the power is approaching the upper limit of the inverter input, at which point the power point tracking deliberately shifts to a non-optimal value in order to protect the inverter from overloading.
If the chosen panel is capable of outputting a higher current than the inverter will tolerate, then the inverter will present an non-optimal load in order to protect itself, hence the power output from the panel will be lower than the panel is capable of if matched with an inverter that can tolerate the higher current.
It is about matching each component from different manufacturers so that they are not restricting the performance of each other.

The Trina Vertex S 415W All Black Panel does appear to be a more suitable match for the GE 5kW hybrid inverter with Impp of 10.11 Amps.

Your installer will still need to validate for themselves, as it them who provide the initial system warranty.
There are many parameters that need to be checked for full compatibility, including the maximum open circuit voltage under the coldest conditions your household is likely to experience, which will potentially limit the maximum number of panels allowed on each string.

This guide might prove useful.

https://midsummerwholesale.co.uk/panel-characteristics-guide

Simon, thank you very much. You can sleep well tonight knowing you have been a star.

Mark