[UK] Help me achieve an Open Source home solar energy installation

[solartist]

@SeaGal, thanks so much for the helpful reply!

Quite a few of us are using Solis Hybrid inverters in the UK - they can be used without cloud / apps. They have UK approvals, so could be worth you looking into.

Great tip - will check them out!

Have you calculated how many panels can be fitted [on the house roof]? An East-West configuration is working well for us. But with a narrow house and your wish list for heat pumps and EVs, my concern would be generating enough power.

Roughly 10m2 of solar panels on the front slope, same on the rear, so ~20m2 total.

Will depend upon panel dimensions, and upon whether we stick with the plan for Velux windows/skylights/rooflights and if so what size we choose.

My intention is to see which longlife panels are available at a good (W/£)/year price point closer to the time, and probably choose rooflights of a shape/size to fit between the panels, allowing as much of the roof as possible to be solar-panelled.

In-roof solar is our preference, as some of the slates are nearing end-of-life anyway. So, it makes sense to save the good slates and use them around the edges of the in-roof mounts (and the rooflights, if fitted). But this would limit us to panels that fit the BBA-certified in-roof mounts available commercially (GSE; Edilians; maybe others?).

I assume you have done some calculations as you have already mentioned installing panels on the top of your house, the side of your house, the outbuilding, the fence, hanging some from your trees and tying some flexible panels to your cat....

Yes, the panels on the house roof definitely won't cover our consumption, so we've got to find other places to mount panels, ideally within Permitted Development rules - I don't want the hassle of a planning application if I can avoid it.

May not be a show-stopper if you deploy Tigo optimisers. ...

micro inverters worked out more expensive than string inverter.. It also required having internet access and giving all your data away for someone else to monetise.

Thanks, and I agree. Optimisers feeding into an AIO or string inverter is probably the best approach for me.

Do you know if Tigo optimisers can be used with GSE/Edilians/other in-roof mounts?

As mentioned above 1kW sounds too much. Base load here of 2 servers, 2 fridges, freezers, multiple wifi, routers, network switches, NAS boxes etc is only around 400W.
If the laundry includes tumble-dryer, that a big consumer of kWh.
I'd recommend that you invest in the monitoring equipment ASAP (we use emonPi) to get a real-life measurement of peak and daily usage - to help your planning.

Our tumble dryer is A++ energy rated, but yes, it gets lots of use.

Some of the computer/networking equipment is in storage pending the renovation. Much of it is older equipment that I like but that isn't as energy-efficient as newer equipment. Still, given that you and dmsims both flagged up that load as being excessive, I'll aim to check my records to see if what I posted above as average load is in fact peak load. GPU is the main culprit, IIRC. Anyhow, I'd rather have headroom than overload the inverter.

Good idea about installing power monitoring sooner rather than later. While most of the loads will be different post-renovation, some of them won't be and at least it will let me ballpark those and get used to the monitoring hardware and software. Thanks!

Hybrid refers to the inverter supporting battery. The essential loads can be supplied from an AC-backup (Solis terminology) output, but will require their own circuits from your CU (just noticed you already thought of that).

Thanks so much for confirming this!

Batteries should be capable of being safely charged at 0.5C irrespective of ambient temperatures, even if this means adding heating/cooling/insulation to keep them at ~25°C or whatever is optimal for their chemistry. (Ambient temperatures fluctuate from about -10°C in winter to almost 40°C in summer.) ... even if that means e.g.: ... DIY such as assembling batteries using prismatic LiFePO4 cells from Fogstar/similar.

Been there, done those

Please tell me more! Which cells/heaters/BMS/etc did you use? Did your electrician or solar installer make you jump through any hoops in relation to connecting them to your inverter?

 

[SolarRich]

Are you looking for all equipment to use open source software? I don't think this exists for any inverters. As far as I know the SolarAssistant software is closed and not open source. Yes it runs on Linux but the SA software code is not available for you to inspect as far as I know.

 

[solartist]

Are you looking for all equipment to use open source software? I don't think this exists for any inverters.

I'm looking for what I outlined in my first post:

Desiderata:

• Once commissioned, can be controlled & monitored using free as in freedom (aka Open Source, aka FOSS) software only.
  • OK: emonPi, iotaWatt, Home Assistant, and similar control/monitoring systems; physical control panels on the wall (if not "cloud"-connected).
  • NOT OK: proprietary smartphone or cloud apps.

Regardless what's running inside the solar hardware (where "solar hardware" means inverter, charge controller, etc; and "what's running inside" that hardware means its firmware if it has any), if controlling or monitoring that hardware will require me to use software - a smartphone app, a PC app, or a server-side ("cloud") app accessed through a web browser - then that software must be:

• FOSS, and
• running on hardware I control.

As far as I know the SolarAssistant software is closed and not open source. Yes it runs on Linux but the SA software code is not available for you to inspect as far as I know.

Thank you for corroborating the conclusion that I drew earlier in this thread (here and here). I agree: SolarAssistant is proprietary software (closed-source, not FOSS). It does not meet my needs and should be avoided.

Thanks for your interest.

 

[solartist]

Quite a few of us are using Solis Hybrid inverters in the UK - they can be used without cloud / apps. They have UK approvals, so could be worth you looking into.

Great tip - will check them out!

I've now checked them out!

AFAICT, the only Solis series that are single-phase, and are capable of being paralleled in order to provide adequate power, are:

• S5-EO1P(4-5)K-48 series
• S6-EH1P(3-6)K-L-EU series

The S5-EO1P(4-5)K-48 series doesn't seem to allow feeding/selling excess power to the grid, so doesn't meet my desideratum "excess daytime solar (if any) can go to grid instead of being wasted". That leaves the S6-EH1P(3-6)K-L-EU series. But I'm struggling to understand from the manual how the S6-EH1P(3-6)K-L-EU series meets the following desiderata:

• Automatic anti-islanding, so essential loads are seamlessly switched to solar and/or battery power if grid goes down (power outage).
• Automatic recovery from anti-islanding when grid comes back up.

Have I understood this correctly? Is this the S6-EH1P(3-6)K-L-EU series the series you had in mind to meet my desiderata? Thanks!

UPDATE: it seems the S6-EH1P(3-6)K-L-EU series doesn't support parallel operation after all

 

[peufeu]

IS6-EH1P(3-6)K-L-EU series. But I'm struggling to understand from the manual how the S6-EH1P(3-6)K-L-EU series meets the following desiderata:

• Automatic anti-islanding, so essential loads are seamlessly switched to solar and/or battery power if grid goes down (power outage).
• Automatic recovery from anti-islanding when grid comes back up.

I have the S5 version and it does this.

Note anti-islanding is mandatory and it means the inverter disconnects from the grid in case of blackout. "Anti-islanding" does not mean anything about backup loads.
The inverter outputs power on the backup port (if you enable it) which you can use for your essential loads.

Regarding open source friendliness, I think DEYE may be a little bit more open.

 

[solartist]

I'm struggling to understand from the manual how the S6-EH1P(3-6)K-L-EU series meets the following desiderata:

• Automatic anti-islanding, so essential loads are seamlessly switched to solar and/or battery power if grid goes down (power outage).
• Automatic recovery from anti-islanding when grid comes back up.

I have the S5 version and it does this. ... The inverter outputs power on the backup port (if you enable it) which you can use for your essential loads.

Thanks. I guess yours is from the S5-EH1P(3-6)K-L series?

Looking at the manual for that series, side-by-side with the manual how the S6-EH1P(3-6)K-L-EU series, was illuminating:

• The S5-EH1P(3-6)K-L series won't suit my needs because it can't supply enough power, and doesn't support parallel operation to increase total power output.
• The S6-EH1P(3-6)K-L-EU series also might not suit me, for the above reason! This Solis blog post says "S6-EH1P(3-6)K-L supports up to 10 units in parallel on Grid and Backup", so I initially thought this series could suit me. But now I see that the manual says "The S6-EH1P-L Series does not support parallel (three- and single-phase) operation on the AC-BACKUP port. Connecting multiple units in parallel will void the warranty."
  I guess I should trust the manual over the blog post? (And maybe I shouldn't trust a product whose manufacturer's blog posts contradict their manuals!)
  Worse still, the S6-EH1P(3-6)K-L series lacks physical controls! No screen/buttons/keypad! Eek! So, even if users find another way to control/monitor it (e.g. via RS-485), they are then dependent upon that (or the crappy proprietary app) - no last resort of using the inverter's own LCD display if the remote control/monitoring fails.

So, it seems Solis doesn't make anything that will meet my needs after all

Note anti-islanding is mandatory and it means the inverter disconnects from the grid in case of blackout. "Anti-islanding" does not mean anything about backup loads.

Thank you, yes. I have now amended that part of my original post:

• Automatic UPS functionality, so essential loads are seamlessly switched to solar and/or battery power if grid goes down (power outage). (Is "hybrid" the term for this?)
• Automatic anti-islanding: disconnects from the grid if grid goes down (power outage).
• Automatic recovery from anti-islanding when grid comes back up. (Is "automatic reclosing" the term for this?)

Is that correct, and clearer?

Regarding open source friendliness, I think DEYE may be a little bit more open.

Thanks for the Deye modbus spec PDF. I understand from here that Sunsynk are rebadged Deye. I'm still researching Sunsynk/Deye and will update the thread when I have progress on that.

 

[peufeu]

> Automatic UPS functionality, so essential loads are seamlessly switched to solar and/or battery power if grid goes down (power outage). (Is "hybrid" the term for this?)

"Hybrid" just means a grid-tied inverter with PV input, a battery, and a backup output. Being a grid-tied inverter it is capable of exporting power to the grid both from PV and battery in order to cancel power used by your house and cut your bills. With an hybrid you wire only the critical loads on the backup output and the rest of the house is still connected to the grid. Well it's possible to wire the whole house to the backup output but then in a blackout all the useless stuff in your house will suck your battery dry pretty fast.

Now most hybrid will do "UPS" but you need to be careful about the "U" lol. For example Solis switches from grid to battery in about the time it takes for the relay to click, so a couple milliseconds, that's "Uninterrupted". However Fronius Gen24 will shut down for a minute then reboot before activating backup mode, so it's definitely not "Uninterrupted". Whatever inverter you buy, make sure to check. Personally I don't think it's important, since I just put the freezer on the backup output, I don't care if it's unpowered for a minute.

> The S5-EH1P(3-6)K-L series won't suit my needs because it can't supply enough power, and doesn't support parallel operation to increase total power output.

Pretty much all grid tied inverters can be paralleled on the grid port, they'll just export to the grid. Whether you have two inverters in your house, or one in your house and one in the neighbor's, they're in parallel on the same grid. It makes no difference

Backup output on Solis cannot be paralelled. This is only a problem if you need more than 4-5kW backup, which you don't.

If you need more power than one inverter can provide, you can use a larger hybrid, or a hybrid AC coupled with a normal grid-tied, but there are subtleties (ie, the grid-tied one will not work in a blackout, unless it's designed to).

However if you want to do export control and zero export, and you have two inverters, then they need to talk to each other and coordinate, and you have to check if this is doable, if this is built-in, or how much the add-on to do it costs. Solis S5 does not offer this feature.

> I guess I should trust the manual over the blog post?

Send an email to the manufacturer

> Worse still, the S6-EH1P(3-6)K-L series lacks physical controls!

Yeah that's a big no-no

 

[solartist]

> Automatic UPS functionality, so essential loads are seamlessly switched to solar and/or battery power if grid goes down (power outage). (Is "hybrid" the term for this?)

"Hybrid" just means a grid-tied inverter with PV input, a battery, and a backup output.

Thanks, this is similar to what SeaGal said:

Hybrid refers to the inverter supporting battery. The essential loads can be supplied from an AC-backup (Solis terminology) output, but will require their own circuits from your CU (just noticed you already thought of that).

I'm sorry that it took me a while to understand this.

> Being a grid-tied inverter it is capable of exporting power to the grid both from PV and battery in order to cancel power used by your house and cut your bills. With an hybrid you wire only the critical loads on the backup output and the rest of the house is still connected to the grid. Well it's possible to wire the whole house to the backup output but then in a blackout all the useless stuff in your house will suck your battery dry pretty fast.

Thanks, yes, this makes sense.

Now most hybrid will do "UPS" but you need to be careful about the "U" lol. For example Solis switches from grid to battery in about the time it takes for the relay to click, so a couple milliseconds, that's "Uninterrupted". However Fronius Gen24 will shut down for a minute then reboot before activating backup mode, so it's definitely not "Uninterrupted". Whatever inverter you buy, make sure to check.

Thanks for drawing my attention to this. Since I want servers & networking equipment to stay online during a power outage, I would either need a hybrid that switches the backup circuit in within milliseconds, or would have to maintain a small dedicated UPS for the server rack to cover the delay while the inverter reboots.

> The S5-EH1P(3-6)K-L series won't suit my needs because it can't supply enough power, and doesn't support parallel operation to increase total power output.

Pretty much all grid tied inverters can be paralleled on the grid port, they'll just export to the grid. Whether you have two inverters in your house, or one in your house and one in the neighbor's, they're in parallel on the same grid. It makes no difference

Backup output on Solis cannot be paralelled. This is only a problem if you need more than 4-5kW backup, which you don't.

Ah, thank you for this helpful distinction!

If you need more power than one inverter can provide, you can use a larger hybrid, or a hybrid AC coupled with a normal grid-tied, but there are subtleties (ie, the grid-tied one will not work in a blackout, unless it's designed to).

However if you want to do export control and zero export, and you have two inverters, then they need to talk to each other and coordinate, and you have to check if this is doable, if this is built-in, or how much the add-on to do it costs. Solis S5 does not offer this feature.

OK, I'll give this some thought.

Thank you again for the helpful advice!

 

[houseofancients]

I have the S5 version and it does this.

Note anti-islanding is mandatory and it means the inverter disconnects from the grid in case of blackout. "Anti-islanding" does not mean anything about backup loads.
The inverter outputs power on the backup port (if you enable it) which you can use for your essential loads.

Regarding open source friendliness, I think DEYE may be a little bit more open.

Deye = sunsynk = sol-ark

 

[SeaGal]

Please tell me more! Which cells/heaters/BMS/etc did you use? Did your electrician or solar installer make you jump through any hoops in relation to connecting them to your inverter?

EVE 280K from Fogstar & Overkill BMS. DIY ESP32/Arduino based system for BMS to Solis and emonPi comms, temp monitoring and heater control. I was the electrician, programmer and solar installer ?‍??‍?‍?