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dnshorto
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October 20, 2021

What's the best Home Energy Storage option for retaining domestic stored solar power in preparation for power cuts?

  • October 20, 2021
  • 89 replies
  • 3518 views

Due to inept official planning and misguided political priorities there seems to be a consensus that power cuts are more likely than usual this coming winter. In fact. preparation for power cuts was a strong motivation to me for installing extra storage batteries to keep systems operating during outages.

However, I am looking for some help in how best to achieve this.

I live in Cheshire in the NW and have 28 JASolar PVMono 345 south-facing panels, nominal output 9.5kW.

4 Pylontech 3.5kWh batteries = nominally 14kWh capacity.

Pre-solar my domestic load averaged around 10 kWh per 24 hours and is still similar.

I don’t fully understand the relationship or the interface between the AC grid and my installation as it was all put in by a professional team.

The main inverter is Solis 5G Single Phase.

Batteries are controlled by Growatt SPA3000TL BL (AC Coupled inverter)

(BTW, does anyone really know what SPA means in this context? There are vague possibilities among the over 200 meanings listed in “thefreedictionary.com”: Switching Power Amplifier, or Serial Port Adaptor, or Solar Panel Assembly, and several more.)

On any reasonably bright day between April and September and especially with some sunshine my batteries become fully charged, the HW cistern is heated and the grid receives all my excess. The smart meter doesn’t move from one day to the next and I’m basically using solar for everything, which is gratifying.

As the community will be aware, October to March can be rather different. Much less solar input so that a lot of my power is drawn from the grid and the batteries are down to less than 10% capacity each morning.

They do sometimes fill right up after a few hours of winter sunshine, but are used up quickly once the day darkens.

I would like to explore 2 possibilities in preparation for if power cuts start happening:

  1. Some way to manually isolate the batteries once they are filled so as to preserve the stored energy to be available when the lights go out.
  2. When there is very little daylight and not much chance of charging the batteries from the panels, some way to manually charge them from the grid while it is live and then reconnect then during the next power cut.

Does anyone have experience of this, or do you think it could be done?

Thanks, David 101

    89 replies

    Blastoise186
    Super User
    Blastoise186Super User
    Super User
    October 20, 2021

    Howdy @dnshorto !

    This is definitely something that a few forum volunteers know about. I’m not one of them myself, but no doubt they’ll stop by soon.

    In the meantime, do you have the wiring diagram and a list of all components in your system handy by any chance? It’ll almost certainly prove quite useful if you’re OK with sharing that.

    Thanks!

    Securing energy by zapping security bugs... For that is The Blastoise Way! Remember, I'm just like you - AI Powered Evil Geniuses aren't Staff!
      D
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      dnshortoAuthor
      Rank 4
      October 20, 2021

      Thanks @blastoise186

      Good idea. I will attached the schematic which was prepared recently by the actual Oct 2020 installers, (not the deceptive Sales company who claimed the installers were their own team), plus some photos. I’m not sure all the isolating switches shown on the schematic are there in reality. 

       

       

       

      David101

      DShorto
        nealmurphy
        Newcomer
        nealmurphy
        Newcomer
        October 20, 2021

        Not an expert either, but it’s something I’ve been interested in. The battery back-up was the main reason I’d consider the Tesla Powerwall.

        It looks like Victron offer an inverter with a grid disconnection relay. Some info from Joju Solar:

        https://www.jojusolar.co.uk/batteries-smart-grids/using-home-battery-power-cut/

        The main issue will be meeting the strict safety rules to make sure you don’t fry anyone working on the network during the power cut!

          Blastoise186
          Super User
          Blastoise186Super User
          Super User
          October 20, 2021

          Mind you, I’d heard the backlight on the Landis+Gyr E470 was horrible, but I never thought it’d be so terrible that you need to supplement it with a lamp to see the display! XD

          That’s a pretty nice looking Geo Trio II IHD you’ve got there mind you.

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          dnshortoAuthor
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          October 20, 2021

          Thanks nealmurphy

          That is a very useful link, as I find that juju solar have some other highly relevant articles.

          David101

          DShorto
          Blastoise186
          Super User
          Blastoise186Super User
          Super User
          October 21, 2021

          Hey @Transparent @PeterR1947 , I’ve got a present for you two! It’s your favourite solar inverter style too! XD

          Securing energy by zapping security bugs... For that is The Blastoise Way! Remember, I'm just like you - AI Powered Evil Geniuses aren't Staff!
            Transparent
            Rank 20
            Transparent
            Rank 20
            October 21, 2021

            As it so happens, I’ve just started trying to decipher the workings of a similar installation owned by a Forum Member in Scotland.

            If you look at the photos of the kit and the schematic diagrams which we’ve been exchanging, it seems that his Solis inverter differs from yours @dnshorto. But we may need to clarify this.

            As I currently understand his set-up, his 4x Pylontech batteries are directly connected to a Solis RHI-3.6k-48ES Inverter.

            Moreover the specification for that inverter series, which I’ve obtained from the Chinese manufacturer, shows that it has a mains (240v?) output for devices that must be kept live in the event of a power-cut.

            I don’t yet know if that feature is present on the models available for sale in the UK, nor how they could pass the G98/G99 certification for grid-connection. A key feature of those standards is that there must be no possibility of power being sent back onto the house supply when there is an outage on the Distribution Grid.

            A UK manufacturer of Storage Batteries, PowerVault, also used to have an auxiliary mains-out connection of their hardware. But this was removed a couple of years ago in order to better comply with the UK safety requirements.

            Save energy... recycle electrons!
              Transparent
              Rank 20
              Transparent
              Rank 20
              October 21, 2021

              @dnshorto - you might also want to look at the suggestion I made on the topic about Heat Pump Installation in order to avoid using electricity during the evening period of peak demand.

              Rather than store the energy as heat, which would require a massive tank, I proposed a grid-connected battery feeding an off-grid inverter.

              You might think that this somewhat pushes the subject of safety. However, that off-grid inverter could not be grid-connected because it has no inbuilt facility for synchronisation to the 50Hz grid frequency. It can only work when its output is regulated by its internal clock.

              If grid-connection were attempted, then the clash of the two 50Hz frequencies would blow the output fuses on the inverter. However powerful your inverter is, it’s no match for your nearest commercial power-station!  :thinking:

              This goes some way towards answering the other part of the original question you posted above about having power during an outage.

              Save energy... recycle electrons!
                PeterR1947
                Newcomer
                PeterR1947
                Newcomer
                October 21, 2021

                Having survived the power cuts of 1976, as the only house with a gas fire in the family, the house was kept warm by the gas far and family body heat; candles or torches provided the light and we enjoyed family time together, much easier to arrange than all these teccy solutions!

                Old timer Peter

                PeterR
                  Jess_OVO
                  OVO Staff
                  Jess_OVO
                  OVO Staff
                  October 22, 2021

                  Very much intrigued by this discussion, @dnshorto.

                   

                  As I’m by no-means the expert in Home Energy Storage I’m happy to be learning too!

                   

                   

                  I don’t yet know if that feature is present on the models available for sale in the UK, nor how they could pass the G98/G99 certification for grid-connection. A key feature of those standards is that there must be no possibility of power being sent back onto the house supply when there is an outage on the Distribution Grid.

                   

                  I’m confused by this point, @Transparent - so would this mean any grid-connected battery can’t be used to supply your house in case of a power cut?

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