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Domestic Battery Storage - G83/G98 - Earthing Arrangements + More

vantech
Hi,


I am looking to add a battery storage system to my own home (I am an NICEIC registered contractor, just to make it clear this is a project for myself). This will be a battery only solution, and will not feature any solar arrangements. 


If there are any experts here that can advise on a few questions, that would be superb. 

 
  • GN98 (formally GN83) allows systems up to 16A per phase to be connected without the need for any sort of site inspection before the install (so the solution is notified after). I plan on doing this myself, and I am not part of a microgeneration scheme, but assume self certification is ok, following Part P requirements and issuing the relevant certs to the NIC. 


 

  • The battery I plan on using is the Alpha ESS (combined battery and inverter), which is grid tied with separate backup output(s) for things like lighting circuits and small power circuits. I have a smart meter, however I do not have a feed-in tariff, therefore by means of a CT connected to the battery I plan to set the feed-in to zero using the inverters user interface, so that the battery just delivers power to loads as and when its required. My question here however leads me onto earthing - when running in backup mode, the inverter automatically disconnects the grid and provides power on its dedicated backup connection - what do I do with the Earthing? I am on a TN-C-S supply from the DNO - I would assume an earth rod is required, connected into the MET (as the DNO earthing cannot be relied upon during an outage) which would be combined the DNO earthing (so a rod in the ground connected to the MET and bonded onto the battery inverter). Assuming this is correct, does the inverter need to tie its backup output neutral and earth conductors together, forming its own TN system (it could even be doing this internally I'm not sure and need to check). 


 

  • Anything else I may be missing?



Thanks.

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  • 0
    RichardCS2:

    vantech:



    The product is a combined inverter, battery and additional add-on batteries, which all come with a 10 year warranty, so this isn't a concern. The solution will pay for itself over a 10 year period - this is more of a nice to have rather than something to save money on - the lower economy rates are of course essential in ensuring the system pays for itself. 

     

    Fair enough. Is there no cycle or throughput limit in the warranty on the unit you are considering? The Tesla Powerwall for example it limited to 37.8 MWh total which you would reach in just under 7 years. https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_europe_1-5_english.pdf


    Your numbers look better than I had expected anyway.

     


    Yeah I have taken that into consideration, this is based on full use every day, and this simply won’t be the case with work, travelling etc - days when washers/dryers aren’t used, summer months etc. 


    The Tesla product is 37.8MWh over 10 years, this is 3780kWh a year, with our use sitting at around 5500kWh per annum - so we are just over (assuming we use the battery for all of our requirements). Another factor actually is that the inverter is limited to 16A, so for peak power demand like induction hobs, ovens and whatever else is running at the same time, the load is split between the battery and the grid, so this will reduce the overall battery use over its lifecycle - it could break even (give or take). 


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  • 0
    RichardCS2:

    vantech:



    The product is a combined inverter, battery and additional add-on batteries, which all come with a 10 year warranty, so this isn't a concern. The solution will pay for itself over a 10 year period - this is more of a nice to have rather than something to save money on - the lower economy rates are of course essential in ensuring the system pays for itself. 

     

    Fair enough. Is there no cycle or throughput limit in the warranty on the unit you are considering? The Tesla Powerwall for example it limited to 37.8 MWh total which you would reach in just under 7 years. https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_europe_1-5_english.pdf


    Your numbers look better than I had expected anyway.

     


    Yeah I have taken that into consideration, this is based on full use every day, and this simply won’t be the case with work, travelling etc - days when washers/dryers aren’t used, summer months etc. 


    The Tesla product is 37.8MWh over 10 years, this is 3780kWh a year, with our use sitting at around 5500kWh per annum - so we are just over (assuming we use the battery for all of our requirements). Another factor actually is that the inverter is limited to 16A, so for peak power demand like induction hobs, ovens and whatever else is running at the same time, the load is split between the battery and the grid, so this will reduce the overall battery use over its lifecycle - it could break even (give or take). 


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