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

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.

Parents
  • Former Community Member
    0 Former Community Member
    vantech:
    The idea would be to charge the battery on special night time rates (and lowered tariffs for EV charging) and then discharging during the day. The battery is grid tied, so during the day and up until the economy tariff begins, it will discharge with zero feed to the grid. 

    Does this actually make economic sense? If your battery costs say £5k, stored 10 kWh and lasts 2000 cycles, and was charged at £0.05/kWh overnight (somewhat guessed / made up numbers), the overall cost of a daytime kWh of electricity is £0.05+ (£5000 / (10*2000)) = £0.30. Sounds pretty expensive to me, how's it look with your actual figures?

Reply
  • Former Community Member
    0 Former Community Member
    vantech:
    The idea would be to charge the battery on special night time rates (and lowered tariffs for EV charging) and then discharging during the day. The battery is grid tied, so during the day and up until the economy tariff begins, it will discharge with zero feed to the grid. 

    Does this actually make economic sense? If your battery costs say £5k, stored 10 kWh and lasts 2000 cycles, and was charged at £0.05/kWh overnight (somewhat guessed / made up numbers), the overall cost of a daytime kWh of electricity is £0.05+ (£5000 / (10*2000)) = £0.30. Sounds pretty expensive to me, how's it look with your actual figures?

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