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Solar for Self Build Off grid as much as poss

Started by IanP, February 21, 2022, 06:51:11 PM

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First Off can I apologize if this has been raised before and if so please point me to the answer.
This is my first adventure into Solar power and whilst I have read a lot about it, I am still unsure if my thoughts are practical.

I am embarking on a self build in Scotland and want to utilize as much solar power as possible.
The plot is quite rural but does have access to single phase grid power.

Ideally, It would be fantastic to be fully off grid, but given that I will have a ASHP and at least one EV point on top of the normal power usage of a 4 bed home (and its in Scotland 😊 ) I appreciate that it would need a very, very large array and many, many batteries! (quite like the idea of server rack batteries but they appear to be still hard to buy in UK).

As the feedback tariff is quite small and would be limited to a max of 3.68kw, then I was wondering if there is a way to generate more, use it directly/via battery, with the added ability to charge the battery from the grid when there is no sun.

I did have one thought of having 2 (duplicated) consumer units, one fed from grid and the other fed from solar/battery and then having the circuits coming out of these into a third consumer unit filled with changeover switches (break before make).
This would then give you (albeit manually), the ability to decide what circuit is supplied by grid and what from solar by setting the changeover switches as appropriate.

This would than allow you to power, for example, all the lighting circuits and downstairs ring main from Solar with all others from the grid.

If you then found the battery was coping or draining too quickly, you could add or remove circuits as needed to then balance the load to use as much of the solar as possible.

This may sound a bit crazy and not 'Smart' but does it sound feasible? or am I missing something such as a smart inverter that can limit (or even stop) the export, whilst using as much power as I can generate/store, take additional power from the grid when needed, allow the battery to charge from the grid when solar output is insufficient AND provide backup when the grid goes down?

I have tried to contact a few companies to discuss options but they must be very busy at the moment as they either don't answer or try to arrange consultations in several weeks time!

The way I have tried to describe using change over switches, sounds a bit Heath Robinson and I can only feel that I'm not the first person wanting to generate more but limit the amount feed back to the grid so thinking that there must be hybrid charger/inverter's out there that would fit the bill.

I am still at the planning stage of the build, but want to understand the best way to have the system set up.
Sorry for being vague on power needed, but just looking for some general guidance and help from other a lot more experienced than me.
Any thoughts would be gratefully received.


Hi IanP I am 6 months into a solar build and still learning along the way!
the way i went was to identify the electrical equipment that was connected and used most or all of the time, in my mind it was pointless to build a system to incorporate the energy load of a toaster that burns 2 slices of bread once a day  ::)
What i will say is that  its much easier to build a system that will automatically provide mains charge voltage to the Backup Batteries if the voltage drops below the required battery voltage, this would mean you dont have or need to switch between mains or inverter mains, you only need to connect the circuits that are solar powered to one D.B. that is powered via solar/mains augmented battery charge (At Night on the EV Tariff) This is the route i am going on the next stage to reduce the day time cost if the sun is not out to play :-)
I am still doing the math but its a No Brainer in my mind as i can charge the Batteries over night "IF" they need it at 1/3rd the cost and use they energy the next day when its needed.
My system at the moment kicks in the chargers when the battery voltage drops on a dull day but even then the solar panels do add charge voltage too, its kinda a balance of all things :-) Using the EV tariff will let me chose to charge up the battery based on "IF" its gonna be a Dull Dark Day with just one press of a button based on next days weather forecast  ::)
Hopw this helps