DIY home battery storage with an EE degree? Where to find electricians with correct qualfication?

Hmm, No regulation stops you opening your own CU. But certain types of wiring and a new circuit is one is notifiable to the local council under building regs.  In principle they can inspect, but in reality they prefer you to employ someone belonging to an organisation that allows self notification. When comparing electricians quotes, also perhaps call the council and see what they would charge to inspect if you did it yourself, but be prepared for a level set high enough to discourage.

Mike

I am not aware of any regulation that prohibits opening the consumer unit. It is however foolhardy if not experienced in such work. It IS forbidden to open or interfere with the supply companies fuse, electricity meter, or the connections thereto.

If you simply require back up power in case of failures, then this is simple, just purchase a ready made UPS unit, with extended run time battery. The smaller ones simply plug in like any other appliance.

If you require a standard grid tied solar energy system, then many companies sell and install these. They do not normally incorporate back up power, this may be supplied via UPS as above.

If you want to charge batteries from solar energy, and then use this stored energy instead of or as well as grid power then this is a lot more complex and should be done by a renewable energy specialist who is familiar  with UK regulations.

The inverter you show is one of these (click for manual) that uses the direction of current into or out of the grid with the current transformer to decide if the solar panels are exporting and to charge the batteries, or if there is power coming form the grid, to run the batteries down. The wiring of the mains side is straightforward, and any electrician should be able to do that in a regs compliant way to a breaker or RCBO in the consumer unit.

For the UK the inverter will need to self shut down in the event of a total failure of the external grid, and the instructions capture that, however grey imports  may not be set up for that - some places are less worried about houses exporting power onto a dead street main that may be being worked on. Setting that up and verifying it is working requires a bot of thought, not difficult, but perhaps not something the run of the mill sparks will be familiar with.

If you anticipate this being a bit of an experiment and do not have one already consider arranging an isolator between meter and consumer unit rather than calling someone out to pull the company fuse or workgin semi-live each time the CU configuration  needs to be changed.

Also some types of grid tied generation are notifiable to the DNO, as they like to know about things with potential to reverse the voltage drop slope along the street, and this may well fall into that category.

Mike

There should definitely be isolators between both of the inverters and your mains supply.  Otherwise you are relying on a bit of software for safe isolation when you disconnect the supply to the home for maintenance.

Connecting a system like this DOES have some legal requirements over and above Part P of the Building Regulations - see Sections 21 and 22 of the Electricity Safety, Quality and Continuity Regulations.

The legislation effectively requires:

• DNO notification - probably in this case, with the schematic shown, using the G99 process with notification required prior to work commencing
• The whole installation to comply with BS 7671. The schematic shown in the OP does not appear to comply with BS 7671 requirements as there is no means of earthing for the "backup" - to achieve this would also require isolation and N-E connection switching. The only option would be for "floating" output, but this is not recommended for supply to fixed wiring circuits as discussed in the IET Code of Practice for Electrical Energy Storage Systems.

There are other things to consider:

• Location and temperature control of batteries
• Ventilation, that is, fresh air for air refresh (if required dependent on battery chemistry or battery manufacturer's requirements)
• Whether fire detection is required where power conversion equipment or batteries are installed, see BS 5839-6.
• Housings and location of battery to cover fire safety in the events of faults etc.
• CDM Regulations Designer's Duties which require consideration that the system must be safe to maintain - others have already mentioned safe isolation).

Might also be worth considering the insurance side if something were to go wrong.