Newbie hybrid no feedback advice

[Subjated]

Hi all , I’m new here in the Uk and would be grateful for any advice as there is still a lot I don’t understand so though this would be a great place to ask!

I’d like to do a diy install of a roughly 4kw system on my summer house/ garage roof as I can more easily face the panels south. I’m pretty ok with electrics when it’s ac but dc systems are relatively new to me! My question is that I understand the idea of an off grid and on grid system, but I want to do a combination of both where I can store power in batteries when I’m over producing but never send excess power back to the grid. I understand a stand alone system but how do I connect this back to the house fuse board without sending any excess power down the grid? So its a kind of solar to ac priority then storage and If both “full” then energy to waste if that makes sense and I use the batteries at night or grid power if they are empty.

I am not sure how to connect up a system like this or what’s the best components to invest in to achieve this as there are so many out there. If anyone can offer me any advice/diagrams/parts list or point me in the right direction of research is really appreciate it as I have spent hours and can find much of this.

Many thanks in advance!

 

[svetz]

Welcome to the forums!

The good news is you have lots of options! Before delving into that, you might want check on net-metering in your local area as wikipedia suggests that the UK is running some pilot projects. A zero-export solution might be best for you, because in 5 years, even though it's not an option now, you might be able to get net-metering and turn off the zero-export to make more from any excess power.

... where I can store power in batteries when I’m over producing but never send excess power back to the grid....

Option 1 - Off grid inverter
Use an off-grid inverter with an ATS that will cut-over to the grid when the batteries are exhausted. The batteries will be recharged by the MPPT.
The downside to this is some devices (e.g., Air conditioning) have enormous startup power costs requiring a bigger (more expensive) inverter.

Option 2 - Hybrid inverter
Hybrid inverters have both grid-tied and off-grid behavior. Most can be set to "zero-export". Most of these are only designed to power critical-circuits, but some like Victron's can merge solar power with grid to provide startup power when needed.

Option 3 - Enphase MicroInverters / Ensemble
This puts AC on your roof instead of high voltage DC. The system can be set for zero export.
Microinverters are really advantageous in a myriad of ways (especially if you think you might want to grow the system later). The downside is the battery costs are about 3x DIY battery costs. Adding "AC batteries" from different vendors is tricky in general. Although, there might be a way around this now for Enphase (haven't tried it yet though).

Option 4 - Tesla Solar & Powerwall
Not sure this is available in the UK, but the online prices for an installed system here are about $2.10/w (DIY is about $1.20/W and other installed is $3-$3.50/w). They use the inverter of your choice, so there are options for zero export.

TOU Thoughts
Ideally, with any of these, if you have time-of-use (TOU) rate plan, you can use the batteries when the costs are highest. You might also want to check out GXMnow's thread. He started with Enphase, then rather than use Ensemble added a hybrid inverter (Schneider XW-Pro) and battery (with more panels) to get around his TOU costs.

DIY Thoughts
Check out upnorthandpersonal's thread, he built a 10kW solar system with 28kWh LiFePO4 battery, inverter, BMS and charge controllers in Finland for under $12k U.S. dollars.

Hope that's of some help! Best of luck!

 

[Steve_S]

Welcome to the Forum, Svetz gave you a really good rundown on options. Well Done !
I know the Feed-In-Tariff system over there is just as quirky as ours (I'm Canadian), can't blame you for wanting to avoid that bodged up pile of.... "muck" lol.

An option to consider IF possible and as you say, you are AC literate so it's not a biggy. One option is to run a separate Circuit Panel for all "offgrid" circuits you want to remain live if/when grid fails. Fridge, Freezer, Heating of some kind, AC in Summer if really needed and of course a few Light Circuits to keep you "in the light".

There is a Huge Variety of equipment out there to suit just about any conceivable configuration you can imagine. Many can be used in the manner which you would like. The most common flavouring without FIT is to have a programmable system that will draw Grid Power ONLY to charge batteries when low from a standard wall plug input. No switching or any nonsense required, as these units have built-in ATS (Auto-Transfer-Switches) which can turn on/off the input as required. These CANNOT push out to grid so there is no issue with that.

I would make a suggestion for you to seriously consider...
Any system, be it an AIO (All-In-One) or Component Build (Separate Inverter/Charger, Solar Charge Controller etc), you want to be able to charge the batteries From Grid if you do not get enough solar OR from a Genset in the event Grid is unavialable & sun is playing hide & seek. Most AIO's and Good Quality Inverter/Chargers have an AGS Port... Auto-Generator-Start signalling is needed if you want the system to Auto-Start/Stop a Generator for charging purposes. The AGS will connect to a GCSM (Generator Control Start Module) that does the heavy lifting.


Here is a Link to the EU/AU/UK 220VAC/50HZ GSCM-Mini from Atkinson.
The wiring-diagrams PDF, lists compatible gensets. IF your generator is NOT in that list, NO GSCM will work with it !

GSCM-mini-50Hz (Europe, Australia & Japan)

manufacturing, circuit boards, solar charge controllers, honeywell, STAEFA, LON, Airstream, Trailers, RV, motor homes, Atkinson Electronics, HVAC, Circuit Boards,

atkinsonelectronics.com

Hope it helps a bit, Good Luck