Battery storage and FIT?

Hi everyone,

1st time poster here, so apologies if this has been covered before, I did try a search which came up with nothing.

I live in Bonnie Scotland in the not so sunny UK. I already have a grid tied3Kw solar array. Here in Scotland I still have the benifit of the fleedin tariff whereby I get paid fo anything my panels generate, whether I use it all or not. I really love to build my own storage/powerwall to make the most of it however the downsideis that my FIT payments areits by a generation meter which connected on the AC side of the system.

Now onto my question, batteries charge using DC power however if I did that my generation meter would hardly move as almost all of my solar would go into charging a battery bank. Is there a way in which I could have my cake and eat by manufacturing a powerwall that would charge after the generation meter?

Thanks in advance for any guidance given.

If the grid "stores" your power for free, why would you want local storage?

Because I have to buy it back. Although thinking on that, if I work it out between FIT tariff and export payments I get in the region of 17p per kWh and buy it back at just 12.49p per kWh. So I guess until the FIT runs out it wouldnt really be cost effective.

Kenny.j said:

Because I have to buy it back. Although thinking on that, if I work it out between FIT tariff and export payments I get in the region of 17p per kWh and buy it back at just 12.49p per kWh. So I guess until the FIT runs out it wouldnt really be cost effective.

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Well it my be worth considering. However do you get off peak rates at night like we do? If so then its not worth your while. However, if like in Australia, the rug gets pulled out from under you, then yes. I used to get 30c per kwh. Now I only get 11c. Im abit upset about that. Given I pay 34c per kwh. So it is well worth investing in local storage, in my situation.

Hi Kenny,

Yes you can do it. I'm in the same situation as you: 3kWp of solar grid tied with a solaredge inverter. See my thread here:

http://secondlifestorage.com/t-Grid-Connected-Powerwall-Design-Build

You have two options depending on what you want to change. If you don't want to change your existing inverter (it may effect your FIT if you do) then you should buy a Sofar ME3000SP AC coupled inverter and build batteries for it:

https://midsummerwholesale.co.uk/buy/sofar-storage/sofar-me3000sp.html

In the end I decided to buy the batteries as well as it seems like such a good deal. Should be arriving today!

http://www.homeswitch.co.uk/sofar-solar-7-2kwh

If you want a neater solution and are happy replacing your current solar inverter, then you can change it for a hybrid inverter and add batteries to that. Something like this Solax inverter:

https://midsummerwholesale.co.uk/buy/solax/solax-sk-su3000.html

Regards,

Greg

Hi Kenny

Ive been facingthe same problems!

Weve all signed up for solar,enjoyed the benefits and now want to add storage!

Retro fitting batteries doesnt seem to be as easy as installing them at the beginning. (Or as cheap now the new VAT laws apply)

Regarding FiT payments - these will not be affected by adding storage, however....... all storagehas losses associated with it, charging, invertion,etc. Where these losses happen will effect the amount of FiT payments,even if very small.
DC coupled systems - These losses happen before your FiT meter and will effect the amount of payments
AC couple systems - These losses happen after the FiT meter, therefore not affecting payments.

Im personally looking at the Sofar Solar inverter/charger as a starting point.

Hope that helps

Greg said:

Hi Kenny,

Yes you can do it. I'm in the same situation as you: 3kWp of solar grid tied with a solaredge inverter. See my thread here:

http://secondlifestorage.com/t-Grid-Connected-Powerwall-Design-Build

You have two options depending on what you want to change. If you don't want to change your existing inverter (it may effect your FIT if you do) then you should buy a Sofar ME3000SP AC coupled inverter and build batteries for it:

https://midsummerwholesale.co.uk/buy/sofar-storage/sofar-me3000sp.html

In the end I decided to buy the batteries as well as it seems like such a good deal. Should be arriving today!

http://www.homeswitch.co.uk/sofar-solar-7-2kwh

If you want a neater solution and are happy replacing your current solar inverter, then you can change it for a hybrid inverter and add batteries to that. Something like this Solax inverter:

https://midsummerwholesale.co.uk/buy/solax/solax-sk-su3000.html

Regards,

Greg

Click to expand...

Hi Greg, thanks for your input. That seems like itd be just the thing Idbeen looking for. Much as I like the idea of building my own this is a very neat and compact solution. Saves worrying about any BMS software safety cut outs and linking batteries together etc. Admittedly it would probably work out cheaper to DIY (as you could add to it as and when) but I have to say I quite like the idea of LiFePO4batteries as they seem to be a bit safer if not as energy dense as Li-ion.

Did yours arrive today what did you order? Ill watch your post for updates with a view to perhaps adding this system to my solar array in the future.

Yep most of the stuff arrived today:

Sofar ME3000SP inverter
3 x Pylontech 2.4kWh batteries
Cable & trunking
Two 4U vertical 19" racks for wall mounting of batteries

Still wainting for:
25A MCB for connecting the inverter to the main circuit board.

I had a look inside the inverter and it looks very nicly put together, seems high quality. Also took one of the batteries apart. It's made up of 3 smaller packs each of which is 2P5S of their 25Ah pouch cell. I'd say the battery pack is about as basic as you could get, just cells soldered together and wrapped in plastic. PCB in each pack for cell voltage measurements going to the central BMS and front panel. Doesn't feel as high quality as the inverter but seems like it should do the job.

Had to do some prep on the wall I'm mounting it on so the build is a bit delayed. I may get it done tomorrow, if not it'll be Tuesday.

Also on another note, you mentioned about being able to add more to it if you went custom. You can also with this system, you can add more 2.4kWh packs, don't know what the upper limit is. i'm building mine with three packs and space for a 4th if I need it.

Greg

Hi Greg,

Why do you need another 25amp mcb, can you not just use the one that already connects your solar to the grid?

Kenny

P.S. Im looking forward to seeing how you get on with this. Im thinking ofpossibly 2 battery packs to start and see how it goes from there. Id want to charge it with purely solar as Im not on an economy 7 tariff so Id set it to auto and solar only and let it do its own thing and monitor how that goes for a while.

But before I get to that I really have to finish the bathroom and front garden 1st, the Mrs would never let me spend on battery storage before those 2 are done.