Domestic Solar PV battery addition

[EdH]

Hi all,

Considering adding a battery storage system to my existing 2kW Solar PV. Given the recent/current energy prices I am thinking more and more about this, we had panels fitted around 6 years ago on our house. On a sunny day my little system generates around 8-12kW, we use some but the rest will go into the grid which is rather shame as if I had a battery storage system we could use that accumulated energy in the night to offset some use. Has anyone had one retrofitted to their existing Solar PV system and any recommendations/advice would be greatly appreciated.

Many thanks in advance

 

[saronica]

If you generate more than you use, are you not in credit without any additional expense?

 

[EdH]

If you generate more than you use, are you not in credit without any additional expense?

sorry I don't understand what you mean?

 

[saronica]

Are you on a feed in tariff? As in are you paid for the excess that you generate and put onto the grid.

 

[EdH]

Yes I am, but it's deemed payment. There is no meter which measures export units, only what is generated and then half of that is then classed as export units.

 

[Skyliner33]

I would be interested to know this as well.

 

[saronica]

A long time ago I was involved in this industry, before feed in tariffs were rolled out. What it’s like today I’m not sure but the science/electrics behind it haven’t changed I’m sure:

Your array on your property generates in DC at somewhere between 600 and 1000 volts depending on panel make up and size of array, that is then put through an inverter to harmonise it with the national grid, this is fine locally as in your house but can float up to the area sub station. Your inverter has a shut off switch which should stop you adding to the grid when a power cut comes, this is to protect the national grid workers from getting shocked when they think the circuit is dead. From that you use your requirement of power and any excess is put into the grid and in some way is counted, there used to something called a count back meter, maybe that’s a thing of the past. I guess it all depends on whether you own your kit or rent your roof space to the company who installed or sold it.

So you generate at DC high voltage, you invert to AC 230, there really is not a route as far as I can see to siphon of DC into batteries for storage at 12 or 24 vdc.
And each time there is an inversion there are losses. So the export units that are applied to your account/bill are they credited against your usage, there has to be some benefit to you from those. It used to be something along the lines of “you generate 10kw daily, your usage is 7kw daily therefore you add 3kw to the grid and get £xx:xx per unit as a credit or feed in tariff applied to your account.

I know in recent years companies essentially rented folks roof space milked all the tariff money and the homeowners got free power when they generated. Also I think the tariffs are either very low now or no longer exist.