Battery connection to wind turbine & PV

[djs63]

Hope the holiday has been OK. Keep safe.
As a non electrician (I used to measure mV and femto Amps! Which does not count) I want to ask advice about connecting a battery system to an existing generation system.

We have grid connection for a 6 kWp wind turbine and a 1.8 kWp PV system both with SMA inverters and I am looking at adding battery storage to protect our supply in the event of grid failure and eventually charge the EV (e-Niro).

Tesla Powerwall emailed to say that you can’t connect a wind turbine to their system. Other suppliers concentrate on PV in the example systems. Does anyone know of a commercially available set up which will allow connection to existing wind and PV generation please?

If my wishes come true, the other complication will be wiring it all together (expert job) and including a switch to allow house essentials to run during loss of grid power.

As luck would have it, the two inverters are 20 metres apart, one in the loft (of a bungalow) and one in a garage at the other end of the house. Thus monitoring, all by itself, will be awkward.

Here goes: I presume that connections will be on the AC side though we will, I am sure, add more PV at some stage.

Thank you for getting this far along my rambling road, David

[biff]

Perhaps there is some form of ImmerSun in DC
 that could perform that simple operation.
 I am sure there are SMA operatives here who would have a good idea. Seasons Greetings  djs63 
     Biff

[billi]

 hi ,

it might be worth while to study the Victron  information too   and  as  far as i remember one can ask questions tooo  https://www.victronenergy.com/live/system_integration:hub4_grid_parallel

My wisdom is now outdated , i assume ( without a tear) , but AC- coupling  , ie,   attach  AC Grid tie inverters to off Grid inverters is pretty simple , it gets more complex if  a FIT  payment is involved    , my understanding of a basic AC coupling idea was to  avoid the generating side has to be smaller than the offgrid Inverter/charger s capacity  so my outdated conclusion would be , that you would need quite a strong off grid inverter for the combined  max input of 7.8 kW , but this was me having no grid connection , your case is different having one , so the grid can be your drainage for excess too , beside hot water

Technically and operative wise i was pretty amazed how AC-coupling  works smooth ( with some reservations  of being a DC fan )

Billi 

[kdmnx]

There are battery systems that work independently of your wt/pv. They sense the power flowing in/out of your grid connection and charge/discharge a battery to keep the flow to/from the grid at zero as far as is possible.

LuxPower make such a device.

Power backup in the event of an outage is a whole other kettle of fish. Firstly to cover your whole house isn’t really economically feasible. How many kW are your oven, dishwasher, washing machine, and all the other high-power devices altogether? How many kWh of batteries would you need to run all that for howeverlong?

Many inverter/chargers (eg the abovementioned Lux) have the facility for a “UPS” circuit. This can power: lights, fridge/freezer, Internet router, phone/laptop chargers, TV, and a few other low-power essential devices, in the event of an outage but not much else. The expense here is wiring in a 2nd “fuse box” for the “ups” circuit, wiring your lights to that, wiring a special “fridge/freezer” circuit, and wiring a circuit for a string of sockets around your house for the low-power / essential devices. Basically you can take this as far as you want to.

Re. Charging the EV: some EV chargers (eg the Zappi) can charge from your wind/solar PV and avoid using grid power.

[Fintray]

I have a Tesla Powerwall and it is AC coupled so I can't see how it would make any difference that the AC is coming from a wind turbine rather than a PV, surely it just sees the excess being exported and charges the battery. They also have the Powerwall with backup facility if the mains goes down.

[nowty]

If the Wind turbine is AC coupled then obviously it will work, at least one company out there will do it, https://www.moleenergy.com/faq/i-have-a-wind-turbine-can-mole-energy-install-my-battery/

Tesla might think that most are DC coupled onto batteries and Telsa don't allow the Powerwall to work with an existing battery system. Or they might think that the wind turbine inverter will be an uncertificated one and don't want any complications.

So I suspect if you ask Tesla, they say no because its a standard response, but if you ask an actual installer and they understand all your generation equipment is AC coupled, they may say yes.

[Fintray]

Have a read of the Tesla support site https://www.tesla.com/en_gb/support/energy/powerwall/learn/combining-systems

As it says "Powerwall & Other Renewable Energy Sources
If installed outside the backup circuits, Powerwall can also charge from other renewable energy sources like wind, hydro and co-generation.

[billi]

well , no need to concentrate on Tesla here , as they are not up to the  requirements  of dealing with that charging input
   and even otherwise i would stay away