Hybrid Solar / Wind Solution using two inverters

Welcome to the forum Vince,

Since local electrical Codes matter--I am guessing you are in South East UK ("around" London?).

Backing up a moment... If you are looking for Inverter+Battery backup--I would take a guess that you want "backup" power available at your home (not only the shed)?

Generally, this is done with some sort of AC power transfer switch (could be a manual/automatic/separate xfer switch, or even many AC inverters have multiple inputs--Grid & Backup Genset--Which allows the AC inverter to "disconnect" from the Grid and provide AC power to the "protected power" sub panel/circuits).

Also, knowing how much energy (kWH per day/per month) you will need for your home is helpful too... And looking at your loads--Conservation is critical too... Solar/Wind power is not cheap. It is almost always cheaper to conserve power than to generate it. Insulation, LED Lighting, heat pump A/C and heating (mini-split heat pump systems can be 2x more efficient at heating vs simple electric/resistance heating), etc....

So--There can be significant paneling/permitting/cost issues to "rewire" the home/shed to support a protected subpanel (i.e., all the circuits you want to run from AC Inverter--Typically some lights, wall outlets--And not an electric water heater or electric stove--Which can be "energy hogs" for solar/wind power systems).

As you know--Grid Tied solar (no batteries, just GT Inverter(s) that take the solar power and connect to the home's AC power system) are great for saving money (relatively low cost to install, efficient, and no batteries to maintain/replace every X years)--But most do not provide any support of "backup" power during grid/mains failure).

There are "hybrid" AC inverters that do both AC Off grid/backup power support and have backup Genset/transfer switch connections). And you should be able to connect solar/wind turbine(s) to your battery bank, and the hybrid inverter can feed "excess" power to the battery, and dump it to the grid.

Such a system is not "trivial" to design, setup, and maintain... Finding a Hybrid Inverter system that can interface through the battery bank to the grid (and probably add a wind turbine and/or dump controller) manage the AC/Solar/Wind power (and your battery bank type--Lead Acid, Lithium Ion, etc.)--You need to find a good vendor and check references for systems that are similar to what you want.

Your present GT Solar system which provides 220 VAC @ 50 Hz output via GT inverters--You have the option of connecting the appropriate hybrid AC inverter to the GT inverters and use those existing panels+GT inverters... Or you get MPPT Solar Charge controller, and connect it to your existing array to charge your DC Battery bank directly. Depending on the array/GT inverter(s) you choose, there can be other "array configuration issues too" (different charge controllers have different array voltage/current configuration requirements).

Wind Turbines typically have very different electrical/controller requirements... The typical horizontal axis wind turbine (HAWT) needs "constant" loading on the alternator (AC generator). With solar panels, the controller can just "turn the panels off" when the battery bank is full. With HAWT's, they need to be loaded 100% of the time, or they can overspeed and self destruct (on the electrical side). Or have mechanical control (furly, feathering, brakes) to limit RPM/shutdown when charging is not needed. This is usually done (on the battery side) through a "dump controller/function". The "dump controller" simply "dumps" excess charging current (bank is full) to a resistor "load bank" to prevent overcharging of the batteries.

This can also be done with a Hybrid AC inverter... The Hybrid (aka Utility Interactive) AC inverter, when the battery is full, feed excess power back to the grid (and save you money by "turning your meter backwards"). You still have the dump/RPM issues for when the AS mains fail and the turbine needs to be shutdown and/or a dump load connected with the batteries are "full" and there is no grid power connection.

I am not a Wind/Solar power systems designer--Others here may be able to give you more details--But those are the basic options and issues that you have.

Looking at London, not a lot of sun:

http://www.solarelectricityhandbook.com/solar-irradiance.html

London
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 38° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
1.27	2.04	2.76	3.67	4.17	4.20
Jul	Aug	Sep	Oct	Nov	Dec
4.25	4.16	3.26	2.41	1.53	1.05

More or less, I would say >3 hours of sun is "descent"... 5 months of the year is less than 3 hours of sun per day...

Generally, I like to suggest spending the extra money that would go into Wind (turbine, tower, concrete, noise from wind, maintenance access, etc.) and simply put in a larger solar array instead (no maintenance, no noise, 20+ year array life, etc.).

But you are not in a very "solar friendly" region... So I understand looking at wind turbine(s).

As you do your research--I would also look very closely at the hardware and support for wind turbines. You need to be in a good wind area (clean airflow, no up wind trees/building/etc.) and it needs to be "reasonably" (miserably) location windy too (flagging trees from consistent winds)..

And reviewing actual logs from wind turbine installations in your area. Poor wind and poorly engineered wind turbines can have very poor energy harvest/reliability).

Your thoughts/questions?

-Bill