Hybrid Solar / Wind Solution using two inverters

vinceconner

Hi

I have an existing ON-GRID Solar PV System. The panels are mounted on an outbuilding and the inverter is located in the same outbuilding connected to sub consumer unit which feeds back to the main consumer unit in the house.

I would like to add a Wind Turbine (and battery) too, however, the best location for the Wind Turbine is further away near our garage.
Is there an issue connecting a second inverter to the sub consumer unit in the garage which again feeds back to the main consumer unit in the house.

So in this scenario i would not be connecting both inverters in parallel as they would be remote from each other, but they would both be feeding back to the main consumer unit via the two sub consumer units.

The theory then being the Wind Turbine would charge the battery and also provide any excess to the internal power system and the existing solar system would just provide power to the internal power system. I assume any excess from both systems would then flow back to the grid.

Thoughts please, as i cant seem to get a straight answer from anyone locally.

Many thanks

Vince Conner

BB.

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

vinceconner

Hi BIll
Thanks for your prompt and detailed response.
South East London, yes.
Our current GT-Solar system, is working well in the summer months, saving us on average 48% May-Sept. This does feed back to the grid but we are not getting any pay back on that as changing tariff's (a requirement) isn't ideal at this time.
I was looking at a Tesup HAWT with their charge controller (which includes a braking system). This would seem to do the job, my biggest issue at the moment was / is to connect up possible two inverters or if thats not possible then what sort of hybrid to look at.
I have not yet found anyone in the UK keen to take it on. They prefer to stick with either Solar or Wind not both, I can understand why and at present they have a good market place so dont need to try too hard!
We are fairly energy efficient (all LED lighting for example). I have looked at heat pumps for heating but everyone i speak to, suggests in our circumstances it wouldn't be effective. Our heating is currently LPG so not really part of this project i guess.
The main purpose was to simply reduce our use of grid power. Cost over here currently crazy and the GT-Solar system I estimate will have paid for itself within 24 months given current gird costs! so thats very attractive. Currently i have 16 390W panels so not too bad and I would struggle to make that any bigger (and obviously winter months are no where near is productive) but we do have good clean wind and in a rural area in a valley which is more often than not windy and in a pretty uniform direction. This is also the reason I would prefer to location the HAWT away from the GT-Solar as it would be a far more appropriate area for the prevailing wind and not obstructed in any way. The battery side was not for Grid failure but to provide power when the solar or wins was not. (I do have a 6.5Kva generator on an ATS switch already that provides grid failure cover) I have friends that have GT-Solar systems with batteries, where the battery charges during the day from the excess power and discharges to the home at night.
All potentially good stuff, I will continue my research and see if i can find a good solution
Thanks
Vince