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Small Cabin Forum / General Forum / Simple PV and Wind Question
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# Posted: 8 Jan 2021 10:17

Sorry if this is too simple a question:
After much deliberation I have finally ordered some solar PV for my off-grid cabin project. I've gone for basic on the premise that:
1. The less complexity the least there is that can go wrong.
2. If I break it, I won't have wasted too much money.
We plan to use minimal electricity, so the system is as follows:
100W PV array, basic charge controller (along with fuses in-line).
I am connecting this to my existing 110Ah wet leisure battery. All will be 12V DC.
Now, due to the low sunshine (and high winds) in north Scotland, I am also planning to get a small 50W vertical axis wind turbine (as used on boats). I know that wind turbines are less reliable and I have spent a long time making this decision.
The turbine manufacturer (in the UK) has sent me an installation sheet that shows how to combine the turbine and PV. The turbine does not need a charge controller and dump load as it is so small and self regulates.
Both PV and turbine are connected to the positive and negative terminals on the battery along with the cabin load connections.
As I'm a simpleton with electrics, I just wanted to be sure that this configuration will be okay. Specifically, might it be possible for the power generated from the wind turbine to affect the performance of the solar PV or vice-versa, since they are both connected at the battery terminals? Or is this a silly question?

# Posted: 8 Jan 2021 11:28

They should be connected to the input of your charge controller. That to you battery terminals and your loads to the output of your CC or direct to the battery

# Posted: 8 Jan 2021 11:34

I find it very hard to believe that a wind turbine dosnt need a charge controller nor a dump load. Can you post the link to it?

# Posted: 9 Jan 2021 11:10 - Edited by: gcrank1

Fwiw, some small 'maintenance' solar panels are said to not 'need' a charge controller either (keep in mind the cc doesnt not protect the device it protects the battery(s). Iirc the rule of thumb is said to be about 1amp.
After having played with a couple of low output solar panels like that I would have to put them and a comparable wind turbine into the 'trickle charger' class.
That is the same class as a small battery wall charger of 1ish amps 12vdc output, usually said to be to 'maintain' a fully charge battery, not 'recharge' a depleted battery.
I have no idea if the wind turbine fits this criteria or not, but I must wonder.
A plus for an occasional use place is that a small system can have a chance to actually recharge far better in your absence than a daily use place, but while you are there it does become a daily use place.
Wind turbines are very mechanically intensive and build quality is paramount, also expensive. Imo a cheap wind turbine isnt worth the money.
Sounds like you are concerned about 'breaking your solar'.....dont be, plenty of good info here by folks who likely started their small systems with as much knowledge as you.
Were I you, Id buy more solar panels and a bigger, if needed, charge controller (I like panels in series and mppt cc) but a pair of 100w panels (in spite of claims plan on about 5amps charge per panel) in parallel with a pwm cc will keep your 'leisure' battery charged pretty well for small scale use (ie, No high draw devices).
Parallel keeps both 12v panels at 12v paired but the amps output is cumulative. Pretty common claims are 6-7ish amps but when you de-rate that by about 70% for typical 'losses' you get 5ish amps. Two panels putting out 10-14ish amps on the most optimistic end will be a good C-10+ charge rate for a 100 to 120 ah battery. At any point in the future you could tie in another panel for 15+ amps If you run a 20amp, or more charge controller. A 30amp cc would let you eventually have 4 100w panels for about 20a charging with 2x100ah batteries which is a pretty good, rather inexpensive and usable small scale solar set up. at that point of multiple batteries Id be looking at 2x6v 'golf cart' batteries wired in series though (for some 200-225ish ah's). You may have trouble sourcing them where you are? They do give you more, real deep cycle use and life; ie, more bang for the pound sterling.

# Posted: 11 Jan 2021 03:47

Thanks for all the helpful replies.
I made a mistake in my system description: the PV does, of course, have a charge controller in-line before sending current to the battery.
Yes, both are trickle chargers.
The turbine is indeed specified as not requiring a dump load/charge controller because it 'self regulates'. What this means is explained on page 12 of the manual - accessible from a link on the right near the top of the webpage:

I identified this turbine because it is British made and it is said to be robust. The company are also good to deal with. It is not cheap. I know that this does not guarantee that the product will be good, but it appears to be the best of a bad bunch.
I don't know what the renewables market is like in the US, but in the UK I have found the following since first stepping into this about six months ago:
1. It is full of people advertising things without adequate knowledge of their products.
2. Most products come from China and have little or no instructions. (I also avoid Chinese products due to poor quality).
3. I can't buy anything from a shop - everything is online, and the websites advertising these products are merely intermediary companies, usually without an address or phone number, and only with an e-mail that is answered by someone at 2am in the morning and clearly in a different continent.

I am actually an engineer, but not of electronics, and I have read lots of books on these technologies. What about simply putting a diode in line on the solar PV side to protect it from possible damage by the turbine? Or is it just folly to have the turbine without its own charge controller?

Thanks for all the help. It is much appreciated.

# Posted: 11 Jan 2021 07:51 - Edited by: FishHog

why not run both into the same controller if you want to make sure there is one on the turbine

Nate R
# Posted: 11 Jan 2021 08:57

Yeah, I'd consider running both into the same controller, or even their own independent controllers, both connected to the battery.

Is it really worth having that turbine? 26 MPH winds to get 10 watts out of it? Are the winds high enough to justify it in that location

# Posted: 11 Jan 2021 11:34

The WT is likely rated at a maximized rpm for its design output, thus the '@26mph. Wonder what it is at a more sensible 8mph, 3amps? Some places might have that 26mph quite often, I know we dont. And the height above ground will have a huge bearing upon wind capture; ie, the higher the better, but then you run into pole and guy wire issues as well as accessibility for repair/maintenance.
I suspect the 'self regulating' on a unit that small may just be a basic pwm cc stuck somewhere inside.
If you have good solar exposure and room for solar array(s) (I had roof mount before, sure like my ground racks now!) I still think more bang with PV with no pole, no guy wires and no moving parts.

# Posted: 11 Jan 2021 13:32 - Edited by: Nobadays

Quoting: gcrank1
I still think more bang with PV with no pole, no guy wires and no moving parts.

Quoting: AndrewHighlands
Now, due to the low sunshine (and high winds) in north Scotland, I am also planning to get a small 50W vertical axis wind turbine

He is in the FAR NORTH of Scotland, an area known for lots of wind and inclement weather. The wind turbine will likely produce well. Like Brett though I've not heard of a wind turbine without a charge controller and a dump load.... curious. As GC says it might have an internal pwm controller built in... but it would still seem to need a dump load. I'll follow his link and read...

So the manual says it self regulates, as the batteries increase in charge the turbine will slow down... except in high wind applications where a charge controller is recommended. It says in, like Arctic conditions but I would guess just about any windy area could experience high wind days that could cause issues. IMHO I think a charge controller would be important and if it is intended for that particular turbine - they recommend a specific CC - my guess is it contains a dump load.

# Posted: 11 Jan 2021 14:24

Thanks again everyone. It is a great help and much appreciated.
Best wishes,

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