24volt wind generator-rectifier between generator & battery?

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Re: 24volt wind generator rectifier between generator and ba

Postby bergy » Tue Nov 01, 2016 5:33 pm

Gordon,
Since my last post i have trolled my laptop operating programme (watchpower ) connects via usb to inverter.
My cut off voltage was set at default of 23 volts.I have just changed it to 24.5 volts which should be better
My float charging voltage is 27Vdc.can't find reference to absorb time or end amps (they are no doubt hidden away I will keep looking.
There are a endless amount of adjustable settings but not understanding things i defer to the default settings.
The 5mm size of cable is wire only not including insulation.I expected larger because we can output 60 amps. (I would have thought 60 amps would fry the 5mm cable,) clearly not.
I have just discovered i can change most of the parameters ( once i find them)
Today i connected the controller and it has 2 wires which connect to 12 volt only to power the unit and the 6mm cable goes to the battery and then to the dump.I am surprised that 5mm cable will carry up to 60 amps.I have installed a 200 amp fuse inline.
As you would have worked out i am not electrically trained but love to have a project and this has been a big learning curve for me and i am appreciative for your support and help
Thanks
Brian
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Re: 24volt wind generator rectifier between generator and ba

Postby Gordon-Loomberah » Tue Nov 01, 2016 6:12 pm

bergy wrote:Today i connected the controller and it has 2 wires which connect to 12 volt only to power the unit and the 6mm cable goes to the battery and then to the dump.I am surprised that 5mm cable will carry up to 60 amps.I have installed a 200 amp fuse inline.


Does the power from the wind generator not go through the controller at all? That would suggest a very simple controller that only regulates to a single voltage- you need to make sure it is the correct voltage- ideally the same as your solar Vfloat.

That 200A fuse wont offer any protection- the fuse should prevent the wires from melting/burning the cable insulation, and 220+A* will definitely risk damage if you have a short circuit in controller with only ~25mm^ cable. (cable is measured in cross-sectional area, rather than diameter). I'd be reducing the fuse to maybe 80A.

Where are you getting the 12V from for the controller? Any idea how much power it uses? If powered from just one of the 12V batteries, and it uses say a few tens of milliamps, then you might want swap it back and forth between the 2 batteries every now and then, to even things out.

* a 220A fuse will typically conduct 440A for a minute before blowing, but probably wont blow with 25mm^ cable and 180A battery, so things could get messy!
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Re: 24volt wind generator rectifier between generator and ba

Postby bergy » Tue Nov 01, 2016 7:03 pm

The power from the wind generator varies from 0 to 36 volts dependant on rpm (i think ) clearly not the same as the float level.
The power goes to the battery first then to the solonoid.
Yes the 12volt goes to on of the batteries.
I do have a 80 amp blade fuse i will insert it tomorrow.
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Re: 24volt wind generator rectifier between generator and ba

Postby Gordon-Loomberah » Tue Nov 01, 2016 7:30 pm

Yes the voltage will vary depending on rpm, but I suspect that it will go higher than 36V if insufficient load on it. In use, voltage will be limited by battery and/or dump load, other than when there is more power produced than load to absorb it, that's when battery damage will occur, unless you can control the speed, or stop it entirely.
Vertical axis turbines are a lot less efficient than horizontal, so I suspect it wont reach rated output all that often. However, it only takes one uncontrolled charging episode to do damage.

Can you email me the controller and turbine manuals at gordon.garradd@energymatters.com.au? I'll see if I can make any sense of them, but from past experience, Chinese equipment manuals are generally not very helpful, but sometimes quite amusing ;)

thanks
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Re: 24volt wind generator rectifier between generator and ba

Postby Gordon-Loomberah » Wed Nov 02, 2016 11:53 am

The inverter-charger manual indicates Vabsorb= 29.2/28.2 (flooded/AGM) and float of 27.0V
You probably didn't recognise it because they are calling the absorb voltage a bulk voltage, which is incorrect, there is no bulk voltage - bulk charging is max current from the PV panels at some voltage below Vabsorb.
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Re: 24volt wind generator rectifier between generator and ba

Postby bergy » Wed Nov 02, 2016 12:23 pm

Thanks Gordon,
Interesting note, Further to our discussion yesterday re cable size I today took a sample of the turbine cable to Jaycar because i was concerned that the size was not what we expected.
They advised me the turbine cable is 12 gauge rated at 25 amps (interesting when the max out put is rated at 60 amp.I have put a 25 amp circuit breaker in line and will watch with interest.
I also took a sample of the solar cable (from panel to inverter with mc4 plugs fitted ) and they rated that also at 25 amps but thicker insulation. (That cable carries up to 2.0 kw at unknown amps )
My next question would be, what size cable will i use from the solonoid to the power dump ( given the size of cable to the solonoid ) ???
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Re: 24volt wind generator rectifier between generator and ba

Postby Gordon-Loomberah » Wed Nov 02, 2016 1:52 pm

I really wish people would stop using AWG for wire size! Jaycar should know better.

However, I see a big discrepancy- you suggested the wire was 5 or 6mm diameter, yet AWG 12 is only 2.05mm across, so I don't know what to make of that. That would make it a bit over 3mm^2, which is certainly ok for 25A, but not 60A. Maybe the know 60A output is unlikely to be seen?

What are the dimensions of your wind turbine? IE I'm interested in the cross sectional area presented to the wind, so need the height of the outer blades, and the distanse from the axle to the blade. With that I can calculate whether 60A is likely or not.

2kW at 25V is 80A, far too much for cable rated at 25A.
Solenoid to dump load cable, (if 700W), use 4mm^2 for a short run, or 6mm^2 if its a fair distance away in the hot water system..
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Re: 24volt wind generator rectifier between generator and ba

Postby bergy » Wed Nov 02, 2016 5:53 pm

Hi, Yes I was surprised by the revalation that it was 12 gauge.I would still put money on larger than 2mm diam.I am not at all familiar with wire sizes,but I will have someone else look at it.Jaycar didn't say 2mm or i would have disputed it
I purchased some twin cable rated at 56 amp (no idea what gauge or whatever ) to run to the dump. $8 l/m
And 60 amp breaker.
The turbine is 1.3 metres diam and blades are 1.4 metres high.
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Re: 24volt wind generator rectifier between generator and ba

Postby Gordon-Loomberah » Wed Nov 02, 2016 6:30 pm

OK, quite small then, brace yourself for some bad news...

I honestly cant see it making more than a few hundred watts on a reasonably windy day, and mostly much less than that. It is only equivalent in swept area to a horizontal axis turbine of ~1.5m diameter, and much less efficient- those bits inside the blades needed to get it started create a lot of drag. You would be very lucky if it was as much 25% efficient - the theoretical maximum is 59%, only approached by the very best aerofoil blades on horizontal axis turbines.

plugging the numbers into the standard formula:
P = 1/2 ρ A v^3 * efficiency (rho = air density)

= 0.5 X 1.2 (kg/m^3) * 1.82 * 10^3 (10m/s = 36km/hr wind)

Power = 1.09kW ie the amount of energy in the mass of air moving across the swept area.

X efficiency of say 0.25 (I suspect it is actually lower) = ~250W

What is it they claim, 1.5kW @10m/s?

I'll leave you to draw your own conclusions about the claimed output, but one explanation I can think of is that it must have some magic power that transcends the laws of physics :lol: These sorts of output claims for wind generators are unfortunately all too common.

It is possible you might see 1.5kW in a wind around 70km/hr or more, if there is minimal turbulence, but I'm not sure how safe it would be in such a strong wind.
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Re: 24volt wind generator rectifier between generator and ba

Postby bergy » Wed Nov 02, 2016 7:07 pm

That is interesting .
Takes the pressure of the cable sizing.
I am not seeking a lot.What I am seeking is some imput overnight.
We tend to hammer the batteries first thing in the morning before the sun hits the panels,once the sun hits the panels at about 9am we are in clover.
It will take probably 1 week before i can get the turbine operating and it will be interesting to watch.
I would be happy with 250 watts.
Will keep you posted .
Brian
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