# Adding small wind turbine to existing solar

Registered Users Posts: 1
edited May 2017 #1
I have a 100w panel going to a 30amp pwm solar controller and 35ah 12v battery I use mostly to run a modem/router that pulls 15w 24/7...I got a very small 2amp max 12v wind turbine to keep a lil charge at night...the seller claims it can be hooked up through the controller with no need for a load dump...could I hook it inline with the panel if so would it be as simple as getting a y connector and hooking it to the panel?...heres a link to the turbine

Look at this on eBay http://www.ebay.com/itm/142363334811

It is a small turbine and with so many blades will probably not over speed in high winds if "unloaded" (put through a series charge controller).

You could have an issue with the solar panel and PWM controller maximum input voltage ratings--It depends on how high of voltage the little wind turbine generates when unloaded... In high winds, it is possible that it could generate 48 volts or more--That could be enough to ruin your paralleled solar panel and/or the PWM controller.

In practice, most small wind turbines produce almost no useful energy. And therefore may not cause you any problems with the array+controller.

One alternative would be to connect the wind turbine (through a blocking diode) directly to the battery. And install a switch to turn off the turbine (or install between turbine and blocking diode, short out the turbine) and simply turn off when high winds (stormy weather) is forecast.

Realistically--Your 35 AH battery and solar panel are too small to "reliably" support a 15 Watt draw 24x7. A quick set of math would suggest:

Battery sizing:
• 15 watts / 12 volts = 1.25 Amp draw
• 1.25 amps * 24 hours per day = 30 AH per day
• 30 AH per day * 2 days stored power (no sun) * 1/0.50 max discharge (for longer battery life) = 120 AH battery minimum
Solar Array sizing (based on battery bank AH capacity and 13% rate of charge for daytime+nighttime energy usage):
• 120 AH battery * 14.5 volts charging * 0.13 rate of charge = 226 Watts charging
• 226 Watts charging * 1/0.77 panel+controller derating = 294 Watt array "cost effective" maximum
And then there is based on the amount of sun based on where you live... Say fixed array tilted for Winter (worst case sun) production:

### Des MoinesAverage Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 33° angle from vertical:
(Optimal winter settings)  Jan Feb Mar Apr May Jun 3.46 3.65 4.16 4.20 4.29 4.48 Jul Aug Sep Oct Nov Dec 4.59 4.62 4.78 4.35 3.37 3.17
So, 15 watts 24 hours per day for Des Moines Iowa:
• 15 watts * 24 hours per day * 1/0.80 flooded cell battery eff * 1/0.77 panel+controller derating * 1/3.17 hours of sun Dec avg * 1/0.66 full time energy usage fudge factor = 279 Watt array "minimum" (with fudge factor for days with poor sun)
So--Forgetting wind at the moment--I would be suggesting somewhere around a 294 Watt solar array for this system. If this is a full time load in a remote location (i.e., wireless repeater on a hill top). minimum with a 120 AH @ 12 volt minimum battery bank (deep cycle type).

You might look at a pair of "golf cart" batteries (6 volt @ ~200 AH) wired in series (12 volts @ ~200 AH)... They are relatively cheap (~\$100 or less each) and rugged. You just need to monitor water levels once a month and check state of charge with a hydrometer... And you could support a larger solar array:
• 200 AH * 14.5 volts charging * 0.13 charging * 1/0.77 panel+controller derating = 490 Watt cost effective maximum array
This would give you 3+ days of "no sun"--And carry you through most bad weather events without service (shutting down to prevent battery damage from over discharging, or running a genset to recharge the batteries during stormy weather).

Anyway--Just some ideas. If you have the ability to run a trench and 120 VAC to the location--It might be a better idea.

For the wind turbine, generally suggest 60 feet in the air and 20 feet above any nearby trees and buildings. May not be worht putting a 2 amp wind turbine on such a tower. Also, is the turbine weather proof (water, ice) and do you have lightning in the area (30-60 foot tower on hill==lightning magnet).

If the installation is on a hill in lightning area--Lightning rods, grounding, and surge suppressors are probably highly desirable too (whether wind, solar, or AC powered).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset