Small winter only solar/wind system

[Ryan Neve]

I have a somewhat unique situation. I've got to generate power for some scientific instrumentation from December to the end of March each year. The location has good wind (NC outer banks) so I've been thinking of a hybrid Wind/Solar system.
This site gets around 4 KWh/m2/Day of sun in the winter and has an average wind speed of around 6 m/s.

The 24V load is fairly consistent never exceeding 140 watts and seldom much lower than 120 watts. I'm assuming 3360 Watt Hours/Day or at 24 volts, 140 Ah.

For storage I was thinking 16 T105s would give me 900Ah@24V. This should let me get through a few dark windless winter days.

My first thought is 1200 watts of solar in a fixed frame and an Air Breeze wind generator. Does this sound reasonable? If I wanted to be more biased toward wind, can anyone recommend a larger wind generator which might work reliably in a very salty environment.

I have another nearby site successfully using an AirBreeze with 330W of PV and 450 Ah storage on a much smaller 25 Ah/Day load.

[John Merial]

Solar wind hybrid systems are needed to generate electricity during the summer and winter seasons. The variation in the intensity of sunlight and wind speed throughout the year does not organically affect the working of hybrid solar wind systems. It can produce power at any time of the year.

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[Rob Beckers]

Hi Ryan,

Some suggestions: Instead of T-105s have a look at Trojan's SPRE 06 255s. Those are only slightly more expensive, but last at least twice as long.

Be careful in oversizing the battery bank. Lead-acid batteries do not like sitting at partial charge too long, and really need a full 100% charge every 2 - 4 weeks or sulphating becomes permanent (and you lose capacity). So, a large battery bank also requires large charging sources, or they'll never see a good 100% charge.

The Outer Banks is not a bad location, as you noted, lots of wind, so a (small) wind turbine would do well, but given the rather low price-point I would still put up lots of solar PV. Even in winter that location still gets enough light to produce well.

We once had a similar challenge with river monitor stations (in Canada, very little sun in winter, and panels covered in snow). Wind wasn't an option, so we ended up oversizing solar PV by about a factor 10 vs. what calculations indicated as strictly needed (on average). That worked. Moral of that story is that oversizing your charging sources, if you can, is the way to go if you need to keep things going.

-RoB-