Wednesday, February 27, 2013

What wind generators ought to look like

A recent craigslist ad here in Seattle really caught my eye (it may not be there by the time this gets published, but if you are interested, let me know).  The ad offered a wind generator, but not like any I had ever seen.  The generator was manufactured by BalMar, a well-respected manufacturer of marine alternators and regulators.  And when I say local, I do mean local - BalMar is here in Ballard (I suspect that BalMar is a contraction of 'Ballard Marine').  A web search did not turn up any references to it, so it is apparently out of manufacture, sadly.

Now why was I so intrigued by it?

Well, first, a wind generator would seem to be a natural fit for an alternator manufacturer like BalMar.  And based on our experience with their other products, I'd expect that this thing is bullet-proof.

But more importantly, look at this:

It has self-adjusting variable pitch blades!  See those lead balls?  The faster the hub spins, the more they are thrown out, rotating the blades, changing their pitch.  The movement is resisted by the spring on the axle; adjusting the spring tension adjusts the rate of pitch change with RPM.

Why is this a big deal?  Because whatever pitch is set by the manufacturer of any fixed-pitch design (and that's all of them, I think...  somebody prove me wrong), it is really only optimal for a single wind speed.  And here is the proof of the pudding:  Virtually all current wind generators are just starting to turn at 10 mph.  This one, however, starts to deliver power at 5 mph, and produces 187 amp-hours a day at 12 mph.

And in high winds, it self-feathers to prevent overspeed.  Wow. 

Here is a view of the hub from the side:

As you can see, BalMar has fixed the 'rotor' portion of the alternator to the base plate, meaning that there are no slip rings.  The wiring just attaches directly to the coil.  The actual rotor (it would by the 'stator' in a conventional alternator) consists of a series of permanent magnets embedded in the white rotating hub.  And the hub is provided with fins to generate a flow of cooling air.  BalMar seems to have a well-thought out mature design here.

Huh.  So why aren't all contemporary wind generators derivatives of this design?  Well perhaps because it was sold for over $1000 more than 20 years ago.  In today's market, a $1000 generator would be at the high end.  Twenty years ago? 

Sadly, the adequate is often the enemy of the superior.

1 comment:

Kelvin Meeks said...

How timely. I'm planning to add a wind generator in the near future. Appreciated your posting this info.

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