Roof-top Wind Farms

 - The Symphonic Sounds of a Lifestyle

by Chris Devaney   

Is a roof-top wind farm for you?  They’re not for everybody, but it could very well be, for some, the first step toward a greener lifestyle and energy independence.  This article will supply some groundwork to help you decide.  Along the way, I’ll debunk some common myths surrounding roof-top wind generators (RTGs) and describe some features built in to most units that further enhance the sleepability and general pleasure of experiencing life with a roof-top wind generator, or two, or three, or...

First off, though, RTGs make noise.  It’s a fact, as it is true, more or less, for all rotating machinery.  Like people, some noise is just more pleasing, more interesting, and overall more fun to be around. Take music, for example.  In regards to nature sounds, you’d be hard-pressed to read a novel and not find a reference to some specific nerve-calming sound derived from the wind.  Wind sounds seem a nice part of the human experience.  Except perhaps for Hilda. 

With a slightly increased beat of my heart, still, even after 25 years, I recall with a strange fondness when I was secretly in love with Hateful Hilda the Widowed Waitress.  It was rumored her husband had died of the bloody flux.  I met her at the Moose Lip Café where she was doling out late-night food and coffee, some free advice, and psychiatric amendments to anyone in need, even those not in need.  She was widowed way too young and it seemed to have an ill effect on her disposition.  But Hateful Hilda was a good listener.  One ear was much bigger than the other so she couldn’t help hearing from that side even if she didn’t want to.  I suppose, because of that ailment nothing was ever in harmony for her.  She once flat out told me she hated music.  All music.  Gasp!  My best guess is that H.H., hardy as she was, would NOT be a very good candidate for a roof-top wind generator.  But she was one-of-a- kind!  Alas, she married again shortly after I met her... to someone else, and moved away. 

Wind gennys, as they are affectionately known, are dynamic.  I think that’s why we like them so much.  You can watch them work; hear them sing.  They transform seamlessly from a whisper to a song, to a whine and a howl.  And they will do it all day, all night whenever the wind asks.  To me, it’s the sound of electrons filling a bank of batteries for later use.  What I previously had to purchase from a soot-belching, highly impersonal conglomerate, one adept at splitting apart unnaturally high concentrations of already unstable nuclei, now comes my way on the wind along with a song...without cancer, without radiation, and most noticeably, without a monthly bill.  If I don’t listen to the song, it rewards me with electrons and a symphony anyway.  

            Over the course of several years, I installed two Southwest Windpower Air-X 400 watt wind turbines and a Mallard 800 watt wind generator on my small homestead using a roof-top mounting instead of towers.

The two Air-X’s have a 46-inch rotor and come to life when the wind speed reaches 7 mph.  The third wind generator, the odd ball, the Mallard 800E, lies dormant until 9-10 mph.  It has a 5-foot rotor with 6 blades.  Plenty of torque but it seems to lack in power over most of the wind spectrum prevalent here, (but read on)!

7-10 MPH

At 7 to 10 mph, the Air-X gennys spring to life.  With a barely audible, low-pitched, bearing-rumble, sounding more like Elvis starting up Blue Christmas at 33-1/3.  The rotors turn ever-so-slowly, almost begrudgingly.  If you listen closely, a slight whoosh of air can be heard, although it’s usually drowned out by the other sounds of life in and around the house.  At this slow speed, each rev of the rotor can be discerned and matched with a spot in the air, perhaps corresponding to a relative flat spot on a ball in the bearing.  It’s more noticeable if I’m up in the loft or outside but hardly so in the living quarters.

No power is generated at the lower end of this regime as the output of the alternator is way below the 12 volts of my battery bank.  A not-so-convenient red LED light is positioned on the underbelly of the Air-X that illuminates when the output exceeds the battery voltage and the unit starts charging.  Depending on the state of the batteries, as the wind speed increases to around 10 mph, the LED comes on and the Air-X’s begin to feed the batteries a breakfast of electrons...and the fun begins.

Here the internal alternator starts to load up and the low-frequency bearing-rumble gets louder.  No more Elvis, he’s dead.  It sounds more like a bass cello whose fat strings are set vibrating from the gentle strokes of nature’s bow - mellow, vibrant, well-plucked.  Shortly, the rumble is overshadowed by an increasing whooshing of air, a soft whisper that gently touches the ear, plainly audible now from inside the house.  At the upper end, around 9-10 mph, the whoosh is more like the sound of a summer breeze whistling through a slightly-open, screened window.  Sometimes I think to myself that perhaps a delicate honeysuckle fragrance should be riding in on the breeze but abruptly I remember that I’m a bachelor, on a farm with livestock, so...

Suddenly, my thoughts are interrupted.

On the other side of the house, the east side genny kicks in, and now there’s two part harmony adding dimension and flavor to a freshly nucleated symphony of wind.

The Mallard, the bigger brother, wakes up sluggishly around 9-10 mph.  Noticeably absent is the bearing rumble sound, for he seems to be built of stronger stuff.  Quieter as well.  The Mallard’s slower rotational speed results in a lower-frequency, lower-pitched air whoosh that adds depth and bottom-end to the slowly growing wind song.  However, at this stage of the game, it is positioned too far away from the symphony to play a major role.

Everything at this wind speed is slow, soft, leisurely.  The low wind speed fails to keep the rotors moving for any length of time so the music is inconsistently punctuated with lots of empty space.  Interesting, but it leaves you asking “Is that all there is?”  Output isn’t even worth measuring, but it’s there.

I installed a homemade power panel right by the ladder into the loft. It consists of a volt and ammeter for each device (including the solar panels) and stop switches for the wind generators plus a cut-off switch for the solar end of things. The gauges allow me to monitor the instantaneous voltage and current output of each device as well as the state of my batteries. The stop switches are designed so that I can shut down a generator in case of high damaging winds or for maintenance. The gauges are an automotive item and come equipped with a small bulb that, when I switch it on, acts as a convenient night-light.

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