The Answer May Be Blowin’ in the Wind

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Television networks have worked continuously to maximize their return on investment by making spectator sports more exciting. For example, I once heard a proposal about how NASCAR races could be more compelling by putting the beer stand in the middle of the track. “Now that would be a sport!” said one producer. News organizations have long operated in accordance with the same doctrine “If it bleeds it leads.” They’ve been pushing the fine line between news and entertainment for a long, long time. One of the initiation rituals is to put young, low seniority reporters downtown to describe an incoming hurricane.

As they stand, waiting to be decapitated by a flying stop sign, they often struggle to be heard above the wind as it messes with the big furry microphone they’re holding. The synthetic fur cover you often see on a microphone is referred to as a “dead cat” or “wind muff” by TV news crews. Experience hath shewn the funny looking covers can actually help to reduce the amount of wind noise that gets broadcast or recorded. One time, when I was tilting at windmills on a calm day, it occurred to me that I was missing the glorious battle. While windmills are ferocious noisemakers, they are highly efficient energy generators because of the wind. 

In recent decades some engineers, after spending years trying to protect microphones from the effects of wind while recording on location, have finally decided to just go with the flow. Among them are those who investigated the possibility of using microphones to charge batteries from noise. While the idea behind microphones has always been to capture intelligible sound, what if they could be used to produce electrical energy from brute force noisemakers like a Boeing 747? Such experiments are ongoing.

They’ve considered numerous ways of converting otherwise wasted energy into useful energy. They measured the noise produced by aircraft, elevated trains, industrial plants, auto horns, jazz bands, trucks, quiet conversations, and enraged spouses. The’ve imagined fences running along the side of busy highways where over 20,000 cars would pass by daily, all of them generating sound. They mused about giant puppy mills with thousands upon thousands of puppies, all hooked up to microphones, with a few cats wandering around outside the cages.

All of these schemes had just one drawback. There isn’t enough energy in the sound to make it worth-while. Think about it. We have little tiny, highly sensitive eardrums. It doesn’t take much to move them. Even very loud sounds, while perceived as big, are only a tiny vibration within our ears. Big noises only sound loud to us because we have evolved very sensitive auditory systems. We can’t harvest large amounts of energy from sound if it just ain’t there.

What if, instead, we take another look at our perceived enemy. Not just the noisy windmills but the wind that drives them. A well designed microphone that is sensitive enough to respond to acoustical energy would also resonate with the wind. Air is always on the move and some combination of upslope anabatic current and downslope katabatic current is always present. It may not be thought of as wind. It may not be enough to move a windmill. But it is likely to contain more energy than sound.

Breezes that are visible as they move across the grass and leaves that flutter when all seems calm, are indications of atmospheric turbulence that can be harvested. While a pressure wave and a mass flow wave may be associated with an acoustic wave, they may have potential beyond that of the acoustic wave. A microphone is simply a transducer between air current and electrical current. While it may be, and usually is, tuned for intelligible sound, it doesn’t have to be. It can also be optimized to respond to tiny convection currents and built to withstand powerful gusts.

An array of microphones installed on a slope or in windy places can perform like a windmill with little environmental impact, posing no threat to birds, and at very low cost. Aggregating the small about of electricity produced by each individual mic could be achieved as many small capacitors give up their charge to a larger one. Several of those burst to an even larger one and so on until they top off a battery somewhere.

Does it sound complicated? Yes. Is it more complicated than your 4k flat panel TV? Certainly not! Is the array of crystals in your TV the same as an array of crystal microphones? No. But, there are similarities when it comes to getting those boys in line to work in synchrony if not idiosyncratically.

The ultimate success of failure of micro-wind technology, as a means to harvest energy, is largely dependent upon the way such systems are configured. Installing individual microphones on a slope should require no more skill than installing low-voltage landscape lighting. A roof covered with photo-voltaic panels on parts that are illuminated by the sun, would look far less kludgy if they could also be covered by resonant panels on the parts that are shaded. Light sensitive shingles and wall panels could be complemented by vibration sensitive panels that are identical in outward appearance.

The technology that must be leveraged to make electricity from blades, leaves, or panels that are responsive to weak convection currents while, at the same time, able to survive being slammed by a rogue rain drop, is well within our grasp.

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