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Bite-size Energy

The new idea of harvesting energy has nothing to do with growing plants to make biofuels. It’s a much broader and very different concept. Harvesting energy means using whatever kind of energy is available in a particular place and converting it to electricity.

Untapped energy resources are just about everywhere. Some occur naturally, such as light energy from the sun or wind energy from local weather patterns. Other kinds of energy are byproducts of human activities, such as the extra mechanical energy produced from the movements of devices doing other jobs.

Wouldn’t it be nice to “harvest” all that extra energy, turn it into electricity, and put it to good use? Instead of developing enormous systems for these unconventional energy resources, the key to success often depends on thinking small.

Products harvest power just about anywhere
The “smaller is better” concept is expanding the range of locations where the sun’s energy can be harvested. Ordinary rigid glass-based photovoltaic solar panels are very heavy. That added weight is often too much for existing structures to support.

Xunlight (www.xunlight.com), a company based in Toledo, Ohio, offers ultrathin permanent solar modules that only weigh about half a pound per square foot. These flexible solar arrays arrive looking like rolls of roofing paper. When unrolled, they can be added to the tops of buildings without the need for expensive roof reinforcements or other modifications.

Even smaller flexible solar arrays are helping hikers and campers solve the problem of keeping digital cameras, cell phones, and other electronic gadgets powered up far off the beaten path. Instead of hauling around clunky extra batteries, which are heavy and take up valuable backpack space, outdoor adventurers can just bring along a small portable solar panel that will recharge everything on the spot.

Brunton Outdoor (www.bruntonoutdoor.com), a company based in Riverton, Wyoming, makes several styles of portable solar panels in compact sizes to harvest the energy in sunshine anywhere. One product line features rolled-up solar arrays about the size of a roll of paper towels that, when opened out flat, can operate electronic devices, recharge batteries, or both. These mini solar-panels-to-go are waterproof and can be used over and over again.

Some families are adding these handy little solar arrays to their household emergency kits to use when regular grid power is disrupted.

Engineers in the U.S. Navy and Marine Corps are crafting their own versions of take-along solar panels that are even thinner—about the size of placemats. The military’s ultrathin solar collectors can be unrolled or unfolded in minutes to begin harvesting energy on the spot, no matter how far away troops are from base camp or supply depots. The ability to convert sunshine into electrical energy anywhere means troops don’t need to wait for convoys to bring in bulky generators and the diesel fuel to operate them.

To harvest more energy from wind resources, engineers are also thinking small—and sideways. Instead of extremely long blades spinning in huge circles hundreds of feet above the ground, the new vertical axis wind turbines from California Energy & Power (www.cal-epower.com) are less than 50 feet tall and only 10 feet wide. A narrow housing with a side opening helps direct the flow of wind toward the spinning blades inside.

About 20 of these short, slim turbines can generate around 10 times the amount of electricity per acre compared to typically sprawling wind farms with tall horizontal axis turbines, a giant leap in power density. Other advantages of these wind turbines are that they produce little noise, do not interfere with radar or other communications, and are less likely to harm birds and bats.

Producing electricity from roads and runways
Another place to harvest previously unused energy is right at ground level. As cars and trucks roll across pavement, the pressure of the tires and the weight of the vehicles compress the surface slightly. As the paving surface is continually deformed and then expands back to its normal thickness, mechanical energy becomes available. As certain materials respond to these changes in pressure, they produce electrical charges through processes known as piezoelectric phenomena.

University professors and engineers at Innowattech (www.innowattech.co.il), a new company based near Haifa, Israel, have developed small piezoelectric disks (some about the size of cake pans) that can be installed just below a road surface.

Tiny wires connected to the disks gather the bits of electricity being produced as vehicles travel across the road, combine them, and make the electricity available for immediate use in roadside signs and signals. This harvested energy can also be sent into the local power grid for homes and businesses, or into storage systems for later use.

Innowattech’s process can also harvest the mechanical energy in airport runways, railway lines, and even pedestrian sidewalks. There’s no need to acquire additional land to produce useable electric power, and since everything is actually slightly belowground, the devices work in all weather conditions, day or night.


KEYWORD EXCLUSIVE: POWER IN PAVEMENT To watch a short video about how the mechanical energy from vehicles traveling over roads can be converted to electricity, and to meet the engineers behind this innovative way to harvest more energy, click electric roads.

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