Harvesting Power for Fun and Profit

Harvesting Power for Fun and ProfitWhat limits gadgets? Often it is power consumption. The lower the power needed to run a gadget, the more applications are available. Early computers less powerful than my phone took massive cooling towers to operate. Another major limitation is cost. Both cost and power requirements have fallen sufficiently that new ways of doing things are slowly becoming mainstream. Low-cost power-conserving devices produce effects beyond simply making computers portable.

Scavenging power is sometimes referred to as a parasitic power supply. That is an unfortunate name for a good thing. Consider the changes that scavenging can make in construction. My father was an electrician. I spent many summers with him running wires in new houses. Houses built today are wired essentially the same way they were 70 or more years ago. To control a light, wires run from the switch through the walls to the overhead lights. Electricians are good at drilling holes to run wires. But with reductions in price and power consumption, a new paradigm is possible. Several companies make wireless switches that do not require expensive drilling and manual running of wires through walls. Some switches are battery powered, but the more interesting ones scavenge power from the effort of throwing the switch. Pressing the button generates electricity, which is stored in a capacitor to power a wireless signal to the light fixture. Lower power consumption combined with low-cost electronics will change the way that houses are built.

Scavenging power has interested me ever since I saw a perpetual clock around 1950. It is an amazing example of mechanical technology. Changes in temperature and barometric pressure are harvested to power the mechanism. It never needs winding. Similarly, I had a mechanical wristwatch that wound itself by harvesting energy from my arm movements. Today, my solar-powered Casio G-Shock not only powers itself, but it also listens to WWV to keep itself accurate. YouTube has many videos on scavenging or harvesting energy; for instance, see this excellent presentation:

Scavenging power is related to green energy, but is not necessarily driven by the same considerations. I was a consultant to a company that makes micro-metering devices to monitor water consumption in apartment buildings. Normally an entire building is on a single meter, and residents are not individually motivated to conserve water, but by adding individual meters, they can be charged fairly. Retrofitting is an issue since the devices need power and need to communicate. Sufficient power can be generated by the sensing vanes inserted to measure the water flow. Power is harvested as the vane spins to send occasional updates to a central unit without the expense of running wires throughout. This results in water conservation since now tenants are charged for what they use (which is good for everyone), and probably results in the owner collecting more income (which is bad for tenants).

Self-powered remote sensors can optimize irrigation by reporting ground conditions to a central unit.

Some uses of scavenged energy are just for fun, like the lights on children’s shoes that flash when they walk, but more serious technology can power a wearable computer. Embeddable sensors inside a human body can be powered by temperature differences or muscle flexing. The December 2012 issue of Scientific American mentions the possibilities of electronic tattoos, which could be purely decorative or contain sensors to monitor body functions. Heart pacemakers are traditionally powered by replaceable batteries (which requires open heart surgery every seven years or so — ouch and $$s). New devices that harvest power internally can eliminate that process.

My wife and I have a beach bag painted with a design that changes color in sunlight. This is just one example of flexible fabrics being used to harvest solar power. That application is decorative, but some people charge laptops from solar energy collected by a normal-looking backpack.

Do you know of any novel way that energy is being collected on small scales? What small-scale energy now being wasted will be harvested in the near future? How will that change the way we live? Would you volunteer to test an embedded electronic device like a direct access calculator or Internet?

Image: Perpetual by Ghetu Daniel

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