GRABBING FREE ENERGY FROM THIN AIR. BATTERY FREE DESIGNS.

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Powering Up

the Battery-Free World

Oct 31, 2010 23:58 ideyoshi Kume

The enormous attention garnered by the growing market, in spite of the tiny amounts of power available, is due to the high convenience it promises. The major selling point for energy harvesting is that equipment can use it to eliminate primary battery replacement, wiring and maintenance (Fig. 2). It will mean a switch from low power to no power.

Fig. 2 Battery-Free Design for Enhanced Convenience
The key point is that primary batteries and wiring are no longer needed (a). Vibrator “battery” combines a capacitor and generator (b). The same size as a battery, it can be swapped into a remote control. A remote control for relay truck jacks was jointly developed by NHK Toyama Broadcasting Station and Yuasa (c), driven by the force of the finger pressing the buttons.

The range of applications is gradually expanding as industry makes an effort to realize this convenience. The Hoki Museum in Chiba City, Chiba prefecture, which opened on Nov. 13, 2010, for example, adopted energy harvesting technology for voice guidance switches. The system is already in operation.

Control signals are handled via wireless, eliminating the need for new wiring for the switches. Setting up the power cables and other wiring for frequently changing exhibits has always been a major load for art museums, and energy harvesting’s wire-free strengths are invaluable here.

Changing Peripheral Components

A representative energy harvesting system consists of four major steps, namely (1) detecting the energy source and generating electricity, (2) converting the acquired electricity as needed in a power supply circuit for storage in capacitors or rechargeable batteries, (3) using the stored power to drive microcontrollers and sensors, and (4) using a wireless transceiver to pass information acquired from sensors to the outside world Note 1).

Note 1) The price of a unit implementing these four functions, according to Linear Technology’s Armstrong, is “about US$12 in lots of 50,000.”

The concept of energy harvesting is quite old, and research in the field also has a long history. The rapid expansion in application fields of late is due to evolution in the peripheral components to make best use of the generating devices, corresponding to steps (2) through (4) above. This evolution has made it possible to utilize the technology in an increasing range of applications.

Fig. 3 Generated power Exceeds Self-Consumption
The performance of generating devices is rising, while the power needs of peripheral components drops. The appearance of high-tech startups with superior technical expertise is especially significant in radio transceiver ICs, which dissipated the most power.

Peripheral component evolution here refers to significant reductions in power consumption by the power supply circuits needed to efficiently utilize generated power, the wireless ICs that send and receive signals, microcontrollers and sensors (Fig. 3). Until recently, the electricity collected by the generating devices was expended by the peripheral components themselves, making the target function impossible to achieve. Now that there are a number of ICs available with high-efficiency, low-dissipation circuits, energy harvesting has finally entered the realm of the practical.

Received & published by Henry Sapiecha

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