Energy in vibrations is a potential source of power for low power sensing nodes. Sensing nodes are employed for intelligent ambient monitoring and information dissemination. The primary challenge in making a sensing node autonomous is the ability to power it continuously. The conventional method of powering these nodes through batteries has an associated drawback of periodic maintenance and replacement. Alternative methods of powering sensing nodes are gaining impetus with the advent of low power electronics. Power harvesters based on piezoelectric effect are more promising in harnessing energy from ambient vibrations.
The piezoelectric harvesters are ideal for low power sensing nodes that operate in a vibration rich environment. Stationary installations such as centralized air conditioning, clean room consists of ducts and blowers which generate vibrations continuously (Fig 1). An attempt of tapping this energy improves the effectiveness of the system as the power developed by the harvester is drawn from the unused portion of the energy supplied to the system (Fig 2).
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| Figure 1 | Figure 2 |
Piezoelectric harvesters in the form of a resonating cantilever are designed and analyzed. The piezoelectric material used for fabricating the harvester is lead zirconate titanate. Each harvester develops a power of 100 mW from the vibrating surface. A typical acceleration signature of the vibrating surface is shown in figure 3. The alternating output from the harvester is rectified and regulated before delivering it to the load. Figure 4 shows the logo of CeNSE made of 147 low power consuming LEDs. Four harvesters in the form of an array additively power the logo. As the power required by the logo is 3.6 mW, the logo glows intermittently. Sensing nodes and systems that require power below 1 mW can continuously be powered by the array. However, array configuration of the harvesters is essential for the power requirements above 1 mW.
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| Figure 3 | Figure 4 |
The effectiveness of harvesters, availability of the ambient energy, and the methods of scaling the output are under investigation. Nevertheless, experiments with harvesters indicate that the power generated is adequate for operating sensing nodes that require < 1 mW of power.
Contributed by: S. Rammohan, Advisor: Prof. Rudra Pratap.