• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.938-943
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• 2007

In this paper, we show that, in case of piezoelectric micropower generator, just replacing Schottky diodes in the bridge rectifier with ultra-low reverse leakage current diodes improves the mechanical-to-electrical energy conversion efficiency by more than 100%. Experimental and PSPICE simulation results show that, due to the ultra-low leakage current, the charging speed of the circuit employing PAD1 is higher than that of the circuit employing Schottky diodes and the saturation voltage of the circuit employing PAD1 is also higher. This study suggests that , when the internal impedance of source is very large (a few tens of $M{\Omega}$) such that maximum charging current is a few microamperes or less, in order to realize literally the energy scavenging system, ultra-low reverse leakage current diodes should be used for efficient energy conversion. Since low-level vibration is ubiquitous in the environment ranging from human movement to large infrastructures and the mechanical-to-electrical energy conversion efficiency is much more critical for use of these vibrations, we believe that the improvement in the efficiency using ultra-low leakage diodes, as found in this work, will widen greatly the application of piezoelectric micropower generator.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.117-122
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• 2010

The solar cells and fuel cells power are being encouraged to reduce the environmental pollution and combat the global warming. And the electric generation hybrid system is usually more reliable and less costly than the systems that use a single source of energy. HOMER provides a platform to design and simulate the power system and then to choose the optimization results. Based on the electricity demand conditions during a year, this paper simulates with the HOMER and performs the monthly average electrical production and the most feasible economical case includes the net present costs and the annualized costs of the hybrid system components.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.623-628
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• 2010

This paper presents a wind-power-driven portable power source based on piezoelectric effect. Positive piezoelectric effect is one of efficient and widely used mechanisms for converting mechanical energy to electrical energy. However, for this mechanism, a periodic mechanical stress with a high frequency, as in the case of AC, has to be exerted; such stress cannot be exerted by the natural wind in the environment. The natural wind has a constant velocity with slow and irregular variations, as in the case of DC. In this paper, we propose a novel and simple mechanism to convert mechanical energy into electrical energy. The DC-like wind flow is passed through a propeller to convert it to an AC-like wind flow; the resultant AC-like periodic flow induces vibrations in a piezoelectric cantilever, thereby, generating electrical power. This system is expected to be one of practical solutions for wireless energy supply to ubiquitous sensor networks (USNs).