Unlike low-cost massive energy sources for grid systems, energy harvesting is a high-added-value power generation technologies, in which small power can be extracted from energy sources in the environment. Energy harvesting technologies will make an important contribution to autonomous devices including wireless sensor nodes by providing battery-less long-lived power source. Recently, significant efforts have been paid in the country and abroad toward various applications such as building energy management system.
There are various small energy sources such as renewable energy which can be transferred to electrical energy. For example, sunlight, indoor light, heat, vibration, radio wave, etc. Energy harvesting is the technique to transfer these energies to electrical energy. In recent years, energy harvesting devices attract attention as an independent generator of the wireless sensor node. We think human action, heat, indoor light are energy sources to easy to get in our life and we are developing the harvesting devices such as piezoelectric generators and thermoelectric generators, photovoltaic devices which can convert these three energy into electrical energy. In this paper, I mention the structure and characteristics about dye sensitized photovoltaic device which is superior in generating by indoor light, particularly feeble light. Furthermore, I introduce “Watching system” as an applied example about wireless sensor network using this device.
This paper describes a basic concept of thermoelectric tubes. Construction of thermoelectric tubes has been done by making use of the off-diagonal thermoelectric effect, which is one of the direct energy conversion processes from heat into electricity. Here we also present a fabrication process and the current status of a feasibility study at a garbage incineration plant in Kyoto.
A way of energy harvesting technology from ocean power, e.g. tide, current, wave, breaking and vortex, using a flexible piezoelectric device (FPED) has been developed. The FPED consists of a piezoelectric material and an elastic substrate such as rubber, silicon and resin. The FPED can generate electric paper from ocean, wind and vibration energy. An ocean power generator of elastic floating unit with hanging structures (EFHAS) consisting of floating unit and hanging one using the FPEDs has been developed and the EFHAS could be a useful energy harvester as ocean power generator.
Vibration energy harvesting is a method by which kinetic energy present in the environment or by mechanical vibration is captured and then converted into electricity for powering wireless sensors in various applications such as sensor network and structural health monitoring. In the present paper, after a brief introduction to vibration energy harvesting, electret materials and charging technologies, recent progress in MEMS electret generators is overviewed.
Vibration based power generation technology is utilized effectively in various field. Author invents novel vibrational power generator using Fe-Ga alloy, iron-based magnetostrictive material, with large inverse magnetostrictive effect, good machinability and high ductility. The generator is based on parallel beam structure consisting of Fe-Ga plate wound with coil and yoke accompanied with bias magnet. When bending force is applied on the tip of the generator, the magnetization inside the plate varies with induced stress due to the inverse magnetostrictive effect. In vibration, the time variation of the magnetization generates voltage on the wound coil. The magnetostrictive type is advantageous over conventional such using piezoelectric or moving magnet types in high efficiency and high robustness, and low electrical impedance. Author has established device configuration endurable for practical applications. This paper describes the principle and merit of magnetostrictive type, the evaluation results of miniature prototype, its problem and future potential.
This paper reports an electromagnetic vibration energy harvester with magnetic material in which nonlinear oscillation results in broadband operation frequency range for power generation. Moreover, the present harvester is shown to have double-well potential which yields chaotic oscillation.
Power supply is one of the key challenges for perpetual operation of electrical devices in Internet of Things (IoT) era. Low power electrical devices used at home are usually powered by coin cell batteries. However, the battery charging for such devices result in significant increases in operation cost. In this paper, we discuss feasibility of harvesting and storing a small amount of energy from ambient electromagnetic waves. A combination of an antenna and rectifier can be used to collect a few hundreds of microwatts of energy from several energy sources such as TV towers and microwave ovens. By accumulating this energy over time by a capacitor, it is possible to provide power to low-power devices and realize perpetual operation of such devices.
A 5-DOF self-bearing motor has been proposed for achieving a compact active magnetic bearing (AMB) system. The 5-DOF self-bearing motor possesses the functions of a motor, two radial AMBs, and an axial AMB. Therefore, it is possible to downsize the AMB system while maintaining its high performance. In this paper, a downsized outer rotor type 5-DOF self-bearing motor is proposed for the application to an artificial heart pump. An experimental setup was fabricated based on the analytical results obtained by a three-dimensional finite element analysis and was then tested. The proposed outer rotor type 5-DOF self-bearing motor proves to have a sufficiently applicable performance for use as an artificial heart pump.
Experts now know that past iron loss measuring methods cannot quantitatively evaluate iron loss in an actual stator core with a complex shape. As such, we are researching a new method to measure the iron loss and magnetic properties of an actual stator core. We have already proposed a stator winding excitation method (SWEM), which can directly evaluate the iron loss of an actual stator core with a complex shape using a rotating machine to observe the magnetic flux which passes through each tooth. In this method, stator windings were used to generate the excitation magnetic flux in the stator core. In this study we will, report on the evaluation results of the magnetic properties for an actual stator core under conditions in which compressive stress is applied to a stator core. In order to reproduce stress in the manufacturing process, we used a two-axis external stress application device. We measured the magnetic properties in an actual stator core using the proposed method and device. Consequently, the magnetic properties of the actual stator core were affected in an obvious manner by the compressive stress.
The impedance matching is an important technique for the improvement of the transmission efficiency of the waveguide slot array antenna with the dielectric lenses. We apply the electromagnetic field analysis technique to the impedance matching method by inserting the tuning screw into the waveguide wall. To reduce the VSWR over the frequency band, the optimization method of the tuning screw by the μGA is proposed. The objective function of the μGA is calculated by the FDTD method. From the calculation results, the VSWR in the frequency range from 11.8 to 12.2 GHz is improved by optimizing the screw parameters. The antenna matching by the μGA shows good performance as compared with that by the conventional method. Also, the validity of the proposed method is confirmed by the measurement result.
It's possible to measure static load using piezoelectric film by sticking 2 sheets of identical films together. When one of the films is oscillated at its resonant frequency, the other film generates voltage by following up to the motion of the actuator film. The vibration of the body is suppressed due to the impressed load, and then the sensor voltage drops according to the magnitude of the load. Vibration analysis proved that the configuration of the vibration of the sensor body is not bending but in-plane expansion and contraction. It's also turned out that the characteristics of the sensor voltage are dominated not by the magnitude of the load but by the contact area of the load with the film. Therefore introducing the lamination material, which alters the contact area according to the magnitude of the load, will improve the sensitivity and the linearity of the sensor voltage to the load.