Design Study of an HTS Linear Power Generator Suitable for Wave Energy Power Generation

Nov. 29 15:00-15:20

*Petrus Kambo1, Yuhi Yamanouchi1, Antomne A Caunes1, Kota Yamaguchi2, Mitsuru Izumi1,3, Tetsuya Ida1
Tokyo University Of Marine Science And Technology, Japan1
National Institute Of Technology, Oshima College, Japan2
National Institute Of Technology, Toba College, Japan3

In this presentation, we introduce an ocean energy power generator using high-temperature superconducting (HTS) bulks. HTS bulks can trap high magnetic flux density over ten times higher than the maximum magnetic field produced by permanent magnets. Ocean energy power generation using seawater, which has a density 840 times higher than that of the atmosphere, requires power generation devices to be driven at low speeds with high torque. HTS bulks are suitable for power generation because they generate a strong magnetic field. We have conceptually designed a linear generator for wave energy converter using HTS bulk field poles. The large forces generated by ocean waves often place significant loads on the power generation mechanism, requiring them to be combined with the damper. In linear generators for wave power converter that include HTS bulk field poles, the large electromagnetic forces generated by the high magnetic fields associated with the HTS bulk magnetic poles will replace that damper, effectively driving the linear generator's translator power generation system with low mechanical losses. For this reason, in this study we designed a new linear power generation structure for wave energy converter. The proposed linear structure utilizes(Re)Ba2Cu3O(7-δ) HTS bulks for field pole. The HTS bulks were modelled numerically using a finite-element model based on the H-formulation and implemented in COMSOL Multiphysics software. Since the proposed linear generator will be used for power take-off of a wave energy converter, we plan to use a buoy as a primary capture of the kinetic energy from the vertical component of ocean waves speed. But, since the buoy is connected to the translator power generation system of the linear generator, the speed of the translator power generation system is also low as the ocean waves slow down vertically. In order not to reduce its power output, the reciprocating speed of the translator must be increased despite the slow buoy oscillation since output power is a function of the speed and force of the translator power generation system. For this reason, we devised a structure of the linear generator with a dual translator power generation system. This structure has dual layered armatures to improve the amount of electricity generated. It would require extra external force to drive the generator but may be rather desirable in wave energy converter as it would enhance the performance of the damper. And the relative speed between the armature coils and HTS bulk field poles is increased by driving the dual translators. The improved design of the linear generator associated with the use of HTS bulk field poles increases the output power of the proposed linear generator. This is important innovation to improve the operational conditions that were difficult for the conventional generators to cope with: generating practical output power from general waves, which are characterized by low speed and high force.

It is necessary to develop a new design concept generator that operates at low speed with high torque or force ability to make ocean power generation a reality. By improving the speed of the linear generator, we show a new linear power generation structure that aims to improve the output power by adopting the dual translator power generation system, which increases the rate of change of magnetic flux through the armature copper coils. The use of HTS bulks increases the electromagnetic forces, which not only increases the output power of our proposed linear generator but also improves its damping performance. We compared the results of our new conceptual linear generator structure with those of the simulation of the conventional linear generator structure. It was found that the proposed linear generator structure can increase electromagnetic force and power density higher than that of conventional linear generator structure. As expected, the combination of the dual translator power generation system and the HTS bulk field poles has the potential to help us to achieve higher torque, higher power density at a low ocean wave speed, which makes the proposed linear power generation structure suitable for our purpose. The proposed linear power generation structure is devised to meet the conditions required for ocean energy power generation, so it is expected to promote the practical application of ocean energy power generation systems.

Keywords: High-Temperature Superconducting Bulk, Ocean Energy, Wave Energy Converter, Linear Power Generator