Takakazu Shintomi

Technical and Cost Evaluation on SMES for Electric Power Compensation

RASMES (Research Association of Superconducting Magnetic Energy Storage) in Japan developed a road map of SMES for fluctuating electric power compensation of renewable energy systems. Based on the progress of large superconducting coils, the technical status is already established to develop the several MWh class SMES for frequency control, load fluctuation compensation, and generation fluctuation compensation. With integrated operations of several dispersed SMES systems, it is expected that the 100 MWh class SMES for load fluctuation leveling (peak cut) can be introduced in the period of 2020-30, and the first 1 GWh class SMES for daily load leveling can be installed in the period of 2030-40. From the results of Japanese national projects, experimental device developments and SMES design studies, if the output power of SMES is 100 MW, the target cost of SMES can be evaluated with 2000 USD/kW of the unit cost per output power (the unit cost per kW).

Application of SMES and Fuel Cell System Combined With Liquid Hydrogen Vehicle Station to Renewable Energy Control

It is an urgent issue to reduce global carbon-dioxide in the world, and hence the renewable energy, that is environmentally friendly, should be supplied as a large amount of the electric power. Since installation of a large amount of the fluctuating renewable energy, such as wind turbine and photovoltaic, will cause the power utility network unstable, we propose an advanced superconducting power conditioning system (ASPCS) that is composed of Electrolyzer-Hydrogen-FC and SMES cooled with liquid hydrogen from a station for vehicles. The ASPCS has a function of compensating the fluctuating renewable energy with SMES that has quick response and large I/O power, and with that has moderate response and large capacity. The SMES is wound with superconductor with a critical temperature of 39 K from an economical point of view, because it is cooled with through a thermo-siphon system to keep safety against a flammable gas. The ASPCS effectively fulfills a power balance by applying a statistical prediction method of Kalman filter algorithm. The capacity of SMES is optimized by using the trend prediction for a number of wind power data. The overall electric efficiency of the ASPCS is evaluated for a typical wind generator.

Status of Japanese gravitational wave detectors

The Large-scale Cryogenic Gravitational wave Telescope (LCGT) is planned as a future Japanese project for gravitational wave detection. A 3 km interferometer will be built in an underground mine at Kamioka. Cryogenic sapphire mirrors are going to be employed for the test masses. For the demonstration of LCGT technologies, two prototype interferometers, TAMA300 and CLIO, are being developed. This paper describes the current status of the LCGT project and the two prototype interferometers.

Japanese large-scale interferometers

The objective of the TAMA 300 interferometer was to develop advanced technologies for kilometre scale interferometers and to observe gravitational wave events in nearby galaxies. It was designed as a power-recycled Fabry–Perot–Michelson interferometer and was intended as a step towards a final interferometer in Japan. The present successful status of TAMA is presented. TAMA forms a basis for LCGT (large-scale cryogenic gravitational wave telescope), a 3 km scale cryogenic interferometer to be built in the Kamioka mine in Japan, implementing cryogenic mirror techniques. The plan of LCGT is schematically described along with its associated R&D.

Thermal lensing in cryogenic sapphire substrates

We report the reduction of thermal lensing in cryogenic sapphire mirrors, which are planned to be used in the large scale cryogenic gravitational wave telescope project. We measured three key parameters of sapphire substrate for thermal lensing at cryogenic temperature. They are the optical absorption coefficient, thermal conductivity and temperature coefficient of refractive index at cryogenic temperature. On the basis of these measurements, we estimated the shot noise sensitivity of the interferometer with thermal lensing by using a wavefront tracing simulation. We found that thermal lensing in cryogenic sapphire mirrors is negligible.

Design Study of SMES System Cooled by Thermo-Siphon With Liquid Hydrogen for Effective use of Renewable Energy

In order to use effectively renewable energy sources, we propose a new system, called Advanced Superconducting Power Conditioning System (ASPCS), that is composed of SMES and Fuel Cell-Electrolyzer (FC-EL) in connection with a liquid hydrogen station for vehicles. The new system will compensate the fluctuating renewable energy sources with SMES having characteristics of quick response and large I/O power, and with FC-EL having characteristics of moderate response and large storage capacity. The SMES coil with an MgB2 conductor operated at 20 K is cooled with a thermo-siphon cooling system by using cryogen from the liquid hydrogen station. The necessary minimum storage capacity of SMES is estimated as 50 MJ for compensating output power of 1 MW. A four-pole SMES coil is designed by using stranded cable concept. The design study of the SMES coil composed of the MgB2 conductor and the thermo-siphon cooling system is reported.

Current status of the CLIO project

CLIO (Cryogenic Laser Interferometer Observatory) is a Japanese gravitational wave detector project. One of the main purposes of CLIO is to demonstrate thermal-noise suppression by cooling mirrors for a future Japanese project, LCGT (Large-scale Cryogenic Gravitational Telescope). The CLIO site is in Kamioka mine, as is LCGT. The progress of CLIO between 2005 and 2007 (room- and cryogenic-temperature experiments) is introduced in this article. In a room-temperature experiment, we made efforts to improve the sensitivity. The current best sensitivity at 300 K is about 6 × 10-21/√Hz around 400 Hz. Below 20 Hz, the strain (not displacement) sensitivity is comparable to that of LIGO, although the baselines of CLIO are 40-times shorter (CLIO: 100m, LIGO: 4km). This is because seismic noise is extremely small in Kamioka mine. We operated the interferometer at room temperature for gravitational wave observations. We obtained 86 hours of data. In the cryogenic experiment, it was confirmed that the mirrors were sufficiently cooled (14 K). However, we found that the radiation shield ducts transferred 300K radiation into the cryostat more effectively than we had expected. We observed that noise caused by pure aluminum wires to suspend a mirror was suppressed by cooling the mirror.

Current status of Japanese detectors

The current status of the TAMA and CLIO detectors in Japan is reported in this paper. These two interferometric gravitational wave detectors are being developed for the large cryogenic gravitational wave telescope (LCGT) which is a future plan for detecting gravitational wave signals at least once per year. TAMA300 is being upgraded to improve the sensitivity in a low-frequency region after the last observational experiment in 2004. To reduce the seismic noises, we are installing a new seismic isolation system, called the TAMA seismic attenuation system, for the four test masses. We confirmed stable mass locks of a cavity and improvements of length and angular fluctuations by using two SASs. We are currently optimizing the performance of the third and fourth SASs. We continue TAMA300 operation and R&D studies for the LCGT. The next data taking is planned for the summer of 2007. CLIO is a 100 m baseline length prototype detector for LCGT to investigate interferometer performance in cryogenic condition. The key features of CLIO are that it locates the Kamioka underground site for a low-seismic noise level, and adopts cryogenic Sapphire mirrors for low-thermal noise level. The first operation of the cryogenic interferometer was successfully demonstrated in February 2006. Current sensitivity at room temperature is close to the target sensitivity within a factor of 4. Several observational experiments at room temperature have been done. Once the displacement noise reaches the thermal noise level of room temperature, its improvement by cooling test mass mirrors should be demonstrated.

Design Study of

In order to use effectively renewable energy sources such as wind and photovoltaic power generations, we propose a new system, called Advanced Superconducting Power Conditioning System (ASPCS), that is composed of superconducting magnetic energy storage (SMES), fuel cell-electrolyzer (FC-EL), hydrogen storage, dc/dc and dc/ac converters, and controller. The new system compensates the fluctuating electric power generations with SMES having characteristics of quick response and large I/O power and with hydrogen energy having characteristics of large storage capacity. The ASPCS will be combined with a liquid hydrogen station for FC vehicles. The SMES is a key component of the ASPCS to compensate the fast fluctuations of the renewable energy generations that cannot be compensated by prediction using the Kalman filtering method. The design study of the 50 MJ SMES coil was performed with an MgB2 conductor to be operated at 5 T maximum and 20 K by using liquid hydrogen of the FCV stations. The stability and ac losses of the coil were estimated in this study.

\hbox{MgB}_{2}

A large heat load caused by thermal radiation through a metal shield pipe was observed in a cooling test of a cryostat for a prototype of a cryogenic interferometric gravitational wave detector. The heat load was approximately 1000 times larger than the value calculated by the Stefan-Boltzmann law. We studied this phenomenon by simulation and experiment and found that it was caused by the conduction of thermal radiation in a metal shield pipe.