Hokkaido University Research Profiles


Energy: 15

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  • Life Sciences
  • Information and Communication
  • Nanotechnology / Materials
  • Manufacturing Technology
  • Human and Social Sciences
  • Energy
  • Environment
  • Tourism / Community development
  • Arctic Research
  • Social Infrastructure
  • Open Facilities
  • All-solid-state Lithium Secondary Battery with an Inorganic Solid Electrolyte

    Preparation of sulfide solid electrolyte from the liquid phase

    We have successfully deposited sulfide solid electrolyte through a simple process of dissolving sulfide glass, which exhibits high lithium ion conductivity in an organic solvent, and drying the glass. We have also found that this method is applicable to coating of electrode-active materials.


    In all-solid-state lithium secondary batteries that use a lithium-ion conductive solid electrolyte, the construction of a good electrode-electrolyte interface is very important to realize high energy-density batteries. We have conducted this research to construct a good electrode-electrolyte interface by preparing sulfide solid electrolytes from the liquid phase. We prepared a homogeneous solution of Li2S-P2S5-based solid electrolytes by dissolving them in N-methylformamide (NMF), and successfully redepositing Li2S-P2S5-based solid electrolytes by removing NMF from the solution. This solution was mixed with LiCoO2, a cathode material, and solid electrolyte was coated on LiCoO2 by removing NMF. Using this solution, we produced an electrode composite. Then, using the obtained electrode composite and sulfide inorganic solid electrolyte, we successfully produced all-solid-state lithium batteries and confirmed the stable operation of the batteries.

  • Analysis of Thermo-acoustic Vibration Generated by Combustion Equipment

    Thermo-acoustic vibrations often occur in combustion devices and combustion gas exhaust systems, causing noise and reducing the life of the combustion devices. This is caused by acoustic pressure fluctuations coupled with heat generation fluctuations in combustion and exhaust systems. With this study, we analyze this physical process and investigate the suppression technology.


    Thermo-acoustic vibrations are often generated in combustion equipment and combustion gas exhaust systems, leading to noise generation and reduction of the life of combustion equipment. This is caused by acoustic pressure fluctuations linked to heat generation fluctuations in the combustion and exhaust systems, and we are analyzing the physical processes that cause these fluctuations and investigating techniques to suppress them. With this study, a single circular tube is filled with a combustible premixed gas that is ignited at one end, and a thermo-acoustic vibration phenomenon that occurs during flame propagation in the tube is used. Various boundary conditions (open end condition, direction of propagation, composition of the gas mixture, diameter and length of the propagating tube, structure of the flame surface, etc.) are applied to this propagation phenomenon to induce the thermo-acoustic vibration phenomenon, and the factors behind it can then be understood using the combustion instability analysis method. The vibration phenomena reproduced here are observed in a simplified system, but they are general phenomena and lead directly to the understanding of thermo-acoustic vibration phenomena that occur in actual combustion equipment and exhaust systems.

  • Development of Gd?Si?O?-based High-performance Scintillators and Their Application

    Development of high luminescence scintillators for radiation detectors

    Scintillators are materials that emit light by radiation and are used in medical diagnostic equipment, and for oil exploration and other purposes. Gd2Si2O7 (GPS) scintillators have excellent features such as high luminescence, high energy resolution and non-tidal dissolution, and can be made into single crystals, ceramic plates and powders.


    The Gd2Si2O7: Ce (GPS) single crystal scintillator has excellent features such as high luminescence (1.4 times that of NaI:Tl), high energy resolution, non-tidal and no self-radioactivity, and can be used in high temperature environments of 250°C or higher. The technology has been transferred to Oxide Corporation, and is now ready for use in SPECT and other applications. We have also established a stable manufacturing technology for 5 cm square GPS sintered plates. By combining a position sensitive photomultiplier tube, it is now possible to detect nuclear fuel materials emitting alpha rays, which were released in the Fukushima Daiichi Nuclear Power Plant accident, with high sensitivity. The prototype device succeeded in detecting nuclear fuel-induced α-ray-emitting radionuclides in an environment with nuclear fuel-induced α-ray-emitting radionuclides: natural radioactivity (radon progeny) = 1:200, which had been inconceivable with conventional devices.

  • Development of Polymer Electrolyte Fuel Cells with Excellent Sub-zero Start-up Performance

    Elucidation of micro-nano freezing phenomena in fuel cells

    We are visualizing the freezing phenomenon near the reaction layer in fuel cells, which cannot normally be observed, using an ultracold electron microscope. By combining electrochemical measurements, we are also elucidating the freezing phenomenon of produced water, which becomes a problem in cold climate applications, and are developing fuel cells with excellent sub-zero activation performance.


    In the polymer electrolyte fuel cell (PEFC), which is a highly efficient and clean energy conversion device, the water produced by the reaction passes through a catalyst layer pores of several tens of nanometers in diameter and is discharged into the gas diffusion layer and gas supply channel through the microporous layer (MPL), which is a porous layer with pores of several micrometers in diameter, as shown in the left figure below. In the activation in a sub-zero environment in cold regions, the produced water freezes, causing the power generation to stop and degrade. However, the phenomenon is on a micro-nano scale and is thus difficult to measure, so the phenomenon is still insufficiently understood. This study is aimed to clarify where the water freezes and what mechanism leads to performance shutdown and aging degradation. We will conduct microscopic observation, electrochemical measurement and catalyst layer model analysis to contribute to the improvement of activation resistance and extension of the service life. The middle figure below shows the catalyst layer filled with ice, and the right figure is a structural schematic of the catalyst layer modeled in the analysis.

  • Development of Structural Materials for Fusion and High Energy Reactors

    Iron-based composites with high thermal conductivity

    By appropriately arranging high thermal conductive materials in iron-based structural materials, the thermal conductivity of the entire structural materials can be dramatically improved. This will lead to the improvement of the efficiency of energy production and the reduction of radioactive waste, as well as the development of iron-based structural materials for fusion reactors and high energy reactor divertors, for which there has been no solution so far.


    This paper focuses on the low thermal conductivity of iron-based materials, which are expected to be used in actual DEMO reactors, with a view to the development of heat exchange devices facing to the plasma in operation, and is aimed at a significant improvement of thermal conductivity, which is considered to be the key to success. The 500°C temperature gradient near the cooling tube of the DEMO reactor divertor imposes a huge heat load that has never been experienced in engineering equipment before. On various iron-based materials (pure iron, reduced activation ferritic martensitic steel and oxide dispersion strengthened ferritic steel), Cu and W wires of high thermal conductivity are appropriately arranged to ensure strength as a structural material while serving as a heat sink.

  • Elucidation of Combustion Phenomena Using Microgravity Fields

    Combustion phenomena are accompanied by a local temperature rise, which always results in natural convection in the surrounding air . This complicates the phenomenon and makes it difficult to fundamentally understand it. In this study, we will try to understand the combustion phenomena from a fundamental standpoint by utilizing the microgravity environment to remove the natural convection.


    Combustion phenomena are accompanied by a local temperature rise, which always results in natural convection in the surrounding air . This complicates the phenomena and makes it difficult to understand the fundamentals. In this study, we will utilize the microgravity environment to remove the natural convection and understand the fundamental processes (diffusion, heat conduction, soot formation, ignition, flame propagation, etc.) of combustion phenomena, which will be useful for numerical prediction and modeling of combustion devices. Hokkaido University has an approximately 40-meter drop tower that can be used at any time, making it easy to conduct microgravity experiments, and is also involved in international joint research to conduct microgravity experiments using aircraft and the International Space Station. Thus, we are in a favorable environment to conduct combustion research using the microgravity environment.

  • Fire-safety Improvement Technology for Lithium-ion Batteries

    The use of lithium-ion batteries has been expanding rapidly due to their high energy density. On the other hand, since organic solvents are used in lithium-ion batteries, it is important to ensure their fire safety. With this study, we focus on the combustion phenomenon of organic solvents and study combustion inhibition technology.


    The use of lithium-ion batteries has been expanding rapidly due to their high energy density. On the other hand, since organic solvents are used in the battery electrolyte, it is important to ensure their fire safety. With this study, we intend to develop a method to quantify the effect of adding a combustion inhibitor to suppress the combustion of organic solvents, search for additives that are effective in suppressing combustion, and study the effect of the lithium salt contained in the electrolyte itself on the flammability of organic solvents. We also conduct modeling and numerical analysis of fire phenomena taking the elementary reaction kinetics of combustion in an electrolyte into consideration.

  • Geothermal Resource Monitoring and Risk Assessment of Induced Earthquakes

    Monitoring and risk assessment of geothermal resources through geophysical observations

    Evaluation of the subsurface structure necessary for geothermal resource development by gravity survey and precise determination of the seismic source. Monitoring of geothermal reservoir resources by precise gravity measurements and crustal deformation observations. Risk assessment of induced earthquakes associated with geothermal well development and research on seismic activity prediction.


    ○ For geothermal resource development, which has been actively promoted in recent years, geothermal reservoirs are examined through base structure surveys. We have been investigating the basement structure through gravity surveys, precise seismic source distribution, and seismic velocity structure analysis.
    ○ For geothermal power generation, steam is produced and hot water is returned to the underground, but it is necessary to monitor the level of the geothermal reservoir to ensure the sustainable use of resources. We will examine the appropriate resource utilization volume through physical assessment of the subsurface fluid conditions using precise gravity measurements and crustal deformation observations.
    ○ The injection of high-pressure fluids into geothermal wells may induce noticeable tremors and cause problems. We will provide guidelines for appropriate and sustainable resource development by developing a method to evaluate the risk of induced earthquakes based on such parameters as the crustal stress state in the geothermal development area, surrounding faults, the characteristics of the seismic activity, and fluid injection volume.

  • High-efficiency Semiconductor Solar Cells

    New-type solar cell consisting of a multi-striped semiconductor with orthogonal photon-photocarriers that was coupled to a waveguide.

    Temperature rise and device degradation are suppressed by simultaneous optimization of light absorption and photocarrier collection, as well as photoelectric conversion over the entire solar spectrum by multiple semiconductor stripes. This leads to the realization of a highly efficient 2-dimensional PhotoReceptoConversion Scheme (2DPRCS).


    In conventional solar cells, there is a trade-off between carrier collection and the number of absorbed photons because the photo carrier migration direction and the light travel direction are parallel. Based on the orthogonality between the carrier migration direction and the light travel direction, it was possible to optimize both the light absorption and the carrier collection efficiency. Since the sunlight is sequentially photoelectrically converted from high- to low-energy components over the entire spectrum, thermal dissipation is minimized and high efficiency can be achieved. A waveguide type light collection system with a light wave direction conversion membrane can realize a photovoltaic system that is resistant to diffuse light. By preventing high-energy photons from entering the mid-gap and narrow-gap semiconductors, bond degeneration can be prevented and the life of the device can be extended. It is possible to realize the ultimate concentrator solar cell system, which is strong even in cloudy weather, has high conversion efficiency close to the thermodynamic limit, and is highly reliable.

  • High-temperature Latent Heat Storage Microcapsules

    Core (alloy latent heat storage material) ? shell (Al2O3) type latent heat storage microcapsules capable of high-density heat storage in the high temperature range of over 500?C

    The latent heat storage method, which utilizes latent heat generated during the solid-liquid phase change, is attractive for its high-density heat storage capacity. Microencapsulation of latent heat storage material enables not only heat storage but also heat transport and heat control applications, and we have developed latent heat storage microcapsules that can be used in the high temperature range of over 500°C.


    An Al-base alloy with a melting point above 500°C was newly discovered as a latent heat storage material. By skillfully applying chemical conversion/oxidation treatment to the micro-particles of this alloy (approx. 20 μm or larger), we have succeeded in developing core (Al-base alloy) and shell (Al2O3) type latent heat storage microcapsules (Fig. 1). These microcapsules have high heat storage capacity of approximately five times that of solid sensible heat storage materials, and have excellent mechanical properties. Since the shell is made of Al2O3, it can also be treated as a ceramic particle. In other words, it is an epoch-making heat storage material of which the performance can be upgraded while maintaining the current use of ceramic sensible heat storage technology.

  • Monitoring the Output of Renewable Energy Generation and Measures Against Output Fluctuations

    Real-time monitoring of fluctuations in solar and wind power output and control of such fluctuations

    We have developed a method for extracting load power (A) and renewable energy output (B) from power flow information in which (A) and (B) coexist. Although (B) fluctuates greatly depending on the weather conditions, we have developed a control method to suppress fluctuations using storage batteries and a method to evaluate storage battery capacity.


    In this laboratory, we have developed a method to extract the output of renewable energy (RE) power generation hidden in the information of power flowing through distribution lines in real time by applying a signal analysis technique called independent component analysis (ICA). This method enables highly accurate output estimation without having to use preliminary information such as the installed PV capacity in the grid (Fig. 1).
    We have also developed a control method to compensate for RE power output fluctuations using storage batteries (Fig. 2) and simulation technology to estimate the storage battery capacity required to suppress output fluctuations for individual wind farms and mega solar power plants.

  • Multi -beam Ultra-high Voltage Electron Microscope and Materials Research

    Multi-beam science and engineering applications

    At the High-Voltage Electron Microscope (HVEM) Laboratory of Hokkaido University, the world’s first multi -quantum beam HVEM has been developed. It enables in-situ observation of microstructural changes on an atomic scale using multi-quantum beam irradiation.


    The world’s first multi-quantum beam HVEM (left)
    In 2014, we added an optical system that allows the use of multiple lasers, and developed a multi-quantum beam HVEM that allows in-situ observation at the atomic level under irradiation by multi-quantum beams, including ion, laser and electron beams. We are currently developing an in-situ spectroscopy system.

    Nanocrystal growth by UV irradiation (right)
    We have succeeded in growing ZnO nanocrystals by irradiating submerged plasma-treated Zn with UV light. We are now promoting research on the growth mechanism and its application.
    Scientific Report, 5, 11429(2015), AIP Advances, 7(2017) pp. 035220, Other reference: Nano Letters, 17(2017) pp. 2088-2093

  • Numerical Simulation of Flow and Heat Transfer

    Modeling and Simulation of Turbulent Drag Reduction Flow by Surfactant

    Modeling and simulation of turbulent drag reduction is performed by adding a surfactant to clarify the resistance-reducing mechanism. Simultaneously, heat transfer analysis is performed to investigate the flow and heat transfer characteristics in detail.


    The significant drag reduction in turbulent channels due to the addition of a small amount of long-chain polymers or surfactants that form rod micelles in water, is known as Toms effect. A model that simulates polymers with small dumbbell-shaped elements was constructed, and direct numerical simulation (DNS) of turbulent flow in a two-dimensional channel was performed using this model to reproduce Toms effect. It was shown that the discrete element has two mechanisms: one is a resistance reduction mechanism due to the longitudinal vortex damping, and the other is a resistance increasing mechanism due to the additional stress near the wall. Furthermore, by adding the effect of cutting the element to which a strong force is applied, we were able to reproduce the feature that drag reduction occurs in a specific Reynolds number range.

  • Stable and Practical Oxide Thermoelectric Conversion Materials

    As a result of replacing the sodium ions in the layered cobalt oxide with barium ions of heavier atomic mass, only the thermal conductivity decreased while the electrical properties remained unchanged. We have found that the thermoelectric figure of merit ZT reaches 0.11 at room temperature.


    Thermoelectric conversion has been attracting attention as a technology to recycle waste heat. Metal chalcogenides are known as thermoelectric materials, but they have thermal and chemical stability and toxicity issues. Layered cobalt oxides are stable at high temperatures and in air, but have the problems that thermal conductivity is high and conversion performance is low. The research group considered the strategy shown in Fig. 1 to reduce the thermal conductivity of layered cobalt oxide AxCoO2. Figure 2 summarizes the thermoelectric properties in the direction parallel to the layers of Ax-substituted AxCoO2 thin films measured at room temperature. The thermal conductivity shows a monotonically decreasing trend with increasing Ax atomic weight. The room temperature thermoelectric figure of merit of Ba1/3CoO2 is 0.11. The figure of merit ZT increases with increasing temperature. By further enhancing the thermoelectric conversion performance, it is expected to realize stable and practical thermoelectric conversion materials.

  • Web Ground Club, which is a cloud-based geothermal heat pump design and performance prediction program, and Japan's Nationwide 3D Grid Strata Database

    It can also calculate the effect of multi-layered ground and groundwater flow and incidental cooling towers.

    About 10 years ago, we developed Ground Club (GC), a design and performance prediction tool for geothermal heat pump systems (GSHP), and distributed about 150 of these. We have also released an advanced version called Ground Club Cloud (GCC) for cloud computing on a trial basis, and developed a 3D geological properties database for the entire Japan and implemented it in GCC.