摘要： The society and technology that human beings have built for themselves are strongly dependent on the consumption of energy. However, earth’s energy resources have been consumed for a long time, and we will have to face energy resource problems and find solutions now if we wish to develop a sustainable human society. If we continue to use fossil fuels at the current rate, they will be completely exhausted within the 21st century. Therefore, there is an urgent need to shift towards the use of renewable energies such as solar energy, nuclear fusion, wind power, biomass, and geothermal energy instead of continuing to use fossil fuels. Renewable energy resources are abundant and have a low impact on the natural environment. On the other hand, they provide low energy density and strongly fluctuate depending on the place and time. Therefore, creating a stable supply of energy is difficult given the current state of technology and the social system we live in, and there are many difficulties in practically using these energy resources.