The disadvantages of clean solar energy are that its energy density per unit area is low and its supply fluctuates greatly. It is of great importance to develop a diversified, innovative technology that can convert and store solar energy efficiently, economically, and on a large scale. As a promising method to convert solar energy to chemical substances and store them, the CREST project for producing hydrogen through a visible light-driven photocatalyst is currently progressing at our Clean Energy Research Center. Regarding next-generation solar cells (dye-sensitized solar cells, new oxide semiconductor solar cells, and compound-semiconductor solar cells), which could replace conventional silicon-based cells, basic and applied studies and research are provided by this program, as well as our collaborating institute, the National Institute of Materials Science (NIMS). Not limiting itself to solar energy conversion, the program focuses on the development of thermoelectric conversion materials that can convert solar heat or unused low-grade waste heat into usable electricity.