To achieve net-zero greenhouse gas emissions by mid-century, various sustainable energy technologies are being rapidly developed worldwide. This book presents recent advancements in sustainable energy technologies, including renewable energy sources such as solar, wind, bioenergy, and hydropower, as well as hydrogen technologies and energy storage solutions. It addresses key aspects of energy conversion systems associated with renewable energy technologies and their applications. The book features chapters based on selected high-quality papers from the 2025 9th International Conference on New Energy and Applications, which explore cutting-edge solutions and best practices in green and clean energy technologies. Its primary objective is to educate readers about the development and implementation of sustainable energy technologies that can achieve zero-carbon or zero-greenhouse-gas energy systems.

Masafumi Yamaguchi, Ph.D., is a Professor Emeritus and Invited Research Fellow at the Toyota Technological Institute in Nagoya, Japan. Since 2008, he has served as the Chairman of the photovoltaic R&D review committee at the New Energy and Industrial Technology Development Organization (NEDO). From 2009 to 2017, he was the Research Supervisor for the "Creative Clean Energy Generation Using Solar Energy" project under the Japan Science and Technology Agency (JST). Prof. Yamaguchi has made significant contributions to research and development across various areas, including high-efficiency multi-junction solar cells, silicon tandem and silicon solar cells, space solar cells, semiconductor defects, and photovoltaic (PV)-powered vehicle applications. He has received numerous prestigious awards for his work, including the Becquerel Prize from the European Commission in 2004, the William Cherry Award from the IEEE in 2008, the PVSEC Award in 2011, and the WCPEC Award in 2014. Additionally, he was honored with the Science and Technology Award by the Minister of Education, Culture, Sports, Science, and Technology in 2015, the Outstanding Achievement Award from the Japan Society of Applied Physics in 2025, and the Purple Ribbon Medal from the Emperor in 2025. These awards recognize his exceptional contributions to the science and technology of photovoltaics, particularly in developing high-efficiency multi-junction, space, and concentrator solar cells, as well as his role as a world leader in photovoltaic development and international cooperation.