Clean Energy Technologies for a Net-Zero Emissions Future: an Editorial for the Special Issue Comprising of the Selected Papers Presented at the 13th and 14th International Green Energy Conferences (IGEC2021 and IGEC2022), Both Held Online

Clean energy technologies are critical for the transition to a net-zero emissions future. The recently published Tracking Clean Energy Progress by the International Energy Agency showed that only 3 out of the over 50 clean energy components evaluated are “on track” for a net-zero economy by 2050, namely solar PV, electric vehicles and lighting (International Energy Agency, 2023). Significant efforts are needed to speed up the deployment and development of various clean energy technologies in all the sectors of a global economy. It is one of the goals of the International Green Energy Conferences (IGEC), organized annually by the International Association for Green Energy (IAGE), to promote the advancement of clean energy systems and technologies. This special issue highlights some of the high-quality research results disseminated in both IGEC2021 and IGEC2022. A total of 15 invited papers are published in this issue, which provide excellent examples of the efforts undertaken by researchers in the field to promote a net-zero emissions future. Topics include low-carbon power generation (e.g., fuel cells, geothermal, wind power, and clean fuels), efficiency improvement (e.g., heat pumps and waste heat recovery), and waste and emission reduction (e.g., water treatment and carbon emission prediction). As clean energy technologies are gaining momentum in the transition to a net-zero future, we expect significant progress in the coming years to improve the performances and reduce the costs of these technologies, such that clean energy technologies will be deployed in a larger scale and a more equitable manner.