The main aim of the CleanHME proposal is to develop a new, clean, safe, compact and very efficient energy source based on Hydrogen-Metal and plasma systems, which could be a breakthrough for both private use as well as for industrial applications. The new energy source could be employed both as a small mobile system or alternatively as a stand-alone heat and electricity generator. Hydrogen-Metal Energy (HME) is gained when hydrogen reacts with some metals under slightly increased temperature and pressure. First experiments have shown that the total heat energy produced exceeds by many orders of magnitude the chemical energy and strongly depends on applied active metallic materials and gas conditions in special reactors. Furthermore, accelerator experiments performed at higher energies of hydrogen isotopes have shown that the reaction rates can be enhanced by many orders of magnitude due to so-called electron screening effect if metallic samples with special nanostructures or crystal lattice defects are utilized. Thus, the main objectives of our proposal are to elaborate a comprehensive theory of HME phenomena and optimize the choice of the best materials for energy production in hydrogen-metal systems by combining accelerator and gas-loading experiments and to improve the reactors design leading to higher and stable energy production. We plan to construct a new compact reactor to test the HME technology during the long-term experiments and increase its technology readiness level. The proposed solutions have a potential to be a breakthrough for the power supply industry and present a solution for a carbon-free technology contributing to the climate and natural environment protection. To ensure it, we would like to build a broad multidisciplinary European consortium of scientific institutions, start-ups and commercial companies spread over 9 European countries, collaborating with leading scientists in USA and Canada.