Abstract: The invention relates to a method for producing thermal energy, wherein, by means of a plasma arc which is located between a cathode and an anode, light initial material that is suitable for fusion processes is put into the plasma state by supplying electric energy. Use is made of a cathode made of a metal that is suitable for allowing the particles which are produced in the plasma to be diffused and for allowing a fusion process to take place in the metal grid. The invention has a high degree of efficiency in corresponding systems such that said methods can be used anywhere where fossil and/or renewable and/or chemical fuels are used, in order to use the thermal energy directly or by conversion.