Any combination of at least two cyclic processes converting thermal energy (‘heat’) to work forms a combined cycle. In principle, the potential number of options is almost infinite. If, however, pressurized fluidized bed combustion (PFBC) of coal is to be the main source of heat, the number of options reduces to a variety of cycles consisting of at least: (a) an open gas turbine cycle, characterized by the working fluid remaining in the gaseous state throughout the cycle and by the addition of heat achieved by internal combustion, and (b) a closed steam cycle, characterized by the working fluid being evaporated from the liquid to the gaseous state during the addition of heat from an external heat source, and being condensed from the gaseous to the liquid state during the rejection of heat to the environment (in case of a power generating process) and/or to a heat sink (in case of some cogeneration processes).