A hybrid receiver-combustor (100) for capturing heat energy from a solar source and a fuel source. The hybrid receiver-combustor (100) includes a vessel (110) for acting both as a combustion furnace and as a solar receiver, and a plurality of burners (180) for combusting an oxidant stream, such as an air stream, and a fuel stream. The vessel (110) includes a casing (120) defining a cavity (125) having an aperture (130) for receiving the concentrated solar radiation from the solar source. The cavity (125) provides a chamber defining a zone (126) which can function as a combustion zone for production of heat energy through a combustion process using the fuel and into which concentrated solar radiation can be received from the solar source through the aperture (130). A heat energy absorber (190) configured as a heat exchanger is provided to receive heat energy from concentrated solar radiation entering the cavity (125) through the aperture (130) and from combustion within the cavity. A fluidic seal system (135) is associated with the aperture (130) and is operable to establish a fluidic seal to restrict fluid flow through the aperture (130) during the combustion process. The fluidic seal comprises exhaust gas from the combustion process within the cavity (125).