Solar receivers which produce heat at very high temperatures (in excess of 1000° C.) are described herein. The receiver produces the high temperature heat and radiates the heat to a containment element (e.g., pipe) that contains a heat transfer fluid which absorbs the heat. The fluid is preferably a material which is thermally and chemically stable at the temperatures involved. The heat transfer fluid absorbs the heat and can deliver it to a reactor system to drive an endothermic reaction, such as thermochemical water splitting, CO2 capture, and/or syngas production. Alternatively, the heat can be used to directly generate electricity through a high temperature heat engine such as a Brayton or combined Brayton+Rankine cycle.