Abstract: This invention relates to a solar furnace. In particular, this invention relates to a solar furnace which is capable of raising the temperature of transfer medium. In use, the heated transfer medium can be used to generate electricity or put to other work, such as, for example, air conditioning, pasteurisation or desalination. In fact, for any situation that requires a source to generate work or power. The present invention describes a solar furnace for raising the temperature of a heat transfer medium, comprising a lens array for admitting incident thermal and solar energy onto a reflector portion and a pressure vessel. The reflector portion being generally shaped so as to concentrate said solar energy onto said pressure vessel. The pressure vessel having an inlet through which said heat transfer medium is injected and a central core which defines a continuous heat transfer path for said heat transfer medium to contact the surface of said pressure vessel and exit said pressure vessel at an outlet.