the outside surface of the host in a preferred sixth embodiment three light pipes are disposed within the combustion chamber 40 of the fuel combustion system 42 each light pipe 46 is formed in a spirally wound configuration having a different diameter so that light pipes can be nested concentrically together end portions of the light pipes 46 are collected together and direct toward at least one pv cell 7 positioned adjacent the light pipes a band pass filter 8 is interposed between the end portions of the light pipes and the pv cell to ensure that radiation directed to the pv cell from each light pipe end is within a predetermined wavelength alternatively the superemissive light pipes 46 may be woven into an advanced emissive matrix as described in u s patent application ser no 08 237 306 filed on may 3 1994 the subject matter of which is hereby incorporated by reference fig5 a 5b illustrate a seventh embodiment of a superemissive light pipe positioned adjacent a jet engine the seventh embodiment of a light pipe 57 is disposed adjacent an exhaust stream of a jet engine 50 which serves as the external thermal energy source the seventh embodiment includes a number of light pipes 57 that can be arranged to form a matrix in a preferred seventh embodiment the light pipes 57 are configured in two light pipe systems wherein each system includes a number of similarly oriented light pipes that intersect with.