non - focusing solar energy concentration apparatus comprising one or more solar energy absorbing surfaces defining a first area and solar energy transmissive material disposed adjacent the absorbing surfaces and defining an incident surface having a second area greater than the first area , the incident surface being arranged to receive incident radiation from the sun , the solar energy transmissive material also defining a second surface for transmitting radiation to the at least one absorbing surface , the transmissive material having an index of refraction and a configuration selected to provide total internal reflection at the incident surface of radiation incident on the incident surface within a predetermined azimuthal range .