TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred System: The system comprises primary light concentrators and respective light directing structures. The primary light concentrators are in the form of a planar, spaced array. It is also in the form of at least a portion of immediately adjacent concentric rings, where the intended light propagation direction is in a radially inward direction. The primary light concentrators are in the form of immediately transversely adjacent, straight cylinders, where the intended light propagation direction is transverse to the longitudinal axes of the cylinders. The primary light concentrator is a reflective element, a refractive element, or a diffractive element. The light transport structure is also in the form of a low aspect ratio sheet. The light directing structure comprises an angled light-reflecting surface extending inwardly from at least one of the top surface portion and the bottom surface portion of the transport structure. The light directing structure comprises a lateral cut in at least one of the top surface portion and the bottom surface portion of the transport structure. The angled light-reflecting surface is flat or curved. The angled light-reflecting surface has a transverse extent in the transport structure that coincides with a transverse extent of a respective primary light concentrator. The top surface and the bottom surface of the transport structure is flat and at least one of the bottom surface and the top surface of the transport structure is stepped, where the angled light-reflecting surface of the light directing structure connects a stepped region and an immediately adjacent stepped region of the transport structure. The stepped regions are flat or inclined. The angled light-reflecting surface is disposed at an angle that supports total internal reflection from the top or bottom surface immediately adjacent the angled light-reflecting surface. The light directing structure is an air prism. The system further comprises a photo-voltaic cell disposed to receive the light out-coupled from the exit end of the light transport structure. It further comprises a secondary light concentrator that is coupled to the exit-end to further concentrate and out-couple the propagated light from within the light transport structure, where the secondary light concentrator has an exit-end having an area that is smaller than the exit-end area of the light transport structure. The secondary light concentrator is an optical element directly coupled to the exit-end of the transport structure. The secondary light concentrator is in the form of an integrally shaped exit-end region of the light transport structure. The secondary light concentrator is a compound parabolically-shaped exit-end region of the transport structure or a compound trapezoidally-shaped exit-end region of the transport structure. A unit-system comprises the primary light concentrators, respective light directing structures, and only a single light transport structure. The system further comprises a PV cell disposed in a location to receive light out-coupled from the exit-end of one of the light transport structure and an exit-end of a secondary light concentrator. The secondary light concentrator is disposed between the exit-end of the light transport structure and the PV cell. Transporting light comprises changing the propagation direction of the light only at a top surface region of the light transport structure. It also comprises changing the propagation direction of the light only at a bottom surface region of the light transport structure. It further comprises changing the propagation direction of the light at both a top surface region and a bottom surface region of the light transport structure. The method comprises changing the propagation direction of the light by approximately 90 degrees . The method also comprises changing the propagation direction of the light only by total internal reflection. It also comprises propagating the light through the light transport structure only by total internal reflection or by total internal reflection and diffuse reflection. The method further comprises concentrating the light propagating through the light transport structure prior to outputting the light from the light transport structure and inputting the light to the PV cell. The method also comprises optically concentrating the initial light input into a circular spot, optically concentrating the initial light input into a rectangular spot, or optically concentrating the initial light input into a non-circular, non-rectangular spot. The method also comprises: (i) collecting initial light inputs; (ii) optically concentrating each of the initial light inputs into respective light concentration locations; where the only a single light transport structure includes respective integral light directing structures in locations coinciding with the light concentration locations.