Abstract: Photovoltaic apparatus comprising a photovoltaic cell comprising an optical component of transparent material of cross section having a first surface forming an entry aperture for solar radiation, a second surface forming an exit aperture for the solar radiation passing through the entry aperture, opposite surfaces which are curved in shape, photovoltaic material positioned to receive solar radiation from the exit aperture, the opposite side surfaces being shaped to provide total internal reflection of solar radiation passing from the entry to the exit apertures, a mirror surface being positioned to reflect radiation away from one of said side surfaces.

Abstract: A window unit comprising at least one transparent pane, a frame 130 around the perimeter of the at least one transparent pane, at least one rotatable linear concave mirror 110 extending at least partially across the frame, and at least one energy conversion device 120 extending at least partially across the frame wherein the unit is arranged such that substantially parallel radiation incident on the mirror is reflected onto the energy conversion device.