A solar powered system, comprising: a heat exchanger surface or a photo-voltaic generator; and a focussing system configured to concentrate solar radiation onto the heat exchanger surface or the photo-voltaic generator, comprising: a first reflective element forming part of the surface of a cone axially aligned along a first alignment axis, wherein the surface of the cone is defined such that each point on the surface satisfies z = ar, where z is the displacement of the point on the surface from the vertex of the cone along the axis of the cone, r is the radial distance from the point on the surface to the axis of the cone, and a is a constant, the first reflective element being positioned such that when planar radiation is incident on the first reflective element in a direction parallel to the first alignment axis, the planar radiation is focussed towards a first focus lying along the first alignment axis, wherein said part of the surface of the cone is contained within a sector having an included angle of less than 180 degrees; and a second reflective element having a reflective surface that has no curvature in a direction parallel to a single reference direction, the second reflective element being positioned between the first reflective element and the first focus such that, when planar radiation is incident on the first reflective element in a direction parallel to the first alignment axis, radiation reflected from the first reflective element onto the second reflective element is focussed towards a second focus, wherein: the first focus is a line focus and the second focus is a point focus. a heat exchanger surface or a photo-voltaic generator; and a focussing system configured to concentrate solar radiation onto the heat exchanger surface or the photo-voltaic generator, comprising: a first reflective element forming part of the surface of a cone axially aligned along a first alignment axis, wherein the surface of the cone is defined such that each point on the surface satisfies z = ar, where z is the displacement of the point on the surface from the vertex of the cone along the axis of the cone, r is the radial distance from the point on the surface to the axis of the cone, and a is a constant, the first reflective element being positioned such that when planar radiation is incident on the first reflective element in a direction parallel to the first alignment axis, the planar radiation is focussed towards a first focus lying along the first alignment axis, wherein said part of the surface of the cone is contained within a sector having an included angle of less than 180 degrees; and a second reflective element having a reflective surface that has no curvature in a direction parallel to a single reference direction, the second reflective element being positioned between the first reflective element and the first focus such that, when planar radiation is incident on the first reflective element in a direction parallel to the first alignment axis, radiation reflected from the first reflective element onto the second reflective element is focussed towards a second focus, wherein: the first focus is a line focus and the second focus is a point focus. a first reflective element forming part of the surface of a cone axially aligned along a first alignment axis, wherein the surface of the cone is defined such that each point on the surface satisfies z = ar, where z is the displacement of the point on the surface from the vertex of the cone along the axis of the cone, r is the radial distance from the point on the surface to the axis of the cone, and a is a constant, the first reflective element being positioned such that when planar radiation is incident on the first reflective element in a direction parallel to the first alignment axis, the planar radiation is focussed towards a first focus lying along the first alignment axis, wherein said part of the surface of the cone is contained within a sector having an included angle of less than 180 degrees; and a second reflective element having a reflective surface that has no curvature in a direction parallel to a single reference direction, the second reflective element being positioned between the first reflective element and the first focus such that, when planar radiation is incident on the first reflective element in a direction parallel to the first alignment axis, radiation reflected from the first reflective element onto the second reflective element is focussed towards a second focus, wherein: the first focus is a line focus and the second focus is a point focus.