NOVELTY - A solar collection device comprises conversion body having luminescent body (12) which has first principal surface (3) which can be exposed to incident spectrum radiation (1), second principal surface remote from the first principal surface, and edge surfaces (5, 6) joining the first and second principal surfaces; and comprises luminescent material, which, when the first principal surface is exposed to incident spectrum radiation, receives and absorbs some, of the incident radiation, and as a result generates luminescent radiation (2).    USE - When using the invention to transmit a part of the incident radiation, the transmitted radiation can for example be used to illuminate an operation which requires the use of human eyesight, e.g. for reading written material, watching television or a film, operating a machine (e.g. a computer), conducting operations of any kind for business, education or pleasure (e.g. in an office, shop, school, kindergarten, television or radio studio), greenhouse, plant nursery, nursing home, or domestic dwelling.    ADVANTAGE - The apparatus exhibits features such as, (a) the luminescent material is such that, when the first principal surface is exposed to incident radiation, part of the radiation of a selected wavelength range or ranges is absorbed by the luminescent material, thus generating luminescent radiation which is transmitted to the edge surfaces of the luminescent body, and the remainder of the radiation of the selected wavelength range or ranges is transmitted through the luminescent body, the transmitted radiation emerging from the second principal surface; (b) the luminescent material is such that, when the first principal surface is exposed to incident radiation, some of the radiation in first selected wavelength range or ranges of the incident radiation is absorbed by the luminescent material, thus generating luminescent radiation which is transmitted to the edge surfaces of the luminescent body, and some of the radiation in second selected wavelength range or ranges of the incident radiation is transmitted, the transmitted radiation emerging from the second principal surface; (c) the PV cells is bifacial and is capable of receiving luminescent radiation on both faces; (d) some of the PV cells comprise electrodes which do not cover any substantial part of the face of the PV cell which receives luminescent radiation; (e) the PV cells have different absorption capacities such that, when the luminescent body is uniformly illuminated, the amounts of current generated by the different PV cells are closer to the same value than they would be if all the PV cells were the same; (f) The luminescent material is non-uniformly distributed at right angles to the plane of the luminescent body so that greater than or equal to50% of the luminescent material lies in a layer constituting at less than or equal to30% of the thickness of the body; (g) the luminescent material is non-uniformly distributed across the plane of the luminescent body, for example so that greater than or equal to50% of the luminescent material lies in an area constituting less than or equal to30% of the area of the body; (h) the amount of luminescent radiation received by each of the PV cells is less than or equal to1.5 times the smallest amount of luminescent radiation received by any of the PV cells; and (f) the shape of the luminescent body is a regular polyhedron, a rectangle, or includes a regular or irregular curve.    DETAILED DESCRIPTION - The solar collection device comprises conversion body having (1) luminescent body which (i) has a first principal surface which can be exposed to incident spectrum radiation, a second principal surface remote from the first principal surface, and edge surfaces joining the first and second principal surfaces, and (ii) comprises luminescent material, which, when the first principal surface is exposed to incident spectrum radiation, receives and absorbs some, of the incident radiation, and as a result generates luminescent radiation which has a different wavelength from the absorbed radiation, and some of which is transmitted to the edge surfaces of the body; and (2) photovoltaic (PV) cells which, when the first principal surface is exposed to incident spectrum radiation and as a result, the luminescent material generates luminescent radiation, (i) receive some of the luminescent radiation which is transmitted to the edge surfaces and (ii) convert some of the luminescent radiation into electrical energy.    INDEPENDENT CLAIMS are included for:    (a) a method of generating electrical energy;    (b) a luminescent body; and    (c) a method of preparing the luminescent body.    DESCRIPTION OF DRAWING(S) - The figure is a schematic cross-sectional view of the solar collection device.    Incident radiation (1)    Luminescent radiation (2)    First principal surface (3)    Edge surfaces (5, 6)    Transparent glass (11)    Body (12)    PV cells (15)