The optics of various types of solar tower configurations and receivers are analyzed. The power values that are finally available for the process, for a given field and different optical arrangements at specified operating temperatures (above 1100 K), are compared, At these temperatures the use of secondary concentrators placed in front of the receivers is peremptorily justified from optical and energetical points of view. A model for calculating the efficiencies of central solar receivers with secondary concentrators is presented. This model permits the optimization of these secondary concentrators taking into account the different losses of real devices. The effect of heliostat field density and the performance of ＇tower-top＇ and ＇tower-reflector＇ solar plants are discussed and compared.