This paper presents the analysis of an original design of small hybrid solar plant using Organic Rankine Cycles with hermetic scroll expander- generators. The hot supply is provided from vacuumed collector tubes along the focal line of solar concentrators made of mirror bands fixed on a plane surface (CEP). The plant is integrated with a cogeneration Diesel engine unit to ensure power availability independently from the variations of solar radiation. It is primarily intended for isolated sites in developing countries. Measurements on the power unit of 13 kWel show an excellent behavior over a broad range of parameters with an efficiency of the order of 18% (50% exergetic efficiency), which is very promising, particularly when considering that the concept of superposed cycles will allow operations at higher supply temperatures with further technological developments.