This master thesis deals with the performance calculations of a 9MW linear Fresnel CSP plant withdirect steam generation built by the Solar Division of the CNIM Company. The aim was to calculate theannual electricity production taking into account the weather conditions as well as some steam storage.At first, a steam accumulator model was developed with Excel, in order to estimate the pressureevolution in the tanks during the charging, storage and discharging processes. The data obtained withthis model was then integrated to the thermodynamic cycle model, programmed with Excel, whichcalculated the electrical power production knowing the thermal power available in the solar field. Theelectricity production calculations were made every 600 seconds during one year.To improve the results accuracy, the influence of the plant location slope was estimated, calculating theequivalent azimuth and elevation angles in a new spherical coordinates system. For an average slope of4.21° at the plant location, the annual thermal energy gain is 14.4% (with a gain up to 60% duringwinter days) and the annual electricity production is increased by 12.59%. The influence of frost on themirrors during cold and humid nights was also estimated with a simple model of the energy needed toheat up a constant layer of ice. Depending on the assumptions, the electricity production losses werebetween 1.27 and 2.84% of annual electricity production. The losses due to plant shutdowns set by theelectrical network manager RTE during the snowmelt months were also estimated. The annualelectricity production could decrease by 8.02 to 11.57 % because of the load management, dependingon the days during which the plant is shutdown.Finally, an economic optimisation was led with prices estimated by CNIM, which gave an optimal solarfield design with 31 lines and 5 steam accumulators. The payback time would then be 9.887 years.