This study deals with the performance calculations of a 9MW linear Fresnel CSP plant with direct steam generation built by the Solar Division of the CNIM Company. The aim was to calculate the annual 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 pressure evolution in the tanks during the charging, storage and discharging processes. The data obtained with this model was then integrated to the thermodynamic cycle model, programmed with Excel, which calculated the electrical power production knowing the thermal power available in the solar field.
The electricity 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 the equivalent 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% during winter days) and the annual electricity production is increased by 12.59%. The influence of frost on the mirrors during cold and humid nights was also estimated with a simple model of the energy needed to heat up a constant layer of ice.
Depending on the assumptions, the electricity production losses were between 1.27 and 2.84% of annual electricity production. The losses due to plant shutdowns set by the electrical network manager RTE during the snow melt months were also estimated.
The annual electricity production could decrease by 8.02 to 11.57 % because of the load management, depending on 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.
Source: KTH
Author: Schlaifer, Perrine
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