In this work transient simulation results of a hybrid solar tower power plant with open volumetric receiver technology are presented for several locations in China. The open volumetric receiver uses ambient air as heat transfer fluid and the hybridization can be realized with additional firing. The solar receiver and/or the additional firing heat up the air which is then passed through a boiler of a conventional Rankine cycle. The simulated plant is based on the configuration of the solar thermal test and demonstration power plant located in Jülich (STJ). The investigated plant operates in hybrid -parallel mode which allows a constant power generation. The meteorological data for the different sites in China was taken from the software Meteonorm in a time resolution of one hour. The solar tower power simulation tool was developed in the simulation environment MATLAB/Simulink.

Electricity production costs and overall net efficiency of the system are determining factors regarding the quality and cost effectiveness of a solar tower power plant. These factors are strongly dependent on the quality of heliostats, the receiver and the thermal storage concept. This work describes the optimization of load states of a storage system through applying internal process control strategies for the air circuit of the Solar Tower Jülich which works with open volumetric air receiver technology. A concept for optimal operation of the thermal storage system was formulated and developed. Storage concepts include both technical adjustments of the existing storage system as well as the control process of the thermal storage. For simulating the optimized operating strategy of the power plant systems all main power plant components were modeled in MATLAB ® /Simulink ® and interconnected to form a complete system. The focus of the simulation lies in optimizing the operating strategy of a discretized thermal energy storage model. BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer review by the scientific conference committee of SolarPACES 2014 under responsibility of PSE AG 908 V. Kronhardt et al. / Energy Procedia 69 ( 2015 ) 907 -912

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Existing thermal oil based parabolic trough collector (PTC) power plants have been commercially deployed since 2008. Parabolic trough technology dominates by ca. 90 % the global market of all operational commercial concentrated solar power (CSP) plants. Worldwide over 32 % of these PTC power plants have an indirect salt thermal storage system that enables night operation [1, 2]. Since existing parabolic trough power plants with thermal oil are limited regarding their maximum operating temperature, the addition and integration with a molten salt tower systems (MSTS) could be an attractive option to increase the temperature level of the thermal storage and steam cycle and thus the overall efficiency of the plant. This paper describes the conception, investigation and techno-economic evaluation for retrofitting an existing Andasol type parabolic trough power plant. The most promising out of five coupling configurations has been analyzed and evaluated for three different retrofitting concepts using greenius and EBSILON ® Professional simulation tools. The analysis shows that retrofitting concepts based on the addition of a MSTS are only economically attractive, if the capital expenditure for the power block modification does not exceed 440 $/kW. The retrofitting of existing PTCs with a MSTS is economically unviable.