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For the future market potential of parabolic trough power plants with direct steam generation (DSG), it is beneficial to integrate a thermal storage system. Heat storage media based on phase change materials offer heat transfer at constant temperatures needed for the evaporation process. Different options for a plant layout are presented and discussed. The interactions between the three subsystems—solar field, power block, and thermal storage—are analyzed, and boundary conditions arising from the thermal storage system are identified. Compared with a system without storage the number of operating points increases significantly since different combinations of storage charge and discharge operations go along with a varying power output of the solar field. It is shown that the large number of theoretical operating points can be reduced to a subset with practical relevance. Depending on the live steam parameters a reheat is necessary within the power block. Compared with parabolic trough fields with a single phase heat transfer medium such as oil, a special heat exchanger configuration is needed for a DSG plant. Different alternatives based on available technologies are presented and evaluated.

Fast reaction times and high discharge rates make steam accumulators a promising option for compensation of fast transients in insolation for solarthermal systems using steam as working medium. Using the volume of components like separator drums or heat exchangers for storage of pressurized hot water is a cost-effective approach to integrate buffer storage capacity. While the basic steam accumulator shows a decline in pressure during the discharge process, there are also concepts maintaining constant pressure. The integration of latent heat storage material allows an increase in volumetric storage capacity. The availability of steam accumulators for compensation of fast transients also helps to reduce the requirements concerning reaction time and discharge rate for storage systems intended for supplying stored energy over longer periods.

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