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The integration of high temperature thermal energy storages into existing conventional power plants can help to reduce the CO2 emissions of those plants and lead to lower capital expenditures for building energy storage systems, due to the use of synergy effects [1]. One possibility to implement that, is a molten salt storage system with a powerful power-to-heat unit. This paper presents two possible control concepts for the startup of the charging system of such a facility. The procedures are implemented in a detailed dynamic process model. The performance and safety regarding the film temperatures at heat transmitting surfaces are investigated in the process simulations. To improve the accuracy in predicting the film temperatures, CFD simulations of the electrical heater are carried out and the results are merged with the dynamic model. The results show that both investigated control concepts are safe regarding the temperature limits. The gradient controlled startup performed better than the temperature-controlled startup. Nevertheless, there are several uncertainties that need to be investigated further. [ABSTRACT FROM AUTHOR]

In implementing thermochemical energy storage, the selection of storage medium and the design of the associated discharge process are crucial; in this work the CaO/Ca(OH)2 system was chosen as it is well understood in the literature and is a cheap and accessible material though the associated storage/discharge process has not been studied in depth, particularly in the context of fluidized bed reactor configurations which offer superior technical performance but remain challenging to operate and study. This work sought to design a combined energy storage and discharge fluidized- bed based process flowsheet involving the CaO/Ca(OH)2 system coupled with a CSP receiver setup and discharge power cycle (CSP-TCES). AspenPlus V9 was used to design fluidized bed reactors for each process, and then simulate and optimize fluidized bed-based flowsheets with a sensitivity analysis, and results were compared with analytical models from literature. Historical solar irradiance data for Seville, Spain, was used to dynamically simulate hourly solar loads coupled with multiple discharging schedules considered for a rough sensitivity analysis to assess the average loading and discharge trends of the designed plant. A subsequent techno-economic analysis yielded estimated levelised costs of electricity of 0.118-0.163 $/kWh and levelised costs of storage of 0.057-0.078 $/kWh showing the CSP-TCES system as very competitive with alternative more-developed storage technologies and associated discharge technologies. [ABSTRACT FROM AUTHOR]

The objective of this paper is the evaluation of trends when a power-to-heat system with electrical heaters is integrated to a molten salt solar tower to additionally charge the thermal energy storage system and to expand the capacity of the CSP plant. Therefore a techno-economic analysis was carried out considering several economical and technical boundary conditions. The results show a significant impact on the availability of excess electricity and its cost. Depending on system layout and the cost of the used electricity the overall LCOE of such plants can be reduced by up to 25%. Therefore such power-to-heat systems can offer an economic and strategic benefit to solar thermal power plants. [ABSTRACT FROM AUTHOR]