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Abstract: To optimize the start-up schedules of steam turbines operating in concentrating solar power plants, accurate predictions of the temperatures within the turbine are required. In previous work by the authors, thermal models of steam turbines have been developed and validated for parabolic trough solar power plant applications. Building on these results, there is an interest to increase the adaptability of the models with respect to different turbine geometries due to the growing trend of having larger steam turbines in parabolic trough and solar tower power plants. In this work, a modular geometric approach has been developed and compared against both the previous modeling approach and 96h of measured data from an operational parabolic trough power plant. Results show a large degree of agreement with respect to the measured data in spite of the different detail levels. The new model allows for simple and fast prediction of the thermal behavior of different steam turbine sizes and geometries, which is expected to be of significant importance for future concentrating solar power plants. [Copyright &y& Elsevier]

Abstract: Steam turbines in solar thermal power plants experience a much greater number of starts than those operating in base-load plants. By maintaining higher internal temperature during idle periods, faster start-up times can be achieved, increasing the flexibility of the plant as well as increasing net electrical production. Prior work by the authors identified a number of methods for achieving this, with strong increases in daily production predicted; only two specific start-up cases were studied however. In order to obtain a more representative evaluation of the performance increase that can be achieved through increased dispatchability of the turbine, the annual improvement needs to be studied. Building on the existing results, a dynamic system model of a parabolic trough power plant has been established and used to determine the distribution of different cool-down times experienced throughout the year, with a view to evaluating the potential annual production increase. A modification of the start-up curves allows an increase in annual electrical production between 6.4% and 2.4% depending upon the operating mode (free operation versus day-time operation). Through application of a combination of heat blankets and an increase in gland steam temperature, further annual production increases between 2.2% and 3.1% are predicted. [Copyright &y& Elsevier]

Abstract: Direct steam generation (DSG) is one alternative to the current oil-based parabolic trough solar thermal power plants. Within the German research project ITES, the dynamic behavior of a DSG collector field and the interactions with the conventional power block are assessed in detail. A transient solar field model developed by DLR is used to simulate the steam temperature behavior. Artificial irradiance disturbances as well as real irradiance data are used as input to the system. The resulting main steam temperature gradients are then analyzed by Siemens considering the standards for steam turbines. This paper presents the transient simulation results of the steam temperature as well as the corresponding results of the steam turbine analysis. It is found that the occurring temperature gradients are challenging for a safe turbine operation, if a conservative control system is used. Therefore, the use of an additional thermal inertia to stabilize the steam temperature is suggested. Its impact is also analyzed and discussed in this paper. [Copyright &y& Elsevier]