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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]

Plant developers of parabolic trough collector (PTC) systems for industrial steam generation face various challenges. Some of the main challenges are availability of land, buildings in the vicinity of the plant that cast shadows on the collectors as well as land restrictions. The typical north-south collector axis alignment in many cases may not be possible due to limits of available ground. These were challenges that were faced in the planning phase for installing a PTC plant on the premises of the KEAN Soft Drinks Ltd factory in Limassol, Cyprus. As these issues cannot be avoided they must be accounted for by the plant developer, especially when a performance guarantee is given. This work presents, amongst other things, factors that should be analysed in order to predict the energy yield in the planning phase as best as possible by using a simulation model. In the sensitivity study presented in this paper, several effects on the energy yield were investigated theoretically. These effects include: Tracking inaccuracy, non-parallel collector row axis orientations as well as north-south vs. east-west collector alignment. A dynamic simulation model developed by the Solar-Institut Jülich (SIJ) [1] was further developed and used for the analysis. The simulation model features a deviation between the measured and simulated oil temperature at the collector outlet of only 1.5 K (rms). The findings are presented in this paper and give an insight into the effectiveness of mid-sized PTC systems for the industry sector. [ABSTRACT FROM AUTHOR]

Parabolic trough collector (PTC) systems are commercially available concentrating solar power plants widely known for their application to generate electrical power. To further reduce the dependency on fossil fuels, such systems can also be deployed for producing process heat for industrial purposes. In combination with a thermal energy storage system, this technology has the ability to reliably supply on-demand process heat. This paper gives details on a fully automated PTC system with concrete thermal energy storage (C-TES) and kettle-type boiler that supplies saturated steam for a beverage factory in Limassol, Cyprus. In the focus is the validation of a dynamic simulation model in Modelica® that physically describes the entire PTC system. The simulation model uses various plant data as inputs including mirror reflectivity and weather data from on-site measurements. The validation was carried out in three steps. First, the PTC was validated as a stand-alone component. A time-dependent inlet oil temperature vector was given as input and the outlet oil temperature was computed. The root mean square (rms) error between the measured to simulated outlet oil temperature values results in 3.86% (equivalent to about 1.9 K). The second part of the validation then considered a complete PTC oil cycle in PTC-and-boiler operation mode (without C-TES). In the simulation, both the PTC inlet and outlet oil temperatures were computed. The result is a deviation < 4.25 % (rms) between measured to simulated values. Finally, in the third step, the C-TES model was validated as a stand-alone component. The deviation between measurement and simulated values is < 5% compared to the design point. [ABSTRACT FROM AUTHOR]

For the evaluation of functional material developments in the EU-project RAISELIFE, a tool chain of ray tracing, thermal FEM simulation and dynamic system simulation has been created. Multi-year simulations allow considering degradation of optical parameters. With this tool chain, the thermal energy output of a reference plant with one non-selective and one generic selective coating was simulated. The LCOE (Levelized Cost of Electricity) was calculated based on these results. The LCOE of the selective coating is 2.6 % lower, if the same costs are assumed. Furthermore, the ideal recoating interval for the reference system was identified. Finally, it was demonstrated that dynamic system simulation shows benefits to evaluate in-service performance of functional materials as dynamic behavior of solar thermal power plants can change quite significantly, if another coating is used. [ABSTRACT FROM AUTHOR]

The present article is focused on the dynamic analysis and the control system implementation of a Molten Salt Solar Tower plant. The purpose of this simulation is studying thermal and fluid dynamic transient processes related to a Central Tower Power Plant. These phenomena are often difficult to simulate, to show and to analyze making it complicated to calibrate the plant main components' responses. Particular attention is dedicated to the drainage and filling procedures of the solar tower receiver system, with a description of the Molten Salt (MS) recirculation strategies in case of long absence of Direct Normal Irradiance (DNI) and transient responses of the receiver during cloudy days. The objective of this paper is to demonstrate that carrying out a long-term simulation is of fundamental importance for studying and designing the plant in order to avoid problems during transient phenomena or particularly delicate procedures. [ABSTRACT FROM AUTHOR]

Modeling and simulation activities play a key role in the design phase and performance optimization of complex energy processes. It is also expected that they will play a significant role in the future for power plant maintenance and operation (load variation, system startup, system shutdown …). Molten salt technology represents nowadays the most cost-effective technology for electricity generation for solar power plant. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. Typically 90 to 95 percent of the reflected energy is absorbed into the working fluid (molten salt), which is pumped through the receiver. The objective of this study is to evaluate the risk of salt crystallization in the receiver tubes for the gravity drainage scenario in the case of absence of solar irradiation. The temperature of the molten salt in the pipes will be calculated during the drainage of the receiver. A detailed dynamic model of Solar Two molten salt central receiver has been developed. The component model is meant to be used for receiver modeling with the ThermoSysPro library, developed by EDF and released under open source license. The paper gives a detailed description of the model, data and the results of the dynamic simulation for several scenarios. [ABSTRACT FROM AUTHOR]

The hybridization of combined-cycle power plants with solar energy is an attractive means of reducing carbon dioxide emissions. That could be an intermediate step on the way to a 100 % renewable era. Parabolic Trough Solar Collector (PTSCs) constitute a proven source of thermal energy for industrial process heat and pour generation. Parabolic trough solar power plants are, as of today, the concentrating solar power (CSP) technology with the largest track record. The purpose of this study is to simulate the impact of converting an existing combined cycle power plant to an integrated solar combined cycle (ISCC) plant using a solar field based on a parabolic trough solar collector system. The solar field is used to generate solar steam which is supplied to the steam turbine to increase the power output (by around 15%) during the sunny periods and reduce the fuel consumption, which results in a reduction in CO2 emissions. The objectives of this study are: the sizing of the main components of the solar system, the assessment of the impact of start-up phase of the solar field on the Solar Hybrid Power Plant dynamic behavior and the demonstration of the capability of the model to simulate the operating conditions of an ISCC power plant. A detailed dynamic model of the ISCC has been developed in Modelica. The component models used belong to the ThermoSysPro library developed by EDF and released under open source license. The paper also gives the results of the dynamic simulation for selected scenarios. This paper focuses on the hybridization of Parabolic Trough Power Plants with an existing GCC and the operation mode of the hybrid system is booster type. The solar fraction is then limited by the GCC part which remains unchanged. [ABSTRACT FROM AUTHOR]

Parabolic trough power plants are complex hydraulic and thermal systems that use parabolic mirrors to heat a fluid for energy generation. The solar field is divided into several loops through which the fluid flows and is heated. A loop can be more than 600 m long [3] and consists of parabolic mirrors that focus the sun's radiation onto an absorber tube. To achieve the desired outlet temperature, the amount of fluid brought into the solar field can be controlled. The fluid is distributed in the solar field in such a way that approximately the same amount flows through each loop. In case of homogeneously distributed irradiation, e.g. under clear sky conditions, the control with the mass flow works well. Problems may occur in transient conditions such as cloud passing. In this case, shaded loops can receive too much mass flow and the fluid cools down, or loops that are not shaded by a cloud can receive insufficient mass flow and overheat in the process. As an emergency function, the parabolic mirrors are moved out of focus to prevent damage in the event of high temperatures. In order to be able to react better in such situations, a system was developed that provides a better overview of the irradiation in the solar field. A camera system with an all sky imager (ASI) takes pictures of the sky and the software creates spatially resolved irradiation maps. This information can be used in different ways. This paper presents different implementation depths for parabolic trough power plants. The implementation levels range from the ASI system as stand-alone system up to a fully integrated automatic control of the solar field. For each implementation level, the benefits of the provided information are shown and an overview on the implementation for the operator effort is provided. [ABSTRACT FROM AUTHOR]

This paper outlines the development of the modeling and simulation of an elevated temperature particle lift intended to transport solid particles from the lower temperature storage bin to the top of the commercial-scale solid particle concentrated solar power tower. Traditional industry spreadsheet modeling is used as a starting point for the development of a complex non-linear design optimization model and a physics-based dynamic model that has the ability to simulate failures and analyze the particle response to such failures. [ABSTRACT FROM AUTHOR]

Concentrated Solar Power (CSP) systems are able to store energy cost-effectively in their integrated thermal energy storage (TES). By intelligently combining Photovoltaics (PV) systems with CSP, a further cost reduction of solar power plants is expected, as well as an increase in dispatchability and flexibility of power generation. PV-powered Resistance Heaters (RH) can be deployed to raise the temperature of the molten salt hot storage from 385 °C up to 565 °C in a Parabolic Trough Collector (PTC) plant. To avoid freezing and decomposition of molten salt, the temperature distribution in the electrical resistance heater is investigated in the present study. For this purpose, a RH has been modeled and CFD simulations have been performed. The simulation results show that the hottest regions occur on the electric rod surface behind the last baffle. A technical optimization was performed by adjusting three parameters: Shell-baffle clearance, electric rod-baffle clearance and number of baffles. After the technical optimization was carried out, the temperature difference between the maximum temperature and the average outlet temperature of the salt is within the acceptable limits, thus critical salt decomposition has been avoided. Additionally, the CFD simulations results were analyzed and compared with results obtained with a one-dimensional model in Modelica. [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 present work deals with the initial design and performance evaluation of a novel thermal energy storage concept consisting of a packed bed of rocks with a radial gas flow, suitable for the a generation of air-driven concentrating solar power plants. In doing so, this article also presents a state of the art of most promising packed bed concepts, highlighting their advantages and disadvantages, all considered in the design of the new proposed system. A thermomechanical model of the concept was developed and used in simulations to assess its behavior during both charging and discharging processes, as well as to evaluate the influence of critical design parameters. This same model was used to compare the technical performance of the concept against that of more conventional packed-beds with axial-flow. Results show that the novel concept is able to outperform the other systems by enabling a theoretical reduction of 46% and 50% in radiation losses and pressure drops, respectively, thus calling for future investigations, including an in-depth thermosmechanical study and life-cycle analysis of the concept prior to building a lab-scale prototype. [ABSTRACT FROM AUTHOR]

The yield of solar thermal power plants is strongly affected by disturbances in the irradiation condition through passing clouds. This effect is even more prominent when the clouds shade the solar field only partially as the irradiance situation cannot be fully measured by few measurement points in the field. In this paper, the benefit of using nowcasting systems to produce highly resolved irradiance maps on the field during start-up is studied. A simulation tool is used to dynamically model all the loops and piping in a reference commercial solar field. Automatic solar field controllers allow the model to operate during different situations. The performance of the field under a reference state-of-the-art controller is compared against a controller using the irradiance maps from nowcasting systems. The benefit during start-up processes is found to be significantly lower than the benefit the system makes during normal solar field operation. However, there is more potential shown for more advanced controllers, like model-predictive control. [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]

Supercritical CO2 (SCO2) Brayton cycle is a promising alternative power generation technology as a substitute for steam Rankin cycle, mainly due to its high efficiency and compact turbo-machinery. Concentrated Solar Power (CSP) plant could be a first industrial application of SCO2 cycle for the next generation tower technology. In order to better understand cycle dynamics during operation and to design dedicated control strategies, dynamic modeling and simulation is necessary. In this work, a preliminary SCO2 Brayton recompression cycle model is developed, with all the key cycle components modeled in different details. Based on this model, some typical transient scenarios such as cycle maximum temperature variation, cycle minimum temperature variation and inventory injection & extraction are simulated and the resulted are presented and analyzed. The simulations show that highly non-linear behavior of thermodynamic properties and efficiency, especially near the low temperature and high temperature recuperator. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis of experimental studies on a 1MWe superheated steam tower CSP demonstrator in Beijing. The demonstrator includes solar field with 100 heliostats of 100 m², a cavity steam receiver composed of a steam tank, evaporator panels and superheater panels, power block and thermal energy storage system using thermal oil as storage fluid. A series of campaigns have been carried out since 2012 to study the demonstrator performance. The campaign topics cover superheated steam production, power generation, system start-up/shut-down, transient scenario response, and thermal storage system charging/discharging. Through the feedback of campaigns, experiences have been gained on system operation, maintenance, transient scenario response and thermal energy storage. [ABSTRACT FROM AUTHOR]

In this paper the results of a techno-economic analysis of improved and optimized molten salt solar tower plants (MSSTP plants) are presented. The potential improvements that were analyzed include different receiver designs, different designs of the HTF-system and plant control, increased molten salt temperatures (up to 640°C) and multi-tower systems. Detailed technological and economic models of the solar field, solar receiver and high temperature fluid system (HTF-system) were developed and used to find potential improvements compared to a reference plant based on Solar Two technology and up-to-date cost estimations. The annual yield model calculates the annual outputs and the LCOE of all variants. An improved external tubular receiver and improved HTF-system achieves a significant decrease of LCOE compared to the reference. This is caused by lower receiver cost as well as improvements of the HTF-system and plant operation strategy, significantly reducing the plant own consumption. A novel star receiver shows potential for further cost decrease. The cavity receiver concepts result in higher LCOE due to their high investment cost, despite achieving higher efficiencies. Increased molten salt temperatures seem possible with an adapted, closed loop HTF-system and achieve comparable results to the original improved system (with 565°C) under the given boundary conditions. In this analysis all multi tower systems show lower economic viability compared to single tower systems, caused by high additional cost for piping connections and higher cost of the receivers. [ABSTRACT FROM AUTHOR]

The continued decrease in the cost of photovoltaics, particularly in comparison to concentrating solar thermal power plants has led to a recent case where a CSP plant was decommissioned in favour of replacement with a pure PV plant. In this paper a second option is considered where the existing CSP power plant is retrofit with a bolt-on PV apparatus that achieves 93% of the output of the PV replacement but at 18% of the cost. [ABSTRACT FROM AUTHOR]

Under the collaboration framework between EDF China R&D Centre and CAS-IEE, a preliminary numerical model of 1MWth molten salt tower solar power demonstration plant in Badaling, Beijing is presented in this paper. All key components in the plant are presented throughout detailed modules in the model according to its design specifications. Control strategies are also implemented to maintain the design system performance at transient scenario. By this model some key design figures of plant has been validated and it will be used to guide experiment set-up and plant commissioning. [ABSTRACT FROM AUTHOR]

The dispatchability offered by thermal energy storage (TES) in concentrated solar power (CSP) and solar hybrid plants based on such technology presents the most important difference compared to power generation based only on photovoltaics (PV). This has also been one reason for recent hybridization efforts of the two technologies and the creation of Power Purchase Agreement (PPA) payment schemes based on offering higher payment multiples during daily hours of higher (peak or priority) demand. Recent studies involving plant-level thermal energy storage control strategies are however to a large extent based on pre-determined approaches, thereby not taking into account the actual dynamics of thermal energy storage system operation. In this study, the implementation of a dynamic dispatch strategy in the form of a TRNSYS controller for hybrid PV-CSP plants in the power-plant modelling tool DYESOPT is presented. In doing this it was attempted to gauge the benefits of incorporating a day-ahead approach to dispatch control compared to a fully pre-determined approach determining hourly dispatch only once prior to annual simulation. By implementing a dynamic strategy, it was found possible to enhance technical and economic performance for CSP-only plants designed for peaking operation and featuring low values of the solar multiple. This was achieved by enhancing dispatch control, primarily by taking storage levels at the beginning of every simulation day into account. The sequential prediction of the TES level could therefore be improved, notably for evaluated plants without integrated PV, for which the predicted storage levels deviated less than when PV was present in the design. While also featuring dispatch performance gains, optimal plant configurations for hybrid PV-CSP was found to present a trade-off in economic performance in the form of an increase in break-even electricity price when using the dynamic strategy which was offset to some extent by a reduction in upfront investment cost. An increase in turbine starts for the implemented strategy however highlights that this is where further improvements can be made. [ABSTRACT FROM AUTHOR]

Concentrating solar power plants, even though they can be integrated with thermal energy storage, are still subjected to cyclic start-up and shut-downs. As a consequence, in order to maximize their profitability and performance, the flexibility with respect to transient operations is essential. In this regard, two of the key components identified are the steam generation system and steam turbine. In general it is desirable to have fast ramp-up rates during the start-up of a power plant. However ramp-up rates are limited by, among other things, thermal stresses, which if high enough can compromise the life of the components. Moreover, from an operability perspective it might not be optimal to have designs for the highest heating rates, as there may be other components limiting the power plant start-up. Therefore, it is important to look at the interaction between the steam turbine and steam generator to determine the optimal ramp rates. This paper presents a methodology to account for thermal stresses limitations during the power plant start up, aiming at identifying which components limit the ramp rates. A detailed dynamic model of a parabolic trough power plant was developed and integrated with a control strategy to account for the start-up limitations of both the turbine and steam generator. The models have been introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results indicated that for each application, an optimal heating rates range can be identified. For the specific case presented in the paper, an optimal range of 7-10 K/min of evaporator heating rate can result in a 1.7-2.1% increase in electricity production compared to a slower component (4 K/min). [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide (sCO2) has recently gained a lot of interest as a working fluid in different power generation applications. For concentrated solar power (CSP) applications, sCO2 provides especially interesting option if it could be used both as the heat transfer fluid (HTF) in the solar field and as the working fluid in the power conversion unit. This work presents development of a dynamic model of CSP plant concept, in which sCO2 is used for extracting the solar heat in Linear Fresnel collector field, and directly applied as the working fluid in the recuperative Brayton cycle; these both in a single flow loop. We consider the dynamic model is capable to predict the system behavior in typical operational transients in a physically plausible way. The novel concept was tested through simulation cases under different weather conditions. The results suggest that the concept can be successfully controlled and operated in the supercritical region to generate electric power during the daytime, and perform start-up and shut down procedures in order to stay overnight in sub-critical conditions. Besides the normal daily operation, the control system was demonstrated to manage disturbances due to sudden irradiance changes. [ABSTRACT FROM AUTHOR]

The present study quantifies the reduction in the levelized cost of electricity (LCoE) and capital expenditure (CAPEX) of a dish Stirling power plant (DSPP) through an increase in localization and unit production volume. Furthermore, the localization value of the plant is examined to determine how much investment is brought into the local economy. Ouarzazate, Morocco, was chosen as the location of the study due to the country's favorable regulatory framework with regards to solar power technologies and its established industry in the concentrating solar power (CSP) field. A detailed techno-economic model of a DSPP was developed using KTH's in-house modelling tool DYESOPT, which allows power plant evaluation by means of technical and economic performance indicators. Results on the basis of LCoE and CAPEX were compared between two different cases of production volume, examining both a minimum and maximum level of localization. Thereafter, the DSPP LCoE and localization value were compared against competing solar technologies to evaluate its competitiveness. In addition, a sensitivity analysis was conducted around key design parameters. The study confirms that the LCoE of a DSPP can be reduced to values similar to solar photovoltaic (PV) and lower than other CSP technologies. Furthermore, the investment in the local economy is far greater when compared to PV and of the same magnitude to other CSP technologies. The competiveness of a DSPP has the potential to increase further when coupled with thermal energy storage (TES), which is currently under development. [ABSTRACT FROM AUTHOR]

Concentrated Solar Power plants (CSP) coupled with thermal storage have the potential to guarantee both flexible and continuous energy production, thus being competitive with conventional fossil fuel and hydro power plants, in terms of dispatchability and provision of ancillary services. Hence, the plant equipment and control design have to be focused on flexible operation on one hand, and on plant safety concerning the molten salt freezing on the other hand. The PreFlexMS European project aims to introduce a molten salt Once-Through Steam Generator (OTSG) within a Rankine cycle based power unit, a technology that has greater flexibility potential if compared to steam drum boilers, currently used in CSP plants. The dynamic modelling and simulation from the early design stages is, thus, of paramount importance, to assess the plant dynamic behavior and controllability, and to predict the achievable closed-loop dynamic performance, potentially saving money and time during the detailed design, construction and commissioning phases. The present paper reports the main results of the analysis carried out during the first part of the project, regarding the system analysis and control design. In particular, two different control systems have been studied and tested with the plant dynamic model: a decentralized control strategy based on PI controllers and a Linear Model Predictive Control (LMPC). [ABSTRACT FROM AUTHOR]

The present work presents the validation process carried out for a simulation tool especially designed for the energy yield assessment of concentrating solar plants based on parabolic through (PT) technology. The validation has been carried out by comparing the model estimations with real data collected from a commercial CSP plant. In order to adjust the model parameters used for the simulation, 12 different days were selected among one-year of operational data measured at the real plant. The 12 days were simulated and the estimations compared with the measured data, focusing on the most important variables from the simulation point of view: temperatures, pressures and mass flow of the solar field, gross power, parasitic power, and net power delivered by the plant. Based on these 12 days, the key parameters for simulating the model were properly fixed and the simulation of a whole year performed. The results obtained for a complete year simulation showed very good agreement for the gross and net electric total production. The estimations for these magnitudes show a 1.47% and 2.02% BIAS respectively. The results proved that the simulation software describes with great accuracy the real operation of the power plant and correctly reproduces its transient behavior. [ABSTRACT FROM AUTHOR]

Alstom is developing solar power tower plants utilizing molten salt as the working fluid. In solar power tower, the molten salt central receiver (MSCR) atop of the tower is constructed of banks of tubes arranged in panels creating a heat transfer surface exposed to the solar irradiation from the heliostat field. The molten salt heat transfer fluid (HTF), in this case 60/40%wt NaNO3-KNO3, flows in serpentine flow through the surface collecting sensible heat thus raising the HTF temperature from 290?C to 565?C. The hot molten salt is stored and dispatched to produce superheated steam in a steam generator, which in turn produces electricity in the steam turbine generator. The MSCR based power plant with a thermal energy storage system (TESS) is a fully dispatchable renewable power plant with a number of opportunities for operational and economic optimization. This paper presents operation and controls challenges to the MSCR and the overall power plant, and the use of dynamic model computer simulation based transient analyses applied to molten salt based solar thermal power plant. This study presents the evaluation of the current MSCR design, using a dynamic model, with emphasis on severe events affecting critical process response, such as MS temperature deviations, and recommend MSCR control design improvements based on the results. Cloud events are the scope of the transient analysis presented in this paper. The paper presents results from a comparative study to examine impacts or effects on key process variables related to controls and operation of the MSCR plant. [ABSTRACT FROM AUTHOR]

Among concentrating solar power technologies, direct steam generation solar tower power plants represent a promising option. These systems eliminate the usage of heat transfer fluids allowing for the power block to be run at greater operating temperatures and therefore further increasing the thermal efficiency of the power cycle. On the other hand, the current state of the art of these systems does not comprise thermal energy storage as there are no currently available and techno-economically feasible storage integration options. This situation makes direct steam generation configurations even more susceptible to the already existing variability of operating conditions due to the fluctuation of the solar supply. In the interest of improving the annual performance and competitiveness of direct steam generation solar tower systems, the present study examines the influence of implementing two flexibility enhancing concepts which control the steam flow to the turbine as a function of the incoming solar irradiation. The proposed concepts were implemented in a reference plant model previously developed by the authors. Then, a multi-objective optimization was carried out in order to understand which configurations of the steam turbine concepts yield reductions of the levelized cost of electricity at a lower investment costs when compared to the reference model. Results show that the implementation of the proposed strategies can enhance the thermo-economic performance of direct steam generation systems by yielding a reduction of up to 9.2% on the levelized cost of electricity, mainly due to allowing 20% increase in the capacity factor, while increasing the investment costs by 7.8%. [ABSTRACT FROM AUTHOR]