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In a previous work, a solar chimney power plant integrated with a solid sorption cooling system for power and cold cogeneration was developed. This prior work showed that reusing the heat released from the adsorption bed enhances the system's utilization of solar energy and increases the turbine's output power. In the present paper, a subsequent modification to the arrangement and operation of the preceding system is introduced. The primary objective of the modification is to enhance performance and increase the plant's capacity to effectively harness the available solar radiation. The method involves placing the condenser tubes at the solar collector entrance. Therefore, the airflow captures the condenser-released heat before it enters the collector. The modified configuration and operation of the system are discussed. A dynamic mathematical model is established to simulate the hybrid system's operation and evaluate its parameters. The obtained results show that a 5.95% increase in output power can be achieved by recovering the heat of condensation. Furthermore, the modified system attains a 6% increase in solar-to-electricity conversion efficiency compared with the basic system. The findings suggest that the modified system, which recycles condenser heat, provides noticeable enhanced performance compared with the basic system. [ABSTRACT FROM AUTHOR]

As the urgency to mitigate climate change intensifies, the achievement of zero carbon targets in the built environment has become a critical objective. Building retrofitting plays a vital role in reducing energy consumption and carbon emissions in existing buildings. This paper presents an approach that combines Building Information Modeling (BIM) with multiple domains to strive for zero carbon targets in building retrofit projects. The proposed approach is based on a dynamic multi-parameter analysis that integrates indoor comfort, energy savings, CO2eq reduction, and the social cost of carbon while considering investment costs. Renewable energy technologies, such as photovoltaic panels and solar thermal systems, are emphasized to achieve the desired zero-carbon outcomes. Real-time monitoring mechanisms enable continuous performance evaluation and adaptive retrofit strategies for further energy savings. This approach is validated through a case study of an existing thermal bath building, known as "Terme Lucane", located in southern Italy. The results of the study demonstrate significant reductions in energy consumption and carbon emissions, highlighting the potential of the proposed approach to achieve zero carbon targets through the integration of multi-data BIM implementation. These findings offer a promising pathway for building retrofit projects aiming for zero carbon targets through multi-data BIM modeling. [ABSTRACT FROM AUTHOR]

Parabolic Trough Solar Receiver-Reactor (PTSRR) of Methanol Decomposition Reaction process (MDR), which can achieve chemical storage and efficient utilization of solar energy, has gained increasing attention recently. To comprehensively study the performance of PTSRR of MDR under off-design conditions and during dynamic processes, a model of PTSRR-MDR is developed and validated. Detailed energy and exergy analysis model are developed to figure out the irreversibility distribution. Results indicate that exergy destructions caused by solar concentrating and thermochemical reaction processes limit the improvement of exergy efficiency, which account 39.32% and 18.32%, respectively, under 800 DNI. When DNI step decreases from 800 to 400 W m−2, the methanol conversion rate decreases from 90.0% to 40.9% in ∼400 s. The solar-to-chemical exergy efficiency increases from 16.39% to 32.80% immediately, then decreases to the lowest value in 30 s, and rises to 11.23%. The efficiency is lower than the stable value transiently because the exergy stored in solid phase is partly destructed when converted to chemical exergy. Then, dynamic performance under DNI step increase is studied. Due to thermal inertia, additional chemical energy and exergy are gained or lost, compared to the ideal process. The results may provide some guidance for further efficient operation control. [ABSTRACT FROM AUTHOR]

This numerical study aims at assessing the impact of the thermal energy storage (TES) operation strategy on the performance of a parabolic trough concentrated solar power plant (PT-CSP). This strategy consists of managing the TES charging process in order to minimize the plant's parasitic consumption. The study was conducted using a TRNSYS based dynamic simulation model of a 55 MW e PT-CSP plant similar to the ANDASOL plant located in the South of Spain. The simulation results were validated in comparison with the available experimental data in the literature. The results showed that the suggested operating strategy is efficient as the heat transfer fluid and the TES molten salt pumps' total parasitic consumption is reduced by 21% during a typical clear day of July. Consequently, the plant's net energy production was improved by 0.8%. The resulting improvement in the overall efficiency of the plant was found to be 2.4%. [ABSTRACT FROM AUTHOR]

Solar heating technology has the advantages of being high efficiency, energy-saving, and environment protecting; however, the instability of solar energy and its mismatch with the variation characteristics of building heat load have caused great difficulties in the design and the efficient operation strategy of a solar system. A heat storage tank is an important part of a solar hot water system. In order to improve system efficiency, this paper proposes a flat plate PCM storage tank, establishes a mathematical model, and conducts experimental verification under different working conditions. Experiments show that in the heat storage process, the phase change material (PCM) only accounts for less than 20% of the space of the PCM storage tank, and its heat storage can reach 50% of the total heat storage of the tank. In the discharge process, the water temperature of the ordinary tank decreases by 20 °C within 1.5 h, and the phase change process lasts approximately 3 h, with the water temperature remaining at 45~50 °C during this period. In the natural cooling process, the heat discharge of the two water tanks at night was similar, while the temperature of the ordinary water tank decreased by 12 °C and that of the phase change water tank decreased by 7 °C. By simulating the dynamic simulation model of the composite solar phase change thermal storage combined with an air-cooled heat pump system, the results show that the solar heating system with a PCM storage tank (SHS-PCM) saves 34% more energy than a solar heating system with a common tank (SHS-without PCM), and the volume of the PCM storage tank is reduced to 1/5 of the ordinary tank. The investment payback period method of energy saving reconstruction is used to analyze the economy of the SHS-PCM and the SHS-without PCM, the initial investment cost of the SHS-PCM is CNY 9858 higher than the SHS-without PCM, but the annual operation cost is saved by CNY 12,100, and the project investment payback period is 0.81 years, which has energy-saving potential and economic benefits. [ABSTRACT FROM AUTHOR]

This works proposes a dynamic thermoeconomic analysis of a liquefied biomethane production plant to meet the fuel demand of a fleet of heavy duty trucks in the south of Italy. The biomethane is obtained from the upgrading of the biogas produced by means of anaerobic digestion through a plug flow reactor fed by organic fraction of municipal solid waste. The upgrading of the biogas is realized using a three-stage membrane compression process, producing a 96 % pure biomethane. The biomethane liquefaction is realized using a single-mixed refrigerant process and compared to a Linde cycle process. The whole system is assisted by solar energy to reduce the fossil energy consumption of the process and feed-in tariffs are considered as funding policy. The models for the anaerobic digestion, the biogas upgrading, and the biomethane liquefaction are in detail developed in MatLab. The anaerobic digestion model is based on the ADM1 biological model, integrated with a suitable heat transfer model. The biogas upgrading model is based on a simplified Fick model. The liquefaction model is based on an equivalent two heat-exchangers model, taking into account the transient heat transfer. All the components are then integrated in TRNSYS to perform the dynamic simulation for one operating year of the whole system. Results from the thermoeconomic analysis are outstanding in terms of profitability, showing a payback period of less than 2 years and a Net Present Value of the system of 402 M€. The great environmental impact is also confirmed by a Primary Energy Saving of 91 % and a dramatic reduction of 86 % of the CO 2 equivalent emissions. • Feasible LBM production for heavy-duty trucks. • SMR liquefaction is more efficient than Linde cycle process. • Government incentives are needed in both cases. • Incentives for waste disposal is even more effective. [ABSTRACT FROM AUTHOR]

State-of-art power systems are progressing rapidly due to the advent of converter-interfaced power generation. Power system stabilizers are commonly employed in synchronous generators to damp low-frequency oscillations. However, many of these generators have been decommissioned by converter-interfaced generations. This means that converter-interface-based wind and solar power plants should also commit to oscillation damping. In addition, renewable generators may be coordinated with power system stabilizers to enhance the damping. This paper recommended a new advanced design of damping control system using wide-area signal with converter-interfaced generations. The major contribution of this work is to improve the damping of low-frequency oscillations while keeping the frequency in the specified range taking into account renewable energy sources. This paper introduced a mixed H 2 / H ∞ using non-convex optimization utilized to design damping controllers for renewable integrated power systems to secure system operation against low-frequency oscillation modes. This multi-objective control design permits for more reliable and precise specification of the recommendable closed-loop behavior. The proposed robust controller is tested on grid-forming wind turbine type-III DFIGs and generic dynamic PV plants integrated large study power systems, whereas robustness is evaluated against several perturbations and communication delay through dynamic simulation. [ABSTRACT FROM AUTHOR]

• A multi-scale numerical approach is developed to quantify the fluid-structural responses of floating solar farms. • Static and dynamic simulations of connected floating modules subjected to different loadings are carried out. • A laboratory study was performed to verify the predictions on the displacement of the floating array under wave action. • Discussion is provided on how the approach can optimize mooring configurations and prevent possible overwash. Floating solar farms (FSFs) are emerging to be a viable option for large scale solar power production. The present study develops an original approach for the design assessment of the maximum stress/strain and displacement of massively connected modular FSFs under wave action. The scope includes two parts: (1) numerical simulations for the fluid structural analysis with two-way coupling of a global array of connected modular floaters that hold the massive number of solar panels; and (2) experimental validation of the numerical predictions for the dynamic response of the global array under wave action. The numerical approaches are based on finite element simulations. Both static and dynamic simulations are carried out with and without using the Fluid Structure Interaction (FSI) method, under different incident wave characteristics, rheological properties of the global array, and mooring configurations. The experiments were performed with a flexible perforated sheet using Froude scaling for dynamic similitude, with ultrasonic measurements to quantify the wave profile as well as the displacement responses of the array under wave action. The comparison shows reasonable agreement between the predictions and measurements at discrete locations along the array. Finally, a summary is provided on how the new approach can aid in the design assessment of modular FSFs under wave motion. [ABSTRACT FROM AUTHOR]

Daily start-up is a typical feature of concentrated solar power plants (CSPs) due to solar energy intermittency. Therefore, appropriate start-up operation strategies are significant for CSPs. A parabolic trough concentrated solar power plant (PTCSP) with molten salt (MS) is a potential technical route. However, little attention has been paid to the dynamic start-up performance of PTCSP using MS. To mend the research gap, the dynamic start-up simulation of PTCSP using MS is conducted. Main contributions of this study are the dynamic start-up simulation of PTCSP using MS and evaluation of two MS anti-freezing solutions. Results indicate that the outlet MS temperature of solar field transiently exceeds nominal values during start-up processes. The inlet feedwater temperature of the preheater is much lower than MS freezing temperature during start-up processes. Therefore, two anti-freezing solutions were used to avoid MS solidification. Compared with utilizing the recirculating pump, utilizing the low-load regenerative heater can enhance anti-freezing performance, which could reduce the maximum control deviation of the preheater inlet feedwater temperature by 2.0 °C and increase the average outlet MS temperature of the preheater by 2.4 °C. This study may provide guidance for the dynamic simulation and operation optimization of CSPs during start-up processes. • Dynamic models of concentrated solar power plants using molten salt are developed. • The start-up process of parabolic trough concentrated solar plants is simulated. • Two molten salt anti-freezing solutions are compared during the start-up process. • Using a low-load regenerative heater can enhance the anti-freezing performance. • Using a low-load regenerative heater may increase feedwater subcooled boiling risk. [ABSTRACT FROM AUTHOR]

Thermodynamic analyses of concentrating solar power plants and optimizing these cycles relying on the energetic and exergetic optimal efficiencies are quite common. However, it is found that just considering the efficiency of the system for performance optimization and neglecting the adverse effects of the plant's wrong operation timings, which is a function of the solar working fluid flow rate, can easily give misleading optimization results. This study's primary goal is to find the optimal operating point of the cycle in terms of the thermodynamic efficiencies considering the system's operating time. Thus, the Sliding Mode Control (SMC) approach is employed to provide a proper mass flow rate for the working fluid from the solar collector field to achieve a precise output temperature from the collectors in different operating conditions. Multi-objective optimization is performed using the Particle Swarm Optimization (PSO) algorithm. The results of power block sensitivity analysis indicate that a 70? increase in the solar collector outlet temperature remarkably enhances electricity generation and exergetic efficiency by 67 and 48%. The twoobjective optimization shows 22.01%, 2.10%, and 5.46% enhancement in response time, thermal efficiency, and exergetic efficiency, and the three-objective optimization reveals 3.68% and 3.74% improvement in efficiency (thermal and exergetic), respectively. [ABSTRACT FROM AUTHOR]

The present work focuses on the development of a detailed dynamic model of an existing parabolic trough solar power plant (PTSPP) in Spain. This work is the first attempt to analyse the dynamic interaction of all parts, including solar field (SF), thermal storage system (TSS) and power block (PB), and describes the heat transfer fluid (HTF) and steam/water paths in detail. Advanced control circuits, including drum level, economiser water bypass, attemperator and steam bypass controllers, are also included. The parabolic trough power plant is modelled using Advanced Process Simulation Software (APROS). An accurate description of control structures and operation strategy is necessary in order to achieve a reasonable dynamic response. This model would help to identify the best operation strategy due to DNI (direct normal irradiation) variations during the daytime. The operation strategy used in this model has also been shown to be effective compared to decisions made by operators on cloudy periods by improving power plant performance and increasing operating hours. [ABSTRACT FROM AUTHOR]

Dynamic simulation provides an efficient approach for improving the efficiency of parabolic trough power plants and control circuits. In the dynamic simulation, the possibilities and operating conditions of the plant are evaluated regarding materials, processes, emissions, or economics. Several studies related to the dynamic simulation of the parabolic trough technology are summarised and discussed in this work. This study is the first research that presents a thorough description of the advanced control circuits used in the solar field and thermal storage system of a parabolic trough power plant. This power plant was implemented using advanced process simulation software (APROS). The dynamic model was built based on the real specifications of the power plant. [ABSTRACT FROM AUTHOR]

Introduction. In recent years, transmission systems comprise more direct current structures; their effects on alternating current power system may become significant and important. Also, multi-terminal direct current is favorable to the integration of large wind and solar power plants with a very beneficial ecological effect. The novelty of the proposed work consists in the effects of the aforementioned modern devices on transient stability, thus turn out to be an interesting research issue. In our view, they constitute a new challenge and an additional complexity for studying the dynamic behavior of modern electrical systems. Purpose. We sought a resolution to the problem of the transient stability constrained optimal power flow in the alternating current / direct current meshed networks. Convergence to security optimal power flow has been globally achieved. Methods. The solution of the problem was carried out in MATLAB environment, by an iterative combinatorial approach between optimized power flow computation and dynamic simulation. Results. A new transient stability constrained optimal power flow approach considering multi-terminal direct current systems can improve the transient stability after a contingency occurrence and operate the system economically within the system physical bounds. Practical value. The effectiveness and robustness of the proposed method is tested on the modified IEEE 14- bus test system with multi-objective optimization problem that reflect active power generation cost minimization and stability of the networks. It should be mentioned that active power losses are small in meshed networks relative to the standard network. The meshed networks led to a gain up to 46,214 % from the base case. References 24, table 3, figures 11. [ABSTRACT FROM AUTHOR]

Abstract Concentrated solar power (CSP) plant with thermal energy storage can be operated as a peak load regulation plant. The steam generation system (SGS) is the central hub between the heat transfer fluid and the working fluid, of which the dynamic characteristics need to be further investigated. The SGS of Solar Two power tower plant was selected as the object. The mathematical model with lumped parameter method was developed and verified to analyze its dynamic characteristics. Five simulation tests were carried out under the disturbances that the solar tower power plant may encounter under various solar irradiations and output electrical loads. Both dynamic and static characteristics of SGS were analyzed with the response curves of the system state parameters. The dynamic response and time constants of the working fluids out of SGS was obtained when the step disturbances are imposed. It was indicated that the disturbances imposed to both working fluids lead to heat load reassignment to the preheater, evaporator and superheater. The proposed step-by-step disturbance method could reduce the fluid temperature and pressure fluctuations by 1.5 °C and 0.03 MPa, respectively. The results could be references for control strategies as well as the safe operation of and SGS. Highlights • Mathematical model with lumped parameter method established for dynamic characteristics simulation of SGS. • Dynamic responses of working fluids out of SGS obtained under different disturbances during operation of CSP. • Impacts of five disturbance factors investigated that PT may encounter as peak load regulation plant. • Temperature and pressure fluctuations of working fluids could be reduced with the proposed step-by-step disturbance method. [ABSTRACT FROM AUTHOR]

In this work, a dynamic model of a high-temperature integrated solar combined cycle power plant is presented. The system includes a three-pressure combined cycle power plant coupled to parabolic trough solar collectors. Thermal storage, a heat solar steam generator, pumps, heat exchangers, and several controllers are also included in the system. Solar energy is used to produce additional steam to be supplied to the steam turbine of the combined cycle power plant. The integrated solar combined cycle system is based on the heat transfer fluid arrangement, exploiting solar energy to produce steam. The analysis is developed by a dynamic simulation model including detailed algorithms for the calculation of the performances of system components. Special control strategies are included in the model in order to accurately manage the steam production of the heat solar steam generator. The paper presents a thermo-economic and environmental comparison between the integrated solar combined cycle and a conventional combined cycle, powered by fossil fuels, based on dynamic simulations. A case study, referred to a plant with a maximum power of around 100 MW, located in Almeria (Southern Spain), is presented and discussed. A parametric analysis was also performed to show the effect of the variation of total solar field reflector area on the system performance. For the case under evaluation, a simple pay-back of 15 years was found, for a solar field aperture area of 80 000 m 2 ; however, the parametric analysis suggests that a smallest solar field area should be used under the hypotheses of the case study. [ABSTRACT FROM AUTHOR]

This paper outlines the development of models of a solar field designed to provide thermal energy to a Multi-Effect Desalination (MED) plant. The dynamic model can be used both for simulation and control purposes. Some of these models have been developed based on static and dynamic energy and mass balances, and some others are based on step response methods (experimental tests). The solar field comprises a flat-plate collector field, an air cooler, a heat exchanger and the corresponding pipelines and interconnections. The main purpose of the solar field is to feed the MED unit with hot water within a specific temperature range using two thermal storage tanks as input buffers to the MED system. The main achievement of this paper is that the developed model provides an adequate tradeoff between complexity and performance. [ABSTRACT FROM AUTHOR]

In developing building energy sector, employment of smart energy plants with advanced control strategies is essential to reduce energy consumption and to increase inhabitants' comfort. The solar Photovoltaic-Thermal (PVT) panels are considered as the key elements for smart building energy supply. In the present research, a combination of solar PVTs with a reversible heat pump is designed and analyzed to provide electricity, cooling, and heating energies of a case study building. The plant also includes control equipment and energy storage tank to insure smart operation under different climate conditions. The proposed plant can also be employed for a larger scale to provide energy demands of a district area. Thermal characteristics and economic features of the proposed plant are taken into account to assess its transient performance using TRNSYS software for a case study location in China with considering real climate conditions of ambient temperature and sun radiation. The produced electricity as well as cooling and heating duties are evaluated for different specifications of PVT panels and the storage tanks' volumes. The plant performance is appraised in terms of total capital cost, CO 2 saving ratio, and the payback period. Finally a multi-objective optimization is carried out and the Pareto frontier for three objectives is represented. It has been concluded that, under optimal operation, the proposed building energy plant has a 5 year payback period with 1.93 CO 2 saving ratio and 513328 $. Also it is found that, the volume of storage tanks has a significant effect on economic indicators as well as the CO 2 saving ratio. [Display omitted] • A novel building energy plant driven by solar PVT panels is proposed. • The plant is integrated with a reversible heat pump to operate as a CCHP system. • Dynamic modeling and annually transient performance evaluation is represented. • Optimization is conducted based on total cost, CO 2 saving ratio and payback period. [ABSTRACT FROM AUTHOR]

To improve the energy utilization efficiency of the solar-coal hybrid power plant, a solar power tower plant with the supercritical CO 2 (S–CO 2) Brayton cycle is proposed. In this study, the dynamic mathematical model is established by lumped parameter method. Meanwhile, the thermodynamic performance of the system is analyzed by exergy and energy analysis methods. The results show that the maximum error of dynamic mathematical model is less than 5%. The exergy analysis shows that exergy destruction mainly occurs in the heat exchanger, followed by the recuperator and precooler. In addition, the thermal efficiency of the S–CO 2 solar units is improved by approximately 2.5% after coupling with coal-fired thermal power units. The dynamic mathematical model proposed in this study can be used to analyze the dynamic characteristics, and achieve high solar power generation efficiency. It provides a reference for the efficient utilization of solar-coal energy complementation. [Display omitted] • A novel waste heat recovery system with the S–CO 2 cycle is proposed. • S–CO 2 cycle cooling using condensate from coal-fired units. • Thermodynamic analysis and dynamic characteristics of the system are studied. • The system improved by 2.5% after coupling coal-fired units. • The off-design performance of the system based on the S–CO 2 cycle is studied. [ABSTRACT FROM AUTHOR]

The present study further investigates a novel concentrating solar thermal desalination process using a dual tank system, which addresses one of the biggest challenges in wider adoption of solar applications: 24-h dispatching of solar energy. Direct use of solar energy only during daily sun hours might be acceptable on a small scale, but not economically viable on a larger scale. In this study, a complete once through multi-stage flash (MSF-OT) desalination plant powered by solar thermal energy was modeled using the TRNSYS modeling environment. The model results are in good agreement with previous general studies, but the novelty here is development and use of a component-based, dynamic simulation model of the entire desalination plant, which more accurately represents real situations, and allows parametric analyses of important design variables such as the number of stages, top brine temperature, operating pressures, and solar concentrator area. Key indicators were used to evaluate this novel concept, which included the performance ratio, PR (the ratio of the total energy required to evaporate the brine to the total solar energy gained), the recovery ratio, RR (the relative amount of distillate extracted from the feed water), the specific mass feed water flow, SMF (the ratio of the feed water mass to the mass of the produced distillate water), as well as a detailed economic analysis. System improvements relative to previous studies included use of series/parallel configuration of the solar concentrator array and improved thermodynamic modeling of vacuum pressures in flashing tanks. Results of this study showed that the size of the solar concentrator array can be reduced by 54 % relative to previous studies. The average daily values of the performance ratio (PR). the recovery ratio (RR), and the specific mass feed water flow (SMF) were approximately15.2, 13.8 %, and 7.25. Finally, based on a detailed economic analysis, it was found that the water price could be reduced by nearly 15 % to $2.33/m3. • A whole-plant solar thermal desalination plant model allows examination and optimization of plant performance. • Solar thermal desalination plants can be economically viable with continuous thermal storage. • Component-based system simulation allowed examination of plant performance on an hourly basis for a full year. • Plant performance metrics were evaluated and a detailed economic analysis was conducted. [ABSTRACT FROM AUTHOR]

The integration of solar thermal energy into the coal-fired power plant is a cost-effective method to compensate for the solar energy intermittency. With the increasing penetration of renewable energy in the power grid, the solar-aided coal-fired power plant (SACFPP) should undertake peak-shaving tasks, which receives little attention in previous studies. This study examines the SACFPP flexibility and finds out that the reheat steam temperature easily exceeding the safety range limits the maximum load cycling rate during processes simultaneously accompanied with direct normal irradiance (DNI) disturbances. An improved control strategy is proposed accordingly to enhance the SACFPP flexibility. The feedforward control signal to regulate the flue gas damper is generated corresponding to the DNI and load cycling requirements. The effectiveness of the proposed control under sunny/cloud cover cases and actual conditions is verified. Results show that the maximum load cycling rate of a 660 MW SACFPP increases from 3.3 MW min−1to 13.2/13.2/9.9 MW min−1 under sunny/light cloud cover/strong cloud cover cases, respectively. The reheat steam temperature deviations are reduced from 9.7 °C to 4.0 °C and 18.6 °C to 4.0 °C, when DNI step decreases from 700 W m−2 to 400 W m−2 and 0 W m−2 in load up processes, respectively. • Load cycling performance of solar-aided coal-fired power plant is evaluated. • Bottleneck for load cycling rate is found to be reheat steam temperature control. • The control strategy is improved to enhance the operational flexibility. • Load cycling rate increases from 3.3 to 13.2 MW min−1 in light cloud cover cases. [ABSTRACT FROM AUTHOR]

The transient performance of solar thermal power plants is critical to the system design and optimization. This study numerically investigates the dynamic efficiencies of an open-loop air receiver and a thermal energy storage unit. One-dimensional dynamic models of the air receiver and thermal energy storage were developed using the Modelica language with a graphical user interface and the Dymola solver to provide comprehensive thermal simulation at low computational cost. An air receiver and thermal energy storage experimental platforms were built to validate the simulation models. The simulation results compare well with the experimental data, so the models can be used to predict the variations of air receiver and thermal energy storage efficiencies. The models were then combined into a receiver and thermal energy storage system model with control schemes. The schemes control the air receiver outlet air temperature at relatively stable values while the thermal energy storage automatically switches between charging, discharging and stand-by modes. [ABSTRACT FROM AUTHOR]

This paper presents the design and evaluation of a dynamic simulator for an ISCC (integrated solar combined cycle) plant. The design of the simulator is based on the phenomenological equations for both a combined cycle plant and a solar plant. The simulator incorporates a regulatory control strategy based on PI (proportional-integral) controllers and was developed in the MATLAB/Simulink ® environment. A MPC (model predictive control) strategy established at a supervisory level is presented. The intent of the strategy is to regulate the steam pressure of the superheater of the ISCC plant. The combined use of the simulator and the supervisory control strategy allows for the quantification of the reduction in fuel consumption that can be achieved when integrated solar collectors are used in a combined cycle plant. The ISCC plant simulator is suitable for designing, evaluating and testing control strategies and for planning the integration of solar and combined cycle plants. [ABSTRACT FROM AUTHOR]

Molten salt receivers play an important role in converting solar energy to thermal energy in concentrating solar power plants. This paper describes a dynamic mathematical model of the molten salt cavity receiver that couples the conduction, convection and radiation heat transfer processes in the receiver. The temperature dependence of the material properties is also considered. The radiosity method is used to calculate the radiation heat transfer inside the cavity. The outlet temperature of the receiver is calculated for 11 sets of transient working conditions. The simulation results compare well with experimental data, thus the model can be further used in system simulations of entire power plants. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of an innovative renewable energy plant serving an existing indoor/outdoor swimming pool located in Naples. The proposed solar hybrid system is designed in order to balance the remarkable energy demand of the swimming pool facility and to ensure suitable comfort conditions for swimmers. With the aim to accomplish such goals, the dynamic thermal behavior of the swimming pool was analyzed as a function of the thermo-hygrometric conditions of the indoor space and on the meteorological conditions of the pool site. In order to properly design and size the proposed renewable energy system, different thermal pool loss formulations for the calculation of the swimming pool thermal balance, in indoor and outdoor regimes, are adopted. The solar hybrid system consists of a water cooled photovoltaic/thermal collectors plant (PV/T), designed to meet a part of the facility demands of electricity and heat. Electricity is completely utilized by the facility, while the produced thermal energy is primarily used to meet the pool thermal demand and secondarily for sanitary hot water scopes. In order to carry out dynamic simulations and sensitivity analyses, the system performance is designed and dynamically simulated in TRNSYS environment. The developed simulation model enables the calculation of both the indoor and outdoor swimming pool thermal losses and the overall energy and economic system performance. Such results are obtained as a function of the thermo-hygrometric conditions of the environment, of the occupants and the energy production of the renewable energy system. A sensitivity analysis, aiming to analyze the effect of some operation and design parameters on the energy and economic performance, is carried out. Finally, simulation results highlight: (i) the remarkable energy performance of the system due to the full utilization of the energy produced; (ii) need of incentive policies for improving the economic profitable of the proposed system. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic simulation model of a novel prototype of a 6 kW e solar power plant. The system is based on the coupling of innovative solar thermal collectors with a small Organic Rankine Cycle (ORC), simultaneously producing electric energy and low temperature heat. The novelty of the proposed system lies in the solar collector field, which is based on stationary evacuated flat-plate solar thermal collectors capable to achieve the operating temperatures typical of the concentrating solar thermal collectors. The solar field consists of about 73.5 m 2 of flat-plate evacuated solar collectors, heating a diathermic oil up to a maximum temperature of 230 °C. A diathermic oil storage tank is employed in order to mitigate the fluctuations due to the variability of solar energy availability. The hot diathermic oil exiting from the tank passes through an auxiliary gas-fired burner which provides eventual additional thermal energy. The inlet temperature of the diathermic oil entering the ORC system varies as a function of the availability of solar energy, also determining an oscillating response of the ORC. The ORC was simulated in Engineering Equation Solver (EES), using zero-dimensional energy and mass balances. The ORC model was subsequently implemented in a more general TRNSYS model, including all the remaining components of the system. The model was used to evaluate the energy and economic performance of the solar CHP system under analysis, in different climatic conditions. The results show that the efficiency of the ORC does not significantly vary during the year, remaining always close to 10%. On the other hand, the efficiency of the solar collectors is very high in summer (>50%) and significantly lower during the coldest winter days (down to 20%). Pay-back periods are extremely attractive in case of feed-in tariffs (about 5 years), whereas the profitability of the system is scarce when no public funding is available. A sensitivity analysis was also performed, in order to determine the combination of system/design parameters able to maximize the thermo-economic performance of the system. It was found that the system may be economically feasible for the majority of locations in the Mediterranean area (pay-back periods around 10 years), whereas the profitability is unsatisfactory for Central-Europe sites. [ABSTRACT FROM AUTHOR]

A fundamental task in the dynamic simulation of parabolic trough power plants (PTPP) is to understand the behavior of the system physics and control loops in the presence of weather variations. This study provides a detailed description of the advanced controllers used in the power block (PB) of a 50 MWel parabolic trough power plant (PTPP). The PB model is achieved using APROS software based on the actual specifications of the existing power plant. To verify the behaviour of the PB model, a comparison between the simulated results and given real data is documented depending on a previous study, and the results indicate a reasonable degree of correspondence. The purpose of this study is to create reference models for the PB. Thereby, developers and engineers will have a better understanding of the state of the art of advanced control loops in these power plants. Moreover, these types of models can be used to specify the most suitable mode of operation for the power plant. In addition, this study gives an overview of dynamic simulation for the design, optimisation and development of power blocks in parabolic trough power plants. [ABSTRACT FROM AUTHOR]

Abstract: The discontinuous nature of the solar energy forces to study the dynamic behavior of solar plants to characterize their operations, to deepen their process understanding and to improve the performance and maintenance. The present paper focuses on the dynamic simulation and control of concentrating solar plants with the aim to define a reasonably simplified layout as well as to highlight the main issues to characterize the process dynamics of these energy systems and their related energy storages. Detailed first-principles mathematical models of key unit operations are developed, implemented, and integrated into commercial codes to improve the reliability of the plant dynamic simulation as well as the prevision accuracy. The case of Archimede concentrating solar power plant with the related two-tanks direct thermal energy storage technology is investigated. [Copyright &y& Elsevier]

Abstract: An innovative steam generation system for a solar power plant has been designed in Germany by Balcke-Duerr. In order to assist its construction, a dynamic simulation of the thermal oil heated boiler has been developed by the Vienna University of Technology. Aim of this work is to assess how critical is the boiler behavior for the plant operation during a start-up phase, and especially to check if the natural water circulation starts correctly. After a description of the heat exchanger design, the different stages of the simulation build-up with the software APROS are described. As a result of the model validation, the improvement of the model discretization is outlined along with the calibration of the heat transfer coefficients. Further on, the observation of relevant parameters of the system (water circulation rate, steam mass fraction and critical heat flux) during the simulated start-up, allow characterizing the boiler. Thus, the natural circulation start can be described with a good fidelity. Findings about the economizer behavior and the occurrence of boiling crisis are also exposed. Eventually, a design optimization can be carried out through the applied method. [Copyright &y& Elsevier]

Abstract: The dynamic simulator design and development of a direct steam generation parabolic-trough solar thermal power plant is detailed in this paper. The dynamic simulator is not only the equation-based object-oriented model but also includes features to facilitate the simulation process. A whole simulator scheme has been developed for that purpose. This simulator scheme considers the issues of fetching and converting sensors data to model inputs and obtaining suitable initial values for the boundary condition problem in the numerical integration. The calibration and validation processes have been tackled, using Matlab as the primary tool. However, several tools were studied and tested. A multi-objective genetic algorithm approach has been chosen for calibrating the dynamic model. [Copyright &y& Elsevier]

Abstract: Solar central receiver, which plays a dominant role in the radiation–heat conversion, is one of the most important components in the solar tower plants. Its performance can directly affect the efficiency of the entire solar power generation system. In this study, an integrated receiver model for full range operation conditions was proposed in order to simulate and evaluate the dynamic characteristics of a solar cavity receiver. It mainly couples the radiation–heat conversion process, the determination of convective heat transfer coefficient, the temperature computation of receiver walls and the calculation and analysis of the thermal losses. Based on this model, the dynamic characteristics of the solar cavity receiver were tested by encountering a sudden solar radiation disturbance. In addition, the thermal loss was also calculated and analyzed with different wind conditions. The results indicated that the parameters of the receiver had a significant variation under the sharp disturbance of DNI if no control rules were imposed. The wind conditions can obviously affect the thermal losses and the value reaches its maximum when the wind blows from the side of the receiver (α =90°). In order to verify the validity of this model, the simulation results were used to compare the design points under the same input conditions, and the results showed that simulation data had a good agreement with design data. [Copyright &y& Elsevier]

• Unsteady model established for thermal performance of external receiver. • Heat transport and thermal stress characteristics of receiver investigated. • Highest temperature difference and tangential thermal stress along tube discovered. • Dynamic responses of receiver under ambient and operating disturbances revealed. • Thermal inertia of receiver and effect on dampen weather fluctuation illustrated. The practical operation of the receiver for solar power tower plant is under unsteady conditions because of the variation of direct normal irradiation, as well as the output power load. A 100 MW external receiver was designed and selected as the object. The unsteady one-dimensional model was established for the receiver and validated by comparing the simulation results with the published experimental data, aiming to launch the thermal, hydraulic and mechanical analysis. The heat transfer characteristics, thermal efficiency, as well as the thermal stress in the flow direction, are demonstrated by the static analysis. By comparison of different panels, the harsh working condition of the first and the last panels is discovered, including that of the highest temperature difference and tangential thermal stress along tubes. The tangential thermal stress is prominent at the light spot. The molten salt at the last panel is most likely to decompose. Dynamic simulation is carried out to analyze the thermal inertia and heat transport characteristics. The response curves and time constants of the receiver under step and periodical disturbances of different factors from the environment and load side are acquired. The thermal inertia of the receiver and its effect to dampen weather fluctuation are illustrated. These security problems and thermal performance will make demands on the control strategy and control accuracy. The results can provide a reference for the control strategy development of the solar power tower plant. [ABSTRACT FROM AUTHOR]

This study presents a techno-economic performance evaluation of a hybrid low-concentrating photovoltaic/thermal (LCPV/T) plant, which operates in a student sports and wellness center building situated at a university campus in Mexico. The solar plant comprises 144 LCPV/T collectors based on a hybridized version of a local parabolic trough technology. Dynamic thermal and electrical performance analyses were performed in the TRNSYS simulation studio. The results showed that the solar field could cover up to 72% of the hot water demand of the building during the summer season and 24% during the winter season. The hybrid system could annually save 7185 USD, accounting for heat (natural gas boiler) and electricity generation. However, the payback time was of 19.23 years, which was mainly attributed to a reduced natural gas price in Monterrey, Mexico. A new approach to evaluating the equivalent levelized cost of heat (LCOHeq), is proposed. This results in an LCOHeq of 0.065 USD/kWh, which is nearly equivalent to the LCOH of a natural gas-fired boiler (0.067 USD/kWh). Finally, the hybrid plant could achieve a specific CO2e emission reduction of 77.87 kg CO2e per square meter of the required installation area. [ABSTRACT FROM AUTHOR]

Thermal energy storage system in concentrating solar power plants can guarantee sustainable and stable electricity output in case of highly unstable solar irradiation conditions. In this paper, the lumped parameter method is used to develop the models of different thermal energy storage systems. In order to improve the reliability as well as the prediction accuracy of developed models, the charging/discharging process is firstly simulated, and then the dynamic characteristics of thermal energy storage systems are fully tested by imposing 15% step disturbance of mass flow. The results show that the charging/discharging characteristics of the three different thermal energy storage systems are almost the same, which have little to do with the storage mediums used in the systems. Besides, for the representative 1MWe solar parabolic trough power plant, a 15% step up disturbance of oil mass flow will result in a small increase (1.8% and 1.3% respectively) on the outlet temperature of oil and molten salt. On the other side, a 15% step down disturbance of oil mass flow will lead a 2.7% and 2.2% decrease on the outlet temperature of oil and molten salt respectively. In order to verify the validity of the proposed models, the simulation results are compared with both the design points and representative experimental data from the 1MWe solar parabolic trough power plant. The results show that the maximum relative error is not more than 1% when comparing with the design points and the maximum relative error is not more than 12% when comparing with the representative experimental data. Conclusions of this paper are good references for system design, control and commissioning of concentrating solar power plants. • Thermal energy storage can provide sustainable and stable electricity output. • Lumped parameter method is used to build the model of thermal energy storage. • The dynamic characteristics are tested by a 15% step disturbance of mass flow. • A 15% step-up will result in a 1.3% increase in molten salt outlet temperature. • A 15% step down will result in a 2.2% decrease in molten salt outlet temperature. [ABSTRACT FROM AUTHOR]

In this paper a novel solar combined heat and power (CHP) system incorporating absorption heat pump (AHP) driven by mid-temperature solar heat and exhaust heat is proposed to improve solar energy utilization and electricity power generation. To validate thermodynamic performance of the proposed system, a case study is carried out based on 1 MW solar tower power plant located in Beijing. Depending on the well-developed mathematical model in accordance with actual equipment, the relevant module is coded in TRNSYS application environment. Besides, control and operation strategy is deeply analyzed to efficiently utilize solar energy with principal of cascade utilization. The dynamic simulation effectively predicts thermodynamic performance under the different operation modes in a typical winter day. Results indicate that flexible heating supply of the proposed system can meet well with user-generated heating loads. The AHP system recovers the condensate heat of 914 MJ with the average COP of 1.52. The proposed system generates the additional power of 217 kWh due to the regenerative cycle. Accompanying with power generation of 6214 kWh and useable thermal energy of 14502 MJ of the proposed system, the overall utilization efficiency of solar energy is up to 15.96% with the increase of 4.55 percentages. • Propose a novel CHP system with heat recovery process based on STP tower plant. • Develop mathematical models and simulation modules in TRNSYS application. • Develop control and operation strategy for efficient utilization of solar energy. • Simulate thermodynamic performances of the CHP system at 1 min intervals. [ABSTRACT FROM AUTHOR]