The heat-discharging kinetics of an iron-substituted Mnsub.2Osub.3/Mnsub.3Osub.4 redox pair subjected to long-term thermal cycling tests using a temperature swing process at high temperatures was ...investigated for next-generation concentrated solar power plants equipped with thermochemical energy storage. The heat-discharge mode kinetics for long-term thermal-cycled samples have never been reported. Additionally, comparisons of the heat-discharge mode kinetics for both long-term thermal-cycled and as-prepared samples have never been discussed. In terms of the reproducibility and sustainability of thermochemical energy storage, kinetic evaluations of samples with thermally stable morphologies subjected to long-term thermal cycling at high temperatures are important for next-generation solar thermal power plants. For the long-term thermal-cycled sample, the A2 model based on the Avrami-Erofeev reaction describes the discharging mode behavior in a fractional conversion range of 0-0.24, the contracting area (R2) model best fits in a fractional conversion range of 0.24-0.50, and the third-order (F3) model matches in a fractional conversion range of 0.50-0.70. For the as-prepared sample, the power-law (P2) model describes the behavior of the first part of the discharging mode, whereas the Avrami-Erofeev (A4) model best fits the last half of the discharging mode. The predicted theoretical models for both samples were compared with previous kinetic data.
This paper summarizes Electromagnetic Transient (EMT) simulation studies using PSCAD/EMTDC undertaken to evaluate the capability and suitability of commercially available large scale Grid Forming ...Inverters (GFMI) to dampen oscillations in a real bulk power transmission network. Faults and a range of grid voltage oscillation frequencies are tested on GFMI and synchronous condenser (SC) models using single source equivalent network model and comparisons of transient, post fault and oscillatory rejection tests are presented. A critical credible fault in the West Murray Zone (WMZ) was simulated on a wide‐area EMT model of the Australian National Electricity Market (NEM) to show the effectiveness of GFMI in providing system strength services and improving damping of network sub‐synchronous control interactions (SSCI). Two scenarios were examined: Direct replacement of existing centralized synchronous condensers in the WMZ of the NEM, and a decentralized distribution of GFMI in the transmission network (treated as expansion or repowering solution for existing grid following inverter equipped solar farms). Simulation results show that commercially available GFMI are a viable option for improving system strength in a practical transmission system with a high proportion of Inverter Based Resources (IBR).
The concentrating solar power plants (CSP) have well potential in coordinating with the ever-increasing wind energy during power scheduling. However, the existing studies individually design the ...day-ahead or intra-day optimization of coordinated scheduling between CSP and wind power, which makes the scheduling decisions not optimal in terms of economic and environmental benefits. Additionally, the non-anticipativity of scheduling decisions are not considered in most of them. This paper proposes a novel dynamic programming (DP) formulated multi-stage robust reserve scheduling (DPMRS) model, which is the first attempt to realize the day-ahead and intra-day joint optimization for coordinated scheduling of CSP and wind power. Under the framework of multi-stage adaptive robust optimization (ARO), DPMRS model enforces the non-anticipativity of scheduling. Besides, a convex modelling technique for thermal energy storage (TES) is presented to ensure the tractability of DPMRS model, whose effectiveness is proved mathematically. Moreover, to efficient solve the DPMRS model, a robust dual dynamic programming with accelerated upper approximation (RDDP-AU) solution methodology is developed, and the mathematical proof for its convergence is provided. Numerical studies on the modified IEEE RTS-79 system and a real-world system in Northwest China validate the effectiveness of the proposed scheduling model and solution methodology. The simulation results demonstrate the DPMRS model brings a 17.22% reduction in scheduling cost, and reduces 57.39% curtailment of renewable energy. Compared with the conventional algorithm, the RDDP-AU significantly reduces the computational consumption by 87.56%, and with the error less than 0.074%.
•DP formulated multi-stage ARO model is proposed for the coordinated scheduling of CSP and wind energy.•Novel day-ahead and intra-day joint optimization for power scheduling is realized via solving DPMRS model.•Convex modelling technique for energy storage systems is presented.•Efficient RDDP-AU solution methodology is developed.
•Charging characteristics of a LHTES unit with embedded metal foam, has been numerically studied.•Impact of graded porosity and location of porous metal foam on charging time and total entropy ...generation has been investigated.•In order to conduct sensitivity analysis, response surface methodology has been employed.•Optimised structure of metal foam in which significant improvement in charging time and total entropy generation are achieved, has been proposed.
Thermal energy storage (TES) units are needed to balance the incompatibility between energy supplies and demand in concentrated solar power plants. However, low thermal conductivity of phase change materials limits the efficiency of TES. In this paper, gradient metal foams with graded morphologies are proposed to be implemented into the PCM and numerical simulations are done to investigate their performance. A 2D axisymmetric simulation was conducted to study the characteristics of the charging process in a shell-and-tube latent heat thermal energy storage unit. Open-cell metal foams with various porosities ranging from 0.65 to 0.94 were stacked up in the axial direction of simulation module, forming a porous layer with graded porosities arranged in PCM domain. The impact of gradient porosity and the location of porous metal foam on total entropy generation and charging time of TES were studied. Central composite design was implemented to study the effects of metal foam gradient porosity on the total entropy generation and charging time. Moreover, in pursuit of detecting the optimum structure, results were illustrated in response surface plots. Comparing the optimum structure to the structure with constant porosity of 0.7225, indicates 3.35% and 7.96% improvement in charging time and total entropy generation, respectively.
This study utilizes Thermal Infrared (TIR) imaging technology to detect hotspots in photovoltaic (PV) modules of solar power plants. Unmanned aerial vehicle (UAV)-based TIR imagery is crucial for ...efficiently analyzing fault detection in solar power plants. This research explores optimal operational parameters for generating high-quality TIR images using UAV technology. In addition to existing variables such as humidity, emissivity, height, wind speed, irradiance, and ambient temperature, newly considered variables including the angle of incidence between the target object and the thermal infrared camera are analyzed for their impact on TIR images. Based on the solar power plant’s tilt (20°) and the location coordinate data of the hotspot modules, the inner and outer products of the vectors were used to obtain the normal vector and angle of incidence of the solar power plant. It was discovered that the difference between measured TIR temperature data and Land Surface Temperature (LST) data varies with changes in the angle of incidence. The analysis presented in this study was conducted using multiple regression analysis to explore the relationships between dependent and independent variables. The Ordinary Least Squares (OLS) regression model employed was able to explain 63.6% of the variability in the dependent variable. Further, the use of the Condition Number (Cond. No.) and the Variance Inflation Factor (VIF) revealed that the multicollinearity among all variables was below 10, ensuring that the independence among variables was well-preserved while maintaining statistically significant correlations. Furthermore, a positive correlation was observed with the actual measured temperature values, while a negative correlation was observed between the TIR image data values and the angle of incidence. Moreover, it was found that an angle of incidence between 15° and 20° yields the closest similarity to LST temperature data. In conclusion, our research emphasizes the importance of adjusting the angle of incidence to 15–20° to enhance the accuracy of TIR imaging by mitigating overestimated TIR temperature values.
One of the most promising concentrated solar power technologies is the central receiver tower power station with heliostat field, which has attracted renewed research interest in the current decade. ...The introduction of the sCOsub.2 recompression Brayton cycles in the near future installations instead of the Rankine cycle is very probable, due to the prospects of a significant efficiency improvement, process equipment size and capital cost reduction. In this study, energy and exergy analysis of a recompression Brayton cycle configuration for a central receiver power station are performed. Special emphasis is given to the computation of actual performance for the High-Temperature Recuperator and the Low-Temperature Recuperator. The results define realistic thermal and exergetic efficiency limits for the specific cycle configurations applied on a central receiver solar power plant with variable turbine entry temperature. Thermal efficiency, predicted with the improved accuracy of heat exchanger computations, does not exceed the 50% target. Overall, a realizable total power plant efficiency of 37% at 900 K turbine entry temperature is predicted, which is a significant improvement on the current state-of-the-art with steam Rankine cycles.
While renewable energy sources enjoy high public support, projects are rarely implemented without opposition. The term energy landscapes indicates that landscape change is amongst the most frequent ...issues. This study researched lay people’s perceptions of landscapes changed by solar power plants. The first objective was to discover how likely solar power plants are to be noticed in the landscape. The second objective was to determine the associations observers make when spotting a solar power plant. The data was collected by participatory photography and focus groups. Participants visited six solar power plants. The results show that they are highly noticeable and contentious objects. Participants who understood the landscape as a rural idyll disapproved of solar power plants, while for those who perceived the landscape through a utilitarian narrative, the (mis)fit of the solar power plant depended on its relation to the surrounding landscape structure. Landscape degradation was contrasted with low-carbon energy and developmental benefits. The results provide evidence on the interdependence of visual and non-visual factors and suggest improvements in planning and design of solar power plants. While the method gives a rich in-depth insight into landscape perception, it is also context dependent and needs further research to obtain more generalisable results.
•A novel in situ method shows photovoltaics are highly noticeable landscape elements.•Laypeople mostly contrast energy benefits with landscape degradation.•Mimicking landscape structure improves power plant’s integration with the landscape.•Issues exposed by laypeople correspond well with impacts proposed by experts.
High temperature concentrating solar power plants require suitable thermal energy storage systems to produce electric power efficiently. Thermochemical energy storage based on metal hydrides ...represents a very appealing prospect for low cost and high efficient solar storage systems. The objective of the paper is to assess the properties required by the metal hydride systems to achieve the U.S. Department of Energy's SunShot techno-economic targets. A simplified model has been developed to evaluate the cost and the exergetic efficiency of hydride-based storage systems. Results demonstrate that metal hydride materials, operating at temperatures higher than 650 °C, with reaction enthalpy on the order of 95–110 kJ/molH2, raw material cost on the order of 1.4–2 $/kg, weight capacities on the order of 3–4% and operating pressures on the order of tens of bars have the potential to closely approach the targets. Selected sensitivity analyses have also been carried out showing that the raw material cost, the material weight capacity and the metal hydride reaction enthalpy are the properties that strongly affect the performance of the storage system.
•Metal hydride based thermal energy storage systems have been modeled, by techno-economic models.•Ideal metal hydride material properties have been identified, to meet the DOE targets.•Selected sensitivity analyses have been carried out for the selected metal hydrides.•Performance gap between the ideal metal hydrides and the existing candidate materials has been identified.•The materials having the highest potential to meet the targets have been identified.
•Thermal performance of multilayered PCM(s) thermocline TES tank is analyzed.•A numerical model is used for the thermal evaluation of thermocline configurations.•A parametric study of PCM melting ...temperature and heat of fusion is performed.•Results indicated the optimal values of melting temperature and latent heat for MLSPCM(s).
The current paper presents two parametric studies (inverse Stefan number and dimensionless temperature difference) to optimize the values of latent heat and melting temperature of multilayered phase change materials (MLPCM(s)) in thermocline tank for concentrating solar power (CSP) plants. Spherical capsules filled with PCM(s) of different thermo-physical properties are used to fill the bed region, and the molten salt is used as heat transfer fluid (HTF). The numerical model that has been developed uses the Dispersion-Concentric (D-C) equations. By using MATLAB, the governing equations are solved and validated against the experimental results. The results show that in the optimal configuration of the case (B), the values of InvSte number and dimensionless temperature (θm) are equal to 1.2 and 0.8 for the top PCM layer, respectively; 0.75 and 0.55 for the middle PCM layer, respectively; and 0.65 and 0.3 for the bottom PCM layer, respectively. Moreover, it is also found that to obtain the best design and distribution of temperature for a thermocline tank consisting of three layers of PCM, the top PCM layer should melts by ΔT = 55.4 °C below the HTF charging inlet temperature, the PCM layer at the bottom should solidifies by ΔT = 83.1 °C above HTF discharging inlet temperature.
Evaluation of the Concentrating Solar Power capacity factor is critical to support decision making on possible regional energy investments. For such evaluations, the System Advisor Model is used to ...perform capacity factor assessments. Among the required data, information concerning direct normal irradiance is fundamental. In this context, the Engerer model is used to estimate direct normal irradiance hourly values out of global horizontal irradiance ground measurements and other observed meteorological variables. Model parameters were calibrated for direct normal irradiance measurements in Évora (Southern Portugal), being then applied to a network of 90 stations, part of the Portuguese Meteorological Service. From the modelled direct normal irradiance, and for stations that comprise 20 years of data, typical meteorological years were determined. Finally, to identify locations of interest for possible installations of Concentrating Solar Power systems, annual direct normal irradiance availabilities and the respective capacity factor, for a predefined power plant using the System Advisor Model, were produced. Results show annual direct normal irradiance availabilities and capacity factors of up to ~2310 kWh/m2 and ~36.2% in Castro Marim and in Faro, respectively. Moreover, this study supports energy policies that would promote Concentrating Solar Power investments in Southern Portugal (Alentejo and Algarve regions) and eastern centre Portugal (Beira Interior region), which have capacity factors above 30%.
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