Thermal Power Output Research Articles

The sampling and removal of tritiated water vapor in Taiwan research reactor

The Taiwan Research Reactor (TRR) is a research facility in Taiwan. TRR is a heavy water reactor designed based on the National Research Experiment (NRX) with output thermal power 40 MW. On January 3, 1973, it reach criticality. TRR had been operated for 15 years and was permanently shut down in early 1988. TRR uses heavy water moderation and light water cooling. Hence, some tritium was created when deuterium captures a neutron. The inside of the Calandria has been washed with clean water after shutdown. After draining the water in the interior, it is inevitable that some residual water would remain at the bottom of the Calandria. Air sampling and analysis techniques were employed to detect and quantify tritiated water vapor. The investigation of tritiated water vapor in the TRR Calandria proved potential tritium contamination risks. Adopting the vapor condensation drying technique proved effective in removing tritiated water vapor from the TRR Calandria. After the removal of tritiated water vapor, the air in the Calandria no longer contains rich concentration of tritiated water vapor. That will help to ensure a safe environment for decommissioning operations.

A novel dual-split layout for transcritical CO2 power cycle adapted to variable heat sources

Transcritical CO2 power cycle is widely used as the bottom cycle of natural gas engine to recover waste heat. However, owing to the large variation in waste heat sources caused by changes in engine operating conditions, the adaptability of the CO2 power cycle is poor, reflected in severe performance deterioration in thermal match, components and system power output. Hence, to improve the adaptability of the CO2 power cycle to wide-range fluctuation in heat sources, a novel dual-split configuration is proposed in this paper. The freedom of regulation is effectively enhanced by the supplementary split branches, and the mass flow rate through different heat exchangers can be actively adjusted with high flexibility. Furthermore, off-design performance models and a calculation procedure are built to present the off-design performance of the different cycles under the engine operational profile. The results indicate that the proposed configuration can improves the adaptability of the CO2 cycle to fluctuating heat sources effectively. Specifically, for all engine operational conditions, the invalidated operating region was contracted from eight to four points, with the engine coolant and exhaust gas utilisation rates exceeding 90 % and 97.4 % respectively. In addition, under low engine operating conditions, the cycle pressure ratio and mass flow rate were maintained at relatively high values, contributing to enhanced pump and turbine efficiencies. The maximum net power output increased by 8.3 kW, and the minimum brake-specific fuel consumption decreased by 16.9 %.

Mathematical modelling and optimizing design of heliostat field

The heliostat field is a form of solar thermal power plant, The heliostat field is a crucial component of solar thermal power plants and establishing a heliostat field is of great significance for reducing carbon emissions. and is of great significance in reducing carbon emissions This paper focuses on the mathematical modeling and optimization design problem of the heliostat field. For three different design scenarios, firstly, based on the data provided by the China Undergraduate Mathematical Contest in Modeling 2023, a geometric optical efficiency model is proposed to determine the annual average optical efficiency and output thermal power under specific heliostat field design parameters. Secondly, aiming at the optimal design parameters of the solar furnace field under the condition of rated annual average output thermal power is 60 MW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{MW}$$\\end{document}, Particle Swarm Optimization (PSO) combing with efficiency model is utilized to determine the optimal design parameters of the heliostat field. Finally, this paper uses Quasi-Monte Carlo ray tracing (QMCRT) model to perform simulations, exploring how to obtain the optimal design parameters of the heliostat field with the goals of maximizing the output thermal power and ensuring high efficiency. Furthermore, the influence of normal disturbances on the annual average annual average thermal output power is investigated.

Source-load coordinated dispatching model taking into account the similarity between renewable energy and load power

With the deployment of renewable energy, the load curve is expected to follow the renewable energy output curve to minimize the fluctuation of thermal power output in the source-load coordinated dispatching. The traditional indicators for the load curve are no longer enough to describe the load characteristics. A new load indicator called the source-load similarity distance is proposed by improving the similarity measurement method of the time series and calculating the similarity distance between the renewable energy output curve and the load curve. By combining the Euclidean distance with the improved dynamic time warping, the source-load similarity distance is obtained and the data distribution and morphological fluctuation characteristics can be simultaneously considered. The source-load coordinated dispatching model is also established to minimize the source-load similarity distance. The simulation results show that the source-load similarity distance can effectively describe the similarity characteristics of the renewable energy output curve and the load curve. Increasing the source-load similarity distance can reduce the thermal power operation cost by 56.2 % and the cost of demand response by 25.3 %, and increase the utilization rate of wind power by 4.6 % compared to the dispatching model with the standard deviation indicator.

Design, analysis and optimisation of a novel adiabatic-isothermal CAES system with coupled stepped phase change energy storage unit

Compressed air energy storage (CAES) technology is one of the important technologies to address the instability of renewable energy sources. To further make full use of the system heat of compression and reduce the problem of energy grade dissipation inside the accumulator, this paper proposes a novel CAES system coupled with a graded phase change thermal energy storage unit (SP-TES) and near isothermal compression of a liquid piston. A combination of adiabatic compression and near-isothermal compression is used to reduce the generation of compression heat, while the graded storage of compression heat through SP-TES reduces the reduction of energy grade. The design of the proposed SP-TES is carried out through the binary eutectic theory, and a one-dimensional transient entransy dissipation model, a thermodynamic model and an economic model are developed to analyze the 4E performance (energy, exergy, entransy, and exergoeconomic) of the proposed SP-TES. Further, the effect patterns of key node parameters on the proposed system are investigated by developing system related models and the system is optimized with multiple objectives from the point of view of economic and thermodynamic performances. The results show that the 4E performance of SP-TES is in between that of high and low temperature single-stage accumulators, and that SP-TES combines the advantages of higher economic performance of single-stage low-temperature accumulators and higher thermal performance of single-stage high-temperature accumulators. The SP-TES with a temperature range of 350 K-451 K is gradually stabilized with the number of charging and discharging, and the efficiency of the system in the stabilization stage is 73.24 %. The SP-TES with a temperature range of 407 K-440 K has the best economic performance with exergoeconomic parameter of 360.05 kJ/USD. The thermal storage performance and power output of the SP-TES decreases with the increase in the number of stages. The multi-objective optimization results show that the new CAES system efficiency is 63.03 % and the design is optimal when the unit energy cost is 0.2217 $/kWh.

Effect of crosslinker molecular weight on the characteristics of thermoelectric ionogels

Abstract The present study investigates an ionic thermoelectric gel with adjustable functionality through the manipulation of crosslinker molecular weight. The thermoelectric properties of 2-hydroxyethyl acrylate (2-HEA) ionogels, prepared using PEGDA200, PEGDA575, and PEGDA1000 as crosslinkers, were thoroughly examined. Furthermore, dynamic thermal mechanical analysis (DMA) and X-ray diffraction (XRD) techniques were employed to elucidate the underlying reasons for variations in the thermoelectric material properties resulting from changes in crosslinker molecular weight. Notably, the thermoelectric gel synthesized with PEGDA575 exhibited a remarkable thermal power output of 19.19 mV•K-1 along with a tensile capacity of 231%. Additionally, the developed ionic thermoelectric capacitor demonstrated an impressive energy density of 4.288 J•m−2, thereby showcasing its potential application in flexible low-grade heat energy recovery devices.

Optimization design model of heliostat field based on gravitational search algorithm

In todays society, non-renewable resources are becoming increasingly precious, making the utilization and conversion of renewable resources more critical. Heliostat fields play a significant role in the actions taken by various countries to achieve carbon peaking and carbon neutrality. How can the installation and arrangement of heliostats maximize the annual average thermal power output per unit mirror area while achieving the rated power? This paper establishes an efficiency calculation model based on the flat-plate projection-Monte Carlo algorithm and an optimization design model of heliostat fields based on the gravitational search algorithm. The research progresses from shallow to deep, investigating methods to maximize the output thermal power under different constraints. First, it addresses the issue of maximizing the average thermal power output per unit mirror area under fixed heliostat field parameters and rated power conditions. Next, it solves the problem of maximizing the annual average thermal power output per unit mirror area under varying heliostat sizes and installation heights, with fixed rated power. Finally, it points out that the models established in this paper are applicable to complex real-world situations and can effectively improve the thermal efficiency of heliostat fields.

Numerical Simulation of Geothermal Energy Development at Mount Meager and Its Impact on In Situ Thermal Stress

The Meager Mountain Geothermal Project stands as one of the pioneering geothermal energy initiatives in its early stages of resource development. Despite its abundant geothermal heat resources, no prior studies have systematically evaluated the potential of implementing coaxial borehole heat exchangers on site. This study addresses this research gap by presenting a comprehensive heat transfer model for an underground closed-loop geothermal system utilizing a single coaxial well. Finite element analysis incorporated fluid and solid heat transfer, as well as solid mechanics. The results obtained facilitated the construction of the temperature and thermal stress profiles induced by the cooling effects resulting from years of heat extraction. After 25 years of operation, the outlet temperature has reached approximately 74 °C, and the maximum radial tensile thermal stress amounts to ~47 MPa. Furthermore, the analysis demonstrates that higher fluid velocities contribute to more perturbed temperature and stress distributions. The study attained maximum thermal and electric power outputs of 208 kW and 17 kW, respectively. This research also underscores the significant impact of geothermal gradient and well length on BHE design, with longer wells yielding more power, especially at higher injection velocities.

Integrating Ray Tracing with Single-Objective Optimization in Heliostat Field Design

Tower solar thermal power generation is a new type of low-carbon and environmentally friendly clean energy technology. Through continuous optimization of the optical efficiency of mirror field and other key technologies, the energy utilization efficiency and economic benefits of solar thermal power stations can be improved, and contribute to the sustainable development of clean energy. This paper establishes a geometric model based on the light tracing method to solve the daily average, average annual optical efficiency, thermal output power, and average optical efficiency of the heliostatic field. The cosine efficiency is the cosine of the incident light and the normal angle, which is the cosine of the incidence angle; the atmospheric transmission is only related to the distance between the mirror center and the collector center; the mirror reflection constant is 0.92. The shadow occlusion efficiency and the truncation efficiency of the collector are the difficulties in the process of calculating the optical efficiency: for the calculation of the shadow occlusion efficiency, the Monte Carlo light tracing method is adopted. Based on the energy density of the helioscope, the occlusion efficiency of the shadow can be expressed as the ratio between the amount of the outgoing light to the total generated amount; for the calculation of the collector truncation efficiency, it links the reflected light with the surface equation of the collector. According to the joint results, if there is a solution, it means that the reflected light can be reflected in the collector, and the collector truncation efficiency can represent the ratio of the number of lights reflected in the collector to the number of unblocked lights in all the reflected lines. Finally, the average annual optical efficiency and output power parameters are respectively: 0.6093, 0.7431, 0.9283, 0.9828, 35. 4430MW, 0.5642kW/m². Results for the remaining months are shown in the main text.

Research on Optimization Design of Heliostat Field Based on Ray Tracing

In tower-type solar thermal power generation systems, the optical efficiency of the mirror field is the primary factor determining the overall system's power generation efficiency. In order to meet the requirement of a rated power of 60MW with different heliostat sizes and installation heights, optimize the various parameters of the heliostat field, establish a tower-type solar thermal power generation system model, and evaluate the model. Taking the maximum annual average output power per unit mirror area as the optimization objective, through simulation, it is found that the heliostat with a side length of 6 meters, a gradient design of installation height, a regular triangular layout, and the use of ray tracing technology can efficiently capture solar energy. The average optical efficiency, average cosine efficiency, average shadow blocking efficiency, average truncation efficiency, and average thermal power factor per unit area mirror are analyzed. The research results show that there is an optimal combination of absorber northward movement, heliostat size, equilateral triangle arrangement, installation height gradient design, and solar trajectory, which enables the annual average output thermal power to reach or even exceed the rated power of 60MW.This model and algorithm compared and analyzed genetic, greedy, and simulated annealing algorithms on the same dataset. The runtime is approximately 8-10 minutes, with CPU utilization around 60%.

Research on the annual average thermal power of heliostat field in tower solar energy

The concentrating mirror field is a concentrating and heat collecting subsystem in the tower solar thermal power station, and its optical performance directly affects the solar energy utilization efficiency of the power station. In this paper, the coordinate system of heliostat field and single heliostat is established, and the grid division technology is introduced to describe its reflection effect on sunlight and its occlusion. In this paper, the shadow occlusion loss that affects the optical efficiency is divided into three parts, including incident light occlusion loss, reflected light occlusion loss and absorption tower shadow occlusion loss. For any time, the output power of the heliostat near the solar direction is small, while the output power of the heliostat far away from the solar direction is large. Compared with other influencing factors, the cosine loss has the greatest influence on the heliostat field, and the center of the absorption tower installed in the circular heliostat field is obtained. The size of the heliostat is a square with a side length of 6m, the installation height is 4m, and the annual average optical efficiency is 0.6216 when the position of the heliostat is determined. The annual average output thermal power is 36.3958 MW, and the annual average output thermal power per unit mirror area is 0.5794 .

Features of a gas turbine combustion chamber in operation with gaseous ammonia

Achieving climate neutrality requires the use of alternative hydrogen carriers for energy purposes, with ammonia currently being considered. One potential application in the energy sector is gas turbine systems, for which combustion chambers need to be designed to efficiently combust ammonia within an airflow. This paper focuses on theoretical investigations of fuel combustion completeness and environmental cleanliness of a gas turbine combustion chamber with a thermal power output of 1.0 MW, operating on gaseous ammonia. A prospective scheme for organizing processes is proposed, based on pre-mixing ammonia with a portion of air in a special pre-chamber, the sequential introduction of the remaining air through a radial-axial swirler and a series of holes in the flame tube, ensuring stable fuel combustion. Two approaches were used for modeling combustion processes in such a combustion chamber: one based on chemical reactor theory and the other on three-dimensional hydrodynamic analysis. After conducting a detailed kinetic analysis, it was concluded that to maintain stable ammonia combustion while varying the air excess coefficient in the primary combustion zone from 1.4 to 2.0, the reactants need to remain in this zone for a duration exceeding 0.025 s. Based on these parameters, design schemes for two combustion chamber variants were developed, differing in combustion tube length and air distribution pattern, for operation with an ammonia flow rate of approximately 50 g/s and a pressure of 0.3 MPa, determining a gas outlet temperature of 1490 K. Three-dimensional calculations of aerodynamic flow structures, ammonia combustion, and formation of toxic components were conducted, revealing that the proposed process organization scheme ensures complete ammonia combustion and small nitrogen oxide emissions. These results have potential applications in the development of new gas turbine combustion chamber designs for decarbonized energy systems, including those integrated with solid oxide fuel cells.

The flow and heat transfer characteristics of supercritical mixed-phase CO2 and N2 in a 3D self-affine rough fracture

Utilizing a three-dimensional self-affine function, we constructed the fracture morphology and established a numerical model considering the thermal-hydraulic coupling (TH) mechanism to simulate the flow and heat transfer processes of CO2 and N2 in a single fracture under supercritical mixed-phase conditions in dry hot rock. The fractal dimension of the fracture was set to 2.5, and the Joint Roughness Coefficient (JRC) roughness coefficient was 13.71. The model accurately simulated the flow and heat transfer processes of supercritical mixed-phase CO2 and N2 fluids within the fracture under the conditions of 50 MPa underground pressure, 200 °C rock exterior temperature, initial temperature of 32 °C for the heat transfer fluid, and inlet velocities ranging from 0.005 to 0.03 m/s. The results revealed that the output thermal power curves for nine different ratios of CO2 and N2 could be classified into three categories.Among the four conventional thermodynamic parameters, specific heat capacity and density significantly impacted output thermal power. The convective heat transfer process between the fluid and the rock wall resulted in temperature fluctuations, primarily influenced by the sharp edges of the fracture wall. As the inlet velocity increased, the outlet-inlet temperature difference monotonically decreased. The fluid with a composition of 45 % N₂ and 55 % CO₂ exhibited the smallest reduction in temperature, with a value of 50.52 °C. Meanwhile, the output thermal power monotonically increased, with the fluid composition of 5 % N2 and 95 % CO2 experiencing the most significant increase, reaching 122.22 W.

Investigating the possibility of using a mixture of thorium with different fissile materials as a fuel in TRISO particles for the PBMR-400 reactor

The increasing demand for nuclear reactors as a source of clean energy forced nuclear researchers to search for ways to enhance the safety operation of nuclear reactors. This paper discusses the viability of using different thorium compounds ((233U, Th)O2, (235U, Th)O2, (RGPu, Th)O2) as an accident tolerant fuel/advanced technology fuel (ATF) for Pebble Bed Modular Reactor 400 (PBMR-400). A comprehensive analysis of thorium-based fuel performance was carried out and compared with UO2 to develop a novel nuclear fuel with the capability to tolerate severe accident conditions. The neutronic characteristics such as the infinity multiplication factor, initial heavy metal concentration, RGPu concentration and fission products concentration were analyzed. In addition to, the main safety parameters have been calculated to distinguish the effect of the proposed fuels on them. The thermal spectrum and thermal output power have been visualized to give a good insight view inside the core about the distribution of the heat. In general, the neutronic analysis demonstrated good behavior of the examined thorium-based fuel in the PBMR-400 and especially in the case of (RGPu, Th)O2. PBMR-400 showed excellent performance in incinerating a large amount of reactor-grade plutonium when it was used in a kernel fuel bed.

Study on the optimal layout of helioscope field based on genetic algorithm

The tower photovoltaic power plant particularly depends on the proper arrangement of the heliostat field, which is a crucial component of the tower solar power system and costs between 40% and 50% of the tower solar power plant's overall investment expenses. In this study, an optimization model is established under the restrictions of the heliostat mirror's size and placement parameters. Then, using numerical optimisation tools such as the simulated annealing algorithm and genetic algorithm, the layout of the heliostat field is repeatedly calculated in order to determine the ideal configuration for the heliostat field, which will maximize its yearly thermal power output. This paper has some significance in optimizing the layout of the heliostatic field.

Thermo-Hydro-mechanical coupling analysis of geothermal reservoirs: optimizing extraction capacities by revealing influential factors

Abstract Extraction of high-temperature geothermal resources from reservoirs is a challenge due to the complex interactions between temperature, permeability, and stress fields. Variations in physical fields are critical to thermal reservoir engineering. In this study, the coupling mechanism between temperature, permeability, and stress fields is systematically explored using theoretical analyses and numerical simulations, by utilizing the three-field coupling model. This study models the changes in porosity and permeability evolution during geothermal extraction, emphasizing the importance of the coupling term. The effects of pressure differences between injection and production wells, reservoir temperature variations, and fluid property changes on the temperature distribution and output thermal power within the geothermal reservoir were modeled and analyzed. The results reveal the significant effect of pressure differences between wells, and show that the geothermal extraction capacity of supercritical carbon dioxide (SC-CO2) is 1.83 times higher than that of water. Based on the statistical characteristics of the distribution pattern of natural fractures within the geothermal reservoir, the study simulated the distribution of natural fractures and developed a coupled THM model containing natural fractures. The results show that increasing the porosity of hydraulic and natural fractures can effectively increase the geothermal production capacity, especially the increase in the porosity of natural fractures is significant. These findings provide a key theoretical basis for understanding the THM coupling mechanism during geothermal extraction, and provide substantial support for optimizing the development and utilization of geothermal resources.

Comprehensive Optimization of Optical Efficiency and Thermal Power Output in Tower Solar Thermal Power Stations

Comprehensive Optimization of Optical Efficiency and Thermal Power Output in Tower Solar Thermal Power Stations

Performance analysis of deep borehole heat exchangers for decarbonization of heating systems

AbstractMeeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector. Heat pumps with deep borehole exchangers are a promising solution to reduce emissions. Here the thermal behavior of deep borehole exchangers (DBHEs) ranging from 1 to 2 km was analyzed for various heat flow profiles. A strong correlation between thermal energy extraction and power output from DBHEs was found, also influenced by the heating profile employed. Longer operating time over the year typically resulted in higher energy production, while shorter one yielded higher average thermal power output, highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs. Short breaks in operation for regenerating the borehole, for example, with waste heat, proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat. The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space. As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year, the technology is best suitable for larger heat loads.

Research on Heliostat Field Optimization Based on Monte Carlo Theorem and Randomized Algorithms

The text discusses a mathematical model established for calculating the optical efficiency of heliostat fields in solar power systems. It's grounded in geometric optics algorithms and considers factors affecting the field's optical efficiency. Each heliostat and the ground have independent coordinate systems for assessing whether light is blocked. The Monte Carlo method is utilized to determine the proportion of blocked light in reflected rays. This approach accommodates the conical nature of solar radiation, enhancing accuracy by transitioning from parallel to conical light representation. The results indicate an annual average optical efficiency of 0.5084 for the heliostat field, an annual average thermal power output of 30.879 MW, and 0.4915 kW/m2 as the annual average thermal power output per unit mirror area.

Research on Multi-Objective Optimization of Heliostat Field Based on DELSOL3 Layout

With the intensification of global climate change, it is urgent to reduce greenhouse gas emissions and protect the environment. To address this issue, it is crucial to develop the new energy industry and increase the proportion of clean energy. Tower solar power, as an innovative and environmentally friendly technology with low carbon emissions, has great potential and broad prospects. This study determines the position of the absorption tower, heliostat size, and installation height. By utilizing the ground coordinates of the heliostats and given formulas, parameters such as average optical efficiency, cosine efficiency, shadow blocking efficiency, and cut-off efficiency are calculated. The focus is on power loss caused by shading, so a shadow blocking model is constructed by using differential methods. The heliostat plane is divided into equal sections, and it is determined whether the transformed coordinates of the mirror plane are within the grid. The effective blocked area is then calculated to obtain the shadow blocking efficiency. To improve the efficiency and reduce costs of solar thermal power plants, the standard radial staggered layout in DELSOL3 empirical layout is adopted. A multi-objective optimization model is established with heliostat size and height as variables. The optimal solution for the average output thermal power per unit mirror area is obtained through genetic algorithms. Through mathematical modeling and solution methods, this study provides theoretical basis for the application of tower solar power.