Thermal Power Generation Research Articles

Super stable coal fly ash-based solid heat-collecting particles with excellent spectral selectivity

Solar thermal power generation has been widely employed as an effective method for efficiently harnessing solar energy, with solid heat-collecting particles serving as the medium for collecting and storing solar energy, thus holding significant developmental potential. However, challenges such as high thermal radiation losses and inadequate high-temperature stability have hindered the further advancement of solid heat-collecting particles. The present study addresses these challenges by utilizing solid waste fly ash to prepare solar-selective absorbing solid heat-collecting particles. Specifically, particles sintered at 1070℃ exhibit impressive characteristics, including an average solar absorptance of 93.26 % at room temperature, an emissivity in the mid-infrared range of 68.12 %, and a specific heat capacity of 0.82 J/(g·℃). Moreover, rigorous high-temperature stability tests demonstrate that these particles maintain a stable solar absorptance in the ultraviolet–visible-near-infrared range, consistently around 93.26 %. Additionally, the particles exhibit outstanding wear resistance and stability, further enhancing their suitability for practical applications. This research achieves the dual objectives of environmental sustainability and cost reduction by utilizing solid waste materials, while the preparation process remains simple, bolstering the feasibility of implementing these findings in real-world scenarios. In summary, this study effectively addresses the challenges of high thermal radiation losses and poor high-temperature stability in solid heat-collecting particles for solar thermal power generation.

High-resolution and reduced-order multi-physics simulation on thermal–hydraulic and thermoelectric characteristics of the thermionic space reactor core

The simulation of a thermionic space reactor core necessitates a comprehensive consideration of the intricate interplay between fluid flow, heat transfer, and thermionic energy conversion, constituting a multi-physics coupling challenge. Given the absence of a thermionic conversion model in contemporary CFD (Computational Fluid Dynamics) codes, accurately simulating the thermal–hydraulic and thermo-electric behavior of thermionic reactors in existing CFD software is particularly challenging. To analyze the multi-physics coupling phenomena in thermionic reactors, this paper revises the conjugate heat transfer solver in the proprietary 3D (three-dimensional) finite-volume CFD code, mFVM (modular Finite-Volume Method Code), to enable bidirectional coupling with the thermionic conversion model. This enhancement aims to predict the high-resolution three-dimensional temperature field and thermoelectric characteristics of the thermionic reactor core. Furthermore, a reduced-order multi-physics model of the thermionic reactor core is established using RESYS (Reactor System Simulation Code). The numerical simulation outcomes for both the high-resolution and reduced-order multi-physics models, pertaining to electrically heated and fission-heated TFEs (Thermionic Fuel Elements), are validated against experimental data. The results indicate that the emitter electron cooling effects caused by thermionic emission reduced the maximum temperature of emitter by about 200 K for both electrically heated and fission-heated TFE. Therefore, a bidirectional coupling between the thermal–hydraulic model and the thermionic conversion model is essential for precisely calculating the temperature field within the TFE and the thermionic reactor core. Thereafter, both the high-resolution model and the reduced-order model are utilized to investigate the thermal–hydraulic and thermoelectric characteristics of the TOPAZ-II reactor core. The calculated electrical power of the TOPAZ-II reactor is 5.39 kWe using the mFVM model and 5.47 kWe using the RESYS model. Finally, an analysis of the thermoelectric conversion characteristics based on the simulation results of the reduced-order model reveals that the TOPAZ-II reactor system is capable of load-following only when the load resistance exceeds 0.06 Ω under nominal full power operation conditions.

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%.

Auxiliary Heat System Design and Off-Design Performance Optimization of OTEC Radial Inflow Turbine

In this paper, solar energy is used as the auxiliary heat source of the ocean thermal energy radial inflow turbine, and the thermodynamic model of the circulation system is established. In addition, the ejector is introduced into the ocean thermal power generation system, and the process simulation is carried out using Aspen Plus V12. To address performance attenuation of the radial turbine under varying working conditions, shape optimization of a 30 kW OTEC radial turbine was conducted. Finally, the off-design performance variation in the radial inflow turbine is analyzed in the presence of a solar auxiliary heat source. The results show that the use of an auxiliary heat source can effectively improve the cycle efficiency of the system and is also conducive to the stable operation of the radial turbine. Under the condition of auxiliary heat source, the system cycle efficiency is increased by 2.269%.

One-step preparation of macropore phase change materials enabled exceptional thermal insulation, thermal energy storage and long-term stability

Phase change materials (PCMs) capable of reversibly storing and releasing thermal energy have been widely used in our daily life to reduce energy consumption. However, traditional PCMs are mainly focused on the promotion of their enthalpy and thermal conductivity yet are rarely noticed on incorporating their thermal energy storage capacity with thermal insulation performance. Herein, a kind of macropore PCMs (MPCMs) was synthesized by directly adding expanded microspheres into polyethylene glycol-based PCMs, in which the microspheres can form an internal closed porous structure in matrix for realizing thermal insulation and polyethylene glycol is used as the phase change component for achieving thermal energy storage. Amazingly, the designed MPCMs have significant latent heat storage capacity reached up to130.2 J g−1 and simultaneously possess extremely low thermal conductivity of 0.08577 W m−1 K−1. The thermal power generation system test further revealed the thermal insulation capability of these MPCMs was eleven times more than that of the commercial wood. Especially, these MPCMs with relatively low density of 0.492 g cm−3 can still maintain the remarkable tensile strength of 11.74 MPa and can also exhibit good toughness via multiple cyclic shape memory analysis. The focus of this work that is to combine the thermal insulation ability of porous materials with the thermal energy storage ability of PCMs, can effectively reduce the heat conduction meanwhile can maintain the stability of internal temperature contributed to reducing energy consumption, applying in food transportation, building energy conservation and other fields.

On the Effectiveness of Emergency Reduction Measures for Ultrafine Dust Concentration in Seoul, Korea

Since 2018, emergency reduction measures (ERMs) have been implemented by the Seoul Metropolitan Government to address air quality in Seoul, Republic of Korea. ERMs are activated when the concentration of ultrafine dust, particulate matter (PM) with an aerodynamic diameter of less than 2.5μm (PM 2.5), exceeds a certain level. In this study, using the daily time series data from 1 January 2018 to 31 June 2023, the effectiveness of ERMs is empirically analyzed by specifying multiple regression models in which PM 2.5 is explained not only by the days of ERMs but also by many other important factors. The empirical analysis shows that (i) PM 2.5 is influenced by its own past values up to three days; (ii) PM 2.5 is negatively influenced by both rainfall and wind speed, but positively related to temperature, humidity and yellow dust. The effect of PM 2.5 from the neighborhood (Dailan, China) is significantly positive; (iii) the effect of vehicle traffic volume and coal thermal power generation on PM 2.5 is not statistically significant; (iv) the effect of ERMs is not very strong when many important control variables are included in the regression equation. In conclusion, the ERMs do not play an effective role in reducing PM 2.5 over the whole period. However, it can be seen that the effectiveness of the ERMs has been increasing in recent years.

Direct calibration of a true-rms ac voltmeter against a He-free pulsed Josephson standard

Starting from 2019 a new central role is played by quantum standards, owing to the redefined SI, where electrical units are directly linked to the fundamental constants e (elementary charge) and h (Planck constant). Thus, metrologists are nowadays trying to extend the astonishing accuracy attainable in dc measurements to ac and beyond, moving towards calibrations aiming quantum ac voltage generation. Programmable Josephson Voltage Standards are nowadays capable of fulfilling primary metrology requirements only for stepwise-approximated voltage signals up to few hundreds Hz. Pulsed Josephson standards are instead capable of generating arbitrary waveforms at higher frequencies, so are generally called Josephson Arbitrary Waveform Standards (JAWS). Despite of the lower attainable voltage, JAWS are very promising and are the subject of intense research activity. In particular, the capability of generating high spectral purity signals allows high accuracy measurements especially at the low voltage levels (<100mV rms), which are challenging to be performed by the traditional ac-dc transfer difference using thermal converters. We report in the following about our setup for quantum-based calibrations of a true-rms ac voltmeter with low uncertainty, first results obtained and unsolved issues.

Effect of high-temperature molten salt corrosion on the mechanical properties of stainless steel

The corrosivity of molten salt can be detrimental to the safe operation and longevity of concentrated solar thermal power generation equipment. Additionally, the presence of impurity Cl− can increase corrosion on metal materials, leading to mechanical property degradation. To assess the extent of this effect, the corrosion behaviour of three types of stainless steel (304, 316L, and 347H) in molten salt at high temperatures was studied using the loss-in-weight method and tensile tests. According to the findings, the Rdepths of 304, 316L, and 347H stainless steels are 0.0018 mm/a, 0.0016 mm/a, and 0.0019 mm/a, respectively, resulting in a decrease in elongation of 12.2%, 7.0%, and 3.7% after 720 h of corrosion at 600°C. Furthermore, at a higher temperature of 680°C, the Rdepths of all stainless steels increased, and the elongation decreased by 25.4%, 18.9%, and 13.5%, respectively. Similar corrosion behaviour was observed in 347H stainless steel with increased chloride ion concentration. However, the yield strength and tensile strength of stainless steel did not exhibit significant changes under different experimental conditions. The corrosion mechanism of metal alloys in molten salt is mainly due to the selective corrosion of Cr and its dissolution into molten salt in the form of ions.

Comparative study of different layouts in the closed-Brayton-cycle-based segmented cooling thermal management system for scramjets

The segmented cooling thermal management system based on the closed-Brayton-cycle (CBC) is an excellent technology for thermal protection and power generation of scramjets. In this paper, a comparative study is conducted to investigate the system performance under different supercritical carbon dioxide CBC layouts. A zero-dimensional thermodynamic model was established to analyze the effects of compressor inlet temperature (T1), turbine inlet temperature (T3), and compressor outlet pressure (p2) on fuel mass flow rate for cooling (mf) and net power (Pnet). A quasi-one-dimensional flow and heat transfer model was developed to study the cooling effectiveness. Results indicate that higher T3 and p2 reduce mf while increasing Pnet in the simple layout (SL) and simple recuperated layout (SRL). However, in the recompressing layout (RCL), the effects of T1, T3, and p2 on mf are more complex due to the split ratio. Moreover, RCL has the lowest maximum wall temperature among the three layouts. Finally, after optimization, RCL has the lowest mf about 0.332 kg/s, which is a 19.8 % reduction compared to the regenerative cooling system. Correspondingly, RCL achieves the highest Pnet, reaching 109.89 kW. In general, the recompressing layout is most suitable for the CBC-based segmented cooling thermal management system for scramjets.

Comparative Numerical Energy and Performance Analysis of Solar Photovoltaic and Solar Thermal Power Generation

This study analyses fixed and tracking solar photovoltaics and, solar thermal power. Performance in different locations was analysed for each configuration and technology using simulations based on a Typical Meteorological Year data. The study analysed a 25MWp solar photovoltaic and solar thermal power plants in each of the eleven selected locations in Zimbabwe. The performance of the solar photovoltaic and solar thermal power plants under different meteorological variables were assessed for all the selected locations. It was shown that different configurations together with different technologies have different conversion efficiencies. A high solar thermal conversion efficiency was found to be 18.718% in Gweru while it was 15.502% for solar photovoltaics in Mutare. The study also showed that highest insolation and clearness index values were found in Gweru. The average energy generated by the fixed photovoltaic collectors, tracking photovoltaic collectors and the Concentrating Solar Power plant were respectively 47.38GWh, 68.18GWh and 192.86GWh. There was a maximum percentage difference in the LCoE generated of 32.03% between the fixed PV collectors and the Concentrating Solar Power plant and a difference of 4.74% was realised between the tracking photovoltaics and Concentration Solar Power.

Public perceptions on net zero energy houses in Japan

AbstractFor Japan, which has not operated nearly all of its nuclear power plants since 2011 and is dependent on thermal power generation, the introduction of renewable energy into homes is extremely important for the future formation of a sustainable society. However, the introduction of net zero energy house (ZEH) in detached houses, which account for 55% of all dwellings in Japan, has not progressed. To promote the introduction of ZEH, this study clarified the awareness of owners of detached houses regarding ZEH. We analyzed factors that influence such perception of solar photovoltaics (PV) technology using a 1000-sample online survey questionnaire. The survey was conducted in late January 2020 and included questions examining the public perception of solar installation and factors that were found to be important in previous research. We found that Japanese respondents who live in detached houses generally lack an understanding of renewables and that the level of interest in installing solar PV for the ZEH is low. We also found that awareness of renewables, such as knowing new energy policy and searching information on solar PV, is the critical factor of installing renewables. At the same time, most socio-demographic and neighborhood variables seem not to influence installing solar PV or other technologies for ZEH. This research will contribute to the Japanese government’s goal of strengthening education on renewable energy to promote ZEH.

Visual smoke recognition based on an inverse-radiating attention pyramid network

In thermal power generation systems, the exhaust gases produced during the process of power generation should be fully burnt before being discharged into the air through a high-altitude chimney, to help maintain safe production and to avoid pollution. A thermal power generation system will emit white smoke when operating normally; otherwise, under abnormal conditions: (1) large amounts of dark smoke may be released into the air due to incomplete combustion of the exhaust gases, leading to hazards to public health and the environment; (2) colorless smoke can be emitted if toxic exhaust gases are directly released into the air, also causing dangerous pollution. To address these issues, we have developed an inverse-radiating attention pyramid network (IRAP-Net) for visual smoke recognition, directed towards monitoring thermal power generation systems. The proposed IRAP-Net exploits various visual smoke features. IRAP-Net is based on three pyramid blocks, composed of 3, 4 and 5 convolution modules, respectively. An attention mechanism is introduced into each pyramid block selective of features. Lastly, an inverse-radiating connection converges all the outputs of the pyramid blocks in a feedforward manner, thereby merging low-level and high-level features. Experiments on a large smoke image database show that the proposed IRAP-Net achieves a recognition rate exceeding 95.5%, superior to other state-of-the-art (SOTA) models.

Thermodynamic and economic analyses of a modified adiabatic compressed air energy storage system coupling with thermal power generation

With the proposal of "Carbon peaking and carbon neutrality", Adiabatic Compressed Air Energy Storage (A-CAES) has emerged as a significant component within China's energy storage infrastructure. But its thermodynamic efficiency and economical return need yet to be raised. The present paper proposed a modified system coupling with thermal power plant to utilize the excess compression heat. Utilizing advanced transient modeling software, an A-CAES plant is modeled and validated. The operation performance of the coupled system is compared with non-coupled system, which shows that the system efficiency is raised from 54.8 % to 76.7 % and the investment return rate is improved from 9.18 % to 10.43 %.

Bremsstrahlung power conversion for fusion power and propulsion in space

Centrifugally confined Direct Fusion Drive propulsion has the capability of greatly advancing humanity’s ability to traverse and explore the solar system. p-11B is a promising fusion fuel to use in such a system because the reaction is aneutronic. However, a large amount of bremsstrahlung radiation is produced and must be converted into electricity to power the electric field used to help confine the fusion plasma. This work details an idealized analytical model to determine the viability of using a thermionic energy converter for this purpose. The model finds a maximum power density of 105W/m2 with a Carnot efficiency of 30%. The required electric and magnetic fields to produce net positive fusion power are >350MV/m and ∼30T respectively. This data is then used to discuss the feasibility of using p-11B as a fusion fuel for Direct Fusion Drive.

Life cycle assessment of the production of an extruded dog food in Brazil

Sustainability is the current focus of the scientific community, governments, and companies in various market segments, such as pet food. Pet food production has increased rapidly in recent years, with a trend toward the development of environmentally friendly products and processes. The first step in creating strategies for mitigating environmental impacts is to assess key points in manufacturing processes. Given this, this study aimed to perform a life cycle assessment (LCA) to estimate the environmental impacts associated with the formulation, production, and distribution phases of an extruded dog food produced in Brazil. System boundaries were from cradle-to-gate, encompassing extraction of raw materials, transportation, processing, production, packaging, and distribution. Estimates were based on the amount of food required to meet the energy requirements for maintenance of a 10 kg dog (functional unit = 2.59 MJ day−1, reference flow = 177.3 g day−1). Environmental impacts were calculated by the environmental footprint method (EF 3.0 v. 1.00) using SimaPro software (v. 9.1.1.1). Product ingredients and packaging materials were modeled under Brazilian conditions using ecoinvent 3.7.1 and Agri-footprint 5.0 databases. Data regarding transportation, processing, distribution, electric and thermal power generation, water usage, and waste generation were obtained from the company's records (2019–2020). In this study, as expected, formulation was the most relevant factor, accounting for 70%–90% of the total environmental impacts. The main impact categories were terrestrial and marine eutrophication, acidification, particulate matter, and climate change (80% of total impacts). Production of the evaluated dog food was associated with the emission of 88.73 kg CO2 eq year−1 or 1.37 kg CO2 eq kg−1 distributed food. The use of animal meals (poultry by-product meal and meat and bone meal) and vegetable by-products (wheat bran and rice bran) contributed to reducing environmental impacts. Therefore, in this study, ingredient selection was considered the most important factor in mitigating the environmental impacts of pet foods. As the overall impact of the formulation depends on data on the use stage, such as nutrient excretion after consumption, future studies should adopt a cradle-to-grave approach for a better comprehension of the feasibility of applying animal and vegetable by-products in the eco-design of pet food products.

A novel design and analysis of hybrid fuzzy logic MPPT controller for solar PV system under partial shading conditions

Renewable energy resources are more useful when associated with the thermal power generation network because of their high accessibility in the environment, good system response, easy manufacturing, plus high scalable. So, the present research is going on solar power to reduce consumer grid dependency. The running of the PV network is quite easier, plus less human sources are involved. However, the solar modules’ power generation is nonlinear fashion. So, the collection of peak power from the sunlight-dependent systems is a highly challenging task. In this article, a Modified Differential Step Grey Wolf Optimization with Adaptive Fuzzy Logic Controller (MDSGWO with FLC) is developed for collecting the maximum power from renewable energy resources under diverse Partial Shading Conditions (PSCs). The introduced method comprehensive analysis has been done along with the other recently existing MPPT methods in terms of convergence speed, MPP tracking accuracy, operating efficiency of the introduced method, functioning duty value of the DC–DC boost power converter, dependence of MPPT on sunlight system, total number of sensing devices are needed, plus peak power extraction from the proposed system. Here, the sunlight power generation cost is more to limit this issue, a power converter is selected in the second objective to develop the voltage source capability of the PV network. The overall PV-interfaced power converter network is examined by utilizing the MATLAB environment.

Analysis of Deep Peak Shaving Methods for Thermal Power Generation Units Based on the Improved Energy Consumption Framework

Because thermal power producing units account for a large portion of the world's energy consumption, their energy consumption is a major concern. Reducing energy consumption and raising the overall efficiency of thermal power production units has become more and more important in recent years. Reducing energy consumption during peak hours is known as bottomless peak shaving, and it is one way to accomplish this. An enhanced framework for energy consumption is presented in this study to assess and examine deep peak shaving techniques for thermal power plants. The framework takes into consideration the various factors that affect energy consumption, such as fuel type, plant size, and external conditions. It also considers the different aspects of peak shaving, such as intensity and duration. Through the use of this framework, various deep peak shaving methods, such as thermal storage systems, load shifting, and demand response, are evaluated. The effectiveness of these methods is assessed based on their impact on energy consumption, cost, and environmental considerations. The framework also takes into account how feasible and useful it would be to apply these techniques in various kinds of thermal power generating units. The analysis's findings demonstrate that deep peak shaving techniques can dramatically lower energy use during peak hours, which can save money and possibly have positive effects on the environment. The best approach would rely on the unique qualities of every thermal power generating unit.

Choosing the Most Suitable Working Fluid for a CTEC

This study aims to explore additional fluids beneficial for coastal thermal energy converter (CTEC) operation. Ammonia’s thermodynamic properties, characterized by higher condensation temperatures and pressures, demand significantly elevated operating pressures, resulting in a substantial energy load for efficient operation. Thus, exploring alternatives such as R134a becomes crucial, particularly considering its potential as a better working fluid for power generation in a Rankine cycle. The research methodology involves employing computational fluid dynamics (CFD) simulations alongside experimental investigations to examine the performance of an axial turbine concept under different working fluids. The results obtained indicate that R134a is the most appropriate working fluid for an axial turbine within a CTEC, outperforming ammonia, thereby implying significantly better operational efficiency.

Surface activation of n-type AlGaN with cesium and oxygen to enhance thermionic emission

The aim of this study is to enhance the characteristics of thermionic emission of AlGaN surface through surface control employing cesium (Cs) and oxygen. Cs-deposited AlGaN has significant applications in thermionic energy converters. However, as the emitter temperature increases, the thermal desorption of Cs from AlGaN surface increases, resulting in a decrease in the thermionic emission current. Therefore, focusing on the high affinity between Cs and oxygen, we investigated the possibility of suppressing thermal desorption by depositing Cs and oxygen on AlGaN surface. The thermionic emission current measured when Cs and oxygen were alternately deposited on AlGaN surface was 1.9 × 10−3 A cm−2 at 500 °C. The thermionic emission current was significantly higher than that obtained with Cs-only deposition (2.0 × 10−5 A cm−2). In addition, we attempted to reproduce the effect of dynamic surface changes on thermionic emission employing a new thermionic emission model (modified Richardson–Dushman model) that considers the correlation between a specific surface reconstruction phase and its thermionic emission component. The results suggest that the adsorbed component of Cs-deposited AlGaN exhibits three Cs adsorption sites with different desorption energies, while the adsorbed component of Cs/O2 co-deposited AlGaN exhibits at least four Cs adsorption sites with different desorption energies. It is suggested that the increase in adsorption components with higher desorption energies, caused by the deposition of oxygen, may have reduced the thermal desorption and improved Cs coverage and stability.