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Many power plants have been transformed and operated using low‐pressure cylinder near‐zero output (LP‐ZO) technology in China to make way for or provide necessary guarantees for renewable energy power generation. This research focuses on utilizing numerical simulation tools to improve the operational economy of units with LP‐ZO. The LP‐ZO thermodynamic and energy‐consumption model of a reference plant is established, and the momentum particle swarm optimization method is used to optimize the unit operations. Moreover, a model to determine the economic operational range of the combined heat and power plant with LP‐ZO is proposed. The results show that the LP‐ZO mode operations of the unit can reduce the minimum peak shaving rate and improve the flexibility of operations. The energy efficiency of the LP‐ZO mode is increased due to the recovery of a significant portion of the cold source losses. However, the irreversible exergy loss caused by large temperature difference heat exchange reduces the exergy efficiency of the unit. After operational optimization, the reference plant can save approximately 68.15 t d−1 of coal and reduce carbon dioxide emissions by about 27 t tce−1 d−1. This study provides an operating approach to the CHP plant with LP‐ZO unit in enhancing flexibility and economy. [ABSTRACT FROM AUTHOR]

Aimed at the medium-temperature solar energy heat source, the use of low-boiling binary non-azeotropic organic mixtures as the supercritical cycle working fluids to generate power was put forward. On the premises of meeting the requirements of thermal property, safety, and economic efficiency, 8 working fluids combining R245fa with R152a according to different mass ratios were used and the supercritical thermal system mathematical model was established based on the first and second laws of thermodynamics. The cycle characteristics were contrasted from the multi-angle aspects including seven indices like thermal efficiency, exergy efficiency, and so on. Considering various factors, the multi-index comprehensive evaluation model of energy efficiency was constructed by using the analytic hierarchy process method. Through simulation calculations, the results show that properly increasing the proportion of R245fa promotes effective improvement of the supercritical cycle characteristics and working fluid R245fa/R152a(0.96/0.04) can improve the indexes including net output power, economy, and environmental performance of the system. The proposed one has the optimal evaluation index value among the candidates. [ABSTRACT FROM AUTHOR]

• Based on the particle swarm algorithm, chaos is introduced to combine the speed advantage of the particle swarm algorithm with the ergodic advantage of the chaos idea, so that the chaotic particle swarm algorithm can find the optimal configuration of the coupled energy system quickly and accurately. • The impact of the introduction of energy storage devices on the investment cost of microgrid systems is explored. • The introduction of hydrogen energy and energy storage equipment completes the integrated energy systems. • It provides a new algorithm to solve the problem of real-time load distribution of microgrids. Integrated energy system (IES) is difficult to achieve the optimal scheduling of the system due to the coupling of multiple energy devices and the high volatility of renewable energy loads. To address the above problems, a chaos-based particle swarm algorithm is proposed, which uses a chaotic mapping of optimal particles by a Logistic algorithm to increase the anisotropy of particles and improve the search accuracy in the case of wide area multi-polarity. The example analysis shows that the chaotic particle swarm algorithm can improve the economic cost by 3.868% compared with the conventional particle swarm after increasing the number of iterations. Finally, based on this algorithm, the economic impact of the energy storage device on the integrated energy system is analyzed. The results show that the IES system based on the composite energy storage can reduce the total economic cost significantly, while avoiding the excessive use of other energy supply devices and ensuring the stability of the overall IES system operation. [ABSTRACT FROM AUTHOR]

With the development of new-power generation sources, the difference between maximum and minimum power requirements from a power grid is growing. However, the peaking power installed capacity, such as pumped-hydro energy storage and gas-fired power, is too small to meet the peaking regulation requirements. Chinese coal-based energy resources structure determines coal-fired power plants to be the main source of power. This means that coal-fired power units will need to undertake more peak shaving tasks for a long period of time. In this paper, we provide an overall review of China׳s coal-fired power units׳ peak regulation with a detailed presentation of the installed capacity, peak shaving operation modes and support policies. High energy-consumption problems, environmental pollutants and safety barriers when coal-fired power units run in low-load operation are noted from the power generation perspective. Some policy recommendations are given to solve the peak shaving problem to some extent and to ensure the sustainable development of the power energy system. [ABSTRACT FROM AUTHOR]

Fully hydraulic wind power generation is an emerging research direction. These hydraulic wind power generators replace the rigid connection between wind turbine and generator with a hydraulic flexible transmission system. This effectively absorbs a majority of the fluctuating load from the wind turbine, thereby achieving step less speed change and enabling the generator within the unit to maintain stable rotational speeds. The fully hydraulic wind power generator is different from the traditional wind power generators in terms of the transmission system used. As a result, the research here is focused on the transmission characteristics of the hydraulic system. Moreover, the transmission characteristics of the fully hydraulic wind turbine were compared to wind turbines with a mechanical transmission, from the analysis of the comparison different operating characteristics were revealed. The experiments using a test bench to study the full hydraulic wind power generator, whereas simulations using a model were carried out for the wind power generator with the mechanical transmission. [ABSTRACT FROM AUTHOR]

• Operation modes were considered in energy consumption of a CHP plant. • The heat rate was obtained considering two units operating in parallel. • Optimization model based on the energy consumption was established. • 304.44 kJ·kWh−1 can be saved for the reference CHP plant. Optimizing thermal–electric load distribution toward combined heat and power (CHP) units can improve the efficiency of thermal power plants. Here, a thermal–electric load distribution method is proposed based on the energy consumption characteristics of CHP plants. The influence of operation modes on the energy consumption characteristics has been considered. Based on the energy consumption characteristics, the influence of load distribution on the heat rate is expounded considering two units operating in parallel. Firstly, a 600 MW unit model is developed using the EBSILON software, and the associated energy consumption model is established by passing the simulation results to a MATLAB routine. Then, three distribution methods are used to study the influence of the thermal–electric load distribution on the heat rate. Finally, the energy consumption model is embedded into a momentum particle swarm optimization (MPSO) algorithm, and the thermal–electric load distribution is optimized using the load data from a characteristic day with the operation feasible region taken as the boundary. The results show that the thermal load plays a major role in the energy efficiency of the unit, and the electric load determines the exergy efficiency distribution. The operation mode of the unit has little influence on the energy utilization rate, but has a significant influence on the exergy efficiency. When two CHP units are running in parallel, their heat rate can be reduced by optimizing the thermal–electric load distribution. A more uneven distribution of thermal–electric load between units results in a lower heat rate. The optimized heat rate given by the MPSO algorithm for a characteristic day is 6887.93 kJ·kWh−1, which is 304.44 kJ·kWh−1 less than under the average thermal–electric load distribution. These findings may be helpful to get insight into the energy consumption characteristics of CHP plants and guide for its economic operation. [ABSTRACT FROM AUTHOR]

In order to overcome the limitations of traditional clean energy utilization methods, this paper proposed an innovative technical solution for a combined heating system that cleverly integrated solar, wind, and geothermal energy to achieve complementarity and synergized among them, thereby ensuring stable and efficient energy utilization. First, a comprehensive mathematical model was developed for the entire heating system, encompassing solar thermal subsystem, geothermal subsystem, wind power generation subsystem, and a second-stage reheating subsystem. Subsequently, Ebsilon simulation software was utilized to cleverly couple these subsystems together, with corresponding boundary conditions set to ensure the overall efficiency and stability of the system. Based on meteorological data and geothermal resource parameters from a typical heating season in Zhengzhou, Henan Province, China, this paper thoroughly analyzed the variations in key performance indicators such as the photothermal conversion efficiency of solar thermal subsystem and the heating capacity of geothermal subsystem. This provided valuable insight for optimizing the design of heating system. The results indicated that during the daylight hours of the heating season, both the photothermal conversion efficiency and the heat supply from the solar thermal subsystem exhibited an increasing trend as solar radiation increased. Among them, the photothermal conversion efficiency peaked at 76.013%, while the maximum heat supply output reached 40.311 kW. When solar direct radiation was relatively weak, the system primarily relied on the heat release process of the thermal storage tank to maintain heating, with a minimum heat supply of 27.268 kW. During nighttime hours of the heating season, the geothermal subsystem dominated the heating process, with a maximum heat supply of 125.556 kW. Additionally, for every 5 °C increased in geothermal water temperature, the heat supply from the geothermal subsystem increased by an average of 6.553 kW, demonstrating excellent heating response performance. Therefore, the integrated clean heating system that combines solar, geothermal, and wind energy not only significantly improves the utilization efficiency of clean energy but also enhances the heating stability of the integrated clean energy coupling system to a certain extent. The clean heating technical solution proposed in the paper had a theoretical total heating capacity of 19 680 kW during the heating season. When converted, this equates to a substitution of 6.9 tons of standard coal, resulting in a reduction of carbon dioxide emissions by 17.94 tons. This demonstrates the considerable cleanliness and environmental benefits of the proposed heating system. This study provides a valuable reference for the engineering application of renewable energy in the field of clean heating. [ABSTRACT FROM AUTHOR]

Two of the most critical issues encountered in the day-ahead scheduling of regional integrated energy systems are the uncertainty of renewable energy resources and complexity of load demand. Furthermore, varying operating conditions also pose challenges for economical day-ahead scheduling. This paper proposes a scenario-based day-ahead scheduling approach for regional integrated energy systems to minimize operating costs by mining historical data. A hybrid dynamic energy hub model with variable efficiency that integrates an extreme gradient boosting (XGBoost) algorithm and analytical formulation is proposed. We developed a scenario-based scheduling optimization model in which climate data and load data are predicted using XGBoost and the probability distributions of their predicted errors are estimated using a Gaussian mixture model. Monte Carlo simulation and K-means clustering were used to generate and reduce scenarios and a success-history-based adaptive differential evolution algorithm was adopted to search for optimal solutions for day-ahead scheduling. Furthermore, a weighted average electricity purchasing strategy was adopted to address uncertainty and further improve operating economy by adjusting the output of gas turbines and electricity purchasing for actual scheduling. Case studies were conducted to verify that the proposed approach can reduce daily operating costs and enhance the operating economy of regional integrated energy systems. • A hybrid DEH model integrating operating data and an analytical formulation characterizes flexible performance accurately. • Considering the uncertainty by scenario-based stochastic optimization method increases the operating cost. • A weighted average electricity purchasing strategy can address the uncertainty and further improve operating economy. [ABSTRACT FROM AUTHOR]

• A high-efficient pressure matcher was proposed, validated and analyzed in Ebsilon. • Low-stent-placed steam supply pipeline module was furtherly investigated and used to transport steam within 4 km. • A steam-driven screw turbine was introduced to satisfy an eco-industrial park's electric and heat need. • Solar thermal utilization part was used to pre-heat domestic water with taking Beijing and Huzhou's DNI into consideration. • Energy, exergy and entransy analysis was simultaneously considered to analyze main equipment in regional system. Regional integrated energy system has been a suitable scheme in China to satisfy eco-industrial park's both electric and heat needs. Combined heat and power (CHP) is an efficient technology for coal-fired plants during heating seasons. Currently, wires transport electric from CHP to destination while urban pipes network transport heat from CHP to destination, respectively. However, this might not be the case in future, when eco-industrial parks are close to plants or pipes network can't carry enough heat. This paper presents a feasible regional integrated energy system which meets both electric and heat's needs with steam from CHP while maintaining photothermal resources' high percent utilization. This system includes a coal-fired CHP plant, pressure matcher, steam supply pipeline, screw turbine and solar thermal utilization part. This paper set up a model of 600 MW electric power CHP with pressure matcher and screw turbine in Ebsilon software. Then the steam supply pipeline and solar thermal utilization part were developed and analyzed based on the basic thermodynamic theories with Beijing and Huzhou's meteorological statistics taken into consideration. Besides, the operational issues of the regional system were also listed. Meanwhile, the regional integrated energy system was obtained and a lot of characteristics were analyzed. Main devices were further investigated with energy, exergy and entransy analysis. Three extreme working situations were also carried out and discussed in the end. Several useful conclusions were drawn. It's necessary for China to masterly integrate regional energy system with multi-energy. Moreover, pressure matcher is high-efficient in general under other parameters' influences. This extracting steam's technology might be considered in future. Besides, low-stent placed pipeline which can transport high-parameter steam 4 km at most was introduced. A proper mass flow value or lower inlet temperature will both reduce loss of pipeline. Furthermore, heat user side can offer electric power about 9.22 MW, heating acreage about 0.79 km2 to the eco-industrial park. More solar heat's import, lower upper temperature difference and less sunlight will favor solar thermal utilization part. Higher heat load or lower CHP's working condition will benefit screw turbine. Peak heat exchanger doesn't need to work when supply domestic water temperature's demand is less than 65 °C. The simulation in this paper might give technological statistics to the regional integrated energy system which has CHP and photothermal. This will help to put this energy system into actual use in future. [ABSTRACT FROM AUTHOR]

Aiming at the large heat loss inside the traditional trough-type vacuum solar heat collecting tube, a new type of spiral three-blade rotor structure was designed and inserted into the inner tube side of the heat collecting tube. Based on the principle of fluid dynamics and field synergy, a mathematical model of the three governing equations of the fluid in the tube was established. Numerical simulations of the heat transfer and flow in the flow field in the two types of collector tubes with or without interpolated rotors were performed. Performance comparisons were made in terms of velocity field, pressure field, temperature field, and field synergy coupling ability. The results of the comprehensive evaluation index of heat transfer performance were finally given. The research shows that the PEC value continues to become larger with the increase in the inlet flow rate, from an initial value of 1.63 to a final value of 2.69. The heat transfer performance enhancement advantage of the new type vacuum heat collector tube is obviously greater than the disadvantage of flow resistance, and the comprehensive performance is better. [ABSTRACT FROM AUTHOR]

Condition-based maintenance is an effective way to reduce operation and maintenance cost of wind turbine. Highly complex and non-stationary operational conditions of wind turbine pose a challenge to conventional condition monitoring technique. Thus, a systematic multi-parameter health condition evaluation framework that considers the dynamic operational conditions is proposed. After characteristic parameter selection and Gaussian mixture model based multi-regime modeling, evidential reasoning is developed to evaluate the health condition of wind turbine. The proposed approach shows good health condition evaluation performance not only on the parameter level but also on the component and system level. Case studies indicate the effectiveness and potential applications of the proposed method for the wind turbine health condition evaluation. [ABSTRACT FROM AUTHOR]

Abstract: The hydro turboset is the key equipment of the electric power system. Thus, it is very important and necessary to monitor and diagnose the running conditions and the faults of the hydro turboset for the safe and normal running of the electric power system. Fault diagnosis of the hydro turbine is a complicated process and requires a high level of expertise. In order to significantly reduce the cost consumed in the fault diagnosis, to increase the consistency of diagnosing decision-making, and to better utilize the turbine’s management information resource, in this paper, an integrated Web-based expert system of the fault diagnosis has been developed for the hydro turbine of a power station. Moreover, it can be regarded as an advisory tool to those who have much technical experience and as a training tool for the less-experienced personnel who seek guidance and advice. This paper describes a research project aiming to develop a Web-based intelligent diagnosis system for the hydro turbine and discusses the process of the fault diagnosis and the difficulties involved in developing the system. The paper also includes several practical issues related to the architectures of the intelligent Web-based applications. The system is built on a three-tier architecture, including the following components: knowledge base, inference engine, knowledge administration interface, user interface, knowledge administration unit and integrated database. The expert system employs heuristic rules to diagnose the hydro turbine fault. Some issues on developing Web-based expert systems are also discussed. [Copyright &y& Elsevier]