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The enhancement of gas turbine (GT) efficiency through inlet air cooling, known as TIAC, in chillers using the heat of exhaust gas is one of the most attractive tendencies in energetics, particularly in thermal engineering. In reality, any combustion engine with cyclic air cooling using waste heat recovery chillers might be considered as a power plant with in-cycle trigeneration focused on enhancing a basic engine efficiency, which results in additional power output or fuel savings, reducing carbon emissions in all cases. The higher the fuel efficiency of the engine, the more efficient its functioning as a source of emissions. The sustainable operation of a GT at stabilized low intake air temperature is impossible without using rational design to determine the cooling capacity of the chiller and TIAC system as a whole to match current duties without overestimation. The most widespread absorption lithium-bromide chillers (ACh) are unable to reduce the GT intake air temperature below 15 °C in a simple cycle because the temperature of their chilled water is approximately 7 °C. Deeper cooling air would be possible by applying a boiling refrigerant as a coolant in ejector chiller (ECh) as the cheapest and simplest in design. However, the coefficients of performance (COP) of EChs are considerably lower than those of AChs: about 0.3 compared to 0.7 of AChs. Therefore, EChs are applied for subsequent cooling of air to less than 15 °C, whereas the efficient ACh is used for ambient air precooling to 15 °C. The application of an absorption–ejector chiller (AECh) enables deeper inlet air cooling and greater effects accordingly. However, the peculiarities of the subtropical climate, characterized by high temperature and humidity and thermal loads, require extended analyses to reveal the character of thermal load and to modify the methodology of designing TIAC systems. The advanced design methodology that can reveal and thereby forecast the peculiarities of the TIAC system's thermal loading was developed to match those peculiarities and gain maximum effect without oversizing. [ABSTRACT FROM AUTHOR]

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Francis-type hydropower units operating in part-load region could lead to adverse effects such as decreased turbine efficiency and increased pressure pulsation amplitude. Nowadays, this type of hydropower units is frequently forced to operate in the part-load region due to their complementary operation with uncertain wind and solar power. This poses potential risk to hydro-wind-solar hybrid energy system (HWSHES). However, existing studies have not adequately addressed the risk of hydropower unit operating in part-load region and misestimate the ideal flexible operating range of units. To address the two issues, this work proposes a risk-management model for HWSHES considering the hydropower part-load operating characteristics, which is based on the framework of "risk recognition-evaluation-control": (1) Risk recognition: identify and quantify potential operation risk of both power source and power grid in HWSHES; and (2) Risk evaluation: build a tri-objective short-term simulation scheduling model to evaluate power sources-power grid risks; (3) Risk control: design a three-stage optimization method for solving the model and effectively controlling risk. A case study of Wudongde hydropower plant, a key project of China's West-to-East power transmission project, in the Jinsha River Basin shows that: (1) The proposed model quantitatively identifies units' part-load risk distribution; (2) The uncertainty of wind and solar is prone to cause the risk of both power shortage and part-load operating in spring and winter; (3) A trade-off between power generation and risk is consistently observed throughout each season; and (4) Implementing the risk-management measures reduces the average part-load operating risk by 57.1% compared with no risk-management. In conclusion, this work contributes to enhancing the risk-management capabilities of large-scale HWSHES. [Display omitted] • Identify and quantify part-load operation risk of units from hydraulic machinery perspective. • Propose a risk-management model for coordinated operation of power sources and grid. • Design a three-stage optimization method for controlling risk. • The risk-management method reduces the part-load operation risk by 57.1%. [ABSTRACT FROM AUTHOR]

Pelton turbine, as its working principle, can perform in the high head condition especially in the southwest mountainous region in China. When the flow contains silt, it will induce the erosion in the bucket and needle structure which affects the efficiency and furthermore the service life. This paper performs unsteady air-liquid-solid three-phases simulation focusing on the distribution tube and needle parts. Volume of Fluid (VOF) method is used for capturing the free surface flow, at the same time, silt particle is simplified as the sphere particle and simulated through the Discrete Particle Model (DPM). Furthermore, flow detail and erosion information are obtained by conjugating both the former methodologies. Finally, particle size is analyzed in order to investigate the effect of erosion characteristic to the flow passage of Pelton turbine which aims to improve the turbine efficiency. [ABSTRACT FROM AUTHOR]

Tidal stream energy has received extensive attention from both academia and energy industry over the past decades. The Zhoushan Archipelago region has been widely recognized as a strong tidal estuary along the Chinese coastline and is therefore attractive for tidal stream energy exploitation. The potential of tapping tidal stream energy in this region was evaluated using a numerical model. The model was validated against field data, and the results showed good agreement (correlation of 0.99 for tidal elevation, average correlation of 0.95 for current speed magnitude). Locations with a large mean tidal stream power density were identified, and their spatial and temporal characteristics were provided. The spatially maximum spring–neap averaged power densities for the Guishan, Guanmen, Xihoumen, and Luotou channels were 6.66, 6.79, 5.22 and 5.88 kW/m2, respectively. Four performance parameters, including the site-specific turbine efficiency, energy output, availability factor, and capacity factor, were determined for an Evopod turbine based on the evolution of the flow in the Luotou channel. The Luotou channel presented a substantial tidal resource employing the Evopod tidal turbine with an annual energy output of 57.175 MWh. The monthly availability factor and capacity factor were approximately 70% and 40% throughout the year, implying more operational hours and equivalent operating hours per annum. [ABSTRACT FROM AUTHOR]

Coal-fired generation units in China often operate under off-design loads. The off-design performance has important influence on operation energy consumption of generation units. An all-condition model is of critical importance for studying the off-design performance. In this paper, an all-condition simulation model of the steam turbine system for a 600 MW generation unit is built. Based on the actual system composition, the steam turbine system is divided into several sub equipment. A sub model is established for each device. In the turbine model, a parameter M is defined as the intermediate variable to calculate the extraction pressure of turbine. The operating data from a 600 MW generation unit are used to verify the all-condition model. The heater fouling conditions are also calculated. The result shows that the model successfully predicts the operation parameters under different loads and forecasts the thermal performance of typical equipment failure. [ABSTRACT FROM AUTHOR]