Aim To determine efficiency of multi-range hydro-mechanical stepless transmis- sion(HMT).Methods Ageneral model of HMT was of HMT was structured.On the basis of power flow analysis, the efficiency was obtained,Results...Aim To determine efficiency of multi-range hydro-mechanical stepless transmis- sion(HMT).Methods Ageneral model of HMT was of HMT was structured.On the basis of power flow analysis, the efficiency was obtained,Results efficiency of multi-range HMT changes continuously with output speed in speed range and is higher than the highest point of the hydraulic efficiency,The volumetric efficiency can potentially result in the speed fluctuation, which can be reduced or eliminated through controlling the ratio of the displacements ofhydraulic unity properly or changing the point of range exchanging .And the mechanical- constant output torque or different output torque under the condition of constant pressure when the transmission works in different parts of a range,Conclusion The multi-range HMT is an ideal stepless transmission with high efficiency.展开更多
Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that c...Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that can be bundled with solar PV to improve the economic feasibility of long-distance transmitted power. In this paper, a quantification model is established taking into account the regulating capacity of the reservoir, the characteristics of solar generation, and cost of hydro and solar PV with long-distance transmission based on the installed capacity ratio of hydro–solar hybrid power. Results indicate that for hydropower stations with high regulating capacity and generation factor of approximately 0.5, a hydro–solar installed capacity ratio of 1:1 will yield overall optimal economic performance, whereas for hydropower stations with daily regulating capacity reservoir and capacity factor of approximately 0.65, the optimal hydro–solar installed capacity ratio is approximately 1:0.3. In addition, the accuracy of the approach used in this study is verified through operation simulation of a hydro–solar hybrid system including ultra high-voltage direct current(UHVDC) transmission using two case studies in Africa.展开更多
The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years,floating offshore wind turbines(FOWTs) have attracted a con...The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years,floating offshore wind turbines(FOWTs) have attracted a considerable amount of attention as a means to exploit steady and strong wind sources available in deep-sea areas. In this study, the coupled aero-hydrodynamic characteristics of a spar-type 5-MW wind turbine are analyzed. An unsteady actuator line model(UALM) coupled with a twophase computational fluid dynamics solver naoe-FOAM-SJTU is applied to solve three-dimensional Reynolds-averaged NavierStokes equations. Simulations with different complexities are performed. First, the wind turbine is parked. Second, the impact of the wind turbine is simplified into equivalent forces and moments. Third, fully coupled dynamic analysis with wind and wave excitation is conducted by utilizing the UALM. From the simulation, aerodynamic forces, including the unsteady aerodynamic power and thrust, can be obtained, and hydrodynamic responses such as the six-degrees-of-freedom motions of the floating platform and the mooring tensions are also available. The coupled responses of the FOWT for cases of different complexities are analyzed based on the simulation results. Findings indicate that the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform are obvious. The aerodynamic loads have a significant effect on the dynamic responses of the floating platform, and the aerodynamic performance of the wind turbine has highly unsteady characteristics due to the motions of the floating platform. A spar-type FOWT consisting of NREL-5-MW baseline wind turbine and OC3-Hywind platform system is investigated. The aerodynamic forces can be obtained by the UALM. The 6 DoF motions and mooring tensions are predicted by the naoe-FOAM-SJTU. To research the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform, simulations with different complexities are performed. Fully coupled aero-hydrodynamic characteristics of FOWTs, including aerodynamic loads, wake vortex, motion responses, and mooring tensions, are compared and analyzed.展开更多
文摘Aim To determine efficiency of multi-range hydro-mechanical stepless transmis- sion(HMT).Methods Ageneral model of HMT was of HMT was structured.On the basis of power flow analysis, the efficiency was obtained,Results efficiency of multi-range HMT changes continuously with output speed in speed range and is higher than the highest point of the hydraulic efficiency,The volumetric efficiency can potentially result in the speed fluctuation, which can be reduced or eliminated through controlling the ratio of the displacements ofhydraulic unity properly or changing the point of range exchanging .And the mechanical- constant output torque or different output torque under the condition of constant pressure when the transmission works in different parts of a range,Conclusion The multi-range HMT is an ideal stepless transmission with high efficiency.
基金supported by the Global Energy Interconnection Group’s Science & Technology Project “Global Clean Energy Potential Estimating Model: Methodology and Application” (524500180011)
文摘Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that can be bundled with solar PV to improve the economic feasibility of long-distance transmitted power. In this paper, a quantification model is established taking into account the regulating capacity of the reservoir, the characteristics of solar generation, and cost of hydro and solar PV with long-distance transmission based on the installed capacity ratio of hydro–solar hybrid power. Results indicate that for hydropower stations with high regulating capacity and generation factor of approximately 0.5, a hydro–solar installed capacity ratio of 1:1 will yield overall optimal economic performance, whereas for hydropower stations with daily regulating capacity reservoir and capacity factor of approximately 0.65, the optimal hydro–solar installed capacity ratio is approximately 1:0.3. In addition, the accuracy of the approach used in this study is verified through operation simulation of a hydro–solar hybrid system including ultra high-voltage direct current(UHVDC) transmission using two case studies in Africa.
文摘The exploration for renewable and clean energies has become crucial due to environmental issues such as global warming and the energy crisis. In recent years,floating offshore wind turbines(FOWTs) have attracted a considerable amount of attention as a means to exploit steady and strong wind sources available in deep-sea areas. In this study, the coupled aero-hydrodynamic characteristics of a spar-type 5-MW wind turbine are analyzed. An unsteady actuator line model(UALM) coupled with a twophase computational fluid dynamics solver naoe-FOAM-SJTU is applied to solve three-dimensional Reynolds-averaged NavierStokes equations. Simulations with different complexities are performed. First, the wind turbine is parked. Second, the impact of the wind turbine is simplified into equivalent forces and moments. Third, fully coupled dynamic analysis with wind and wave excitation is conducted by utilizing the UALM. From the simulation, aerodynamic forces, including the unsteady aerodynamic power and thrust, can be obtained, and hydrodynamic responses such as the six-degrees-of-freedom motions of the floating platform and the mooring tensions are also available. The coupled responses of the FOWT for cases of different complexities are analyzed based on the simulation results. Findings indicate that the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform are obvious. The aerodynamic loads have a significant effect on the dynamic responses of the floating platform, and the aerodynamic performance of the wind turbine has highly unsteady characteristics due to the motions of the floating platform. A spar-type FOWT consisting of NREL-5-MW baseline wind turbine and OC3-Hywind platform system is investigated. The aerodynamic forces can be obtained by the UALM. The 6 DoF motions and mooring tensions are predicted by the naoe-FOAM-SJTU. To research the coupling effects between the aerodynamics of the wind turbine and the hydrodynamics of the floating platform, simulations with different complexities are performed. Fully coupled aero-hydrodynamic characteristics of FOWTs, including aerodynamic loads, wake vortex, motion responses, and mooring tensions, are compared and analyzed.
