The conventional approach to optimizing tilt angles for fixed solar panels aims to maximize energy generation over the entire year. However, in the context of a supply controlled electric grid, where solar energy avai...The conventional approach to optimizing tilt angles for fixed solar panels aims to maximize energy generation over the entire year. However, in the context of a supply controlled electric grid, where solar energy availability varies, this criterion may not be optimal. This study explores two alternative optimization criteria focused on maximizing baseload supply potential and minimizing required storage capacity to address seasonality in energy generation. The optimal tilt angles determined for these criteria differed significantly from the standard approach. This research highlights additional factors crucial for designing solar power systems beyond gross energy generation, essential for the global transition towards a fully renewable energy-based electric grid in the future.展开更多
Ice particles could form under the continuous impingement of incoming supercooled droplets in icing conditions,which will change the surface roughness to enhance the further heat and mass transfer during icing process...Ice particles could form under the continuous impingement of incoming supercooled droplets in icing conditions,which will change the surface roughness to enhance the further heat and mass transfer during icing process.A fixed-grid porous enthalpy method based on the improved Discrete Phase Model(DPM)and Volume of Fluid(VOF)integrated algorithm is developed to solve the multiphase heat transfer problem to give more detailed demonstration of the formation of initial ice roughness.The algorithms to determine the criterion of transformation from DPM to VOF and the allocation of source items during transformation are improved to the general DPM-VOF algorithm.Two verification cases,namely two glycerine-solution droplets impact and single droplet freeze,are conducted to verify the accuracy and reliability of the enthalpy-DPMVOF method,where the simulation results match well with experiment phenomena.Ice roughness on a NACA0012 airfoil is precisely captured and the effects on convective heat transfer characteristics are preliminarily revealed.The results illustrate that the enthalpy-DPM-VOF method could successfully capture the characteristics of motion and the phase change process of droplet,as well as balance the calculation accuracy and efficiency.展开更多
With the steady growth of traffic volume in core networks,it is predicted that future optical network communication will be constrained mainly by cost and power consumption.Thus,for Internet sustainability,it will be ...With the steady growth of traffic volume in core networks,it is predicted that future optical network communication will be constrained mainly by cost and power consumption.Thus,for Internet sustainability,it will be necessary to ensure cost and power efficiency in optical networks.The aims of this study are(i)to identify the main sources of cost and power consumption in fixed-grid(SLR and MLR)and flexi-grid(OFDM)optical networks,and(ii)to compare techniques for improving cost and power efficiency in SLR/MLR-and OFDM-based networks.To this end,we conducted a comparative analysis of cost and power efficiency for the OFDM-and MLR/SLR-based networks,and considering realistic networks,evaluated the cost and power consumed by different components in the optical layer.Our results show that(i)OFDM-based networks outperform those based on MLR/SLR in terms of both cost and power-efficiency,(ii)the extra equipment cost incurred due to under-utilization of spectrum is reduced by switching to a flexi-grid network,(iii)lower power consumption per bit is obtained when the networking solution ensures a finer bit-rate granularity,and(iv)there exists a power and spectrum minimization trade-off that is network characteristic dependent.展开更多
Phase change in ice-water systems in the geometry of horizontal cylindrical annulus with constant inner wall temperature and adiabatic outer wall is modeled with an enthalpy-based mixture model.Solidification and melt...Phase change in ice-water systems in the geometry of horizontal cylindrical annulus with constant inner wall temperature and adiabatic outer wall is modeled with an enthalpy-based mixture model.Solidification and melting phenomena under different temperature conditions are analyzed through a sequence of numerical calculations.In the case of freezing of water,the importance of convection and conduction as well as the influence of cold pipe temperature on time for the complete solidification are examined.As for the case of melting of ice,the influence of the inner pipe wall temperature on the shape of the ice-water interface,the flow and temperature fields in the liquid,the heat transfer coefficients and the rate of melting are analyzed.The results of numerical calculations point to good qualitative agreement with the available experimental and other numerical results.展开更多
文摘The conventional approach to optimizing tilt angles for fixed solar panels aims to maximize energy generation over the entire year. However, in the context of a supply controlled electric grid, where solar energy availability varies, this criterion may not be optimal. This study explores two alternative optimization criteria focused on maximizing baseload supply potential and minimizing required storage capacity to address seasonality in energy generation. The optimal tilt angles determined for these criteria differed significantly from the standard approach. This research highlights additional factors crucial for designing solar power systems beyond gross energy generation, essential for the global transition towards a fully renewable energy-based electric grid in the future.
基金supported by the National Natural Science Foundation of China(No.51706244)National Science and Technology Major Projects of China(No.2017-VIII-0003-0114)。
文摘Ice particles could form under the continuous impingement of incoming supercooled droplets in icing conditions,which will change the surface roughness to enhance the further heat and mass transfer during icing process.A fixed-grid porous enthalpy method based on the improved Discrete Phase Model(DPM)and Volume of Fluid(VOF)integrated algorithm is developed to solve the multiphase heat transfer problem to give more detailed demonstration of the formation of initial ice roughness.The algorithms to determine the criterion of transformation from DPM to VOF and the allocation of source items during transformation are improved to the general DPM-VOF algorithm.Two verification cases,namely two glycerine-solution droplets impact and single droplet freeze,are conducted to verify the accuracy and reliability of the enthalpy-DPMVOF method,where the simulation results match well with experiment phenomena.Ice roughness on a NACA0012 airfoil is precisely captured and the effects on convective heat transfer characteristics are preliminarily revealed.The results illustrate that the enthalpy-DPM-VOF method could successfully capture the characteristics of motion and the phase change process of droplet,as well as balance the calculation accuracy and efficiency.
文摘With the steady growth of traffic volume in core networks,it is predicted that future optical network communication will be constrained mainly by cost and power consumption.Thus,for Internet sustainability,it will be necessary to ensure cost and power efficiency in optical networks.The aims of this study are(i)to identify the main sources of cost and power consumption in fixed-grid(SLR and MLR)and flexi-grid(OFDM)optical networks,and(ii)to compare techniques for improving cost and power efficiency in SLR/MLR-and OFDM-based networks.To this end,we conducted a comparative analysis of cost and power efficiency for the OFDM-and MLR/SLR-based networks,and considering realistic networks,evaluated the cost and power consumed by different components in the optical layer.Our results show that(i)OFDM-based networks outperform those based on MLR/SLR in terms of both cost and power-efficiency,(ii)the extra equipment cost incurred due to under-utilization of spectrum is reduced by switching to a flexi-grid network,(iii)lower power consumption per bit is obtained when the networking solution ensures a finer bit-rate granularity,and(iv)there exists a power and spectrum minimization trade-off that is network characteristic dependent.
文摘Phase change in ice-water systems in the geometry of horizontal cylindrical annulus with constant inner wall temperature and adiabatic outer wall is modeled with an enthalpy-based mixture model.Solidification and melting phenomena under different temperature conditions are analyzed through a sequence of numerical calculations.In the case of freezing of water,the importance of convection and conduction as well as the influence of cold pipe temperature on time for the complete solidification are examined.As for the case of melting of ice,the influence of the inner pipe wall temperature on the shape of the ice-water interface,the flow and temperature fields in the liquid,the heat transfer coefficients and the rate of melting are analyzed.The results of numerical calculations point to good qualitative agreement with the available experimental and other numerical results.
