The optimal yawing angle of sun-tracking solar aircraft is tightly related to the solar azimuth angle,which results in a large arc flight path to dynamically track the sun position.However,the limited detection range ...The optimal yawing angle of sun-tracking solar aircraft is tightly related to the solar azimuth angle,which results in a large arc flight path to dynamically track the sun position.However,the limited detection range of payload usually requires solar aircraft to loiter over areas of interest for persistent surveillance missions.The large arc sun-tracking flight may cause the target area on the ground to be outside the maximum coverage area of payload.The present study therefore develops an optimal flight control approach for planning the flight path of sun-tracking solar aircraft within a mission region.The proposed method enables sun-tracking solar aircraft to maintain the optimal yawing angle most of the time during daylight flight,except when the aircraft reverses its direction by turning flight.For a circular region with a mission radius of 50km,the optimal flight trajectory and controls of an example K-shaped sun-tracking solar aircraft are investigated theoretically.Results demonstrate the effectiveness of the proposed approach to optimize the flight path of the sun-tracking aircraft under the given circular region while maximizing the battery input power.Furthermore,the effects of varying the mission radius on energy performance are explored numerically.It has been proved that both net energy and energy balance remain nearly constant as the radius constraint varies,which enables the solar aircraft to achieve perpetual flight at almost the same latitude as the large arc flight.The method and results presented in this paper can provide reference for the persistent operation of sun-tracking solar aircraft within specific mission areas.展开更多
Current PV cells technology takes advantage mainly from beam radiation. In this context the sun-trackers are such devices for efficiency improvement. On the other hand, projected shadows between devices make mandatory...Current PV cells technology takes advantage mainly from beam radiation. In this context the sun-trackers are such devices for efficiency improvement. On the other hand, projected shadows between devices make mandatory to increase the distances between mounting systems. Thus, the land’s capacity for mounting PV panels can be dramatically decreased. This fact conducts us to wonder where the optimum efficient point is. First, in this paper different types of sun-tracking systems are classified according to the movement they perform (cinematic classification). Further, three real PV installations-fixed, horizontal-axis tracking and dual-axis mount tracking—located in the same geographical area in Spain (they are approximately under the same weather conditions) are analyzed. These installations have been studied in order to establish which one is the most efficient and affordable—Specific Energy Production (SEP) and Performance Ratio (PR) analysis. PVGIS solar radiation estimate tool has been used for comparing the theoretical radiation potential on each plant. The land requirements have been considered in the analysis of the Ground Cover Ratio (GCR) and the Surface Performance Ratio (SPR). Moreover, comparing three main financial indicators let us carry out a financial study: Payback Time (PBT), Net Present Value (NPV) and Internal Rate of Return (IRR). In the case study, final annual energetic results demonstrate that the dual-axis plant shows a relevant SEP advantage, but if we take into account the land occupied for this sort of devices we find much more profitable the horizontal-axis sun-tracking system, with a SPR value 4.24% higher than the fixed system we have studied. Its PBT is also a 22% lower than the dual-axis tracking installation.展开更多
The use of renewable energy resources to produce the electricity is a rising trend in various countries worldwide. This is especially because these energies do not produce the greenhouse gases;therefore, don’t become...The use of renewable energy resources to produce the electricity is a rising trend in various countries worldwide. This is especially because these energies do not produce the greenhouse gases;therefore, don’t become a destructive factor on the ozone layer and the environment. Besides, the fossil energies are always exposed to price changes and will eventually end, while the renewable energies don’t pose such problems and are freely acquired from the nature. Some of the most important of these reproducible energy resources are the energies of the wind and the solar energy. The generation capability of a photovoltaic power plant is largely dependent on the intensity of the sun radiation. On the other hand, the changing of position causes the sun to have a variable shining intensity in different seasons and different times of the year;therefore, some of the solar power plants possess solar tacking systems. This paper studies the different types of photovoltaic systems including fixed panel, photovoltaic farms equipped to the single axis and double axis tracking systems and their effects on the performance of the solar power plants. In order to determine the position of the sun in the sky, the zenith and azimuth angles of it are used to extract the relations between the different parameters of the sun radiation. The resulted parameters are used in the modeling of the single axis and double axis systems. In the paper it is utilized from the sun parameters in Qeshm Island of Iran in the summer of 2011.展开更多
基金the support of the National Natural Science Foundation of China(Nos.11902156 and 11672133)supported by the Fundamental Research Funds for the Central Universities,China(No.309201A8802)。
文摘The optimal yawing angle of sun-tracking solar aircraft is tightly related to the solar azimuth angle,which results in a large arc flight path to dynamically track the sun position.However,the limited detection range of payload usually requires solar aircraft to loiter over areas of interest for persistent surveillance missions.The large arc sun-tracking flight may cause the target area on the ground to be outside the maximum coverage area of payload.The present study therefore develops an optimal flight control approach for planning the flight path of sun-tracking solar aircraft within a mission region.The proposed method enables sun-tracking solar aircraft to maintain the optimal yawing angle most of the time during daylight flight,except when the aircraft reverses its direction by turning flight.For a circular region with a mission radius of 50km,the optimal flight trajectory and controls of an example K-shaped sun-tracking solar aircraft are investigated theoretically.Results demonstrate the effectiveness of the proposed approach to optimize the flight path of the sun-tracking aircraft under the given circular region while maximizing the battery input power.Furthermore,the effects of varying the mission radius on energy performance are explored numerically.It has been proved that both net energy and energy balance remain nearly constant as the radius constraint varies,which enables the solar aircraft to achieve perpetual flight at almost the same latitude as the large arc flight.The method and results presented in this paper can provide reference for the persistent operation of sun-tracking solar aircraft within specific mission areas.
文摘Current PV cells technology takes advantage mainly from beam radiation. In this context the sun-trackers are such devices for efficiency improvement. On the other hand, projected shadows between devices make mandatory to increase the distances between mounting systems. Thus, the land’s capacity for mounting PV panels can be dramatically decreased. This fact conducts us to wonder where the optimum efficient point is. First, in this paper different types of sun-tracking systems are classified according to the movement they perform (cinematic classification). Further, three real PV installations-fixed, horizontal-axis tracking and dual-axis mount tracking—located in the same geographical area in Spain (they are approximately under the same weather conditions) are analyzed. These installations have been studied in order to establish which one is the most efficient and affordable—Specific Energy Production (SEP) and Performance Ratio (PR) analysis. PVGIS solar radiation estimate tool has been used for comparing the theoretical radiation potential on each plant. The land requirements have been considered in the analysis of the Ground Cover Ratio (GCR) and the Surface Performance Ratio (SPR). Moreover, comparing three main financial indicators let us carry out a financial study: Payback Time (PBT), Net Present Value (NPV) and Internal Rate of Return (IRR). In the case study, final annual energetic results demonstrate that the dual-axis plant shows a relevant SEP advantage, but if we take into account the land occupied for this sort of devices we find much more profitable the horizontal-axis sun-tracking system, with a SPR value 4.24% higher than the fixed system we have studied. Its PBT is also a 22% lower than the dual-axis tracking installation.
文摘The use of renewable energy resources to produce the electricity is a rising trend in various countries worldwide. This is especially because these energies do not produce the greenhouse gases;therefore, don’t become a destructive factor on the ozone layer and the environment. Besides, the fossil energies are always exposed to price changes and will eventually end, while the renewable energies don’t pose such problems and are freely acquired from the nature. Some of the most important of these reproducible energy resources are the energies of the wind and the solar energy. The generation capability of a photovoltaic power plant is largely dependent on the intensity of the sun radiation. On the other hand, the changing of position causes the sun to have a variable shining intensity in different seasons and different times of the year;therefore, some of the solar power plants possess solar tacking systems. This paper studies the different types of photovoltaic systems including fixed panel, photovoltaic farms equipped to the single axis and double axis tracking systems and their effects on the performance of the solar power plants. In order to determine the position of the sun in the sky, the zenith and azimuth angles of it are used to extract the relations between the different parameters of the sun radiation. The resulted parameters are used in the modeling of the single axis and double axis systems. In the paper it is utilized from the sun parameters in Qeshm Island of Iran in the summer of 2011.
