Space Solar Power Satellite Research Articles

Secondary concentrator design of an updated space solar power satellite with a spherical concentrator

The Space Solar Power Satellite (SSPS) is a promising project to solve the energy crisis on earth. In this paper, a secondary concentrator design of an updated SSPS-OMEGA concept is proposed aiming at the problems existing in original SSPS-OMEGA concept, such as high power transmission through power brush, thermal management of the photovoltaic (PV) cell arrays and special requirements for the concentrator film brought by the inside placed transmitting antenna. Firstly, the updated concept with a secondary concentrator, a disc PV cell arrays and outside placed transmitting antenna is illustrated and main parts of it are described. Secondly, a design methodology of the secondary concentrator is presented. The characteristics of spherical concentrator are simply described. The generatrix geometry of the secondary concentrator is described using Bézier curve, and the performances of optics and energy density distribution on PV cell arrays are evaluated using the Monte Carlo Ray Tracing method. After that, a mathematical optimization model is established and the Particle Swarm optimization is used to obtain better configuration of secondary concentrator, solar energy collection performance and energy density distribution on PV cell arrays. Finally, the optimal generatrix geometry of secondary concentrator and energy density distribution under different orders of Bézier curve are investigated, the result shows that the effective solar energy collection and solar energy collection can be up to 81.14% and 87.06% respectively when the order of Bézier curve is 5. Moreover, a further energy density distribution optimization is conducted and the relative non-uniformity index of 0.4 is realized.

A long-distance high-power microwave wireless power transmission system based on asymmetrical resonant magnetron and cyclotron-wave rectifier

This paper demonstrates the analysis of a long-distance high-power microwave wireless power transmission (MWPT) system based on asymmetrical resonant magnetron and cyclotron-wave rectifier. In the system, the novel magnetron with the asymmetrical resonant cavity, the straps, and the output loop coupling circuit can effectively promote the beam–wave interaction, suppress the mode competition, and enhance the output coupling, which results in a 400 kW output microwave power with a conversion efficiency of 45%. The transceiver Cassegrain antenna system with its simple structure, high conversion efficiency, and high power capacity can attain an integral power transmission efficiency of 2.6% at 10 km distance. The cyclotron-wave rectifier with high efficiency and single-tube high power capacity can achieve 85% microwave to DC conversion efficiency. Finally, the long-distance high-power MWPT system can achieve 8.5 kW DC power with about 1% DC–DC transmission efficiency at the operating 2.45 GHz frequency and for the 10 km distance. Such a system is likely a potential and attracting solution to remotely power the fuel-free aerial vehicle from the ground, can also provide electrical power to an isolated mountain top or an island, and even an alternative to transmit the power from space solar power satellite in geostationary orbit to the ground.

Multiobjective Optimization Design of Aperture Illuminations for Microwave Power Transmission via Multiobjective Grey Wolf Optimizer

In microwave power transmission (MPT) applications, the problem of maximizing the transmission efficiency has been extensively studied. However, to reduce costs, the power transmission capacity needs also to be considered. Moreover, to ensure safety, the peak radiation level at the edge or outside the rectenna must be taken into account either. To deal with these problems simultaneously, a multiobjective optimization design method of aperture illumination for MPT is proposed. Subsequently, a multiobjective grey wolf optimizer is developed and employed to solve the formulated problem. This new design approach provides antenna engineers with a set of tradeoffs among multiple goals, and therefore, the best compromise can be selected for a given application. To verify the effectiveness of the proposed method, numerical experiments on continuous aperture with different Fresnel parameters are conducted first. Then, the obtained results are applied to a space solar power satellite model, which demonstrates the validity of the proposed method. Finally, the effectiveness of the proposed method is further confirmed via numerical experiments on array antennas.

Attitude control of space solar power satellite with large range of relative motion among subsystems

The transmitting antenna needs to be oriented to the Earth, while the PV cell array of the SSPS-OMEGA system rotates in a large range inside the concentrator for the orientation to the Sun, so that there is a large range of unfixed relative movement among the subsystems. For the study of dynamic characteristics and attitude control problem of the space solar power satellite, the multi-body dynamics model of the system is built, and the gravity gradient torque equation applied on the PV cell array is derived in the process of relative motion. A simple attitude control system and the corresponding electric thrusters configuration scheme are designed. The simulation results show that the attitude of 2-GW SSPS-OMEGA in roll and yaw direction is well controlled. However, due to the large range rotation of the PV cell array, the attitude in the pitch direction is controlled to converge to the microwave beam pointing accuracy of mechanical adjustment in longer time with the residual gravity gradient torque. In the long period, the attitude deviation angle in the pitch direction would stabilize periodically within ±0.018 degree. This provides a reference for further study of beam-control of the transmitting antenna.

Power-Optimal Guidance for Planar Space Solar Power Satellites

This paper presents power-optimal guidance for a planar space solar power satellite (SSPS). Power-optimal guidance is the attitude trajectory that maximizes the solar power transmitted by the SSPS. Planarity is important because it couples the orientations of the SSPS’s photovoltaic and antenna surfaces. Hence, the transmitted power depends on the relative geometry between the SSPS, the sun, and the receiving station. The orientation that maximizes power transfer changes as this relative geometry changes. Both single- and dual-sided SSPS architectures are considered. A single-sided SSPS has one photovoltaic surface and one antenna surface. A dual-sided SSPS is a single-sided SSPS with at least one additional photovoltaic or antenna surface. Geometric arguments show that a dual-sided SSPS has superior performance to a single-sided SSPS. Power-optimal guidance is then presented for the special cases of SSPSs in geostationary Earth orbit, medium Earth orbit, and low Earth orbit transmitting to an equatorial receiving station at the time of Earth’s vernal equinox. These examples emphasize important solution properties, including the need for large slew maneuvers, and they show that, even though system efficiency decreases as orbit altitude decreases, reduced path losses actually increase the amount of received energy per unit aperture area. This has significant system implications for future space solar power missions.

Optical-Structural Integrated Optimization Design of Deployable Beams in OMEGA Space Solar Power Satellite

AbstractThe efficiency of a solar energy collection (SEC) is of great significance to the power generation and overall efficiency of a space solar power satellite (SSPS). The Orb-Shape Membrane Ene...

Solar ray collection rate fluctuation analysis with Monte Carlo Ray Tracing method for space solar power satellite

According to the ideal optical design, the spherical concentrator made by the semi-transparent and semi-reflecting thin film is used in SSPS-OMEGA system. To obtain the continuous power, the PV array should rotate around the spherical concentrator to point the sun when SSPS-OMEGA rotate around the earth on GEO. However, considering the in-orbit assembly, the concentrator is assembled by many planar elements to be approximate to the ideal spherical concentrator. The solar ray collection rate fluctuates in certain scope because the original solar ray path is changed. In addition, planar element is deformed easily by the rotating PV array, which also lead to the fluctuation because the position of the planar element is changed. In this paper, the spherical concentrator is divided into many planar elements by using equal latitude and longitude method. It is studied that the relationship between the number of division layers and the collection rate fluctuation by using Monte Carlo Ray Tracing method. The simulation results indicate that with increasing dividing layers, the collection rate increases and the fluctuation amplitude decreases, which ranges 80.72–83.70% (2.98%) of 24-layers concentrator, ranges 88.45–89.91% (1.47%) of 48-layers concentrator, and ranges 92.46–93.80% (1.33%) of 72-layers concentrator. To solve the deformation of the concentrator, the flexible multibody dynamics model of SSPS-OMEGA is established. Combing the deformation and Monte Carlo Ray Tracing method, it is studied that the relationship between the deformation of the concentrator and the collection rate. The simulation results indicate that the stiffness of 72-layers concentrator is better than 24-layers concentrator and 48-layers concentrator, and the reduction of the collection rate of 72-layers concentrator, which is 0.4%, is less than 24-layers concentrator (1.57%) and 48-layers concentrator (0.81%).

Sensor placement algorithm for structural health monitoring with redundancy elimination model based on sub-clustering strategy

Abstract Considering the limitation of selecting several neighbor sensors in a local region similar to just single one, namely redundant information, a sensor placement algorithm for structural health monitoring is proposed based on sub-clustering strategy, in order to improve the performance of sensor configuration with less redundancy. According to the significance of redundancy, the proposed novel redundancy elimination model considers global and local effect to overcome the previous limitations in sensor distribution. Based on the sub-clustering strategy, the redundancy elimination model reflects the sensor configuration in each sub-clustering and overall structural field. The presented sub-clustering strategy for sensor placement includes three main procedures: sub-clustering algorithm, its check step and smallest enclosing circle method, thus the accuracy can be guaranteed. Combining the effective independence method with normalization and weighting factor, the proposed sensor placement algorithm can balance performance and redundancy by using genetic algorithm, which is more competitive to reduce the order difference between the two objectives. Finally, the effectiveness of the proposed redundancy elimination model is verified by a simple example, and another two engineering numerical examples including space solar power satellite and re-usable launch vehicle are applied to demonstrate the validity of the proposed sensor placement algorithm respectively.

A fresnel concentrator with fiber-optic bundle based space solar power satellite design

A Fresnel concentrator with fiber-optic bundle based space solar power satellite (SSPS) is proposed as an innovative design in this paper. It consists of a flat Fresnel lens array for solar concentration, fiber bundles to transport the condensed sunlight to the photovoltaic panel and a highly modular sandwich module for power generation/transmission. Operating principle, structure configuration and efficiency of the system are presented in detail. Also, Fresnel concentrator with a secondary homogenizer is designed to obtain high concentration ratio and good irradiance uniformity on the solar cell. Lastly, to maintain the temperature fluctuation within a design requirement, the thermal analysis of the sandwich module is investigated. The obtained results demonstrate the feasibility of the proposed SSPS design.

Optimal sensor placement for spatial lattice structure based on three-dimensional redundancy elimination model

Spatial lattice structures are widely applied in engineering fields attributed to their superiorities in weight and reasonable stress. It is essential to select the best sensor placement layout for structural health monitoring and safety purposes, yet it is neither realistic nor efficient to place sensors in every location possible on the structure. To meet the strong requirements for optimal sensor placement in spatial lattice structure, this paper aims to investigate a combined objective function based on effective independence method and three dimensional redundancy elimination model to balance between optimal sensor placement performance and elimination in redundancy. To eliminate redundant information and resource waste caused by the clustered sensor distribution, the three-dimensional redundancy elimination model is constructed with the consideration of nearer nodes and overall sensor distribution ranges in three-dimensional cases. In addition, the combined function is constructed by giving the two component functions equal significance using weighting factors and normalization, and solved by genetic algorithm. Finally, the proposed method for spatial lattice structure is supported by three numerical examples including a simple lattice structure, a ground spatial truss structure and a space docking modular in space solar power satellite.

The main aspects of the theory and key technologies about Space Solar Power Satellite

This paper presents several problems about development of Space Solar Power Satellite (SSPS) systematically. Firstly, the importance of developing SSPS to solve the energy crisis of the world is discussed. Secondly, two main categories of SSPS, non-focusing and focusing concepts, are described with the advantages and disadvantages, such as the specific power to mass ratio (energy produced by unit mass), engineering implementation, reliability and so on. Thirdly, recent achievement of SSPS-OMEGA concept proposed by author’s team in 2014 is provided. Finally, future development on SSPS is discussed.

Sensor placement for structural health monitoring using hybrid optimization algorithm based on sensor distribution index and FE grids

Considering the adjustments for sensor selections attributed by different finite element (FE) grids, a hybrid optimization algorithm including FE grids updating for optimal sensor placement is proposed based on effective independence method and sensor distribution index, in order to improve the algorithm efficient and reduce the redundancy information simultaneously. This study takes into account of the relationship of FE grids, redundancy information, and optimal sensor placement performance by detailed statements. Furthermore, in order to reduce the redundancy information caused by too fine FE grids and too near measurements, the proposed sensor distribution index can synthetically deal with both cases of the nearer nodes and overall sensor distribution ranges. Moreover, by means of normalization and weighted factor, the constituted fitness function, which consists of Fisher information and sensor distribution index, can be more competitive by eliminating the gap of orders caused by the different fitness functions. Therefore, the economical FE grids are suggested, and the corresponding optimum sensor locations are simultaneously obtained by the hybrid optimization algorithm. Finally, the proposed method is verified by a deployable antenna module of space solar power satellite and a wing of reusable launch vehicle, respectively.

Dynamic modeling and simulation of deploying process for space solar power satellite receiver

To reveal some dynamic properties of the deploying process for the solar power satellite via an arbitrarily large phased array (SPS-ALPHA) solar receiver, the symplectic Runge-Kuttamethod is used to simulate the simplified model with the consideration of the Rayleigh damping effect. The system containing the Rayleigh damping can be separated and transformed into the equivalent nondamping system formally to insure the application condition of the symplectic Runge-Kutta method©First, the Lagrange equation with the Rayleigh damping governing the motion of the system is derived via the variational principle. Then, with some reasonable assumptions on the relations among the damping, mass, and stiffness matrices, the Rayleigh damping system is equivalently converted into the nondamping system formally, so that the symplectic Runge-Kutta method can be used to simulate the deploying process for the solar receiver. Finally, some numerical results of the symplectic Runge-Kutta method for the dynamic properties of the solar receiver are reported. The numerical results show that the proposed simplified model is valid for the deploying process for the SPS-ALPHA solar receiver, and the symplectic Runge-Kutta method can preserve the displacement constraints of the system well with excellent long-time numerical stability.

Study of Stepped Amplitude Distribution Taper for Microwave Power Transmission for SSPS

A novel stepped amplitude distribution (SAD) taper for microwave power transmission for space solar power satellite is proposed in this paper. The SAD taper is described by the summation of the Heaviside step functions. Through optimizing the “height” and “radius” of each step of the descriptive function, the maximal beam collection efficiency (BCE) with and without constraints on the radiation levels can be obtained. A large set of numerical experiments on continuous apertures and discrete antenna arrays are carried out. The results show that the obtained BCEs can be close to or even higher than those of the 10-dB Gaussian ones, which shows the superiority of the method. In addition, only several kinds of amplifiers are required in this method, and therefore, the cost and complexity of the system can be greatly reduced.

Optimal sensor placement for deployable antenna module health monitoring in SSPS using genetic algorithm

The concept of space solar power satellite (SSPS) is an advanced system for collecting solar energy in space and transmitting it wirelessly to earth. However, due to the long service life, in-orbit damage may occur in the structural system of SSPS. Therefore, sensor placement layouts for structural health monitoring should be firstly considered in this concept. In this paper, based on genetic algorithm, an optimal sensor placement method for deployable antenna module health monitoring in SSPS is proposed. According to the characteristics of the deployable antenna module, the designs of sensor placement are listed. Furthermore, based on effective independence method and effective interval index, a combined fitness function is defined to maximize linear independence in targeted modes while simultaneously avoiding redundant information at nearby positions. In addition, by considering the reliability of sensors located at deployable mechanisms, another fitness function is constituted. Moreover, the solution process of optimal sensor placement by using genetic algorithm is clearly demonstrated. At last, a numerical example about the sensor placement layout in a deployable antenna module of SSPS is presented, which by synthetically considering all the above mentioned performances. All results can illustrate the effectiveness and feasibility of the proposed sensor placement method in SSPS.

Thermal design, analysis and comparison on three concepts of space solar power satellite

Space solar power satellites (SSPS) have been widely studied as systems for collecting solar energy in space and transmitting it wirelessly to earth. A previously designed planar SSPS concept collects solar power in two huge arrays and then transmits it through one side of the power-conduction joint to the antenna. However, the system's one group of power-conduction joints may induce a single point of failure. As an SSPS concept, the module symmetrical concentrator (MSC) architecture has many advantages. This architecture can help avoid the need for a large, potentially failure-prone conductive rotating joint and limit wiring mass. However, the thermal control system has severely restricted the rapid development of MSC, especially in the sandwich module. Because of the synchronous existence of five suns concentration and solar external heat flux, the sandwich module will have a very high temperature, which will surpass the permissible temperature of the solar cells. Recently, an alternate multi-rotary joints (MR) SSPS concept was designed by the China Academy of Space Technology (CAST). This system has multiple joints to avoid the problem of a single point of failure. Meanwhile, this concept has another advantage for reducing the high power and heat removal in joints. It is well known to us that, because of the huge external flux in SSPS, the thermal management sub-system is an important component that cannot be neglected. Based on the three SSPS concepts, this study investigated the thermal design and analysis of a 1-km, gigawatt-level transmitting antenna in SSPS. This study compares the thermal management sub-systems of power-conduction joints in planar and MR SSPS. Moreover, the study considers three classic thermal control architectures of the MSC's sandwich module: tile, step, and separation. The study also presents an elaborate parameter design, analysis and discussion of step architecture. Finally, the results show the thermal characteristics of each SSPS concept, and the three concepts are compared. The design layouts, analysis results and parameter discussions of the thermal management sub-system proposed in this study can help inform future SSPS thermal designs.

A new concept of space solar power satellite

Space solar power satellite (SSPS) is a tremendous energy system that collects and converts solar power to electric power in space, and then transmits the electric power to earth wirelessly. In this paper, a novel SSPS concept based on ε-near-zero (ENZ) metamaterial is proposed. A spherical condenser made of ENZ metamaterial is developed, by using the refractive property of the ENZ metamaterial sunlight can be captured and redirected to its center. To make the geometric concentration ratio of the PV array reasonable, a hemispherical one located at the center is used to collect and convert the normal-incidence sunlight to DC power, then through a phased array transmitting antenna the DC power is beamed down to the rectenna on the ground. Detailed design of the proposed concept is presented.

Rectenna Array Equipped on Satellites

Space solar-power satellites may one day transmit large amounts of high-powered microwave beams to Earth from geostationary Earth orbit. New spacecraft can be designed to prosper from this new available source of energy by equipping future spacecraft with a rectenna array or hybrid photovoltaic/rectenna array system. This idea offers prospective benefits, such as extending the mission lifetime of the spacecraft through increasing the life of the power generation function and reducing the power generation units mass. This paper explores the integration of rectenna array and hybrid photovoltaic/rectenna array systems into future spacecraft and compares this method to the conventional photovoltaic array method, considering mission and component life, mass, area, and energy harvesting capabilities. Cost is compared between conventional photovoltaic array and the rectenna array. This paper shows that the integrated hybrid photovoltaic/rectenna array power generation unit seems a viable option in obtaining the aforementioned benefits in the case of a retrodirective beam scenario. A power irradiance map is provided, based on former space solar-power satellites reference systems, that shows what lower orbiting satellites could experience from a microwave power beam delivered to Earth if future geostationary-Earth-orbit space solar-power satellites are operational.

SSPS Dynamic Modeling and the Flexible Vibration Suppression

Space solar power satellite (SSPS) as a very large flexible spacecraft structure with complex configuration, large size and number of units bring the difficulties to dynamics modeling and analysis. Considering SSPS structure characteristics, equivalent strain and kinetic energy theory is adopted to establish the equivalent beam model of SSPS truss structure. The assumed mode method is adopted to describe the flexible body. The modal truncation method implements the dynamics system order reduction. Mixed coordinates method is adopted to establish the rigid-flexible coupled dynamic model. The established dynamic model can reflect dynamic characteristics of SSPS, achieve control requirements for SSPS and decrease the workload of simulation calculation. The independent modal space control (IMSC) method is proposed to active control research view of the large displacement, nonlinearity, low and dense mode frequency, light damping of flexible structures. Simulation results on flexible solar array show the effectiveness of the control method.

Tethered actuator for vibration control of space structures

Effectiveness of a micro-tension actuator for vibration control of such flexible space structures as the tethered space solar power satellites is experimentally studied on the ground. A flexible leverage is employed as the micro-tension actuator in order to control the microtension of tether. The flexible leverage is connected through a tether to the flexible beam as an experimental model of the flexible solar panel with the low first modal frequency of order 1Hz. The nonlinearity of the flexible tether is taken into account for the vibration control since the tether becomes ineffective when it slacks, i.e., when it is tension-free. The feedback controller is designed by means of the Mission Function control algorithm. Flexural rigidity of the flexible leverage plays an important role in the vibration suppression and is studied experimentally to shed light on the effectiveness of the leverages with five different kinds of rigidity. The experimental results show not only the effect of the flexural rigidity of the flexible leverage on the control performance of the vibration suppression but also the importance of selection of the rigidity to control the vibration of tethered flexible space structures through the microtension of tethers in space.