Large Solar Arrays Research Articles

Suppression of solar array vibration by torque compensation using a magnetorheological actuator: A hardware-in-the-loop test study

Sun-tracking-induced vibrations of a large flexible solar array are characterized by a wide frequency range and persistent disruptions, making them an important challenge for a high-precision spacecraft. This paper describes a hardware-in-the-loop test for a novel vibration suppression method that employs magnetorheological torque compensation. To provide the compensating torque, a test bench is built using a magnetorheological actuator (MRA). A comprehensive model is employed to quantitatively analyze suppressions in terms of solar array driving, solar array motion, and spacecraft disturbance. For comparison, the test is run in both open-loop and closed-loop modes. The results demonstrate that with closed-loop control, the maximum fluctuation of driving torque decreases by 50.90%. The sun tracking achieves a more stable speed. Moreover, disturbances produced by the vibration of the solar array are decreased by 59.84%. These findings suggest that using torque compensation with an MRA can successfully reduce the sun-tracking-induced vibration of a large flexible solar array while minimizing the impact on the spacecraft platform.

Generation of Secondary Space Debris Risks from Net Capturing in Active Space Debris Removal Missions

Mitigation strategies to eliminate existing space debris, such as with Active Space Debris Removal (ASDR) missions, have become increasingly important. Among the considered ASDR approaches, one involves using a net as a capturing mechanism. A fundamental requirement for any ASDR mission is that the capture process itself should not give rise to new space debris. However, in simulations of net capturing, the potential for structural breaking is often overlooked. A discrete Multi-Spring-Damper net model was employed to simulate the impact of a 30 m × 30 m net travelling at 20 m/s onto an ESA Envisat mock-up. The Envisat was modelled as a two-rigid-body system comprised of the main body and a large solar array with a hinge connection. The analysis revealed that more than two significant substructures had a notable likelihood of breaking, prompting the recommendation of limiting the impacting velocity. The generation of secondary space debris indicates that net capturing is riskier than previously assumed in the literature.

Passive Damping of Solar Array Vibrations Using Hyperelastic Shape Memory Alloy with Multilayered Viscous Lamina

A novel passive vibration-damping device is proposed and investigated for a large deployable solar array. One strategy for achieving high damping in a solar panel is using a yoke structure comprising a hyperelastic shape memory alloy and multiple viscous adhesive layers of acrylic tape. The effectiveness of the proposed system in achieving a high damping performance was demonstrated by conducting free vibration and low-level sine sweep tests using a solar array, and a 0.75-m-long flexible dummy structure was simulated. We also investigated the dependence of the damping performance of the proposed structure on the number of viscous lamina layers. Finally, the damping characteristics of the proposed system were assessed under predictable on-orbit temperature conditions.

A novel transactive integration system for solar renewable energy into smart homes and landscape design: A digital twin simulation case study

The use of solar renewable energy in landscape design is becoming increasingly popular as the world strives to reduce its reliance on fossil fuels. With the cost of solar energy falling, more and more people are turning to solar as a way to power their homes and businesses. In this article, we will explore the integration of solar renewable energy into landscape design through a case study. Using local photovoltaics along with suitable power storage systems, a household power management system is proposed to optimize the scheduling of demand-responsive appliances. The beta likelihood distribution function for sun irradiance is used to model the unpredictable behavior of photovoltaic energy production in residential power management systems. The PV system was integrated into the building’s existing landscape design by incorporating the system’s components into the existing landscape elements. This included the installation of a large solar array on the roof of the building, as well as the integration of solar panels into the existing garden beds and pathways. The solar array was also connected to the building’s existing electrical system, allowing the building to draw power from the solar array when needed. Among the major contributions of the study would be to optimize the planning of demand-responsive devices within a domestic power management system by using the improved leader particle swarm optimization method (ILPSO). The purpose would be to reduce peak-to-average ratios (PARs) and energy usage costs in the smart home. A number of scenarios are designed and simulated in a digital twin structure for a household user with various initial loads, uninterruptible deferrable, and interruptible deferrable devices using a real-time power cost program to demonstrate the performance of the suggested optimization method. Based on comparisons with various metaheuristics previously documented, the new ILPSO algorithm efficiently optimizes energy usage costs and PARs.

Aerocapture: Enabling Small Spacecraft Direct Access to Low-Circular Orbits for Planetary Constellations

Small satellite constellations in multiple-inclination, low-circular orbits around Mars and Venus have the potential to perform a range of high-value science investigations within cost-constrained missions. A major challenge for small satellites is that they require large ΔV to enter low-circular orbits, which can drive up both spacecraft mass and cost. Compared to chemical propulsion, which requires large amounts of propellant, and electric propulsion, which requires large solar arrays and comes with long flight times, aerocapture enables direct access to low-circular orbits at Mars and Venus with minimal ΔV. The study shows how drag-modulation aerocapture, when combined with small B-plane targeting maneuvers, allows the delivery of multiple small satellites to various-inclination, low-circular orbits to establish a constellation. Preliminary cost estimates indicate that by reducing the required ΔV for orbit insertion, aerocapture can potentially reduce the cost of a small satellite going to a low-circular Mars orbit compared to propulsive insertion. The ability of low-cost spacecraft to enter planetary orbits will enable a new paradigm of interplanetary missions using small dedicated launch vehicles and planetary constellations at Mars and Venus.

Modeling and analysis for the deployment dynamic behavior of the large flexible solar array

The large flexible solar array for the satellite will deploy when it reaches the scheduled orbit by the space rocket, which is key for the normal running of the satellite. However, undesirable and unpredicted frequency vibration may be resulted from the flexibility of elements of the solar array. In this paper, the dynamic model of the solar panel was firstly developed based on the modal synthesis method. Moreover, the stretchable mechanism in the solar array was introduced by applying Euler-Bounerlli beam theory. Also, guide ropes, hinges and electric cables were considered in the proposed model. It was found the proposed model could achieve a higher accuracy of simulation compared to the traditional method with the coordinate method. Especially, the dependence of the guide rope tension on the deployment dynamic behavior of the solar array was explored by this model. Results showed that vibrations of the solar array could be reduced by improving the guide rope tension, which could be used in design and operation of the solar array.

STUDY ON GLOBAL MODE DYNAMIC MODELING AND EXPERIMENT FOR A SOLAR ARRAY OF THE FLEXIBLE SPACECRAFT

Modern flexible spacecraft are usually installed with large solar arrays to provide the power needed for the operation of the spacecraft in orbit. The solar arrays are expanded in orbit and locked into hinged multi-panel structures, and the characteristics such as light weight, large span, and low stiffness make the issues on the study of low frequency and nonlinear vibration become more and more important. The key process of dealing with the vibration for such a kind of structure is to establish the exact nonlinear dynamic model of the system. In this paper, an analytic extraction method of the global mode of the multi-panel structure is presented, and the natural frequencies and the global analytic mode functions of the solar array are obtained. Considering the nonlinear stiffness and friction moments of the hinges, and the nonlinear dynamic model of the system can be obtained by the global mode discretization. The nonlinear characteristics of the solar array under periodic excitation are studied. The experimental researches on the solar array are carried out, and the mode shapes are obtained by hammering tests, and the sinusoidal sweep excitation is applied by the vibration table. The physical experimental results are compared with the theoretical results, so as to verify the rationality and accuracy of the global mode dynamic modeling method. The experimental results show that the structural parameters such as hinge stiffness have a great influence on the inherent characteristics of the system, and the existence of hinges will make the dynamic response of the solar array appear nonlinear phenomena such as jump. Global mode dynamical modeling method can well solve the difficult problem of obtaining the analytical global mode for the multi-panel structure with the non-classical boundaries. The global mode of the system can reflect the real elastic vibration mode of the parts in the system, and the established dynamic model is low-dimensional and high-precision. It has important reference value for nonlinear dynamic modeling of complex composite structures.

Robust H∞ Control for the Spacecraft with Flexible Appendages

Aiming at the oscillation suppression of spacecraft with large flexible appendages, we propose a control strategy using H∞ control. The weighting functions are designed for the specific flexible modes of the spacecraft and the frequency of harmonic interference in its operating environment. Taking into account the structural uncertainty of systematic modeling and the comprehensive performance requirements of system bandwidth constraint and attitude stability, the H∞ comprehensive performance matrix is constructed. A space telescope with a large flexible solar array is presented as an illustrative example, and a control design that meets the requirement for pointing accuracy is proposed. The simulation results show that the designed controller satisfies the requirements of attitude stability and high pointing accuracy and has effectively suppressed the disturbance of endemic frequency. The design scheme and selection method of the weight function shown in this paper can be a reference for the controller design for oscillation suppression of this type of spacecraft with flexible structures.

Cymatics inspired self-cleaning mechanism for solar panels

The photovoltaic modules are usually installed on the ground which exposes it to surface deposition of foreign particles. In the Middle East and North Africa region, the primary culprit is dust and sand. They form an insulating and opaque layer on the surface of the glass, which obstructs its heat transfer and optical properties, thereby reducing the overall yield efficiency of the solar panel. Cleaning of this layer is critical to the operation of the solar panel and often requires great effort and energy on a large-scale solar array. In this paper, we propose a novel self-cleaning mechanism for solar panels, with an understanding of the structural integrity of the Photovoltaic laminate and application of external mechanical vibration. By applying an external source of vibration, the solar panels vibrate, excites its fundamental frequencies and cleans by its own. The method is analyzed using finite element analysis method and tested using experiments. Our simulation results based on IEC 61215 show that the maximum principal stress and deformation in the critical layers is within limits. Our experimental results prove the proposed theory is feasible and can be extended to large scale solar arrays. Our proposed method is retrofittable and could save money, energy and effort in cleaning the solar arrays, which can replace current techniques.

Infinite photovoltaic solar arrays: Considering flux of momentum and heat transfer

Large scale solar farms supply an increasing amount of the worlds electricity supply. However, high operation temperatures can strongly reduce efficiency and panel lifetime, negatively affecting the levelized cost of energy. In this work, the convective heat transfer coefficient for a utility-scale solar farm is studied with combined thermal and particle-image-velocimetry measurements in a scaled wind tunnel experiment. The measurements confirm the applicability of the scaled experimental setup to study large solar arrays. Further, the velocity measurements indicate the complex flow structure within the solar array, governed by wakes directed upwards due to the orientation of the solar panels.

Copernicus Sentinel-1 satellites: sensitivity of antenna offset estimation to orbit and observation modelling

Abstract. The SAR (Synthetic Aperture Radar) Copernicus Sentinel-1 satellites require a high orbit accuracy of 5 cm in 3D in comparison to external processing facilities. The official orbit products delivered by the Copernicus POD (Precise Orbit Determination) Service fulfil this requirement. Nevertheless, analyses have shown discrepancies in the orbit results for the two satellites Sentinel-1A and Sentinel-1B. Since the satellites are identical in construction estimated orbit parameters like the scale factor for the radiation pressure are expected to be at the same magnitude, which is not the case. Estimation of GPS antenna offsets leads to differences between the two satellites, which might explain the discrepancies in the estimated orbit parameters. Such offset estimations are, however, very sensitive to orbit and observation modelling. It has to be assured that the results are not biased by insufficient models. First of all, stabilisation of the antenna offset estimation is achieved by improving the observation modelling by applying single receiver ambiguity resolution. The Copernicus Sentinel-1 satellites have a very complex shape with the long SAR antenna and the two large solar arrays. Antenna offset estimation based on different satellite models may give results which differ by up to 1.5 cm. The dispersion of the estimates is quite large depending also on eclipse and non-eclipse periods. Consideration of simple assumptions on satellite self-shadowing effects improves the satellite model and also the results of the antenna offset estimation. Finally, more consistent results for the two Sentinel-1 satellites are achieved by applying the antenna offset estimates.

The dual angle solar harvest (DASH) method: An alternative method for organizing large solar panel arrays that optimizes incident solar energy in conjunction with land use

Plummeting costs of solar panels along with rising costs of land makes it imperative to consider both the per-panel and unit-area incident solar energy. An alternative approach of organizing large solar panel arrays that considers this co-optimization problem is suggested and a new dual-angle technique is introduced, called the dual-angle solar harvest (DASH) method, in which a solar array is composed of two tilt angles. This paper evaluates the DASH method at two climatically and geographically different locations: Akron, OH and Barstow, CA. Use of the DASH method can enable potential better handling of complex radiation fields in partly cloudy climates, allow for preferential weighting of irradiation during different seasons, and may be a tool to increase array-wide incident irradiation at a pre-existing array in a cost-effective manner. This latter example is tested nationwide, in which one angle is constrained at the single optimum tilt angle. Results show the lowest percentage of panel-rows that require an adjustment to a different tilt angle to achieve the desired gain in array-wide incident energy. The more cost-effective solutions tend to be located in cloudier climates and at higher latitudes.

Design Considerations of Sequential Switching Shunt Regulator for High-Power Applications

Sequential switching shunt regulators (S3Rs) are widely used in the satellites owing to their simple structure and high reliability. The high-power communication satellites require a power supply with a high bus voltage and large solar array section current. However, a large solar array capacitance and new time-division multiple access operations complicate the design of a lightweight and cost-effective power supply by increasing the difficulty in dissipation and thermal control. On the basis of passive current limitation, in this article, we propose a novel shunt regulator with only one output diode and a protection strategy to achieve high efficiency, appropriate shunt current limitation, and low turn-off delay. In addition, to reduce the dissipation of an S3R cell when feeding the solar array current to the main bus and to satisfy the single point failure-free requirement, an innovative self-retriggerable diode short-circuit fault detector circuit is proposed, which includes a protection switch for a safe thermal or electrical operation. Finally, simulation and experimental results are presented to validate the proposed shunt regulator and the corresponding control method or protection strategy.

Numerical and Experimental Study of Flow Characteristics in Solar Collector Manifolds

The flow through a forced circulation Z-type flat plate solar collector was investigated by means of combined experimental measurements and numerical simulations. The efficient operation of such collectors depends on the uniformity of the flow rate distribution among their riser tubes, while low pumping power demand is also sought. Mass flow rate measurements in the riser tubes were performed, utilizing a specially adapted ultrasound instrument for various values of total flow rates in the collector. By means of a commercial Computational Fluid Dynamics (CFD) code, laminar and turbulent flow models in different computational grids were tested and validated against the experiments. Appropriate metrics were introduced to quantify flow rate distribution non-uniformity among the risers, and pressure drop through the manifold was calculated. Parametric studies for flow conditions outside the experimental window were performed utilizing the CFD method in order to assess the effect of the Reynolds number in the flow distribution among the riser tubes. Furthermore, aiming to enhance flow rate uniformity, a methodology based on modifying the diameter of each riser tube was applied and successfully demonstrated. The proposed method can be employed in large solar collector arrays, either as stand-alone systems or as belonging to hybrid alternative sources of energy (ASE) systems, aiming to optimize their overall efficiency.

Rigid-flexible-thermal analysis of planar composite solar array with clearance joint considering torsional spring, latch mechanism and attitude controller

This paper establishes a thermal-structural coupling model of planar spacecraft system with large flexible composite solar array under nodal coordinate formulation and absolute nodal coordinate formulation framework. Perfect revolute joint is adopted as connection type to give the different influences from fixed constraint used in previous researches, and consequently, torsional spring, latch mechanism, and attitude controller are involved into the spacecraft system. Imperfect revolute joint is further introduced to investigate the coupling effects of thermal load, adjustment motion, and joint clearance on dynamics of the system, including spacecraft attitude, solar panel responses, and wear prediction. Results of six comparison models (with or without clearance joint, considering thermal environment, or adjustment motion, and considering both these two conditions) show that the coupling effect of thermal environment and overall motion brings dramatic and unmanageable shock to the system with clearance joint, that is no longer can be seen as a simple superposition of each single condition effect like the system with ideal joint, although the suspension damper property of clearance joint can weaken thermal-induced vibration or motion induced vibration separately. For a period after attitude adjustment, wear depth of the system subjected to solar radiation is two orders of magnitude lager than that of the system without considering thermal environment. Joint clearance and thermal environment should be considered both; for on-orbit spacecraft system, the coupling effects of them are significant and non-ignorable for relevant mechanism design and performance analysis.

Plume influence analysis of small bipropellant thruster on solar array of GEO satellite.

An exhaust plume gas flow from a bipropellant thruster has been recognized as a potential source of a load, heat, and contamination on the exposed satellite components which can especially degrade the optical properties and performance of solar panel. Therefore, accurate predictions of a bipropellant thruster plume gas flow and assessments of its influences should be considered at the design phase of a satellite. The objective of the present study is to investigate the plume gas flow behavior of a small bipropellant thruster and to evaluate its influence on the solar array of a GEO satellite numerically. To deal with complex plume flow regimes efficiently, the combined approach of computational fluid dynamics (CFD) and Direct Simulation Monte Carlo (DSMC) was applied depending on the flow characteristic conditions. Throughout the numerical results of the present study, the influences of the plume gas flow exhausted from a single bipropellant thruster were considered for the disturbance, heat, and contamination of the three-dimensional satellite configuration equipped with a large solar array.

Solar Landfills: Economic, Environmental, and Social Benefits

AbstractIdeally suited for hosting large solar photovoltaic arrays feeding electricity into the grid, closed landfills will play a significant role in the undergoing energy transition from fossil‐fuel and nuclear energy to renewable energy. Aimed at sustainability scholars and policy makers, this study identifies the economic, environmental, and social benefits of solar landfills, suggesting avenues for the massive transformation of hazardous landfills into renewable‐energy‐generation plants. Thus, the landfills no longer pose threats to human health and to the ecosystem.

Planar rigid-flexible coupling spacecraft modeling and control considering solar array deployment and joint clearance

Based on Nodal Coordinate Formulation (NCF) and Absolute Nodal Coordinate Formulation (ANCF), this paper establishes rigid-flexible coupling dynamic model of the spacecraft with large deployable solar arrays and multiple clearance joints to analyze and control the satellite attitude under deployment disturbance. Considering torque spring, close cable loop (CCL) configuration and latch mechanisms, a typical spacecraft composed of a rigid main-body described by NCF and two flexible panels described by ANCF is used as a demonstration case. Nonlinear contact force model and modified Coulomb friction model are selected to establish normal contact force and tangential friction model, respectively. Generalized elastic force are derived and all generalized forces are defined in the NCF-ANCF frame. The Newmark-β method is used to solve system equations of motion. The availability and superiority of the proposed model is verified through comparing with numerical co-simulations of Patran and ADAMS software. The numerical results reveal the effects of panel flexibility, joint clearance and their coupling on satellite attitude. The effects of clearance number, clearance size and clearance stiffness on satellite attitude are investigated. Furthermore, a proportional-differential (PD) attitude controller of spacecraft is designed to discuss the effect of attitude control on the dynamic responses of the whole system.

The Europa Charging Environment

The baseline design of the planned Europa Mission includes large solar arrays, which may experience surface charging. The spacecraft would encounter Europa ~40 times with some passes within ~25 km. This paper will describe the plasma environment expected near Europa during these encounters. Emphasis will be on the torus near Europa and on Europa’s ionosphere. Whereas the spacecraft would encounter a cold, corotating torus plasma with a velocity of ~120 km/s near Europa, it may encounter Europa’s ionosphere at a velocity as low as 5 km/s as Europa’s orbital velocity is only ~14 km/s relative to Jupiter. The challenge is to estimate the rapid potential variations associated with these two disparate environments. This paper will present a review of models of the plasma torus and the ionosphere and their interactions with each other. Ultimately, the models will be used to estimate the effects of the varying plasmas near Europa on the planned Europa Mission’s baseline spacecraft design and on its instruments with the intent of hardening that design to surface charging and to help with the interpretation of the effects of the charging environment on its instruments.

Solar array layout optimization for stratospheric airships using numerical method

The solar array layout is one of the critical factors affecting the output performance of a solar array on a stratospheric airship. Optimizing the layout to improve output energy per day is very important for a long endurance vehicle, but the research about this subject is rare. This paper outlines a numerical method based on a rotating model of a stratospheric airship to optimize the solar array layout. Combined with the solar radiation model, the solar array layout optimization model applying genetic algorithm is developed using a MATLAB computer program in this paper. Compared with the design parameters of three stratospheric solar-powered airships, the theoretical model is proved to be feasible. In the course of the study, the effects of the starting point and the central angle of solar array are discussed in detail. In addition, the optimal results of the solar array layout for four common situations are investigated using the method. The results indicate that this method is helpful in the preparation stage for installing large area flexible solar arrays.