High-efficiency GaInP/GaAs tandem solar cells

GaInP/GaAs tandem solar cells have achieved new record efficiencies, specifically 25.7% under air-mass 0 (AMO) illumination, 29.5% under AM 1.5 global (AM1.5G) illumination, and 30.2% at 140-180x concentration under AM 1.5 direct (AM1.5D) illumination. These values are the highest two-terminal efficiencies achieved by any solar cell under these illumination conditions. The monolithic, series-connected design of the tandem cells allows them to be substituted for silicon or gallium arsenide cells in photovoltaic panel systems with minimal design changes. The advantages of using GaInP/GaAs tandem solar cells in space and terrestrial applications are discussed primarily in terms of the reduction in balance-of-system costs that accrues when using a higher efficiency cell. The new efficiency values represent a significant improvement over previous efficiencies for this materials system, and we identify grid design, back interface passivation, and top interface passivation as the three key factors leading to this improvement. In producing the high-efficiency cells, we have addressed nondestructive diagnostics and materials growth reproducibility as well as peak cell performance     

Lightweight (AlGaAs)GaAs/CuInSe2 tandem junction solarcells for space applications

Mechanically stacked tandem cells consisting of GaAs thin-film upper cells and CuInSe₂ thin-film lower cells have been developed to meet the increasing power needs projected for future spacecraft. The authors report the fabrication of the first highly efficient lightweight GaAs/CuInSe₂ tandem cell on a 2-mil thick substrate, update recent performance improvements in thin-film GaAs/CuInSe₂ tandem cells, and discuss their application to space power systems. The efficiency of 4-cm² cells has improved to 21.6% AM0, the highest ever reported for a thin-film photovoltaic cell. Lightweight 4-cm² tandem cells have been successfully fabricated with efficiencies as high as 20.8%. These cells weighed about 180 mg without optimized substrate trimming. Radiation and operating temperature effects on GaAs/CuInSe₂ tandem cells are also discussed, and an interconnect scheme to form a voltage-matched string is described     

Large area solar cells for future space power systems

Space silicon solar cell technology has matured to the extent that large-area planar silicon cells can be fabricated in sizes up to 8 cm×8 cm with efficiencies up to approximately 15%. In order to achieve substantially higher efficiencies, cells based on GaAs are required. It is shown that, subject to certain boundary conditions, the efficiency of GaAs/Ge cells can reach 24% when used in the dual-junction configuration or approximately 19.5% if the Ge substrate is passive. The electrooptical properties of these cells are reviewed, and prospects for achieving these efficiency goals are presented. Experimental performance data are given     

Design and integration of a solar AMTEC power system with anadvanced global positioning satellite

A 1,200-W solar AMTEC (alkali metal thermal-to-electric conversion) power system concept was developed and integrated with an advanced global positioning system (GPS) satellite. The critical integration issues for the SAMTEC with the GPS subsystems included: (1) packaging within the Delta II launch vehicle envelope; (2) deployment and start-up operations for the SAMTEC; (3) SAMTEC operation during all mission phases; (4) satellite field of view restrictions with satellite operations; and (5) effect of the SAMTEC requirements on other satellite subsystems. The SAMTEC power system was compared with a conventional planar solar array/battery power system to assess the differences in system weight, size, and operations, Features of the design include the use of an advanced multitube, vapor anode AMTEC cell design with 24% conversion efficiency, and a direct solar insolation receiver design with integral LiF salt canisters for energy storage to generate power during the maximum solar eclipse cycle, The modular generator design consists of an array of multitube AMTEC cells arranged into a parallel/series electrical network with built-in cell redundancy. Our preliminary assessment indicates that the solar generator design is scaleable over a 500 to 2,500-W range. No battery power is required during the operational phase of the GPS mission. SAMTEC specific power levels greater than 5 We/kg and 160 We/m² are anticipated for a mission duration of 10 to 12 years in orbits with high natural radiation backgrounds     

GaAs系列太阳电池技术与发展

GaAs系列太阳电池是目前太空应用最广泛的电源,这一系列太阳电池已成为太阳电池领域的研究热点.介绍了GaAs太阳电池的研究历程和最新技术动态.     

Thermionic/AMTEC cascade converter concept for high-efficiencyspace power

This paper presents trade studies that address the use of the thermionic/AMTEC cell-a cascaded, high efficiency, static power conversion concept that appears well-suited to space power applications. Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power. Thermionics offers system compactness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature. From a thermal viewpoint, the two are ideally suited for cascaded power conversion: thermionic heat rejection and AMTEC heat source temperatures are essentially the same. In addition to realizing conversion efficiencies potentially as high as 35-40% such a cascade offers the following perceived benefits: Survivability-capable of operation in the Van Allen belts; Simplicity-static conversion, no moving parts; Long lifetime-no inherent life-limiting mechanisms identified; Technology readiness-Large thermionic database; AMTEC efficiencies of 18% currently being demonstrated, with more growth potential available; and Technology growth-applicable to both solar thermal and reactor-based nuclear space power systems. Mechanical approaches and thermal/electric matching criteria for integrating thermionics and AMTEC into a single conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present-day technology in cascaded thermionic/AMTEC systems     

ATS-6 Solar Cell Flight Experiment After 325 Days in Synchronous Orbit

Preliminary Applications Technology Satellite-6 (ATS-6) solar cell flight experiment data through the first 325 days in synchronous orbit is present. The experiment is transmitting data on 16 different solar cell/cover glass configurations. The experiment is designed to study the effect of this orbit on select solar cells and cover glass parameters such as solar cell thickness and base resistivity, cover glass thickness variation, new cover and adhesive processes and materials such as 7940 and 7070 integral covers and the fluorinated ethylene propylene (FEP) covers, the COMSAT "violet" cell, and backside irradiation effects. The in-spece solar cell data indicate short circuit currents are higher by 1 to 8 percent than measurements made with solar simulations; maximum power varied between -1 to +6 percent . Degradation of /sc due to ultraviolet effects was determined to be about 2 percent after 50 days in orbit. All cells performed well through 325 days in orbit, except the FEP-covered cells, which appear to have increased their rate of degradation during the first eclipse season.     

Integration of Large Power Systems into Manned Space Stations

Essential design factors and system characteristics are explored for integration of large power systems into manned space stations. The impact of the type of power system selected upon the space station is outlined, as is the impact of the mission requirements upon the selection of power systems. Criteria for resolving the selection/application/ integration problems are provided. Comparisons between systems are based on recently defined space-station models for 90-day to five-year mission durations in the 1970' s, with four-to nine-man crews. Power systems encompass power levels from 3 to 50 kWe and include solar cell/battery. fuel cell, hybrid fuel cell/solar cell, radioisotope, and nuclear reactor systems. Thermoelectric, Brayton cycle, organic Rankine, and liquid-metal Rankine power conversion systems are considered for the nuclear energy sources. Both rigid and roll-out photovoltaic array configurations are analyzed with respect to the solar energy source.     

考虑局部遮挡的太阳能无人机能源控制

针对太阳能无人机在飞行状态下可能出现的太阳能电池局部遮挡情况，开展相应的太阳能电池最大功率点追踪算法和能源控制研究。通过将发光亮度引入相对吸引力计算过程对萤火虫算法进行改进，实现了局部阴影情况下太阳能电池最大功率点的高效追踪。以此为基础，设计了考虑局部遮挡情况下太阳能无人机的太阳能电池/蓄电池混合能源状态机控制规则。以"蒲公英I"无人机为例，建立了太阳能电池阵列模型，开展了考虑局部遮挡情况下太阳能电池最大功率点追踪仿真实验；基于"蒲公英I"飞行剖面，开展了考虑局部遮挡情况的混合能源控制仿真试验。研究结果表明：改进的萤火虫算法可以实现在局部阴影情况下太阳能电池最大功率点的有效跟踪，与萤火虫算法相比收敛时间更短、且功率波动幅度更小；采用改进萤火虫算法和状态机能源管理策略，在考虑局部遮挡的飞行状态下可以实现太阳能电池/蓄电池之间的合理功率分配与控制。     

Generation Schemes for Wind Power Plants

This paper reviews various electric generation schemes for wind energy conversion suitable for interconnection with a power grid. The schemes can be generally classified as constant speed constant frequency (CSCF) and variable speed constant frequency (VSCF) systems. Historically, only CSCF systems have been used for large power generation in wind power plants. However, with the advent of power electronics and the availability of solid state devices capable of handling large amounts of power, VSCF systems are becoming competitive. Various schemes under each classification are discussed and compared. It is stressed, however, that the optimum choice of the generating scheme is not decided by considering the generator alone. The optimum choice is one which minimizes the cost of energy generated by the wind power plant.     

行波管放大器非线性特性对调幅信号边带压缩影响

为了更精确地测试星上功率放大器的饱和点,研究分析了TWTA(Travelling-Wave Tube Amplifier,行波管放大器)的非线性特性对AM(Amplitude Modulation,调幅)信号的边带压缩影响。文中基于Saleh模型描述TWTA,分析其在AM信号放大过程中的非线性特性,研究表明:随着输入AM信号的功率不断增大,放大后的输出信号畸变越来越严重;该变化主要体现在AM信号的边带上,与线性工作区相比,在TWTA的饱和点处,经放大后的AM信号的边带压缩程度达到最大。实验结果与理论分析结果完全一致。该研究为通信卫星星上功放饱和点测试提供了一种可行方法。     

POWOW: power without wires: a SEP concept for space exploration

Electric propulsion has emerged as a cost-effective solution to a wide range of satellite applications. Deep Space 1 successfully demonstrated electric propulsion as the primary propulsion source for a satellite. The POWOW concept is a solar-electric propelled spacecraft capable of significant cargo and short trip times for traveling to Mars. It would enter aerosynchronous orbit and from there, beam power to surface installations via lasers. The concept has been developed with industrial partner expertise in high efficiency solar cells, advanced concentrator modules, innovative arrays, and high power electric propulsion systems. The latest version of the spacecraft, the technologies used, and trip times to Mars are presented. The POWOW spacecraft is a general purpose solar electric propulsion system that uses new technologies that are directly applicable to commercial and government spacecraft with power levels ranging from a LEO power level of 4 kW up to GEO spacecraft about 1 MW. The system is modular, expandable, and amenable to learning curve cost projection methods     

Ultra-lightweight space power from hybrid thin-film solar cells

The development of hybrid inorganic/organic thin-film solar cells on flexible, lightweight, space-qualified, durable substrates provides an attractive solution for space power generation with high mass specific power (W/kg). The high-volume, low-cost fabrication potential of organic cells will allow for square miles of solar cell production at one-tenth the cost of conventional inorganic materials. Plastic solar cells take a minimum of storage space and can be inflated or unrolled for deployment. We explore a cross-section of NASA in-house and sponsored research efforts that aim to provide new hybrid technologies that include both inorganic and polymer materials as active and substrate materials. For NASA applications, any solar cell or array technology must not only meet weight and AMO efficiency goals, but also must be durable enough to survive launch and space environments. Also, balance of system technologies must be developed to take advantage of ultra-lightweight solar arrays in power generation systems.     

分布式电推进飞机电力系统研究综述

继飞机二次能源逐步统一为电能形成多电/全电飞机之后,电推进技术成为飞机动力系统电气化的重要发展方向,有望进一步提高飞机动力系统能量转换效率、降低燃油消耗和排放,代表了航空电气化的高级阶段。飞机电力系统及相关技术是支撑电推进技术发展的重要基础。系统总结了电推进飞机的类型与发展现状,论述了飞机混合动力系统及分布式电推进系统的基本概念、特点与意义。阐述了航空电推进系统的基本结构,比较了适用于分布式电推进系统的电力系统架构,系统分析了实现电推进技术所需的高效高功率密度电机、高效大容量功率变换器和综合热管理等关键技术。小型纯电动飞机正在逐步迈向实用化,而分布式混合电推进技术是中大型飞机电气化的重要方向,仍然需要航空机电和动力系统等交叉融合与创新发展。     

航空用燃料电池及混合电推进系统发展综述

随着世界范围内碳减排需求的日益增长及长航时飞机的发展需要,高效率的燃料电池航空电推进系统逐渐受到重视,氢能航空的理念被人们所熟知。可使用碳氢燃料的高温燃料电池还可与燃气涡轮组成混合动力系统,发电效率进一步提高至70%。本文首先回顾了燃料电池及燃料电池涡轮混合系统在航空能源、动力系统方向应用概况;接着,概述了几种突破现有涡轮发动机技术瓶颈的新概念混合电推进系统,如发电与推进一体化燃料电池涡轮混合动力系统和无涡轮燃料电池混合推进系统;基于此,本文分析了限制燃料电池混合系统实际应用的关键技术难题,主要体现在混合动力系统功重比较低、大分子碳氢燃料重整技术未突破两方面。     

InAsP cells for solar thermophotovoltaic applications

High temperature wide band gap InAsP cells have been specifically designed and fabricated for operating temperatures up 250°C to match with selective emitters operating near 1 μm in a TPV system. An important assumption is that the emitters can be heated up to the range of 1400 K to 2000 K by either solar concentrators or some other heat source. The efficiency of a selective emitter, which can be selected depending on the emitter operating temperatures, will be significantly higher than either a blackbody or a graybody emitter. The key for the TPV success is that the match between the band gap and selective emission must occur at the cell operating temperature. An appropriate cell band gap needs to be carefully selected; so when the band gap shrinks at the operating temperature, the desired match can be achieved. In this paper, two types of InAsP cells were investigated for this concept. The performance of these cells at elevated temperature and energy conversion efficiency are reported in this paper     

Silicon Solar Cell Performance at High Intensities

The theoretical and experimental work performed since 1960 in the area of high-intensity and high-temperature operation of silicon and gallium arsenide photovoltaic devices is reviewed. Test results for conventional 5-grid silicon cells, for specially designed 13-grid silicon cells, and for a GaAs cell are presented parametrically for the illumination intensity range from 0.07 to 2.8 W/cm2 and the temperature range from 30 to 1 50°C. The data cover the 3 points on the currentvoltage characteristic required to reconstruct the full characteristic in the power-generating quadrant. The 13-grid silicon cells showed much better performance than the GaAs cell.     

Wireless power transmission: the key to solar power satellites

Maturing of the enabling technologies has provided much of the infrastructure to support the development of a commercial Solar Power Satellite program. Solar Space Industries was formed to accomplish this goal. The basis of their development plan is to build a Ground Test Installation that will duplicate, in small scale on the Earth, all aspects of the power generating and power transmission systems except for the space environment and the range and size of the energy beam. Space operations issues will be separated from the power generation fixation and verified by testing. Doing the developmental testing on the ground instead of in space will result in a low cost program that can be accomplished in a very short time. The concept is to build a Ground Test Installation that couples an existing 100 kW terrestrial solar cell array to a phased-array wireless power transmitter based on a subarray. Power will be transmitted over a 1-¼ mile range to a receiving antenna and then fed into a commercial utility power grid. The objective is to demonstrate the complete function of the Solar Power Satellites, with the primary issue being the validation of practical wireless power transmission. The key features to demonstrate are: beam control, stability, steering, efficiency, reliability, cost, and safety     

自动变桨距螺旋桨电推进系统能效优化方法

为了提升自动变桨距螺旋桨电推进系统的整体效率,引入最优功率控制规律：自动变桨距螺旋桨电推进系统可根据飞行工况和推力需求,同时调节桨距角和螺旋桨转速两个变量,最终获得一组桨距角和螺旋桨转速的组合,使得推进系统在满足推力需求的情况下实现最小的功率消耗,最终达成飞行任务剖面内最小能耗控制的目标。为了验证方法的有效性,针对同一电推进系统,分别采用最优功率控制规律和恒速控制规律完成相同的飞行任务剖面,获得了两种控制规律下的螺旋桨推进效率、电动机效率、电推进系统总效率和电推进系统能耗数据。结果证明：相较于恒速控制规律,最优功率控制规律能够有效的提升电推进系统效率并降低能耗,完成相同飞行任务剖面的能耗降低6.3%左右。     

基于自适应滤波的引信噪声调幅干扰抑制

噪声调幅干扰是一种有效的压制性干扰,可压制近炸无线电引信对目标信息的获取。为提高连续波多普勒无线电引信抗噪声调幅干扰的能力,将单频率自适应陷波器应用到连续波多普勒引信中,对噪声调幅干扰进行抑制。分析了噪声干扰抑制原理,并对噪声干扰抑制效果进行了仿真。仿真结果表明：SJR=-10dB时,仍然能达到很好的噪声调幅干扰抑制效果。