High energy density regenerative fuel cell systems for terrestrialapplications

Regenerative Fuel Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system. The results from this study of a lightweight RFCS energy storage system for a remotely piloted, solar-powered, high altitude aircraft indicate an energy density up to 790 wh/kg with electrical efficiency of 53.4% is attainable. Such an energy storage system would allow a solar-powered aircraft to carry hundreds of kilograms of payload and remain in flight indefinitely for use in atmospheric research, Earth observation, resource mapping, and telecommunications. Future developments in the areas of hydrogen and oxygen storage, pressure vessel design, higher temperature and higher pressure fuel cell operation, unitized regenerative fuel cells, and commercial development of fuel cell technology will improve both the energy density and electrical efficiency of the RFCS     

Comparative analysis of energy storage media and techniques

Techniques for storing and converting energy from one form to another are examined. The parameters of interest are storage density (in terms of both energy and power), conversion efficiency, and number of steps in the conversion process. The techniques compared are electrostatic, magnetic, inertial, chemical, thermal, and nuclear. Each technique for storage is discussed in terms of the ease with which the energy can be converted to electricity for powering lightweight compact power systems for a variety of uses. The storage density associated with the various mechanisms spans an enormous range (~0.5 MJ/kg to ~10⁵ MJ/kg). The impact upon time-to-refuel within the context of mobile tactical army applications is discussed     

Space power systems requirements and issues: the next decade

Some of the more important space power technology issues, requirements, and challenges of the 1990s are described, and the impact of new component technology on the overall performance of space power systems is assessed. Advanced component, subsystem and system technologies that will significantly affect the performance, reliability, and survivability of next-generation baseload and burst mode space power systems are emphasized. Technology disciplines related to power sources (solar/nuclear and chemical), power conversion, energy storage, power conditioning/distribution and control, and waste-heat acquisition, transport, and rejection are primarily addressed. For some of them, performance trends that can be used as the basis for projecting future advanced power-system performance are developed. Performance capabilities for several different types of space power system for both baseload and burst mode applications are postulated on the basis of evolving technology and point designs that incorporate projections of advanced component capabilities     

基于冷热电一体化的舱外航天服生命保障系统性能

基于质子交换膜燃料电池（PEMFC）和热驱制冷,提出一种舱外航天服生命保障系统冷热电一体化方案.在分别建立金属储氢装置、PEMFC、热驱制冷系统和辐射散热器数学模型的基础上,利用冷热电一体化的热力学分析理论和方法进行了典型案例的计算,并重点分析了核心构件热驱制冷装置的参数对舱外航天服生命保障系统性能的影响.与传统的冷热电分产舱外航天服生命保障系统比较,该系统仅消耗84.6g氢气,且不需要向空间排放工质,能源利用率高达85.29%,在工质消耗与能源利用率上有较大的优势.      

基于最小跳数的无线传感器网络跨层设计

传统的严格分层参考模型无法实现对无线传感器网络资源的有效管理和运用,跨层设计是提高网络整体性能的一种有效方法。针对无线传感器网络能量、计算资源、存储资源和带宽资源有限的特点,提出一种基于最小跳数的路由层和MAC层的跨层协议设计方案。MAC层和路由层通过共享sensor节点到sink节点的最小跳数信息,在MAC层建立时间梯度,解决多个节点共享无线信道的问题;并在路由层建立路由表,解决路由选择问题。仿真结果表明,该方案在降低网络能耗的同时,在降低传输延迟,提高数据投递率方面也取得了良好的性能。     

Microsatellite combined attitude/energy systems

We have constructed a high-temperature super conductor-magnet momentum wheel for microsatellites and propose a micro high-temperature superconductor energy storage and attitude control system for nano/pico satellites. The momentum wheel for micro satellites has a mass of 1.1 kg with an angular momentum capacity of 3.5 J sec. It occupies a volume of 12.7 cm in diameter and 5 cm in height. It operates within the restricted power budget of a microsatellite with a total power supply of only 10 watts. It consumes less than 1 watt for sustenance. The micro high-temperature superconductor flywheel for nano/pico satellites has an angular momentum capacity of 0.083 Js and stores 2.32 kJ at 530 krpm. Its energy storage capacity is approximately 45 Wh/kg with an energy density of around 370 kJ/L. The HTS systems can perform the dual function of a power/attitude control system and are ideally suited for low Earth orbit energy storage, power generation, and attitude control of spacecraft.     

Optimization of project-ballistic parameters for low earth orbit spacecraft with propulsion systems with energy storage

Optimization of project-ballistic parameters of the spacecraft with propulsion systems with energy accumulation during the orbital transfer between low Earth orbits in the non-central gravitational field of the Earth is considered. The mass model of the spacecraft with an uncontrollable power-limited engine with the energy accumulator is used. The method of the project-ballistic optimization is obtained as an iterative procedure. Energy storage usage efficiency during the orbital transfer between low Earth orbits is estimated.     

多重化双向Buck/Boost变换器控制策略仿真研究

多重化双向Buck/Boost变换器常作为能量交换接口用于储能系统中。采用基本建模法对三重化双向Buck/Boost变换器建立交流小信号模型,基于变换器的开环特性,设计了电压、电流补偿网络,在此基础上提出一种新的基于前馈校正的复合双闭环控制策略。为验证所提控制策略的正确性进行了MATLAB仿真研究。仿真结果表明:该控制策略可为三重化双向Buck/Boost变换器提供良好的动、稳态性能,同时对大范围的负载变化等扰动均具有很好的鲁棒性。     

航天器测控系统数据库特点及性能测试策略

航天器测控系统的数据量大,信息关联复杂,一般都用大型的关系数据库作为其数据存储与管理的基础平台。存储系统建成后,数据库性能究竟如何,数据库性能该如何衡量,这一直是系统集成者和应用者关心的课题。本文从测控数据库的特点出发,客观分析了数据库实际运行性能,提出了一种较为全面的航天器测控系统数据库的性能测试策略。     

一种低温低漏率高可靠的飞轮钎焊工艺方法研究

飞轮壳体密封焊接是飞轮装配的关键工序,针对飞轮在真空环境下长期保持低漏率的真空度稳定性、焊接温度不能超过80℃以及焊缝承压能力超过0.5MPa的高要求,通过低温钎料的选择及润湿性分析、钎焊接头剪切强度分析及飞轮钎焊工艺研究,摸索出了一种低温低漏率高可靠的飞轮钎焊工艺方法。本文以某型飞轮壳体组件焊接为例,通过高低温、振动、冲击等试验后保证飞轮真空度保持不变来验证该焊接方法可行性和可靠性。     

Flywheel technology: past, present, and 21st century projections

This paper describes the present status of flywheel energy storage technology, or mechanical batteries, and discusses realistic future projections that are possible based on stronger composite materials and advancing technology. The origins and use of flywheel technology for mechanical energy storage began several hundred years ago and was developed throughout the Industrial Revolution. One of the first “modern” dissertations on the theoretical stress limitations of rotational disks (isotropic only) is the seminal work by A. Stodola whose first translation to English was made in 1917. The next big milestones were during the 1960s and 1970s when NASA sponsored programs proposed energy storage flywheels as possible primary sources for space missions. However, it was not until the 1980's when microelectronics, magnetic bearing systems and high power density motor-generators became enabling technologies. The next decade proved that a mechanical battery could surpass chemical batteries for many applications     

Synthetic Aperture Processing with Limited Storage and Presumming

The number of transmitted pulses associated with the Doppler histories of a side-looking radar may greatly exceed the desired azimuth compression ratio of the system. This discrepancy is taxing if the storage required for the azimuth processing is provided by cores, magnetic drums, and the like. Thus, as a practical matter, one considers presumming of the data prior to correlation in an attempt to achieve the desired performance with a minimum amount of digital storage. In this paper, the optimum (in terms of resolution) presummer is derived, along with the optimum apportionment of the available storage capacity between the presumming and correlation operations. Under the condition (or generally pessimistic approximation) that the illumination pattern of the antenna uniformly illuminates a Doppler bandwidth equal to the PRF of the radar, the optimum presumming coefficients are the first Np Fourier coefficients of a function which is one of the Doppler bandwidth to be correlated and zero on the remainder of the PRF bandwidth, where Np is the number of transmitted radar pulses over which presumming is provided. Increasing Np reduces the degradation due to presumming, but may leave inadequate storage for correlation. Hence, we optimize the apportionment between the two operations and present the obtainable resolution as a function of total storage and the number of transmitted pulses in the received Doppler history.     

SMES benefit analysis using a production cost model for Puget Soundapplication

Superconducting magnetic energy storage (SMES) is an emerging technology that is expected to provide a means of storing electrical energy for use during peak demand periods. Pacific Northwest Laboratory (PNL) has estimated benefits and costs associated with the use of SMES technology and has provided insight into the overall future potential of SMES in the service area of the Bonneville Power Administration (BPA) and on systems that connect and exchange power with BPA     

What is systems engineering?

There are probably more definitions of “Systems Engineering” than there are AESS members. In its simplest form systems engineering is the design of the whole as opposed to the design of the parts. The vast number, complexity and diversity of elements can overwhelm and degrade system performance and reliability. Embedded processing and software can be both a boon and a bane. A systems engineer analyzes and optimizes an ensemble of elements that relate to the flow of energy, mass and communications into a design that performs the desired function. “Systems engineering” is used herein to cover a very broad spectrum of processes and controls to engineer a product at the many levels required to satisfy all aspects of the original requirement. Our definition is not intended to either include or exclude systems engineering and integration as used in the computer field. In any case, systems engineering is the application of solid engineering principles to design and develop a large enterprise within cost and schedule to satisfy the needs of the ultimate user. It involves conceptualization, design, development, test, implementation, approval/certification and operation (including human factors) of a system. In essence, systems engineering is a problem-solving discipline for the modern world     

Performance characteristics of lithium-ion cells for NASA's Mars2001 Lander application

NASA requires lightweight rechargeable batteries for future missions to Mars and the outer planets that are capable of operating over a wide range of temperatures, with high specific energy and energy densities. Due to the attractive performance characteristics, lithium-ion batteries have been identified as the battery chemistry of choice for a number of future applications, including Mars rovers and landers. The Mars 2001 Lander (Mars Surveyor Program MSP 01) will be one of the first missions which will utilize lithium-ion technology. This application will require two lithium-ion batteries, each being 28 V (eight cells), 25 Ah and 8 kg. In addition to the requirement of being able to supply at least 200 cycles and 90 days of operation on the surface of Mars, the battery must be capable of operation (both charge and discharge) at temperatures as low as -20°C. To assess the viability of lithium-ion cells for these applications, a number of performance characterization tests have been performed, including: assessing the room temperature cycle life, low temperature cycle life (-20°C), rate capability as a function of temperature, pulse capability, self-discharge and storage characteristics, as well as mission profile capability. This paper describes the Mars 2001 Lander mission battery requirements and contains results of the cell testing conducted to-date in support of the mission,     

Heating and cooling battery electric vehicles-the final barrier

Battery electric vehicles (EVs) present a particular challenge to the development of more efficient and effective heating and cooling systems for automotive applications. Because heating-ventilating-air-conditioning (HVAC) systems are electrically powered, vehicle range is reduced when the HVAC system is operating. The alternative solutions to HVAC battery electric vehicles are identified and evaluated. These include a basis for determining HVAC boundary design assumptions and showing mathematical methods for estimating the HVAC load and energy requirements, and evaluation of the new European and Japanese approaches to wintertime heating, such as NaS battery, motor and component waste heat recovery, electric seat warmer, radiant foot warmer, electric windshield and backlight defrost, molten salt latent heat storage, metal hydride hydrogen storage and catalytic heater, and liquid fueled heater     

Electrical power subsystem initial sizing

The basics of performing the initial electrical power subsystem (EPS) sizing for a spacecraft using solar cells for an energy source and batteries for energy storage are covered. The basic engineering inputs are described. The outputs are the first estimate of the number of solar cells, the solar array area, and the number of batteries required. A spreadsheet program to keep track of the inputs, perform the calculations, and document the inputs and outputs was written     

Future trends in space power technology

The status of the US Air Force Space Power Research and Development Program is summarized. Generic issues and requirements affecting the strategic planning of space power advances for the 1990s and beyond are described. The major thrusts of the Air Fore part of the Strategic Defense Initiative Office Space Power Program are highlighted, with emphasis on the ongoing advanced component technology development program. The status of these component technologies in the areas of power sources, energy storage, power management and distribution, and thermal management is described. Technology projections for the full range of envisioned technology options for the foregoing are used as the basis for a series of point designs for deriving the subsystem- and system-level benefits of the technologies. The primary focus is on baseload (CW) power systems operating in the range from 100 W for small satellites to 50 kW for potential large surveillance satellites. The secondary focus is on large, multimegawatt pulsed power systems and related components for potential applications such as directed energy. Potential `trump card' technologies related to energy conversion, storage, power electronics, and thermal management are identified     

多电飞机混合储能系统的设计与仿真

多电飞机直流配电系统是电功率传输的核心,由于涡轮电机的单向性,系统并不完全可逆。为了维持直流汇流条的稳定、提高能源效率,需建立相应的存储和消耗系统。研究了一种带有超级电容器的多电飞机储能系统,分析了该系统中超级电容器的作用及其控制策略,根据超级电容器本身的特性利用Matlab/Simulink软件建立相应仿真模型,并针对于飞机电网突加和突卸负载时电压不同状态设计了相应控制策略,通过仿真实验验证了带有超级电容器的混合储能系统的有效性。