基于最小二乘有限元的导热系数直接反算方法

导热系数是温度场计算分析中的重要参数,针对基于优化方法反演导热系数计算量大、收敛慢、易陷入局部最优解等问题,提出了一种基于最小二乘有限元的直接反算方法,可快速得到材料导热系数。该方法是将有限单元法和最小二乘法引入热传导方程,直接求解材料导热系数时空分布,不需要进行大量的正算和迭代过程,大大提高了计算效率,且由于不需要事先假定导热系数分布函数形式,保证了计算精度。最后,以水泥砂浆导热系数测试试验为例,验证了最小二乘有限单元法在导热系数反算中的适用性和可靠性。     

复杂系统振动能量平衡方程中SEA参数的测定

本讨论了利用功率射入法解决由实验测定结构内部损失参数和耦合损失参数的问题，研究了ＳＥＡ能量平衡方程系数矩阵的方法，提出了一种简便实用的由理论结合实验确定子系统能量和等效质量的方法，并岂此计算能量平衡系统内部损失参数和耦合损失参数。中还导出了在结构２响应频带内存在模态密集和拍振现象时，分析测定系统平衡能量和计算能量损失参数的方法。     

太阳能驱动的固体氧化物电解池制氢系统性能研究

采用太阳能驱动电解水制氢是实现将太阳能转换为氢能来存储的最佳方式。该文提出一种采用光伏、光热协同驱动固体氧化物电解池（SOEC）进行高温蒸汽电解的制氢系统。建立各子系统数学模型,选取北京地区夏至日气象参数,分析太阳辐照度对制氢系统的性能影响,最后对整个系统进行能量及火用分析。结果表明,电流密度和温度是影响SOEC工作的重要因素。在电流密度较大的情况下升高温度,将有利于提高电解效率。耦合太阳能后系统最大能量及火用效率分别达到19.1%和20.3%。火用分析结果表明系统最大有用功损失发生在光电转换过程,火用损比例为87%。提升光电效率,将成为提高太阳能-氢能转换效率的关键。     

大型太阳能烟囱发电站热力分析与计算

利用热力学方法建立太阳能烟囱发电系统中集热棚、烟囱及风力透平的热气流能量转换过程的理论模型及求解方法.鉴于太阳能烟囱发电站的大尺寸特征,采用一维假设建立热气流传热模型,使用龙格-库塔方法对非线性能量方程进行数值求解.对集热棚直径3 600 m,烟囱高950 m,设计功率100 MW的大型太阳能烟囱发电站进行分析与计算,给出了该电站的风力透平轴功率随质量流量和太阳辐射强度变化的规律,为风力透平机组提供热力气动设计参数,为大规模开发利用太阳能提供借鉴.     

水蒸汽热力学性质的通用计算模型

结合汽轮机热力计算的实际需要,以前苏联热工研究所提供的水蒸汽性质计算模型为基础,讨论了当P-t、P-h、P-s、t-h、t-s、h-s等参数为已知时,水蒸汽其它热力学性质参数非线性方程的迭代求解及迭代加速等有关问题。按模型的特点,构造了收敛的迭代函数,给出了水蒸汽热力学性质的通用计算模型,并讨论了迭代初值的计算。     

新型太阳能热泵干燥系统的设计与理论研究

结合金属氢化物热泵的特点,提出了一种耦合氢能的太阳能热泵干燥系统。具体介绍了其系统工作原理及流程,建立了系统各设备的能量转换及炯分析模型;以干燥种子的算例分析了不同参数对系统性能的影响。结果表明,系统具有较高的除湿率(SMER)值,且其主要与太阳能辐射量大小有关;系统优化应以太阳能辐射量为基础,以提高金属氢化物热泵的(火用)效率为目标,而系统与太阳能蓄热技术的耦合运用是发展的另一个方向。     

太阳能驱动的膜式除湿系统能量匹配研究

定义溶液冷却与加热过程的能量匹配系数,分析得到该系数受除湿与再生侧溶液流量比的影响较大,而受太阳能加热器出水温度和冷却水流量的影响小。增加除湿与再生侧的溶液流量比,降低太阳能加热器出水温度,增大冷却水流量,同时调控3个参数可使系统的能量供需平衡。通过中国南方典型湿热气候条件实例分析,得出整个系统的能量达到匹配时的参数,系统的性能得到有效提高,为系统的实际运行提供指导。     

串联直驱浮子式波浪能发电装置能量捕获研究

以振荡浮子式波浪能发电装置为研究对象,探讨在串联不同数量直线发电机的情况下装置在规则波中的能量捕获情况。基于势流理论,并考虑垂荡运动,建立浮子与电机的耦合运动方程,应用四阶龙格库塔法数值求解,得到能量捕获宽度比,并对能量输出系统质量比和弹簧刚度系数的影响进行研究,对串联不同数量直线发电机情况下能量捕获的差异进行分析。结果表明:适当选取参数,串联装置可在波浪频率较低时比单个发电机的装置捕获更多能量,同时能量吸收频谱带宽增加。     

我国研制太阳能无人飞机

记者从在珠海市举办的第四届珠海航展获悉,一项名为“绿色先锋”的中国太阳能无人驾驶飞机探索研制计划已经正式启动,由珠海新概念航空器研究中心设计的世界首创的“复合飞翼”式太阳能无人机已经完成了原机1/4大小的技术验证机试飞,明年底1/2比例的技术验证机也将腾空而起。这标志着我国在太阳能无人驾驶飞机研制方面取得了新的突破。太阳能机可做军事“FBI”据介绍,太阳能无人驾驶飞机由于能在高高空长航时飞行而有着十分广阔的应用前景。这种飞机在发生地震、洪灾或者森林火灾时,可以替代中断的通信,使受灾地区与外界保持联络;还能在台…     

基于太阳能热驱动甲烷重整制氢的燃料电池发电系统性能研究

该文采用Aspen Plus软件建立膜反应器重整制氢及燃料电池模型,根据拉萨某日太阳能直接辐射强度（DNI）变化计算太阳能可供使用的能量,作为外热源输入重整系统,并分析反应温度、水碳比（S/C）及DNI对该系统各性能指标的影响,性能指标包括甲烷转化率、H₂收率、电池功率及电压、太阳能转换为氢能的效率。结果表明：反应温度为500 ℃,S/C为2.5时有利于太阳能甲烷湿重整反应;系统日性能结果显示在某日10:00—20:00时,电池输出功率120 kW,太阳能-化学能转化效率0.368,系统发电效率0.225。     

Double-layer fuzzy adaptive NMPC coordinated control method of energy management and trajectory tracking for hybrid electric fixed wing UAVs

The energy management and trajectory tracking control are crucial to realize long-endurance autonomous flight for hybrid electric UAVs. This study aims to comprehensively consider energy management and trajectory tracking for hybrid electric fixed wing UAVs with photovoltaic panel/fuel cell/battery. A double-layer fuzzy adaptive nonlinear model predictive control method (DFNMPC) is proposed. Separated by the surplus demand power, energy management and trajectory tracking problem are decoupled into the high-layer fuzzy adaptive nonlinear model predictive controll problem (H-FNMPC) and low-layer fuzzy adaptive nonlinear model predictive controll problem (L-FNMPC). H-FNMPC solves the trajectory tracking and navigation control probelm for the greatest benefit of solar energy. L-FNMPC solves the power allocation problem of hybrid energy system for minimum equivalent hydrogen consumption. A fuzzy adaptive prediction horizon adjustment method based on UAV maneuvering degree is proposed to effectively improve proposed method adaptability to different mission profiles. Analogously, a fuzzy adaptive equivalent hydrogen consumption factor adjustment method in L-FNMPC is proposed to ensure the flexible utilization of battery. In addition, an equivalent hydrogen flow rate calculation method based on the real-time current ratio is proposed for PV/FC/Battery hybrid energy system. Numerical simulation results including a spiral trajectory tracking and a quadrilateral trajectory tracking, demonstrate that DFNMPC can simultaneously handle energy management and trajectory tracking problem for hybrid electric UAVs. Compared to hierarchical fuzzy state machine strategy, DFNMPC can save 13.3% hydrogen for the spiral trajectory tracking, and 56.9% for the quadrilateral trajectory tracking. It indicates that the energy efficiency can be improved from both levels of energy management and flight motion. The proposed method prospected for exploring high-energy-efficiency autonomous flight of hybrid electric UAVs in the future.     

Exergetic optimization of flat plate solar collectors

In this paper, an exergetic optimization of flat plate solar collectors is developed to determine the optimal performance and design parameters of these solar to thermal energy conversion systems. A detailed energy and exergy analysis is carried out for evaluating the thermal and optical performance, exergy flows and losses as well as exergetic efficiency for a typical flat plate solar collector under given operating conditions. In this analysis, the following geometric and operating parameters are considered as variables: the absorber plate area, dimensions of solar collector, pipes' diameter, mass flow rate, fluid inlet, outlet temperature, the overall loss coefficient, etc. A simulation program is developed for the thermal and exergetic calculations. The results of this computational program are in good agreement with the experimental measurements noted in the previous literature. Finally, the exergetic optimization has been carried out under given design and operating conditions and the optimum values of the mass flow rate, the absorber plate area and the maximum exergy efficiency have been found. Thus, more accurate results and beneficial applications of the exergy method in the design of solar collectors have been obtained.     

Influence of the aerothermic parameters and the product quantity on the production capacity of an indirect solar dryer

Dryer production capacity can be quantified by the effectiveness coefficient “E_f” defined by the product mass per unit of time in permanent and continuous production. This coefficient depends on the aerothermic parameters and the product quantity contained in the dryer. Previous studies looked at the performances of the solar air collector, the drying chamber and the energy chain, which constituted the coupling of these two components. In this paper, is examined the influence of the aerothermic parameters, and that of product quantity, on the production capacity of this type of solar dryer. The paper concentrates on the elaborate theoretical model making it possible to simulate the running of the energy chain (collector–dryer) in forced convection.     

平流层飞艇能源系统建模与小信号稳定性分析

针对平流层飞艇能源系统,建立能反映该系统特性的小信号模型,特别是加入了推进用直流无刷电机,该模型能够描述能源系统各部分之间的输入输出关系和电源控制器的输出动态特性。另外,基于小信号模型和相应的线性化仿真结果,采用特征值法分析太阳辐照度、太阳电池工作温度、电源控制系统参数、电机转矩系数和电机控制系统参数等一些关键参数对能源系统小干扰稳定性的影响。该小信号模型的建立和分析结果为平流层飞艇能源系统的参数优化设计和稳定性分析提供了重要的参考依据。     

Technical and economic evaluation of solar hydrogen production by supercritical water gasification of biomass in China

A novel thermochemical method for solar hydrogen production was proposed by state key laboratory of multiphase flow in power engineering (SKLMFPE) of Xi’an Jiaotong University. In this paper, a technical and economic evaluation of the new solar hydrogen production technology was conducted. Firstly, the advantages of this new solar hydrogen production process, compared with other processes, were assessed and thermodynamic analysis of the new process was carried out. The results show that biomass gasification in supercritical water driven by concentrating solar energy may be used to achieve high efficiency solar thermal decomposition of water and biomass for hydrogen production. Secondly, the hydrogen production cost was analyzed using the method of the total annual revenue requirement. The estimated hydrogen production cost was 38.46RMB/kg for the experimental demonstration system with a treatment capacity of 1 ton wet biomass per hour, and it would be decreased to 25.1 RMB/kg if the treatment capacity of wet biomass increased from 1 t/h to 10 t/h. A sensitivity analysis was also performed and influence of parameters on the hydrogen production cost was studied. The results from technical and economic evaluation show that supercritical water gasification of biomass driven by concentrated solar energy is a promising technology for hydrogen production and it is competitive compared to other solar hydrogen production technologies.     

基于槽式聚光的光热反应与集热协同实验研究

设计一种全光谱太阳能分级分质利用系统进行光热协同反应与集热一体化实验研究。该系统通过光热协同催化材料将太阳光中紫外及部分可见波段光的能量转化为化学能进行储存,并利用系统中的集热材料将太阳光中部分可见及红外波段的光能转化为热能进行储存,从而实现对全光谱太阳能的综合利用。实验以光热协同分解水制氢为目标反应,利用导热油进行集热。结果表明,在反应材料表面温度为414 ℃的条件下,氢气产量为15.65 μmol/g,系统集热效率可达43.61%。     

Adaptive maximum power point tracking based on Kalman filter for hydrogen fuel cell in hybrid unmanned aerial vehicle applications

In this paper, an adaptive real-time estimation method based on Kalman filter is proposed for tracking the maximum power point (MPP) of a hydrogen fuel cell (FC) in hybrid unmanned aerial vehicle (UAV) applications. To achieve the adaptive MPP tracking (MPPT), a mathematical model for the hydrogen FC is established. Then, the recursive least square method is employed to identify the initial values of model parameters. On this basis, the MPP of the hydrogen FC under steady conditions can be derived. Furthermore, the state and observation equations based on Kalman filter are introduced to adaptively estimate the model parameters in real-time. Moreover, the real-time model parameters would be used to optimize the MPP in accordance with the operating conditions such that the adaptive MPPT can be achieved. Finally, various simulations and experiments are conducted to verify the effectiveness and accuracy of the adaptive MPPT for the hydrogen FC in hybrid UAV applications. Results show that the adaptive MPPT can not only track the MPP accurately in real-time, but also reduce the oscillation of the hydrogen FC. Compared with the MPPT methods based on perturb and observe (P&O) and particle swarm optimization (PSO), the maximum power tracking error of the adaptive MPPT can be improved by 2.83% and 1.10%, respectively.     

Identification of the building parameters that influence heating and cooling energy loads for apartment buildings in hot-humid climates

Identifying the building parameters that significantly impact energy performance is an important step for enabling the reduction of the heating and cooling energy loads of apartment buildings in the design stage. Implementing passive design techniques for these buildings is not a simple task in most dense cities; their energy performance usually depends on uncertainties in the local climate and many building parameters, such as window size, zone height, and features of materials. For this paper, a sensitivity analysis was performed to determine the most significant parameters for buildings in hot-humid climates by considering the design of an existing apartment building in Izmir, Turkey. The Monte Carlo method is selected for sensitivity and uncertainty analyses with the Latin hypercube sampling (LHC) technique. The results show that the sensitivity of parameters in apartment buildings varies based on the purpose of the energy loads and locations in the building, such as the ground, intermediate, and top floors. In addition, the total window area, the heat transfer coefficient (U) and the solar heat gain coefficient (SHGC) of the glazing based on the orientation have the most considerable influence on the energy performance of apartment buildings in hot-humid climates.     

Technoeconomics of large-scale clean hydrogen production – A review

Hydrogen is widely used in many industries, yet its role in the clean energy transition goes beyond being an element of these industries. Near-term practical large-scale clean hydrogen production can be made available by involving nuclear, solar, and other renewable energy sources in the process of hydrogen production, and coupling their energy systems to sustainable carbon-free hydrogen technologies. This requires further investigation and assessment of the different alternatives to achieve clean hydrogen using these pathways. This paper assesses the technoeconomics of promising hydrogen technologies that can be coupled to nuclear and solar energy systems for large-scale hydrogen production. It also provides an overview of the design, status and advances of these technologies.