综合能源系统优化运行研究现状及展望

为了充分消纳清洁能源、提高能源利用效率,综合能源系统的概念应运而生,相较于传统的能源单级利用形式,综合能源系统对电力、冷热和天然气等多种形式能源进行多级利用,通过多能互补提高综合能源利用效率。但是综合能源系统由于系统间耦合紧密,能源流动变化复杂,在优化运行方面相较于传统电网有较大差别。针对综合能源系统优化运行问题的研究现状进行了全面整理,首先介绍了综合能源系统的组成,对电力、热力和天然气的网络潮流模型的研究现状进行了归纳分析;其次对优化运行方法进行了分类总结,分析了现有方法的优缺点和难点;最后进行了展望,指明了综合能源系统优化运行未来的研究方向。     

考虑源-荷-储多能互补的冷-热-电综合能源系统优化运行研究

综合能源系统（integrated energy system,IES）以多能互补和能量阶梯利用为核心,将大大提高系统的能量利用率,实现多种能流互补优化。通过建立冷-热-电综合能源系统,以系统总运行成本最低为目标函数,考虑设备模型约束和功率平衡约束,采用日前负荷模拟综合能源系统经济优化运行;同时考虑到系统在冬、夏季运行工况差异较大,采用分季调节运行模式,利用分支界定（branch and bound,B-a-B）算法求解优化模型。仿真结果表明,系统能量供给平衡,"源-荷-储"互补搭配性强,系统运行灵活、经济高效,同时,系统污染气体排放量少,有利于环境保护。     

综合能源系统多时间尺度复合调度优化运行方法研究

针对综合能源系统多能网络与设备特性差异,该文建立集成热电联产机组、风力发电机组、燃气锅炉以及电转气等设备的综合能源系统运行框架;提出能反映能源站电、气能流耦合特性的系统能量枢纽模型。建立综合能源系统的日前优化模型、日内滚动优化模型、实时计划优化模型。基于三种优化模型,提出日前-滚动-实时的复合协调优化运行策略。根据电、热负荷以及风电出力的日前预测数据制定日前调度方案,为系统全天的运行情况提供初步的参考信息;然后利用短期滚动预测数据进行滚动计划,对日前计划方案进行滚动修正,制定各设备出力的基本运行点;最后利用超短期预测数据进行实时计划,得到与实际电、热负荷与风电出力情况匹配度较高的计划方案。通过算例分析验证,结果表明该文所提综合能源系统复合协调优化运行方法可以有效降低系统的运行成本,可提升可再生能源的消纳能力,并增加可再生能源的利用率。     

考虑碳排放的综合能源系统储能优化配置研究

在碳达峰、碳中和的战略目标下,整合多种异质能源、降低碳排放成为综合能源系统发展的重要议题。储能系统作为综合能源系统的重要组成部分,其系统的优化配置需要考虑碳排放因素的各种影响。该文针对综合能源系统降低碳排放的需求,研究碳排放下储能的优化配置问题,构建电/热混合储能的双层优化模型。首先建立综合能源系统的内层优化运行模型,考虑冷、热、电的能量平衡和蓄电、蓄热设备等运行的约束条件;其次构建综合能源系统电/热混合储能的外层优化配置模型,在分析投资成本、维护成本、运行成本等经济性目标的基础上,将碳排放目标加入优化目标函数中,以分析碳排放因素对综合能源系统储能优化配置的影响;最后,研究以实际数据为算例,对该文提出的模型方法进行仿真分析。结果表明：通过合理配置储电、储热设备可提高综合能源系统运行的经济性,也可减少因供能不足造成的缺电、缺热问题,用户在电储能系统营利时,会一定程度提高系统的碳排放。研究提出优化配置混合储能设施以降低综合能源系统碳排放的建议。     

两级热泵活塞式压缩机模型研究

采用稳态仿真的方法对双级压缩热泵系统的压缩机部件建立模型,并建立中间冷却器模型。由于在低温丁况下试验,模型建立考虑了压缩机和环境的换热。通过建立试验台,采集试验数据并与仿真结果进行比较。结果表明,稳态仿真能够良好地反映系统运行中的参数变化。     

基于仿射可调鲁棒优化的园区综合能源系统经济调度

新能源和负荷的不确定性给综合能源系统（integrated energy system,IES）运行带来挑战。首先,基于线性形式的能源集线器模型,对园区IES进行了建模。其次,构建了基于仿射可调鲁棒优化的园区IES两阶段经济调度模型,通过该模型可求得机组的启停及基准出力,以满足不考虑可再生能源出力的能量平衡要求,并求得机组的参与因子,使得调度方案对可再生能源出力不确定集下的任意场景均可行。最后,将该模型转化为混合整数线性规划模型（mixed integer linear programming,MILP）进行求解。算例分析结果表明：通过可调鲁棒优化的经济调度方法所求得的调度方案较经典鲁棒优化有更好的经济性与鲁棒性。     

变速直膨式空调系统运行特性的稳态ANN模型

在假设系统输出显、潜冷量的相对值在不同的蒸发器入口空气状态下不发生明显变化的前提下,本文针对实验用变速直膨式空调系统建立了稳态人工神经网络(ANN)模型,预测其在不同压缩机、风机转速组合下的系统输出,利用输出显、潜冷量的相对值可以消除室内空气状态对系统输出的影响。通过稳态实验获得数据训练、检测并验证ANN模型预测变速直膨式系统运行特性的准确性,并通过非训练状态点下的稳态实验验证所提出假设与ANN模型的适用性。ANN模型的训练、检测以及验证实验结果的最大误差均小于5%,平均误差均小于3%,表明该稳态ANN模型可以在训练状态点以及非训练状态点较为准确地预测变速直膨式系统的运行特性。     

稳态及非稳态传热条件下膨胀珍珠岩绝热性能的研究

在低温系统工作过程中,绝热材料随工作过程的变化和外界温度的波动交替工作在稳态和非稳态两种传热情况下,绝热材料在非稳态传热条件下的绝热性能对低温系统的影响极为重要。本文以常用低温保温材料膨胀珍珠岩（珠光砂）为研究对象,实验测量了在稳态和非稳态传热条件下的导热性能,热扩散性能及其随温度的变化规律,并对两种传热条件下的绝热特性进行了分析和研究,为工程应用提供可靠的依据,也为低温绝热方案的选择及优化设计提供参考资料。     

基于最小熵增法编程确定非共沸混合工质组分比

以非共沸混合工质在蒸发器中沿程温度分布变化所导致传热不可逆熵增为目标函数,建立混合工质与冷媒水在蒸发器中的稳态换热模型;以换热温差最小值为基准,编程分析计算,得出二元混合工质R290/R600在不同组分比下的相对熵增,选取其中最小值对应组分比为最佳组分比.     

小型冷库制冷系统稳态仿真

对小型冷库制冷系统进行了稳态仿真.建立了压缩机稳态仿真模型,重点考虑了压缩机输运环节的计算.建立了热力膨胀阀模型,重点建立了流量与阀前后压差及制冷剂进出口干度的关系.实验表明,模型精度达到工程实用要求;结合实验和仿真分析,对小型冷库的运行和设计提出了建设性意见.     

考虑运行风险的含储能综合能源系统优化调度

为解决综合能源系统（integrated energy system,IES）中供需双侧不确定因素对运行调度带来的风险问题,提出了一种考虑运行风险的含储能IES优化调度模型。在目标函数中,用设备调整费用、失负荷惩罚费用和弃风弃光惩罚费用来量化系统运行风险。在约束条件中,区分了电能和热能的时间尺度差异,并计及储能的时间耦合性,建立了储能多时段耦合约束。然后提出了一种基于Benders分解的算法进行求解。最后通过算例分析了置信水平、储能功率及容量对IES运行费用及运行风险的影响。     

The Steady-State Microwave Heating of Slabs with Small Arrhenius Absorptivity

The steady-state microwave heating of a finite one-dimensional slab is examined. The temperature dependency of the electrical conductivity and the thermal absorptivity is assumed to be governed by the Arrhenius law, while both the electrical permittivity and magnetic permeability are assumed constant. The governing equations are the steady-state versions of the forced heat equation and Maxwell's Equations while the boundary conditions take into account both convective and radiative heat loss. Approximate analytical solutions, valid for small thermal absorptivity, are found for the steady-state temperature and the electric-field amplitude using the Galerkin method. As the Arrhenius law is not amenable analytically, it is approximated by a rational-cubic function. At the steady-state the temperature versus power relationship is found to be multivalued; at the critical power level thermal runaway occurs when the temperature jumps from the lower (cool) temperature branch to the upper (hot) temperature branch of the solution. The approximate analytical solutions are compared with the numerical solutions of the governing equations in the limits of small and large heat-loss and also for an intermediate case involving radiative heat-loss.     

Energy consumption characteristics of an absorption chiller during the partial load operation

The objectives of this study are to analyze performance characteristics during partial load operation and to calculate energy consumption amount of H₂O/LiBr absorption chiller with a capacity of 210 RT. The effect of cooling water flow rate and cooling water inlet temperature on the absorption performance and energy saving is quantified during the partial load operation. It is found that the performance of absorption system is more sensitive to the change of inlet water temperature rather than the cooling water flow rate. Even if the cooling water flow rate is reduced to 60% of the standard value, the capacity is recovered if the temperature of cooling water decreases about 2.0 °C. The pumping power of cooling water is 4 times higher than that of cooling tower during the partial operation mode and the pumping power of cooling water becomes more significant with decreasing the partial load. It is concluded that when the partial load is in the range of 100–40%, the reduction of the required power by 23% can be realized by decreasing the cooling water inlet temperature of 1.0 °C.     

Simulation and validation of a hybrid-power gas engine heat pump

Hybrid-power gas engine heat pump (HPGHP) combines hybrid power technology with gas engine heat pump, which can keep the gas engine working in the economical zone. In this paper, a steady-state model of the HPGHP in heating condition has been established, the optimal torque curve control strategy is proposed to distribute power between the gas engine and battery pack. The main operating parameters of the HPGHP system are simulated on Matlab/Simulink and validated by experimental data, such as operating temperature, coefficient of performance (COP), fuel-consumed rate, etc. Heating capacity and COP of the heating pump system are validated under different ambient temperatures and water flow rates. The simulation and experiment results shows acceptable agreement, the maximum difference is respectively 8.9%, 5.9%, 9.5% and 8.2% for engine torque, motor torque, reclaimed heat and fuel-consumed rate. Based on the simulation results, HPGHP has the lowest fuel-consumed rate of 283 g (kWh)⁻¹ at engine speed of 3000 rpm; the PER of HPGHP system is about 15.9% and 11.4% higher than the GHP under the same load in Mode C and D.     

独立双埋管太阳能辅助土壤源热泵系统模型建立与影响因素分析

太阳能辅助土壤源热泵复合系统是严寒寒冷地区实施清洁供能的重要手段之一。在该系统中,太阳能集/蓄热系统与土壤源热泵系统有不同的连接方式和运行模式,太阳能系统的运行时间直接影响土壤的热恢复程度。本文基于TRNSYS平台建立了可全年进行蓄热的太阳能辅助土壤源热泵复合系统,提出了独立双埋管土壤蓄热器模拟计算方法,并与现场测试数据进行了对比验证。基于大连市公共建筑实际工程,通过正交试验设计及TRNSYS模拟全面研究了系统运行参数,得到对系统运行能耗与土壤温度变化率有重要影响的运行参数并分析了其影响规律。结果表明：系统运行能耗与冬季热泵供水温度、负荷侧水流量、土壤侧水流量均呈正相关,与夏季热泵供水温度呈负相关;当累计供热供冷量比为1.31时,系统运行能耗与蓄热启动温度呈负相关;当累计供热供冷量比为2.32时,与蓄热启动温度为正相关;当累计供热供冷量比为1.77时且蓄热启动温度为35℃时,系统运行能耗最低。土壤温度变化率与蓄热启动温度呈负相关。应根据系统累计供热供冷量比来相应调节太阳能系统运行时间和运行参数。     

Model for transient behavior of pulse tube cryocooler

This article describes an investigation of the transient behavior of a small (2.0 W at 85 K) pulse tube cryocooler operating at 120 Hz with an average pressure of 3.5 MPa, capable of relatively fast cool-down from ambient to about 60 K. In a series of experiments, the cold end temperature was measured as a function of time in a complete cool-down and subsequent warm-up cycle, with no heat load and different quantities of excess mass at the cold end. A transient heat transfer model was developed, that considers the effects of the cooling power extracted at the cold end and that of the heat gain at the warm end on the cool-down time. The heat gain factor was calculated from warm-up data, and found to be approximately the same for all experiments. Using the same model with cool-down data enables a determination of both the gross and net cooling power as functions of time, but more importantly – as functions of the cold end temperature. An expression was derived for the cold end temperature as a function of time for any amount of excess mass, including zero. The cool-down time of the “lean” cryocooler (with no excess mass) was found to be less than 50 s.This cool-down/warm-up method for evaluating the cooling power of a cryocooler seems simpler than steady-state experiments with a heater simulating load at the cold end. Use of the heat transfer model with data from one or two good experiments conducted in the above manner, can yield both the gross and net cooling powers of a cryocooler as functions of the cold end temperature, and allow the determination of cool-down time with any amount of excess thermal mass. While the net cooling power during cool-down differs somewhat from that under steady-state operation, the former can serve as a good measure for the latter.     

Thermal Conductivity,Thermal Diffusivity,and Heat Capacity of Gaseous Argon and Nitrogen

Low-pressure thermal conductivity and thermal diffusivity measurements are reported for argon and nitrogen in the temperature range from 295 to 350 K at pressures from 0.34 to 6.9 MPa using an absolute transient hot-wire instrument. Thermal conductivity measurements were also made with the same instrument in its steady-state mode of operation. The measurements are estimated to have an uncertainty of 1% for the transient thermal conductivity, 3% for the steady-state thermal conductivity, and 4% for thermal diffusivity. The values of isobaric specific heat, derived from the measured thermal conductivity and thermal diffusivity, are considered accurate to 5% although this is dependent upon the uncertainty of the equation of state utilized.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom     

电磁微锻机构热效应模拟与实验研究

为研究电磁微锻机构在工作过程中的温度分布情况以及提高其功率密度,首先,在现有电磁微锻机构的基础上,从能量角度对其热效应与输出功率的关系进行分析,明确了热效应会限制机构的最大输出功率。然后,利用COMSOL Multiphysics软件分别对风冷和水冷方式下电磁微锻机构的温度场进行CFD （computational fluid dynamics, 计算流体力学）仿真分析,确定了不同入口边界条件下的等效对流换热系数;同时,根据等效对流换热系数与入口边界条件的关系,建立了该机构的瞬态温度分析模型。最后,搭建了电磁微锻机构温度测量实验平台,并对该机构的温升特性和稳态温度特性进行了实验研究。实验结果表明,所提出的电磁微锻机构热效应仿真分析方法较为合理、准确,可为微锻机构的温度控制和结构优化提供参考。     

Study on a design method for hybrid ground heat exchangers of ground-coupled heat pump system

The hybrid ground heat exchangers (GHEs) of ground-coupled heat pump (GCHP) systems refer to a GCHP system using both vertical and horizontal GHEs. With the proposed optimal load ratio of horizontal to vertical GHEs, three-dimensional numerical heat transfer GHE models were established using independent heat transfer calculation method, and a design method for hybrid GHEs of GCHP system was put forward and then applied in one project. A combined heat transfer calculation method considering the mixing outlet water temperature was proposed and validated by a built experimental platform, which shows an improvement in accuracy prediction compared to the independent heat transfer calculation. It indicates the mixing outlet water temperature plays an important role in calculation accuracy and should serve as the boundary condition in modelling. The heat transfer performance of GHEs can be characterized by the independent heat transfer results in a certain range of load ratio.