微网风电系统的储能?模型与?经济研究

微网风电系统加装储能装置联合运行时,存在多种异质能量的相互转化,因此对系统性能的有效评估较为困难。为了准确衡量风能在系统中的利用、转化、损失特性,文章基于?经济学基本原理,建立微网风储系统?平衡及?成本守恒模型,并依据所建模型确定系统各单元?效率;同时确立?优化潜力、成本差及?经济因子的系统性能评估指标,并对微网热力学特性及经济性进行有效分析。通过试验表明,该模型能够可靠地对微网风储系统能效及经济性进行评估,可指明系统?效率极大化的优化目标。     

HAT循环饱和器工质[火用]计算分析及[火用]效率

饱和器是HAT循环中的关键部件，对其性能的认识关系到整个系统的性能分析。运用[火用]的方法，计算了饱和器工质湿空气和水的堋值，分析了不同参考点的温度和湿度对[火用]值的影响规律，以及物理[火用]和化学扩散[火用]随湿空气温度的变化情况。通过建立饱和器[火用]平衡模型，采用了目的[火用]效率作为饱和器[火用]效率。计算结果表明：湿空气[火用]值随参考点的温度和湿度变化规律为：先减小，直到最低点为零，然后不断增加，[火用]值始终大于（等于）零，并且与参考点参数差距越大，[火用]值越大。当湿空气温度增加，物理[火用]所占比重减少，而化学扩散[火用]的比重增加，在到达一定温度后，化学[火用]大于物理[火用]。     

单元初始火用效率和火用流价值分布

分析了火用的不等价性,在此基础上提出了火用弹性系数、初始火用损耗率等概念.以火用弹性系数为计算基础,分析了在单一系统内各组元火用效率对整个系统火用效率的影响,导出了初始火用损耗率的计算方法,并以实例进行了分析计算.分析表明系统内各组元的单位火用所消耗的初始火用更能反映系统各组元的火用耗特性,从而有利于更科学地分析系统各单元的节能潜力.     

热泵系统的(火用)分析

用[火用]分析法对热泵供热循环进行了分析，评价了热泵系统的能质利用和损失状况，指出在环境温度、压缩机效率和两器（蒸发器和冷凝器）换热温差一定时，热泵循环存在一个可使循环[火用]效率达到最大的冷凝温度，可在实际中加以利用。     

带压缩空气储能的冷热电联产系统的(火用)分析

对一种带压缩空气储能的冷热电联产系统进行了热力学[火用]分析，得到了各主要部件和整个系统的[火用]损失及[火用]效率的变化规律。分析结果表明：空气透平绝热效率的提高对系统[火用]效率的贡献大于压缩机效率同样提高的功效；在其它参数确定时，存在最佳压比，可使系统的[火用]效率在该条件下达极值；高温换热器是新型冷热电联产系统中产生[火用]损失的主要部件，而循环水量的大小是影响高温换热器[火用]效率的主要因素。     

中冷回热布雷顿热电联产装置的火用性能分析

建立了恒温热源内可逆中冷回热布雷顿热电联产装置模型,基于火用分析的观点,用有限时间热力学理论和方法研究了装置的性能,导出了无量纲火用输出率和火用效率的解析式。讨论了总压比给定和总压比变化两种情形,优化了中间压比和总压比,通过数值计算分析了回热度、中冷度和高温侧热源温度与环境温度之比等参数对装置一般性能和最优性能的影响,研究了火用输出率和火用效率之间的关系,其特性关系为扭叶型。最后发现分别存在最佳的用户侧温度使火用输出率和火用效率取得双重最大值。     

过冷式小型冰蓄冷系统(火用)分析

通过对过冷式小型冰蓄冷系统火用分析模型的建立,采用[火用]分析的方法,揭示了小型过冷式冰蓄冷系统的能量转换的薄弱环节以及过冷度对各部件[火用]损失系数和系统火用效率的影响。分析了减少火用损失的途径,节约能源。并为系统的改进和优化提供有力的理论参考。     

基于热经济学会计模式的机组节能分析

热经济学会计模式从热经济性和经济性两方面对机组进行分析,从而使得计算结果更加合理、准确。以300MW火力发电机组为例建立热力学模型,将整个系统划分成若干个子系统;根据机组THA的实验工况参数,计算各股能流的火用值,进而计算各子系统的火用效率、火用损率、火用成本和火用经济系数等性能参数,并利用各性能参数对机组进行热经济性和经济性分析。结果表明:低压缸热力学性能比较完善,综合效益好;发电机与中压缸是节能改造的重点。该方法对电厂设备改造和节能效益评价等方面有一定的参考意义。     

低温差下半导体温差发电器(火用)分析

半导体温差发电器的性能通常用输出功率和工作效率来进行评价，但在低温差对低品位能的利用上，只用工作效率来评价是不全面的。从[火用]的角度对低温差下半导体温差发电器的工作性能进行了分析，提出了[火用]效率，用炯效率来作为低温差下半导体温差发电器的评价参数。实验结果表明，随着温差的减小，半导体温差发电器的工作效率明显下降，但[火用]效率则基本稳定。     

热经济系数(火用)分析法在能源管理中的应用

通过对热动力装置系统的(火用)分析,指出了(火用)在能源中的作用.提出了一种对(火用)能系统进行热经济性分析决策的方法-热经济系数法,并以实例探讨了其方法在方案选择中的应用.总结了(火用)效率与热经济系数之间的关系.     

基于RSM和NSGA-Ⅱ法的风电系统经济优化研究

针对风电储能系统复杂多变运行工况引发系统效率低和经济性差问题,提出一种基于响应面法(RSM)和非支配遗传算法(NSGA-Ⅱ)相结合的多目标优化方法.首先建立系统平衡及成本守恒模型,并以效率和成本差作为系统评价指标;其次,以变量转速、蓄电池类型、蓄电池充放电状态及功率波动量组合为设计工况,通过中心复合设计实验(CCD)获...     

Design,modeling and optimization of a renewable-based system for power generation and hydrogen production

Due to the environmental concerns caused by fossil fuels, renewable energy systems came into consideration. In this study, a renewable hybrid system based on ocean thermal, solar and wind energy sources were designed for power generation and hydrogen production. To analyze the system, a techno-economic model was exerted in order to calculate the exergy efficiency as well as the cost rate and the hydrogen production. The main parameters that affect the system performance were identified, and the impact of each parameter on the main outputs of the system was analyzed as well. The thermo-economic analysis showed that the most effective parameters on the exergy efficiency and total cost rate are the wind speed and solar collector area, respectively. To reach the optimum performance of the system, multi-objective optimization, by using genetic algorithm, was applied. The optimization was divided into two separate case studies; in case A, the cost rate and the exergy efficiency were considered as two objective functions; and in case B, the cost rate and the hydrogen production were assigned as two other objective functions. The optimization results of the case A showed that for the total cost rate of 30.5 $/h, the exergy efficiency could achieve 35.57%. While, the optimization of the case B showed that for the total cost rate of 28.06 $/h, the hydrogen production rate could reach 5.104 kg/h. Furthermore, after optimizing, an improvement in exergy efficiency was obtained, approximately 19%.     

计及(火用)分析的综合能源系统多目标优化调度

建立综合能源系统优化调度模型并进行高效求解有利于可再生能源的开发利用,发掘综合能源系统降本增效的潜力。针对含光伏发电的综合能源系统,以系统■效率倒数最小和总运行成本最小为目标,结合电-热-冷综合需求响应模型和运行约束,构建综合能源系统多目标运行模型。针对模型中存在的非凸非线性项进行等价线性转化处理,将问题由多目标混合整数线性分式规划等价转换为多目标混合整数线性规划,进一步采用ε约束法将其转换为一系列单目标混合整数线性规划问题进行高效求解获得帕累托Pareto前沿,并采用TOPSIS法进行决策。算例仿真表明,所建立的含光伏发电的综合能源系统能提升系统运行灵活性,相比于单目标运行,计及■分析的综合能源系统多目标优化调度能够实现系统运行成本和效率的折衷。     

An innovative approach for geothermal-wind hybrid comprehensive energy system and hydrogen production modeling/process analysis

In this paper, the energy, exergy, economic, environmental, steady-state, and process performance modeling/analysis of hybrid renewable energy (RE) based multigeneration system is presented. Beyond the design/performance analysis of an innovative hybrid RE system, this study is novel as it proposes a new methodology for determining the overall process energy and exergy efficiency of multigeneration systems. This novel method integrates EnergPLAN simulation program with EES and Matlab. It considers both the steady-state and the process performance of the modeled system on hourly timesteps in order to determine the overall efficiencies. Based on the proposed new method, it is observed that the overall process thermodynamic efficiencies of a hybrid renewable energy-based multigeneration system are different from its steady-state efficiencies. The overall energy and exergy efficiencies reduce from 81.01% and 52.52% (in steady-state condition) to 58.6% and 39.33% (when considering a one-year process performance). The integration of the hot water production with the multigeneration system enhanced the overall thermodynamic efficiencies in steady-state conditions. The Kalina system produces a total work output of 1171 kW with a thermal and exergy efficiency of 12.23% and 52% respectively while the wind turbine system produces 1297 kW of electricity in steady-state condition and it has the same thermal/exergy efficiency (72%). The economic analysis showed that the Levelized cost of electricity (LCOE) of the geothermal energy-based Kalina system is 0.0103 $/kWh. The greenhouse gas emission reduction analysis showed that the proposed system will save between 1,411,480 kg/yr and 3,518,760 kg/yr of greenhouse gases from being emitted into the atmosphere yearly. The multigeneration system designed in this study will produce electricity, hydrogen, hot water, cooling effect, and freshwater. Also, battery electric vehicle charging is integrated with process performance analysis of the multigeneration system.     

Exergy analysis of industrial pasta drying process

In this study we present an energy and exergy modelling of industrial final macaroni (pasta) drying process for its system analysis, performance evaluation and optimization. Using actual system data, a performance assessment of the industrial macaroni drying process through energy and exergy efficiencies and system exergy destructions is conducted. The heat losses to the surroundings and exergy destructions in the overall system are quantified and illustrated using energy and exergy flow diagrams. The total energy rate input to system is 316.25 kW. The evaporation rate is 72 kg h^?1 (0.02 kg s^?1) and energy consumption rate is found as 4.38 kW for 1 kg water evaporation from product. Humidity product rate is 792 kg h^?1 (0.22 kg s^?1) and energy consumption rate is found about 0.4 kW for 1 kg short cut pasta product. The energy efficiencies of the pasta drying process and the overall system are found to be as 7.55–77.09% and 68.63%. The exergy efficiency of pasta drying process is obtained to be as 72.98–82.15%. For the actual system that is presented the system exergy efficiency vary between 41.90 and 70.94%. Copyright © 2006 John Wiley & Sons, Ltd.     

A feasibility study of using thermal energy storage in a conventional air‐conditioning system

An Erratum has been published for this article in International Journal of Energy Research 2004; 28 (13): 1213. This paper deals with the simulation of thermal energy storage (TES) system for HVAC applications. TES is considered to be one of the most preferred demand side management technologies for shifting cooling electrical demand from peak daytime hours to off peak night hours. TES is incorporated into the conventional HVAC system to store cooling capacity by chilling ethylene glycol, which is used as a storage medium. The thermodynamic performance is assessed using exergy and energy analyses. The effects of various parameters such as ambient temperature, cooling load, and mass of storage are studied on the performance of the TES. A full storage cycle, with charging, storing and discharging stages, is considered. In addition, energy and exergy analysis of the TES is carried out for system design and optimization. The temperature in the storage is found to be as low as 6.4°C after 1 day of charging without load for a mass of 250 000 kg. It is found that COP of the HVAC system increases with the decrease of storage temperature. Energy efficiency of the TES is found to be 80% for all the mass flow rate of the discharging fluid, whereas exergy efficiency varies from 14 to 0.5%. This is in fact due to the irreversibilities in a TES process destroy a significant amount of the input exergy, and the TES exergy efficiencies therefore become always lower than the corresponding energy efficiencies. Copyright © 2004 John Wiley & Sons, Ltd.     

Exergetic analysis of a desiccant cooling system: searching for performance improvement opportunities

The current increase of the energy consumption of buildings requires new approaches to solve economic, environmental and regulatory issues. Exergy methods are thermodynamic tools searching for sources of inefficiencies in energy conversion systems that the current energy techniques may not identify. Desiccant cooling systems (DCS) are equipments applied to dehumidifying and cooling air streams, which may provide reductions of primary energy demand relatively to conventional air‐conditioning units. In this study, a detailed thermodynamic analysis of open‐cycle DCS is presented. It aims to assess the overall energy and exergy performance of the plant and identify its most inefficient sub‐components, associated to higher sources of irreversibilities. The main limitations of the energy methods are highlighted, and the opportunities given by exergy approach for improving the system performance are properly identified. As case study, using a pre‐calibrated TRNSYS model, the overall energy and exergy efficiency of the plant were found as 32.2% and 11.8%, respectively, for a summer week in Mediterranean climate. The exergy efficiency defect identified the boiler (69.0%) and the chiller (12.3%) as the most inefficient components of the plant, so their replacement by high efficient systems is the most rational approach for improving its performance. As alternative heating system to the boiler, a set of different technologies and integration of renewables were proposed and evaluated applying the indicators: primary energy ratio (PER) and exergy efficiency. The heating system fuelled by wood was found as having the best primary energy performance (PER = 109.6%), although the related exergy efficiency is only 11.4%. The highest exergy performance option corresponds to heat pump technology with coefficient of performance (COP) = 4, having a PER of 50.6% and exergy efficiency of 28.2%. Additionally, the parametric analyses conducted for different operating conditions indicate that the overall irreversibility rate increases moderately for larger cooling effects and more significant for higher dehumidification rates. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance assessment and optimization of an integrated solid oxide fuel cell-gas turbine cogeneration system

The combined solid oxide fuel cells and gas turbine (SOFC/GT) system is known to be a potential alternative for distributed power generation. In this paper, a novel SOFC/GT based cogeneration system, which integrated a transcritical carbon dioxide cycle (TRCC) with a LNG cold energy utilization system is proposed. A mathematical (zero-dimensional) model is developed to analyze the co-generation system performance from the perspective of thermodynamic (energy and exergy) and economic costs. The main parameters of the system are chosen to analyze their effects on thermodynamic performance. The results show that the current system can achieve 64.40% thermal efficiency and 62.13% exergy efficiency under given conditions, and can further improve efficiency through parameter optimization. Finally, the multi-objective optimization program using NSGA-II (Non-dominated Sorting Genetic Algorithm II) is used to obtain the optimal value of the system design parameters. In the multi-objective analysis, the thermodynamic efficiency and economic cost of the system are considered as objective functions. The optimization results show that the final optimized design selected from the Pareto front can achieve 63.08% thermal efficiency and 61.10% exergy efficiency, respectively.     

余热驱动的有机朗肯循环-复叠式制冷系统?分析

针对余热的有效利用,建立了有机朗肯循环-复叠式制冷系统的热力学模型,其中:有机朗肯循环系统分别采用R123、R1234ze、R245fa、R600a、RC318、R141b等六种工质;复叠式制冷系统分别采用R22/R23、R404/R23、R290/R744、R717/R744等四种工质对。选择系统?效率作为性能评价指标,运用热力学第二定律研究系统运行参数对系统?效率的影响,分析了系统各部件的?损失,并指出了能量利用的薄弱环节,提出了有效提高系统性能的建议,为系统的优化提供参考。结果表明,对系统?效率而言,R141b和R717/R744是最佳工质。系统主要部件按?损失大小依次为凝汽器、膨胀机、高温级冷凝器、发生器、高温级压缩机、低温级蒸发器、蒸发冷凝器。尽可能提高压缩机的等熵效率,优化设计换热器的结构,减小传热温差,才能减少不可逆损失,提高换热器的?效率。