Evaluation of thermal energy storage and recovery for an electrical energy mediator system

Energy storage both electrical and thermal is a rapidly emerging field of interest toward the development of more sustainable energy systems. The inherent inefficiencies associate with electrical storage can be partially overcome when thermal storage that collects and storage the waste thermal energy for alternative uses is integrated. Consequently, thermal energy storage systems are an enabling technology that will allow increased energy efficiency of a community, permit load levelling to reduce peak electricity demand. In order to facilitate a technology evaluation, a sizing strategy is developed for a phase change material (PCM) thermal storage system that determines system requirements under given thermal energy capture and recovery cycles. The sizing process utilizes a simplified one-dimensional heat transfer model that estimates melt times for a phase change material thickness without detailed geometry information. This melt time estimate allows the proportion of phase change material to fluid routing materials to be calculated, giving an estimate of material cost for the thermal storage cell to determine economic feasibility. The model is compared to both experimental data and computational fluid dynamics models in order to determine its limitations. Through a specific example of hydrogen based distributed electrical energy mediator system, the utility of the sizing model in determining the estimated cost of thermal energy storage is demonstrated.     

Thermodynamic modelling of the ternary Bi-Ga-Te system for potential application in thermoelectric materials

Thermoelectric materials have drawn widespread attention because they can enable the direct conversion between electric and thermal energy. Over the years, different materials such as skutterudites, clathrates, intermetallic alloys, eutectic alloys, chalcogenides have been explored for Thermoelectric (TE) applications. Amongst the eutectic alloys, the Bi-Ga-Te system exhibits promising potential as a TE material. Accordingly, in this study, we performed the thermodynamic optimization and critical evaluation of binary Bi–Ga, Bi–Te, Ga–Te, and ternary Bi-Ga-Te systems using the CALPHAD method. It is observed that the Ga–Te system shows asymmetric liquid solution properties with strong negative enthalpy of mixing, whereas the Bi–Te liquid exhibits the symmetric regular solution behavior. Moreover, the Bi–Ga liquid solution has a positive enthalpy of mixing. Therefore, Modified Quasichemical Model (MQM) using pair approximation was utilized to describe the diversified thermodynamic properties of liquid solution in sub-binaries by taking into account the Short-Range Ordering (SRO). By merging the binary optimization results with a proper interpolation method, the liquid solution properties and phase diagram information in the Bi-Ga-Te ternary system were also reproduced successfully without any adjustable ternary parameter. Several ternary eutectic compositions were suggested for designing TE alloy with enhanced properties using the developed database.     

The reassessment of the Al-V system and new assessment of the Al-Si-V system

The theoretical assessment of the Al-Si-V system has been carried out and has been presented here. The experimental results from Huber et al. [1,2] were used as the basis of the assessment. The relevant binary system assessments for Al-V [9], Al-Si [13] and Si-V [14] were used in the initial stage of the study and it was found that complete reassessment of the Al-V system was necessary. The reassessed dataset for the Al-V system is in very good agreement not only with existing experimental phase diagram and thermodynamic data, but is also consistent with the independent work of Lindahl et al. [22].The final assessment of the Al-Si-V system using our own reassessed Al-V system is in excellent agreement with the experimental data.     

Thermodynamic assessment of orientationally disordered organic molecular crystals: Ternary system pentaerythritol–neopentylglycol–2-amino-2methyl-1,3, propanediol (PE–NPG–AMPL)

Organic crystals such as pentaerythritol [PE-C(CH₂OH)₄], neopentylglycol [NPG-(CH₃)₂C(CH₂OH)₂] and 2-amino-2methyl-1,3,propanediol [AMPL-(HOCH₂)₂C(NH₂)CH₃] store a large amount of thermal energy in their solid state high temperature phases with orientational disorder. There are very few pure compounds of these polyalcohol and amine family that are commercially available exhibiting these properties, leading to limited choices of energy storage materials. Binary and ternary solid solutions allow a wider selection of materials with different phase transition temperature, heat content, and compositions for practical applications. Thermodynamic calculations of the PE–NPG–AMPL system are presented that provide critical thermodynamic data for energy storage systems. Substitutional solution model is used for optimization of interaction parameters. Activities of binaries, ternary isotherms of PE–NPG–AMPL at various temperatures, and pseudo-binary isopleth are presented.     

Thermodynamic description of the Cu-Ge-Pb system: Experiment and modeling

Decades of scientific work dedicated to the investigation of phase diagrams gave significant benefit to industry and science. After all those years of phase diagram investigation still there is missing information about phase diagram of some ternary systems. One of those systems is Cu-Ge-Pb. It is known importance of Cu-based alloys and Ge-based alloys in electro industry. Since such combination is not tested before this work will provide information about phase diagram of ternary Cu-Ge-Pb system. In this work ternary Cu-Ge-Pb system has been tested experimentally and analytically by using Calphad model. Two isothermal sections at 600 and 400 °C and three vertical sections are experimentally tested and results were compared with calculated corresponding phase diagrams. None of the ternary compound and large solubility of third element in binary compound is not confirmed. Liquidus projection, invariant reaction and scheme of invariant reaction are presented. Scheil and Lever simulation of solid phases for Cu₈₀Ge₁₀Pb₁₀ alloy were calculated.     

微电网中混合储能系统的规划运行一体化配置方法

目前针对微电网中储能容量配置的经济优化算法中,大多都是直接以储能系统的全寿命周期成本作为目标函数.然而微电网作为一个整体,不同的能量调度方案会导致不同的储能配置需求,因此微电网的运行目标也会间接影响到储能系统的全寿命周期成本.本文提出的规划运行一体化配置方法,是从微电网的整体经济效益出发,将储能系统全寿命周期成本的直接和间接影响因素都考虑在内,建立了计及微电网经济运行的储能全寿命周期成本复合模型.通过算例验证以及与已有方法优化结果的对比分析,说明了所提方法在提升微电网整体经济效益上的有效性,可以为评估微电网中混合储能系统的配置效果提供更全面的参考依据.     

Influence of the mechanical limitations of a traction system on energy storage design

An innovative subway without supply rail is presented. This article deals with the sizing of the required on-board energy between two stations in the worst case. The influence of the mechanical limitations is studied: acceleration, jerk and torque limitations. These limitations have an impact on the total energy required and thus on the size of the on-bard energy storage element. These mechanical limitations must thus to be taken into account in the energy storage design.     

太阳能热发电蓄热系统的混杂建模与仿真

蓄热系统是太阳能热发电站中保证电站可靠性和经济性的重要组成部分,其工作状况直接影响到太阳能热发电站的正常运行。本文针对单罐式蓄热系统,分析了系统在蓄热和放热模式下的动态数学模型,在此基础上,提出了蓄热系统的混杂动态系统模型。该模型将蓄热和放热模式统一在一个框架下,能够对蓄热系统的各种操作模式及其循环交替过程进行动态模拟。混杂模型采用MATLAB软件进行仿真,仿真结果:表明了模型的有效性。     

可生存的存储系统模型及其体系结构研究*

本文首先提出了一种可生存性存储系统的形式化模型定义,后结合模型给出了可生存性存储系统的体系结构。为可生存存储系统的设计构造提供指导思想,并系统可生存性的衡量提供基本方法。     

应用于风电并网的有源型VSC-HVDC系统控制策略

利用直流输电技术,以解决风电并网的波动问题.研究分析有源型电压源直流输电技术,通过控制并联储能单元的充放电功率,补偿风电的波动功率,从而稳定注入电网的风电场功率,通过储能控制系统达到控制母线电压的稳定.仿真结果验证了控制策略的可行性.     

Medium range forecasting of power system load (energy) demand

The most popular Box-Jenkins method, generally used for short-term forecasting, is modified to make it suitable for medium and long-range forecasting. The non-stationarity and seasonality have been identified and, after removing trends and/or seasonality, the series are tested for stationarity by various methods. The series have been fitted for different auto-regressive moving average (ARMA) models in the multiplicative modes. The parameter values have been determined from autocorrelation function (a.c.f.) and partial auto-correlation function (p.a.c.f.) cor-relograms and the whiteness of the residue has been checked. A forecast has been made for energy demand for one year with the help of this model and the result has been compared with actual demand.     

电动汽车混合储能系统拓扑结构与控制策略综述

混合储能系统兼具高功率密度和高能量密度,可有效提升电动汽车动力性能和续驶里程.围绕电动汽车混合储能系统拓扑结构和控制策略,本文首先对混合储能系统及其典型储能装置进行概述,并对混合储能系统技术难点进行分析.之后在分析隔离型双向DC/DC变换器和非隔离型双向DC/DC变换器拓扑结构、工作原理和基本特性的基础上,综述分析了被动、半主动和全主动3种混合储能系统的工作原理和优缺点.然后,重点分析了基于规则的控制策略、基于优化的控制策略和混合控制策略3大类混合储能系统控制策略的工作原理.最后对混合储能系统的发展趋势进行了展望.     

Thermodynamic modeling of the Ca(NO3)2-MNO3 (M: alkali metal) systems

This work presents a thermodynamic evaluation of the Ca(NO₃)₂-MNO₃ (M: Li, Na, K, Rb, Cs) binary systems using the CALPHAD approach. The required Gibbs energy of liquid Ca(NO₃)₂ is missing in the literature and has been successfully evaluated in the present work with a fusion enthalpy of 23849 J mol⁻¹. The substitutional solution model can thus be employed to describe the Ca(NO₃)₂-base liquid phase. All the intermediate compounds are treated to be stoichiometric and their Gibbs energies comply with the Neumann-Kopp rule. Empirical functions relating mixing enthalpies to ionic parameters are employed to predict the corresponding values of binary melts which are used as input data to assist in parameters optimization for the liquid phases. The final calculated results show good agreement with most of the experimental and predicted data.     

Thermodynamic and diffusion kinetic studies of the Fe-Co system

The phase equilibria, thermodynamic properties and diffusion mobilities of the Fe-Co system were carefully assessed through the CALPHAD methods. As an indispensable tool, the first-principles calculations were carried out to study the magnetic moments and the enthalpies of mixing of the bcc_A2, bcc_B2, fcc_A1 and hcp_A3 phases as well as the point defect types of the bcc_B2 phase. In order to verify the heat capacities reported in the literature, new measurements were conducted in a high-temperature calorimetric apparatus using the three-dimensional calorimetric method. Because of the revision of the thermodynamic parameters in the present work, the diffusion mobilities for the fcc_A1 phase were reassessed. The diffusion mobilities for the bcc_A2 phase were established for the first time based on the experimental diffusion coefficients. For the low-temperature bcc_B2 phase, the diffusion couple experiments conducted in the present work show that the diffusion process is sluggish and the interdiffusion coefficients are difficult to determine. Therefore the tracer diffusivities of Co and Fe in the Fe-Co alloys were used to assess the diffusion mobilities for the bcc_B2 phase, while the composition-distance profile of one diffusion couple was served as a validation of its diffusion mobilities.