Exergy optimization of a novel hydrogen production plant with fuel cell,heat recovery,and MED using NSGAII genetic algorithm

In the current research, 4E analysis and multi-criteria optimization are applied to the poly generation unit for power, heating, refrigeration, and freshwater generation. This system consists of a solid oxide fuel cell (SOFC), multi-effect thermal vapor desalination (MED-TVC), an organic system with ejector refrigeration (OSER), a heat recovery steam generator (HRSG) and a domestic hot water generator. The mathematical simulation is applied to assess the performance of the plant at design conditions and the genetic algorithm finds the optimum operating point with two different scenarios. Parametric analysis and multi-objective optimization are carried out. Findings represent that the developed plant can provide 257.65 kW power, 12.13 kW, 7.44 kW cooling and heating load, and 0.04 kg/s freshwater with a total cost rate of 10.62 $/h. In this case, the plant energy and exergy efficiency is 73.9% and 71.35% respectively. The results of multi-objective optimization show that these values can be improved to 79% and 73.9% respectively. In addition, the plant cost can be reached to 10.07 $/h in this condition.     

考虑弃水电量机会损失的水火电短期联合优化调度

针对传统大型水火电系统联合优化模型成本计算单一问题,考虑水电因弃水导致的机会损失,并考虑水火电爬坡约束、水电振动区约束等多种复杂约束,构建以火电运行成本与水电弃水电量机会损失之和最小为目标的水火电短期优化调度模型。将模型中非线性约束转化为线性化约束,并使用商业优化软件CPLEX中内置的分支定界法进行求解。算例仿真表明,按此优化准则下的最优策略运行,虽然火电运行成本有所增加,但弃水电量大大减小,水电能源利用率明显提升,计算结果更加符合实际情况。     

A flexible analytical model for operational investigation of solar hydrogen plants

Hydrogen will become a dominant energy carrier in the future and the efficiency and lifetime cost of its production through water electrolysis is a major research focus. Alongside efforts to offer optimum solutions through plant design and sizing, it is also necessary to develop a flexible virtualised replica of renewable hydrogen plants, that not only models compatibility with the “plug-and-play” nature of many facilities, but that also identifies key elements for optimisation of system operation. This study presents a model for a renewable hydrogen production plant based on real-time historical and present-day datasets of PV connected to a virtualised grid-connected AC microgrid comprising different technologies of batteries, electrolysers, and fuel cells. Mathematical models for each technology were developed from chemical and physical metrics of the plant. The virtualised replica is the first step toward the implementation of a digital twin of the system, and accurate validation of the system behaviour when updated with real-time data. As a case study, a solar hydrogen pilot plant consisting of a 60 kW Solar PV, a 40 kW PEM electrolyser, a 15 kW LIB battery and a 5 kW PEM fuel cell were simulated and analysed. Two effective operational factors on the plant's performance are defined: (i) electrolyser power settings to determine appropriate hydrogen production over twilight periods and/or overnight and (ii) a user-defined minimum threshold for battery state of charge to prevent charge depletion overnight if the electrolyser load is higher than its capacity. The objective of this modelling is to maximise hydrogen yield while both loss of power supply probability (LPSP) and microgrid excess power are minimised. This analysis determined: (i) a hydrogen yield of 38–39% from solar DC energy to hydrogen energy produced, (ii) an LPSP <2.6 × 10^?4 and (iii) < 2% renewable energy lost to the grid as excess electricity for the case study.     

基于模型预测的多模式供热电厂机组间负荷优化分配调度研究

为解决热电厂机组间负荷分配不合理的问题，提出一种基于模型预测的多模式供热电厂多机组间负荷实时优化分配方法。基于模块化建模原理构建热电厂全厂范围的机理仿真模型,并运用运行数据对模型辨识校准，根据机组特性和电网调峰补贴政策，建立全厂的运行经济性收益评估模型，进而设计基于粒子群算法的负荷实时优化方法，借助性能预测模型预测评估各方案的经济性。以某包含高背压、切缸、抽汽、光轴4种供热模式机组的电厂为例，对不同电、热负荷组合工况下的厂内负荷进行优化分配研究。应用结果表明：该方法可根据热、电负荷的实时指令在线获得经济性优化的厂内机组间负荷分配方案。     

Study on the operation and energy demand of dual-stage Metal Hydride Hydrogen Compressors under effective thermal management

For the commercial viability of a hydrogen-based transportation, hydrogen infrastructure is key. One of the major issues of hydrogen infrastructure is related to the deployment and costs of the Hydrogen Refuelling Stations (HRSs), where up to 40% of the cost is related to hydrogen compression. The introduction of Metal Hydride Hydrogen Compressors (MHHCs) in the HRSs as compression elements is a potential technology to reduce operational costs, ensure noiseless operation and increase efficiency, if renewable-based thermal energy (and/or industrial waste heat) is supplied to the system. In this work, four different two-stage MHHCs are introduced and examined in terms of compression ratio, hydrogen flow rate (compression duration), thermal energy requirements and efficiency. In addition, for comparison purposes, a three-stage MHHC is also studied. The properties of five different materials are used for the individual compression stages of the MHHCs, where all the necessary thermodynamic properties are extracted experimentally and incorporated in a commercial Multiphysics software. The unsteady heat and mass transfer equations are employed for the development of the numerical model. The hydrogenation/dehydrogenation kinetics and the temperature profile were validated against solid experimental results. In addition, to improve and accelerate the storage/release kinetics, an internal thermal management scenario has been introduced. The results show that for compression at the temperature range of 10–90 °C, the most favourable two-stage compression case (Case 3) showed a compression ratio of 11.18 ÷ 1, an isentropic efficiency of 4.54% with a thermal energy demand of 322 kJ/molH₂ and a cycle time of almost 34 min.     

Thermo-economic analysis and optimization of the very high temperature gas-cooled reactor-based nuclear hydrogen production system using copper-chlorine cycle

An improved very high temperature gas-cooled reactor (VHTR) and copper-chlorine (Cu–Cl) cycle-based nuclear hydrogen production system is proposed and investigated in this paper, in order to reveal the unknown thermo-economic characteristics of the system under variable operating conditions. Energy, exergy and economic analysis method and particle swarm optimization algorithm are used to model and optimize the system, respectively. Parametric analysis of the effects of several key operating parameters on the system performance is conducted, and energy loss, exergy loss, and investment cost distributions of the system are discussed under three typical production modes. Results show that increasing the reactor subsystem pressure ratio can enhance the system's thermo-economic performance, and the total efficiencies and cost of producing compressed hydrogen from nuclear energy are respectively lower and higher than that of generating electricity. When the system operates at the maximum hydrogen production rate of 403.1 mol/s, the system's net electrical power output, thermal efficiency, exergy efficiency, and specific energy cost are found to be 38.77 MW, 39.3%, 41.26%, and 0.0731 $/kW·h, respectively. And when the system's hydrogen production load equals to 0, these values are respectively calculated to be 177.25 MW, 50.64%, 53.29%, and 0.0268 $/kW·h. In addition, more than 90% of the system's total energy losses are caused by condenser and Cu–Cl cycle, and about 50–60% of the system's total exergy destructions occur in VHTR. About 60% and 30% of the system's specific energy cost are respectively caused by the equipment investment and the system operation & maintenance, and the investment costs of VHTR and Cu–Cl plant are the system's main capital investment sources.     

基于热电互动的分布式能源系统优化研究

  [目的]  为实现分布式能源系统经济、高效的为工业用户供能,基于工业园区电、热负荷的耦合特性,建立了分布式能源系统供能单元的性能模型,提出了优化运行策略。  [方法]  以广州某工业园区为研究对象,结合实际负荷数据,合理确定优化参数,计算了年发电量、年耗气量和一次能源利用效率,并对负荷增量的影响进行了研究。  [结果]  结果表明:机组启动热负荷对分布式能源系统的年发电量影响较大,采用优化运行策略,年发电量提升约18.7%,可以提高园区自供电比例,一次能源利用效率在85%以上。  [结论]  该优化运行策略是正确并有效的,可应用于热电耦合分布式能源系统的优化,有效提升分布式能源系统的供能,同时维持较高的一次能源综合利用效率。     

Potential evaluation of power-to-hydrogen-to methane conversion technology in robust optimal energy management of a multi-energy industrial park

Multi-energy industrial parks are required to render a huge variety of services in an eco-friendly, secure, reliable, and affordable way. The industrial energy park is a separate area consisting of multiple distributed generations, energy storage systems, etc., which supply local gas, heating, and electrical consumers. Meanwhile, the integration of power-to-X technologies such as power-to-gas and power-to-heat, which convert the electricity into other forms of energies while facilitating the integration of renewable energy in the industrial park, can enhance the flexibility and efficiency of energy supply. Therefore, this paper proposes novel robust energy management of multi-energy industrial parks integrated with wind power resources, cogeneration units, power-to-X technologies, and demand response programs to total operation cost minimization. The industrial park can simultaneously participate in a multi-energy market, including power, thermal, and gas markets, to meet local heating, gas, and electrical load. The robust optimization framework is extended to address the power price uncertainty and manage the conservatism level of the operator against price variability. The proposed model is examined on the industrial park test system, and numerical results will be presented for the different cases. Under the robust energy management, the total operation cost of the multi-energy industrial park reduces up to 53 %.     

火电机组能耗的数据包络分析方法

在一定负荷条件下,对火电厂各机组煤耗量进行优化控制能够节约成本,有效提高运行的经济性。将数据包络分析理论中含有非阿基米德无穷小的BBC模型用于火电厂生产效率评估,以机组煤耗量为输入量、机组有功功率为输出量,建立了火电机组能耗优化模型。应用一种以数据处理为基础的计算方法对模型进行求解,得出煤耗量最小的机组运行情况。将计算结果与未优化前机组的煤耗量进行对比,验证了所建立模型的合理性和有效性。     

熔盐塔式光热电站仿真机设计与开发

  目的  为了解决熔盐塔式光热电站建设和运维过程中,控制逻辑难以验证以及运行人员缺乏操作经验的问题。  方法  开发了一套用于塔式熔盐光热电站的仿真机。逻辑组态方面采用了虚拟DPU技术与软件化对象配置技术,采用了与实际电站完全相同的数值模型和设计参数。  结果  仿真试验结果表明该仿真机能够很好的实现电站生产过程中的工况模拟和仿真操作,满足逻辑组态测试要求,最后通过实例展示了仿真机的主要功能。  结论  研究成果为熔盐塔式光热电站建设过程中的设计优化、工程验证和确认、操纵员培训提供了有效方法和手段。     

Thermal management and power saving operations for improved energy efficiency within a renewable hydrogen energy system utilizing metal hydride hydrogen storage

To ensure the energy efficiency of renewable hydrogen energy systems, power conservation and thermal management are necessary. This study applies these principals to the operation of metal hydride tanks (MHTs) in a bench-scale hydrogen system, named Hydro Q-BiC?, comprising photovoltaic panels (20 kW), an electrolyzer (5 Nm³/h), MHTs containing a TiFe-based MH (40 Nm³), fuel cells (FC; 3.5 kW(power)/2.5 kW(heat)), and Li-ion batteries (20 kW/20 kWh). Here, we show that in a modified hydrogen production operation, with limited use of auxiliaries for cooling the MHTs, the power consumption of the MHTs was reduced by more than 99% compared to a typical operation. The thermal requirements for the MHTs were reduced by ceasing production in a pressurized state. During the hydrogen use operation, the power consumption was reduced to 1/4 and the FC heat output could be fully used; hence, the overall energy efficiency (power-to-hydrogen-to-power/heat) was as high as ~ 60% (43% for the typical operation).     

Renewable hydrogen production concepts from bioethanol reforming with carbon capture

This paper is assessing the hydrogen production from bioethanol at industrial scale (100000 Nm³/h hydrogen equivalent to 300 MW thermal) with carbon capture. Three carbon capture designs were investigated, one based on pre-combustion capture using chemical gas–liquid absorption and two based on chemical looping (one based on syngas and one using direct bioethanol looping). The carbon capture options were compared with the similar designs without carbon capture. The designs were simulated to produce mass and energy balances for quantification of key performance indicators. A particular accent is put on assessment of reforming technologies (steam and oxygen-blown autothermal reforming) and chemical looping units, process integration issues of carbon capture step within the plant, modelling and simulation of whole plant, thermal and power integration of various plant sub-systems by pinch analysis. The results for chemical looping designs (either syngas-based or direct bioethanol) show promising energy efficiency coupled with total carbon capture rate.     

Organic Rankine Cycle coupling with a Parabolic Trough Solar Power Plant for cogeneration and industrial processes

Over the last 25 years solar power plants based on parabolic trough concentrators have been developed for the commercial power industry. On the other hand, in recent years, a way to harness the solar energy is to cogenerate through Concentrated Solar Power (CSP) technology coupled to an Organic Rankine Cycle (ORC) with potential applications to industrial processes. In this work we present a study of a small CSP plant coupled to an ORC with a novel configuration since useful energy is directly used to feed the power block and to charge the thermal storage. In order to analyze this novel configuration we consider a case study with cogeneration applied to textile industrial process at medium temperature. It turns out that this configuration reduces the size of the thermal storage disposal. The performance of the solar power plant was simulated with TRNSYS to emulate real operating conditions. We show the design, study and simulation results, including the production and efficiency curves for our load profile. Our results show that our system is a promising option for applications to medium temperature processes where electrical and heat generation is required.     

Optimization and comparison of two improved very high temperature gas-cooled reactor-based hydrogen and electricity cogeneration systems using iodine-sulfur cycle

To enrich the existing research methods and content, two improved very high temperature gas-cooled reactor and iodine-sulfur (I–S) cycle-based nuclear hydrogen and steam and helium gas turbines electricity cogeneration systems, including the series connection system (SCS) and the parallel connection system (PCS), are proposed and studied. The energy and exergy analysis methods are used to model these two systems, and Aspen Plus is adopted to build the I–S hydrogen production system. The energy consumption and thermal efficiency of the I–S system are analyzed in detail, and the parametric optimization of two improved systems is performed using particle-swarm optimization (PSO) algorithm. Lastly, the performance comparison of the two systems under different operating conditions is conducted. The simulation results show that more than 99% of the energy consumption of the I–S system is occupied by H₂SO₄ section and HIx section, and the system's thermal efficiency is estimated to be in the range of 17.7%–43.3%. After using an internal heat exchange network, a conservative thermal efficiency of 23.7% is achieved. The optimization results show that under zero hydrogen production load, the proposed PCS and SCS can respectively achieve the net electrical power outputs of 172.8 MW and 125.7 MW, the global thermal efficiencies of 49.36% and 35.91%, and the global exergy efficiencies of 51.94% and 37.79%. With the increase of hydrogen production load, the global efficiencies of both systems decrease significantly, but the decreasing rate of PCS is faster than that of SCS. In addition, the performance comparison results indicate that when the hydrogen production load is small or the intermediate heat exchanger's primary side helium outlet temperature is close to the reactor inlet temperature, the PCS would be a better option than the SCS.     

火电站锅炉运行可控性能量损失分析

在用反平衡方法对电站锅炉运行进行热效率计算的基础上，从火电站锅炉实际运行的可操作性出发，对电站锅炉进行热经济性分析，并对一些可控性强的影响因素作了能损分析与计算，有利于提高机组的经济运行水平。     

Real time optimization of steam reforming of methane in an industrial hydrogen plant

The main goal of this research is modeling and real time optimization of an industrial steam methane reformer considering catalyst deactivation. In the first step, the reformer is heterogeneously modeled based on the mass and energy balance equations considering a detailed kinetic model. To prove the accuracy of developed model, the simulation results are compared with the available plant data at steady state condition. In the second step, based on the mechanism of catalyst deactivation, a first order decay model is proposed and the parameters of the model are calculated to minimize the absolute difference between calculated methane conversion and plant data. In the third step, an optimal control problem is formulated to maintain hydrogen production capacity at the desired level. Based on the formulated optimization problem, optimal dynamic trajectories of feed temperature and steam to methane ratio are calculated considering two strategies. Then, the performance of developed optimization procedure is proved considering furnace temperature and feed concentration as disturbance. The simulation results show that operating at the proposed optimal condition increases hydrogen production about 11.6%. In addition, the process emission performance defined as hydrogen to carbon dioxide ratio in the product is 6.72 and 7.03 at the conventional and optimized conditions, respectively.     

基于多储能技术经济性比较的可再生能源发电系统多目标容量优化

研究基于蓄电池、熔盐储热、抽水蓄能及储氢技术经济性比较的可再生能源发电系统多目标容量优化。该容量优化模型以最小化平准化度电成本及失负荷率为目标,应用4种代表性多目标进化算法进行求解。提出基于超体积的多目标算法综合评价指标,此外考虑了储能运行特性及资源不确定性提高仿真计算的准确性。算法性能比较结果表明,非劣排序遗传算法的平均排序等级为1.6,其具有最优的综合性能;储能的定量技术经济性比较结果表明,不同可靠性条件下熔盐储热系统的经济性均为最优;不同负荷曲线及不同资源水平的敏感性分析验证了储能经济性比较结果的有效性。     

Multi-objective optimal allocation strategy for the energy internet in Huangpu District,Guangzhou, China

To improve the overall efficiency of the energy system, the basic structure for the energy internet of coordination and optimization of “generation-grid-load-storage” of Huangpu District, Guangzhou, China is designed, while the arrangement for the output of centralized and distributed energy module and energy storage are proposed. Taking economic benefit maximization, environmental benefit maximization and energy efficiency maximization as sub-objectives, the mathematical model of multi-objective optimal allocation and operation strategy of the energy internet is established considering supply-demand balance constraints, equipment characteristic constraints, operation mode constraints, and energy conditions constraints. The calculation results show that without considering the outsourced electricity, the balanced strategy, the economic development strategy, the environmental protection strategy, and the energy efficiency strategy are obtained by calculation, which are all superior to the traditional energy supply strategy. Moreover, considering the outsourced electricity, the proportion of outsourced electricity to total electricity is 19.8%, which is the system optimization of the energy internet under certain power demand. Compared with other strategies without outsourced electricity, the outsourced electricity strategy can have a certain emission reduction effect, but at the same time reduce the economic benefit. Furthermore, the huge difference in demand for thermal and cooling load between industrial and commercial areas results in the installed capacity of gas distributed energy stations in industrial areas being nearly twice as large as that in commercial areas. The distributed photovoltaic power generation is allocated according to the proportion of the installed roof areas of photovoltaic power generation system in residential, industrial, and commercial areas.     

电力市场环境下风-水电联合优化运行策略研究

为了促进风电场在电力市场环境下的发展,提出了一种风-水电站联合参与电力市场优化运行的策略。该策略综合考虑了从日前能量市场及调节备用容量市场中取得的收益,以期望收益最大化为目标,加入了水电站运行的限制,建立了含全天24个时段的混合整数规划模型,通过求解模型得出了各市场中的最优能量及容量申报,并基于实际的水电站与风电场参数进行了算例仿真。测试结果表明,水电站与风电场联合运行可降低风电出力的随机性对收益的负面影响,经济效益明显;风电出力的波动、能量不平衡的惩罚系数等因素都会对结果造成影响。     

An ocean thermal energy conversion based system for district cooling,ammonia and power production

In this study, a novel Ocean Thermal Energy Conversion (OTEC) based tri-generation system that produces ammonia, cooling and power is developed and analysed. This OTEC plant operates on the naturally existing temperature difference that exists in various depths of the ocean. The OTEC plant used in this study is operated using a single-stage ammonia Rankine cycle. The discharge seawater from the condenser in the organic Rankine cycle is used to provide district cooling. Two different operation cases of the analysed system are considered, where for the first case 50% of the power produced is stored in the form of ammonia during the off-peak hours. The second case is for complete power production proposed for peak hours. For the case where 50% of the power produced (case 1) is used to produce ammonia the highest energy and exergy efficiency is found to be 1.37% and 56.17% respectively. As for the case where, only power is produced (case 2) the maximum energy and exergy efficiency of the OTEC plant is found to be 1.83% and 78.02% respectively. The corresponding maximum power production was 6612 kW and 13,224 kW for cases 1 and 2. The maximum hydrogen and ammonia production rate is found to be 94.35 kg/h and 534.7 kg/h at peak efficiency values. The cooling duty at the peak energy and exergy efficiency is found to be 64.4 MW where the condenser temperature is 11.38 °C.