基于热力学平衡的高温固体氧化物电解水制氢模拟

通过热力学、动力学及通量平衡分析,采用Aspen Plus软件建立固体氧化物电解(SOEC)制氢的热力学平衡模型,并与实验结果进行对比验证。分析运行温度、压力、阴极水蒸气摩尔分数和阳极空气流量对系统运行特性的影响,并建立考虑余热利用的SOEC制氢系统模型,研究余热利用对制氢效率的影响。当电流密度为1.0 A/cm~2时,不同操作条件下的系统可利用热量占总输入能量的比例在26.53%～46.63%之间;在采用余热利用时,余热利用率可达52.27%以上,系统制氢效率可提高14.43%～26.54%。在1223.15 K、0.1 MPa下,阴极通入50 mol/h含水量为50%的氢气、阳极通入10 mol/h空气,电流密度约为0.78 A/cm~2时,制氢效率达到最大值90.56%,与不采用余热利用条件下相比提高约25.89%。     

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。     

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。     

基于超临界CO2循环的地热与太阳能混合系统研究

超临界CO₂循环可以耦合较低温度的地热和较高温度的太阳能热组成混合热源发电系统。相比能量分析方法,火用分析方法更便于分析混合系统对提高能量利用率的作用,以及识别造成可用能损失的设备和过程。115℃地热和200℃地热分别与采用槽式聚光集热技术的太阳能热组成混合热源,构成简单回热超临界CO₂循环。分析结果表明：混合系统的火用效率比单纯太阳能热的循环系统提高了5% ~ 10%;太阳能聚光集热器的?损失最大,占80%以上,其次是除预冷器以外的各类换热器以及透平;相比之下,压缩机和预冷器的火用损失较小。减少?损失的关键是提高太阳能聚光集热器和换热器的性能,包括提高集热管运行温度,以及提高换热器效能。     

基于PV/T的质子交换膜电解制氢系统动态性能研究

将太阳能光伏光热综合利用技术（PV/T）与质子交换膜电解水制氢技术（PEMWE）结合，提出基于PV/T的质子交换膜电解制氢系统（PV/T-PEMWE）。系统由PV/T模块与PEM电解槽通过耦合而集成，建立数学模型分析其在白天的动态光电光热性能及制氢性能，并在相同条件下将其性能与光伏电解制氢系统（PV-PEMWE）进行对比。结果表明：PV/T系统全天总发电量为0.5 kWh，电效率维持在13%～15%之间，总发热量为9.4 MJ，热效率维持在30%～40%之间；PV/T-PEMWE系统制氢效率高于PV-PEMWE系统，PV/T-PEMWE系统全天的制氢量为153 L，平均制氢速率约为19 L/h。     

S-CO2布雷顿循环太阳能电力淡水系统火用分析

设计一种使用S-CO₂布雷顿循环的太阳能电力淡水系统,对系统的工作原理和结构组成进行介绍,并对系统开展运行性能和火用分析。结果表明,设计工况下系统的输出电功率为233.8 MW,布雷顿循环效率为37.5%,淡水日产量为3981.6 t。增大太阳辐照度有利于提高系统的电力输出和总的能量效率。定工况下的火用分析结果表明,太阳塔集热器中的火用损最大,为303.99 MW,对应的火用效率为64.45%。海水淡化换热器的火用效率最低,且其火用损值也较大。随着太阳辐照度的增加,太阳塔集热器、海水淡化系统换热器和回热器内的火用损均有不同幅度的增加。因此,对于该S-CO₂布雷顿循环太阳能电力淡水系统的后续优化而言,应重点考虑改进这些部件的性能。     

电流密度和运行温度对PEM水电解制氢能耗的影响

质子交换膜(PEM)水电解制氢技术是采用绿电制取绿氢的重要方法,对我国实现双碳目标具有重要意义。优化运行参数是降低PEM水电解制氢系统能耗的一种重要途径。建立一套工业级PEM水电解制氢实验装置,通过现场实验,考察电流密度和运行温度对PEM水电解制氢系统能耗的影响,探讨优化运行参数降低运行能耗的方法。结果表明,当电流密度为0.2～1.4 A/cm²、运行温度为20～60℃,PEM水电解制氢系统单位能耗分别与电流密度、运行温度负相关。提高运行温度会引起电解电压下降,系统单位直流能耗显著降低。提高电流密度会造成系统单位直流能耗升高,而单位交流能耗降低。     

世界可再生能源电力制氢现状

氢能可实现从开发到利用全过程的零排放、零污染,是最具发展潜力的高效替代新能源。世界各国都将发展氢能提升到国家战略层面。我国也要大力发展氢能、燃料电池等新一代能源科技。水电解系统结构简单、不用氢分离操作、活动部分少、从电力到氢的能量转换效率比较高(60%~80%),成为制氢技术研发的热点。水电解技术有碱水电解、固体高分子型水电解、高温水蒸气电解。利用可再生能源制氢是新能源领域的一个新发展趋势,被称为拯球地球的动力,已提出了"可再生氢"的概念。利用剩余风电、光伏电力制氢不失为解决弃风、弃光的成功之策。目前可再生能源电力制氢技术研究开发活跃。电解水制氢催化剂技术、固体氧化物型水电解制氢技术和光电化学制氢技术的研究开发取得了很大的进展。我国河北省沽源县建设的世界最大风电制氢综合利用示范项目已全部并网发电。     

太阳能光电-光热综合利用系统

太阳能储量巨大,分布广泛,清洁安全。但太阳能光伏发电存在成本较高和能量转化效率较低的问题。因此本文提出太阳能光电-光热综合利用方式。通过聚光降低成本,通过分频综合利用提高系统效率。在分频利用技术上,寻找具有特定吸收发射特性的纳米流体流经光伏电池上层．吸收光伏电池不能加以利用的部分能量。此外,利用光学薄膜,将光伏电池可利用的波段反射给光伏电池,其余部分的能量透射用以其他形式的能量转换。文章对两种太阳能光电-光热综合利用系统进行了设计和探索。结果表明,通过光电-光热综合利用能够对太阳能利用效率实现有效提升。     

风光互补发电制氢储能系统模拟仿真研究及性能分析

文中利用Matlab/Simulink以河北工程大学风光互补发电制氢储能系统为原型建立了仿真模型,将邯郸地区的气象参数输入模型,得到系统各部分不同容量配置下的发电量、制氢速率以及太阳能、风能、电能转化为氢能的效率。分析出各影响因素对制氢速率的影响程度,太阳能、风能发电的效率,太阳能、风能、网电转化为氢能的效率,为风光互补发电制氢储能系统的开发提供了理论依据。     

碳中和愿景下绿色制氢技术发展趋势及应用前景分析

围绕目前主流的绿色制氢技术,综述国内外“绿氢”技术的最新研究进展,重点阐述电解水制氢技术（碱性电解水法、质子交换膜电解水法、固体氧化物电解水法）、太阳能分解水制氢技术（光催化法、光热分解法、光电化学法）以及生物质制氢技术（热化学转化法、微生物法）的产氢原理、技术难点和改进方法等,讨论比较各类“绿氢”技术的优缺点,分析未来绿色制氢技术的应用前景和发展方向。     

Solar methanol synthesis by clean hydrogen production from seawater on offshore artificial islands

Synthetic fuel production from renewable energy, water, and anthropogenic carbon resources offers a promising alternative to fossil fuels by reducing the consumption of nonrenewable resources and greenhouse gas emissions. This article presents a case study of a solar‐based methanol plant that derives hydrogen and carbon dioxide material inputs from seawater on an offshore artificial island. Photovoltaic cells generate electricity for an electrolytic cation exchange membrane (E‐CEM) reactor that simultaneously produces hydrogen and carbon dioxide, with freshwater for electrolysis via seawater reverse osmosis. Carbon dioxide hydrogenation in a low‐pressure isothermal cascade‐type reactor system produces methanol as a liquid fuel product. Thermodynamic assessment of the integrated system indicates solar‐to‐methanol energy and exergy conversion efficiencies of 1.5% and 1.3%, respectively, with the most significant losses occurring in the offshore concentrator photovoltaic (CPV) and E‐CEM reactor unit.     

A review on solar energy-based indirect water-splitting methods for hydrogen generation

The distinguish generation methods regarding hydrogen generation using solar energy as a triggering agent are discussed in this paper, specifically indirect techniques. Two broadly classified processes are direct and indirect. The Direct processes exhibit high thermal efficiency, but their low conversion efficiency, maximum heat dissipation, and the lack of readily available heat resistive materials in abundance put the indirect processes relatively on the higher rank. The indirect methods include bio photolysis, thermochemical, photolysis, and electrolysis. There are promising features of indirect ways. Bio-photolysis provides zero pollution; the photolysis method reduces the carbon footprint in the environment; Thermochemical is meritorious in low electricity consumption due to high heat generation in the process; Electrolysis proves its worth in negligible pollution and considerable efficiency. The energy and exergy efficiency for hydrogen yielding are compared, and it is found that electrolysis has the highest energy and exergy efficiency. In terms of raw material availability, thermochemical ranks very low as compared to photolysis (abundant solar energy), bio-photolysis (a readily available bio-agent), and electrolysis (electrolytic agents to carry out the process).     

Energy and exergy analysis of novel solar bi‐ejector refrigeration system with injector

Energy and exergy balances were done on a novel solar bi‐ejector refrigeration system with R123, whose circulation pump is replaced by an injector. The analysis result of the novel system was compared with that of the original one. The effect of operation condition on system energy efficiency, exergy efficiency and exergy loss was analyzed, and the dynamic performance of a designed solar bi‐ejector refrigeration system was also studied. The comparative results indicate that under the same operating condition, the novel system and the original system have equal energy efficiency, exergy efficiency and exergy loss, and the only difference between them is the exergy losses of the generators and the added injector. The other conclusions mainly include: the solar collector has the largest exergy loss rate of over 90% and for the bi‐ejector refrigeration subcycle, the ejector has the largest exergy loss rate of about 5%; the total exergy loss changes inversely proportional to the evaporation temperature and positively proportional to the condensation temperature; when the other parameters are fixed, there exists an optimum generation temperature, at which the overall energy and exergy efficiencies are both the maximum and the total exergy loss is the minimum. The study points out the direction for optimizing the novel solar bi‐ejector refrigeration system. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermodynamics analysis of a hybrid system based on a combination of hydrogen fueled compressed air energy storage system and water electrolysis hydrogen generator

In front of the opportunity of the rapid development of renewable energy power generation, energy storage is playing a more important role in improving its utilization efficiency. In this paper, a hybrid energy system based on combination of hydrogen fueled compressed air energy storage system and water electrolysis hydrogen generator is proposed. The superfluous renewable energy power is charged by compressing the air and/or producing hydrogen through water electrolysis. A hydrogen combustor is introduced to raise the air temperature in the discharging process. A thermodynamic model of the proposed system is built. Energy and exergy analysis found that under the design condition, the proposed system can achieve a round trip efficiency of 65.11%, an exergy efficiency of 79.23%, and an energy storage density of 5.85 kWh/m³. The exergy loss of water electrolysis hydrogen generator and hydrogen combustor rank in the top two of all components. Sensitivity analysis indicates that the outlet temperature of hydrogen combustor and specific energy consumption of water electrolysis hydrogen generator are the crucial influencing factor of system performance.     

A review on solar-hydrogen/fuel cell hybrid energy systems for stationary applications

There are several methods for producing hydrogen from solar energy. Currently, the most widely used solar hydrogen production method is to obtain hydrogen by electrolyzing the water at low temperature. In this study, solar hydrogen production methods, and their current status, are assessed. Solar-hydrogen/fuel cell hybrid energy systems for stationary applications, up to the present day are also discussed, and preliminary energy and exergy efficiency analyses are performed for a photovoltaic-hydrogen/fuel cell hybrid energy system in Denizli, Turkey. Three different energy demand paths – from photovoltaic panels to the consumer – are considered. Minimum and maximum overall energy and exergy efficiencies of the system are calculated based on these paths. It is found that the overall energy efficiency values of the system vary between 0.88% and 9.7%, while minimum and maximum overall exergy efficiency values of the system are between 0.77% and 9.3% as a result of selecting various energy paths. More importantly, the hydrogen path appears to be the least efficient one due to the addition of the electrolyzer, the fuel cells and the second inverter for hydrogen production and utilization.     

The integration of parabolic trough solar collectors and evacuated tube collectors to geothermal resource for electricity and hydrogen production

In this study, electricity and hydrogen production of an integrated system with energy and exergy analyses are investigated. The system also produces clean water for the water electrolysis system. The proposed system comprises evacuated tube solar collectors (ETSCs), parabolic trough solar collectors (PTSCs), flash turbine, organic Rankine cycles (ORC), a reverse osmosis unit (RO), a water electrolysis unit (PEM), a greenhouse and a medium temperature level geothermal resource. The surface area of each collector is 500 m². The thermodynamics analysis of the integrated system is carried out under daily solar radiation for a day in August. The fluid temperature of the medium temperature level geothermal resource is upgraded by ETSCs and PTSCs to operate the flash turbine and the ORCs. The temperature of the geothermal fluid is upgraded from 130 °C to 323.6 °C by the ETSCs and PTSCs. As a result, it is found that the integrated system generates 162 kg clean water, 1215.63 g hydrogen, and total electrical energy of 2111.04 MJ. The maximum energy and exergy efficiencies of the overall system are found as 10.43% and 9.35%, respectively.     

Thermodynamic and electrochemical analyses of a solid oxide electrolyzer for hydrogen production

In this paper, a modeling of the Solid Oxide Electrolysis Cell (SOEC), through energetic, exergetic and electrochemical modeling approaches, is conducted, and its performance, particularly through exergy efficiency, is analyzed under various operating conditions and state properties for optimum hydrogen production. In a comprehensively performed parametric study, at a single electrolysis cell scale, the effects of varying some operating conditions, such as temperature, pressure, steam molar fraction and the current density on the cell potential and hence the performance are investigated. In addition, at the electrolyzer system scale, the overall electrolyzer performance is investigated through energy and exergy efficiencies, in addition to the system's power density consumption, hydrogen production rate, heat exchange rates and exergy destruction parameters. The present results show that the overall solid oxide electrolyzer energy efficiency is 53%, while the exergy efficiency is 60%. The exergy destruction at a reduced operating temperature increases significantly. This may be overcome by the integration of this system with a source of steam production.     

High temperature electrolysis of hydrogen bromide gas for hydrogen production using solid oxide membrane electrolyzer

Using solid oxide membrane, this paper presents the theoretical modeling of the high temperature electrolysis of hydrogen bromide gas for hydrogen production. The electrolysis of hydrogen halides such as hydrogen bromide is an attractive process, which can be coupled to hybrid thermochemical cycles. The high temperature electrolyzer model developed in the present study includes concentration, ohmic, and activation losses. Exergy efficiency, as well as energy efficiency parameters, are used to express the thermodynamic performance of the electrolyzer. Moreover, a detailed parametric study is performed to observe the effects of various parameters such as current density and operating temperature on the overall system behavior. The results show that in order to produce 1 mol of hydrogen, 1.1 V of the applied potential is required, which is approximately 0.8 V less compared to high temperature steam electrolysis under same conditions (current density of 1000 A/m² and temperature of 1073 K). Furthermore, it is found that with the use of the presented electrolyzer, one can achieve energy and exergy efficiencies of about 56.7% and 53.8%, respectively. The results presented in this study suggest that, by employing the proposed electrolyzer, two-step thermochemical cycle for hydrogen production may become more attractive especially for nuclear- and concentrated solar-to-hydrogen conversion applications.