A desalination battery

Water desalination is an important approach to provide fresh water around the world, although its high energy consumption, and thus high cost, call for new, efficient technology. Here, we demonstrate the novel concept of a "desalination battery", which operates by performing cycles in reverse on our previously reported mixing entropy battery. Rather than generating electricity from salinity differences, as in mixing entropy batteries, desalination batteries use an electrical energy input to extract sodium and chloride ions from seawater and to generate fresh water. The desalination battery is comprised by a Na(2-x)Mn(5)O(10) nanorod positive electrode and Ag/AgCl negative electrode. Here, we demonstrate an energy consumption of 0.29 Wh l(-1) for the removal of 25% salt using this novel desalination battery, which is promising when compared to reverse osmosis (~ 0.2 Wh l(-1)), the most efficient technique presently available.     

风、光、油互补控制器的设计

本文设计开发的一款基于风、光、油互补的充电控制器,可以实现风能和光能转化为蓄电池电能,在无风、无光照的条件下,且蓄电池的能量不足,可以启动油机进行发电,并对蓄电池进行充电。从而实现对可再生能源的充分利用,在保障设备供电的前提下,最大限度的节省燃油。     

Entropy and entropy of mixing

Entropy as a function of temperature at constant volume, S(T), can be determined by integrating the molar specific entropy capacity C_V/T (C_V: molar specific heat capacity at constant volume). As a second approach, S(T) at constant volume can be determined by differentiating the free energy with respect to the temperature, T. Recently, it has been shown for a system obeying Boltzmann statistics that these mathematical approaches are equivalent to applying the formula of the mixing entropy, if the ground and excited states of the same sub‐systems or elementary systems are considered as mixing objects or quantum components. This result considerably extends the applicability of the formula of the mixing entropy, which is derived in textbooks just for mixing real indifferent components. In the present paper, it is shown that the formula of the mixing entropy can also be applied to calculate the entropy of Bose and Fermi systems. Thus, all entropy can be calculated and interpreted as mixing entropy of real components or quantum components. In reverse, the transitions between the ground and the excited states of any system can be explained as mixing processes. This interpretation is applied to the melting transition of chemically bonded solids and in particular to the glass transition whereby upon cooling the mixing entropy of the melt is (at least partly) frozen in the configuration. These results suggest a new interpretation of the glass transition and a new definition of structural glass.     

能源总线系统多热源混水和热回收过程变分析

在能源互联网时代,区域供冷供热系统将由原本单一形式的热源向多种形式热源并存转变,尤其是可再生能源和未利用能源。不同形式不同品位的热源集成必将引起系统能量变化。能源总线系统是集成化规模化应用区域内可再生能源及未利用能源的多源多用户能源系统。本文针对能源总线系统相对常规分散系统而言特有的多源多用户特征进行系统混水和热回收过程的变分析,将能源总线系统抽象为一系列工作在高温热源和低温热源之间的劳伦兹循环的集成,通过建立能源总线系统与常规分散系统的理想热力学模型,找到能源总线系统混水和热回收过程变的规律及影响因素。结果表明:系统的变化与各子系统低温热源进出口温度、高温热源进口温度以及高低温热源质量流量比相关,不同的设计参数会导致混水过程能量发生增加或者减小,亦或不变。通过分析得到热回收过程影响源侧总线热量变化的相关参数并找到热量变化规律,并得到最佳总线供水温度TEBS1的确定方法。     

能源材料新时代

人类发展的历史, 也是能源变革的历史, 人类社会的每一次技术革命无不伴随着对能源认识、开发和利用的创新与进步。当下, 我国已经成为全球排名第一的能源生产和消费大国, 并且两个总量还在不断攀升。能源技术是解决对传统化石能源过度依赖及环境污染等问题, 构建合理的社会能源结构, 推进可持续发展, 实现“双碳”减排的关键手段。2020年, 我国以太阳能、风能为代表的可再生能源增长达到全世界的三分之一, 发展迅速。这其中, 能源材料是能源工业和能源技术体系中涉及的特殊材料, 在实现清洁能源的转化和利用, 发展新能源技术, 以及支撑整个能源系统中扮演着核心角色。近年来, 能源材料在诸多领域取得了广泛而持续的发展, 包括二次电池、燃料电池、太阳能电池、超级电容器、光电催化、含能材料等。比如, 以高镍三元材料(NCM)为代表的新型锂离子电池正极材料, 正引领着新一代汽车动力电池技术的发展, 以支持更快的充电速度、更久的服役寿命和更长的行驶里程^[1-4]。不断提升的储能需求也催生了一系列新型电池技术, 如锂硫^[5]、锂空气^[6]电池体系, 以及固态电池^[7]技术等, 多种技术并行发展。它们在能量密度、经济性、安全性等方面各具优势, 但也存在如锂硫电池中多硫化锂造成的穿梭效应, 锂空气电池中放电产物易堵塞基底的孔道以及固态电池中电解质的电导率不佳等诸多问题, 其技术完善和产业化推动强烈依赖于电极和电解质材料的创新设计和结构优化。同时, 为了提高非化石能源占一次能源的消费比, 太阳能电池作为新能源技术的翘楚, 被寄予厚望。其中, 以钙钛矿为代表的第三代太阳能电池技术已获得与单晶硅相媲美的光电转换效率^[8], 让人们对光伏产业的未来充满了期待, 然而其对温、湿、光、氧的敏感性和不稳定性^[9], 以及在材料制备过程中难以回避污染环境的含Pb原料, 种种问题仍需从材料的底层设计中寻求解决之道。此外, 以Pt、Pd等贵金属为代表的传统催化剂材料不断优化, 以及开发的新型非贵金属、非金属催化剂, 正逐步提高燃料电池的能量转换效率, 降低其技术成本, 并已取得了一定程度的商业化应用^[10-11]。同时, 涉及如CO₂还原、固氮等过程的光、电催化新材料与新技术, 也为可再生能源的存储及利用形式提供新的出口, 为2030年完成碳达峰、2060年实现碳中和提供技术支撑^[12-13]。在可持续发展的时代大背景以及竞争激烈的国际前沿科技大环境下, 我国在能源材料的理化机理探索、功能发现、精准设计制备以及先进器件组装等方面做出了许多开创性的工作。为集中展示我国学者在相关领域的研究成果, 推动学术交流, 激发社会各界对能源材料的兴趣, 南京理工大学联合中国科学院上海硅酸盐研究所、华中科技大学等单位组织出版“能源材料专辑”, 专辑收录了能源材料相关的最新研究论文和综述文章, 涉及钙钛矿太阳能电池、半透明太阳能电池、锂离子电池、镁电池、锂硫电池、热电、二氧化碳裂解等。期望该专辑能够抛砖引玉, 为促进我国能源材料的科学研究和学科发展提供有益参考。     

反渗透海水淡化能量回收装置中盐水和海水混合过程研究

正位移式能量回收装置利用盐水直接增压进料海水实现反渗透淡化系统余压能回收利用的同时,不可避免会产生盐水和进料海水间的混合．混合使得被增压海水的盐浓度升高,从而导致反渗透系统工作压力及淡化水盐浓度的增加．本文建立了能量回收装置水压缸中盐水和进料海水混合过程的数学模型,利用流体力学模拟软件对水压缸中混合段的形成、混合机理及混合段用作液柱活塞的条件等进行了研究,分析了液柱活塞的局限性和采用实体活塞的重要作用．     

Robust multi-objective optimization for energy production scheduling in microgrids

In order to achieve better economic and environmental benefits of microgrids (MGs) under multiple uncertainties in renewable energy resources and loads, a novel energy production scheduling method is proposed based on robust multi-objective optimization with minimax criterion. Firstly, a mixed integer minimax multi-objective formulation is developed to capture uncertainties as well as minimize economic and environmental objectives. Secondly, the primal problem is decomposed into a bi-level optimization problem, which attempts to seek robust scheduling scheme set under the worst-case realization of uncertainties in a multi-objective framework. Finally, a hierarchical meta-heuristic solution strategy, including multi-objective cross entropy algorithm and δ+ indicator, is designed to solve the reconstructed problem. Numerical results demonstrate that the proposed scheduling method can effectively attenuate the disturbance of uncertainties as well as reduce energy costs and emissions, as compared with single-objective robust optimization and multi-objective optimization scheduling approaches. This study could offer useful insights which help decision-makers balance robustness and comprehensive benefits in the operation of MGs.     

Two-Dimensional Nanofluidic Membranes with Intercalated In-Plane Shortcuts for High-Performance Blue Energy Harvesting

Two-dimensional nanofluidic membranes offer great opportunities for developing efficient and robust devices for ionic/water-nexus energy harvesting. However, low counterion concentration and long pathway through limited ionic flux restrict their output performance. Herein, it is demonstrated that rapid diffusion kinetics can be realized in two-dimensional nanofluidic membranes by introducing in-plane holes across nanosheets, which not only increase counterion concentration but also shorten pathway length through the membranes. Thus, the holey membranes exhibited an enhanced performance relative to the pristine ones in terms of osmotic energy conversion. In particular, a biomimetic multilayered membrane sequentially assembled from pristine and holey sections offers an optimized combination of selectivity and permeability, therefore generating a power density up to 6.78 W m⁻² by mixing seawater and river water, superior to the majority of the state-of-the-art lamellar nanofluidic membranes. This work highlights the importance of channel morphologies and presents a general strategy for effectively improving ion transport through lamellar membranes for high-performance nanofluidic devices.     

Economical study for hydrogen production from seawater using renewable energy in Egypt

This study looks into the possibilities of hydrogen production in the north coast and red-sea Zone, Egypt, to conver renewable energy to hydrogen (power to gas). The main purpose is to estimate the power needed for each kg of hydrogen production from seawater using renewable energy and then the quantity of desalinated seawater needed to cover this cost. We will discuss different scenarios; the main two scenarios are photovoltaic (PV) solar with reverse osmosis (RO) desalination and concentrating solar power (CSP) with multi-effect desalination (MED).     

Room-Temperature Synthesis of a COFs Membrane Via LBL Self-Assembly Strategy for Energy Harvesting

The covalent organic frameworks (COFs) membrane with ordered and confined one-dimensional channel has been considered as a promising material to harvest the salinity gradient energy from the seawater and river water. However, the application of the COFs in the field of energy conversion still faces the challenges in membrane preparation. Herein, energy harvesting is achieved by taking advantage of a COFs membrane where TpDB-HPAN is synthesized via layer-by-layer self-assembly strategy at room temperature. The carboxy-rich TpDB COFs can be expediently assembled onto the substrate with an environmental-friendly method. The increased open-circuit voltage (V_oc) endows TpDB-HPAN membrane with a remarkable energy harvesting performance. More importantly, the application perspective is also illuminated by the cascade system. With the advantages of green synthesis, the TpDB-HPAN membrane can be considered as a low-cost and promising candidate for energy conversion.     

Explosion characteristics of synthesised biogas at various temperatures

Biogas is considered as a valuable source of renewable energy. Indeed, it can be turned into useful energy (heat, electricity, fuel) and can contribute to reduce greenhouse gas emissions. Knowledge of its safety characteristics is a very important practical issue. Experimental investigation of synthesised biogas explosion characteristics was conducted in a 20-L sphere at various temperatures (30-70 degrees C) and at atmospheric pressure. The studied biogas was made of 50% methane (CH(4)) and 50% carbon dioxide (CO(2)). It was also saturated with humidity: this composition is frequently met in digesters during waste methanisation. There are two inert gases in biogas: water vapour and carbon dioxide. Its vapour water content rises along with temperature. The presence of these inert gases modifies considerably biogas characteristics compared to the ones of pure methane: explosion limits are lowered and beyond 70 degrees C, water vapour content is sufficient to inert the mixture. Furthermore, explosion violence (estimated with the maximum rate of pressure rise values, (dp/dt)(max)) is three times lower for biogas than for pure methane at ambient temperature.     

基于局域波信息熵的高速自动机故障诊断

针对小口径火炮自动机工作时产生的短时冲击信号,提出一种将局域波分解与信息熵相结合提取特征量,并利用Elman神经网络进行故障识别的诊断方法。首先运用具有自适应特性的局域波对振动信号进行分解得到IMF分量,再接着利用信息熵理论提取IMF信息熵、局域波能谱熵及能矩谱熵作为故障特征量,最后将特征向量输入Elman神经网络进行故障分类识别。实验结果表明:该方法能准确,有效地识别故障。     

Rechargeable Seawater Batteries—From Concept to Applications

Harvesting energy from natural resources is of significant interest because of their abundance and sustainability. Seawater is the most abundant natural resource on earth, covering two‐thirds of the surface. The rechargeable seawater battery is a new energy storage platform that enables interconversion of electrical energy and chemical energy by tapping into seawater as an infinite medium. Here, an overview of the research and development activities of seawater batteries toward practical applications is presented. Seawater batteries consist of anode and cathode compartments that are separated by a Na‐ion conducting membrane, which allows only Na⁺ ion transport between the two electrodes. The roles and drawbacks of the three key components, as well as the development concept and operation principles of the batteries on the basis of previous reports are covered. Moreover, the prototype manufacturing lines for mass production and automation, and potential applications, particularly in marine environments are introduced. Highlighting the importance of engineering the cell components, as well as optimizing the system level for a particular application and thereby successful market entry, the key issues to be resolved are discussed, so that the seawater battery can emerge as a promising alternative to existing rechargeable batteries.     

Application of thermal battery in the ice storage air-conditioning system as a subcooler

This article experimentally investigates the thermal performance of a thermal battery used in the ice storage air-conditioning system as a subcooler. The thermal battery utilizes the superior heat transfer characteristics of two-phase closed thermosyphon and eliminates the drawbacks found in convectional energy storage systems. Experimental investigations are first conducted to study the thermal behavior of thermal battery under different charge temperatures (−5 °C to −9 °C) in which water is used as the energy storage material. This study also examines the thermal performance of the subcooled ice storage air conditioner under different cooling loads. Experimental data of temperature variation of water, ice fraction, refrigerant mass flow rate and coefficient of performance (COP) are obtained. The results show that supercooling phenomenon appears in the water and it can be ended when the charge temperature is lower than −6 °C. The system gives 28% more cooling capacity and 8% higher COP by the contribution of the thermal battery used as a subcooler.     

Self-assembled core-shell polydopamine@MXene with synergistic solar absorption capability for highly efficient solar-to-vapor generation

As a renewable and environment-friendly technology for seawater desalination and wastewater purification, solar energy triggered steam generation is attractive to address the long-standing global water scarcity issues. However, practical utilization of solar energy for steam generation is severely restricted by the complex synthesis, low energy conversion efficiency, insufficient solar spectrum absorption and water extraction capability of state-of-the-art technologies. Here, for the first time, we report a facile strategy to realize hydrogen bond induced self-assembly of a polydopamine (PDA)@MXene microsphere photothermal layer for synergistically achieving wide-spectrum and highly efficient solar absorption capability (≈ 96% in a wide solar spectrum range of 250–1,500 nm wavelength). Moreover, such a system renders fast water transport and vapor escaping due to the intrinsically hydrophilic nature of both MXene and PDA, as well as the interspacing between core-shell microspheres. The solar-to-vapor conversion efficiencies under the solar illumination of 1 sun and 4 sun are as high as 85.2% and 93.6%, respectively. Besides, the PDA@MXene photothermal layer renders the system durable mechanical properties, allowing producing clean water from seawater with the salt rejection rate beyond 99%. Furthermore, stable light absorption performance can be achieved and well maintained due to the formation of ternary TiO2/C/MXene complex caused by oxidative degradation of MXene. Therefore, this work proposes an attractive MXene-assisted strategy for fabricating high performance photothermal composites for advanced solar-driven seawater desalination applications.

     

7Li MRI of Li batteries reveals location of microstructural lithium

There is an ever-increasing need for advanced batteries for portable electronics, to power electric vehicles and to facilitate the distribution and storage of energy derived from renewable energy sources. The increasing demands on batteries and other electrochemical devices have spurred research into the development of new electrode materials that could lead to better performance and lower cost (increased capacity, stability and cycle life, and safety). These developments have, in turn, given rise to a vigorous search for the development of robust and reliable diagnostic tools to monitor and analyse battery performance, where possible, in situ. Yet, a proven, convenient and non-invasive technology, with an ability to image in three dimensions the chemical changes that occur inside a full battery as it cycles, has yet to emerge. Here we demonstrate techniques based on magnetic resonance imaging, which enable a completely non-invasive visualization and characterization of the changes that occur on battery electrodes and in the electrolyte. The current application focuses on lithium-metal batteries and the observation of electrode microstructure build-up as a result of charging. The methods developed here will be highly valuable in the quest for enhanced battery performance and in the evaluation of other electrochemical devices.     

基于时间-小波能量谱熵的滚动轴承故障诊断研究

针对轴承振动信号中存在周期性冲击这一现象,提出了时间-小波能量谱熵的计算方法,用于滚动轴承的故障诊断。首先构造脉冲小波,采用连续小波变换的方法得到时间域内小波能量谱,再沿时间轴计算能量谱熵,定量描述振动信号沿时间的分布情况,不同故障下轴承的冲击振动随时间变化程度不同,其时间-小波能量谱熵值也就不同。将不同故障轴承信号的时间-小波能量谱熵作为向量特征输入建立支持向量机,实现了对轴承的工作状态和故障类型的判断。实验结果表明,时间-小波能量谱熵可以有效地对滚动轴承进行故障诊断。     

From heat to entropy

Milestones in the development of thermodynamics are the discovery of the absolute temperature scale and the recognition that differential “heat” is a form of energy given as the product of absolute temperature and differential entropy. Following a new path, the last statement results from a careful analysis of the heat transfer applying the first theorem without reference to the usual cycles in thermodynamics. This confirms also characteristic properties of entropy. In particular, the total entropy can never decrease in a process. In thermal equilibrium, the differential thermal energy is proportional to the differential entropy with the constant of proportionality being the temperature of the heat and entropy. Hence, thermal energy and entropy are transferred simultaneously into the same storage facilities, some of which are mentioned. However, the issue which one is the superior quantity is obsolete. The entropy is maximum for a given amount of exchanged thermal energy and, vice versa, for a given amount of exchanged entropy the concomitant energy is minimum. We calculate the thermal energy and entropy of phonons (as bosons) in oscillators and of electrons (as fermions) in their states of solids and melts as examples from statistical thermodynamics. The thermal energy or heat is the sum of the energies of all bosons and fermions in their elementary states or quantum states according to Bose Einstein and Fermi Dirac statistics in thermal equilibrium minus the total energy in the limit T→0 K. The entropy can be written as mixing entropy of all of these quantum states weighted with their occupancies, in agreement with an earlier publication. Thus, entropy is a logarithmic metrics of the number of all possible variants to distribute the respective total energy over all elementary states in thermal equilibrium.     

Electricity generation: options for reduction in carbon emissions

Historically, the bulk production of electricity has been achieved by burning fossil fuels, with unavoidable gaseous emissions, including large quantities of carbon dioxide: an average-sized modern coal-burning power station is responsible for more than 10 Mt of CO(2) each year. This paper details typical emissions from present-day power stations and discusses the options for their reduction. Acknowledging that the cuts achieved in the past decade in the UK CO(2) emissions have been achieved largely by fuel switching, the remaining possibilities offered by this method are discussed. Switching to less-polluting fossil fuels will achieve some measure of reduction, but the basic problem of CO(2) emissions continues. Of the alternatives to fossil fuels, only nuclear power represents a zero-carbon large-scale energy source. Unfortunately, public concerns over safety and radioactive waste have still to be assuaged. Other approaches include the application of improved combustion technology, the removal of harmful gases from power-station flues and the use of waste heat to improve overall power-station efficiency. These all have a part to play, but many consider our best hope for emissions reduction to be the use of renewable energy. The main renewable energy contenders are assessed in this paper and realistic estimates of the contribution that each could provide are indicated. It appears that, in the time-scale envisaged by planners for reduction in CO(2) emission, in many countries renewable energy will be unlikely to deliver. At the same time, it is worth commenting that, again in many countries, the level of penetration of renewable energy will fall short of the present somewhat optimistic targets. Of renewable options, wind energy could be used in the short to medium term to cover for thermal plant closures, but for wind energy to be successful, the network will have to be modified to cope with wind's intermittent nature. Globally, hydroelectricity is currently the largest developed source of renewable electricity, but future large-scale projects will probably be limited to the less-developed world: the best schemes in the developed countries have already been exploited. Wave and tidal can be looked on as medium- to long-term generators of electricity, as their respective industries are not as mature as competing renewable resources. Municipal solid-waste combustion and landfill gas technologies can also be seen as short term, as can their rural equivalents, agriculture and forestry waste. Any widespread exploitation of renewable energy will depend on being able to transmit the energy from source to point of use, so the implications for the electrical network from the penetration of substantial levels of renewable energy are presented. Effective management of renewable energy installations will require technical assessment of the range of exploitation strategies, to compare local production of, say, hydrogen and the more traditional transmission of electricity. Such resources will have to compete with others in any national, or grid, system and detailed economic analysis will be necessary to determine the deployment that best fits the trading regime under which the energy will be sold. Consideration will also be necessary to determine how best to control the introduction of this radically new resource such that it does not attract punitive cost overheads until it is mature enough to cope. Finally, it is inescapable that nuclear power is a proven technology that could take its place in any future generation portfolio. Unfortunately, suspicion and mistrust surround waste management and radioactivity release. Unless this is overcome, the lack of confidence engendered by this public mistrust may result in few, if any, new nuclear power stations being built. In the event of that decision, it is difficult to see how CO(2) levels can be significantly reduced: the irony is that nuclear energy may emerge as environmentally essential.     

Flexural properties of z-pinned composite laminates in seawater environment

Unidirectional carbon-fibre reinforced composite laminates with and without z-pins were immersed in artificial seawater and exposed to two different temperature levels (?1.75 and 50 °C), as well as thaw–freeze cycles (+20/?20 °C). The investigation described is focused on the question to which degree seawater absorption, as well as bending properties are influenced by z-pin reinforcement. The results indicate an increasing influence of the z-pin reinforcement on the water sorption rate, while the sorption rate of unpinned laminates is lower. This is a result of the additional diffusion pathways of the moisture ingress into the laminate caused by the inserted z-pins which in turn change the micro-structure. Furthermore, the sorption rate depends on the immersion temperature. Laminates immersed into seawater with higher temperatures (50 °C) display a significantly higher diffusion rate than those immersed in colder seawater (?1.75 °C) or those immersed under thaw–freeze conditions (+20/?20 °C). Z-pin reinforced laminates with a unidirectional fibre orientation show a reduced bending strength by about 31 %, as well as a reduced flexural modulus by about 11 % in comparison to unpinned samples. Unpinned and z-pinned samples that were exposed to a seawater environment for 1344 h show a reduced flexural modulus depending on the immersion temperatures. As opposed to flexural modulus, flexural strength is not affected by immersion time or temperature. The overall bending strain energy that is necessary for a complete fracture of the unpinned samples under 4-point bending loads can be described with the value of the elastic bending strain energy. In contrast to this the overall bending strain energy of the z-pinned laminates is composed of two different components –the elastic bending strain energy and the post-fracture strain energy. The post-fracture strain energy occurs after exceeding the flexural strength. The overall bending strain energy of z-pinned and unpinned samples without immersion into seawater is around 7.2 J, while the percentage of the post-fracture energy of the pinned samples is 40 % with respect to the overall bending strain energy. The duration of the immersion into water and higher water temperatures increases the overall bending strain energy for both unpinned and pinned samples. The increase is higher for z-pinned samples and is mainly caused by the increase of the post-fracture energy.