Effects of solvents and catalysts in liquefaction of pinewood sawdust for the production of bio-oils

Liquefaction of biomass with proper solvents and catalysts is a promising process to produce liquid biofuels and valuable chemicals. In this study, pinewood sawdust was liquefied in the presence of various supercritical solvents (carbon dioxide, water, acetone, and ethanol) and catalysts (alkali salts and acidic zeolites). The liquid, gas and solid products were analyzed using GC–MS, FT-IR, elemental analyzer, ¹H NMR, ¹³C NMR. The experimental results showed that both solvent and catalyst can significantly improve the liquefaction process by increasing the yield of liquid oil and suppressing the formation of solid residue. K₂CO₃ showed the best performance by doubling the yield of bio oil. Meanwhile, the maximum bio-oil yield (30.8 wt%) and the minimum solid residue yield (28.9 wt%) were obtained when ethanol was employed as the solvent. Solvents can also strongly affect the distribution of liquid products. 2,4,5,7-tetramethyl-phenanthrene and bis(2-ethylhexyl) phthalate were the premier compounds in liquid product as supercritical carbon dioxide is used as solvent while 2-methyl-naphthalene became the main composition when water is used as solvent.     

中外发展低碳经济的比较分析

2007年,胡锦涛主席在APEC第15次领导人会议上提出了四项建议,明确主张"发展低碳经济"。本文以我国能源利用状况为切入点,通过对我国与发达国家及金砖四国低碳经济发展状况进行比较,得出了目前我国在世界范围内低碳经济的发展仍处于较低水平的结论。     

计及碳交易与需求响应的多典型日综合能源系统优化模型

系统负荷作为综合能源系统的约束条件,常以单个典型日加以表征,这难以描述实际负荷波动性与随机性的特点。本文构建了计及碳交易与需求响应的多典型日优化模型。通过引入谱聚类算法获得多个典型日数据,在表征原始负荷数据波动性与随机性的同时,也基于负荷数据构成实现了数据分类,并以负荷构成为基础分别建立优化模型,引入阶梯型碳交易机制与需求响应机制,在Python语言下调用Gurobi求解器完成模型求解仿真,在此基础上对阶梯型碳交易参数的变化开展研究。结果表明,本文提出的优化模型可很好地针对全年不同的负荷特征实现灵活调度,在兼顾经济性与环保性的同时有利于清洁机组出力。     

计及碳排放成本的风光燃储综合能源系统规划

构建了一套耦合风光燃储网的冷、热、电三联供综合能源系统,以系统经济性和环境效益为优化目标对系统的设备和参数进行优化研究,得出了现行约束条件下的最优系统配置。结果表明：5种系统中,“风-光-燃-储-网”系统的年CO₂排放量和系统总成本均最低;“风-光-储-网”系统消纳可再生能源的能力最佳,可再生能源渗透率为69.93%,但总成本为“风-光-燃-储-网”系统的159%;光伏价格和碳税价格与年CO₂排放量呈反比,且当光伏降价比例达到40%后,其对年CO₂排放量的限制作用不再突出。     

阶梯碳下考虑耦合电转气-碳捕集和热电联产灵活输出的综合能源系统优化调度

\"双碳\"目标下,为进一步降低综合能源系统(integrated energy system,IES)碳排放,提升可再生能源消纳能力,提出一种IES低碳经济运行优化策略.首先引入阶梯型碳交易机制约束IES的碳排放;然后建立耦合电转气(power to gas,P2G)和碳捕集系统(carbon capture system,CCS)模型,并细化P2G两阶段运行;接着在传统热电联产机组(combined heat and power,CHP)中引入卡琳娜循环与电锅炉联合运行,构造热电灵活输出的CHP模型;最后以系统运维成本、碳交易成本、购能成本和弃风弃光成本之和最小为优化目标,构建IES低碳经济调度模型,并设置不同运行场景对比分析.结果表明:IES碳排放减少38.45％,运行总成本降低10.37％,验证了所建模型的低碳性和经济性.     

Projecting demand and supply of forest biomass for heating in Norway

This paper assesses the increase in demand and supply for forest biomass for heating in Norway in 2020. By then there is a political aim to double the national production of bioenergy from the level in 2008. The competitiveness of woody biomass in central and district heating is analyzed in a model selecting the least-cost heating technology and scale in municipalities given a set of constraints and under different fuels price scenarios. The supply of forest biomass from roundwood is estimated based on data of forest inventories combined with elasticities regarding price and standing volumes. The supply of biomass from harvesting residues is estimated in an engineering approach based on data from the national forest inventories and roundwood harvest. The results show how the production of bioenergy is affected by changes in energy prices and support schemes for bioenergy. One conclusion from the analyses is that the government target of 14 TWh more bioenergy by 2020 is not likely to be met by current technologies and policy incentives. The contribution of the analysis is the detailed presentation of the heat market potentials and technology choices combined with supply functions for both roundwood and harvesting residues.     

N,P, S co-doped biomass-derived hierarchical porous carbon through simple phosphoric acid-assisted activation for high-performance electrochemical energy storage

Porous carbon materials are the most widely used electrode materials in Electric Double Layer Supercapacitor (EDLS). Optimize specific surface area, improving hierarchical pores structure, and doping heteroatoms are all important methods to improve the capacitance performance of electrodes. Herein, we synthesize walnut shell-derived hierarchical porous carbon (WSPC) with cost-effective and well-developed pore for electrochemical energy storage via simple phosphoric acid-assisted activation method. The final porous carbon products have perfect microporous structure, abundant heteroatom functional groups (the atomic content ratio of nitrogen, phosphorus and sulfur reaches 10.3%), and high specific surface area and pore volume (up to 2583 m² g^?1 and 1.236 cm³ g^?1, respectively). In the three-system, the electrode shows an optimal specific capacitance of up to 332 F g^?1 and excellent rate performance. In the symmetric system, the symmetric device WSPC//WSPC shows a maximum gravimetric specific energy of ~14.08 Wh kg^?1. And the device still has a specific energy of 9.75 Wh kg^?1 even under the high gravimetric specific power of 7 kW kg^?1. In addition, the device has excellent cycle stability and retains an initial specific capacitance of 90.2% after 8000 galvanostatic charge-discharge (GCD) cycle. In summary, these outstanding results suggest the biomass derived porous carbon possessing the potential and will show great commercial value for the fabrication of high performance supercapacitors.     

考虑互联协同的分布式能源站低碳多目标选址规划研究

“双碳”目标和能源转型的大背景下,区域综合能源系统内部耦合关系不断丰富,对于碳排放的管理不断严格,考虑互联协同的分布式能源站低碳规划问题亟待解决。为此,首先讨论了互联协同分布式能源站空间性能参数矩阵;然后计及负荷-能源站的管线建设以及环境成本、能源站-能源站的互联管线长度、各个分布式能源站规划容量等关键因素,提出了一种考虑互联协同的分布式能源站低碳多目标选址规划模型;最后,讨论了负荷不确定性对分布式能源站选址规划的影响,并且基于基准负荷确定性场景,在某城市实际算例中验证并讨论了考虑低碳需求前后各个分布式能源站的选址结果对比。     

An investigation into steam gasification of biomass for hydrogen enriched gas production in presence of CaO

Biomass steam gasification could be an attractive option for sustainable hydrogen production. Biomass, regarded as carbon neutral emitter, could be claimed as carbon negative emitter if carbon dioxide produced is captured and not allowed to emit to the environment during the process. Thus here an experimental study is carried out to find out the potential of hydrogen production from steam gasification of biomass in presence of sorbent CaO and effect of different operating parameters (steam to biomass ratio, temperature, and CaO/biomass ratio). Product gas with hydrogen concentration up to 54.43% is obtained at steam/biomass = 0.83, CaO/biomass = 2 and T = 670 °C. A drop of 93.33% in carbon dioxide concentration was found at CaO/biomass = 2 as compared to the gasification without CaO. Mathematical model based on Gibbs free energy minimization has been developed and is compared with the experimental results.     

考虑动态定价和碳交易的多园区综合能源服务商低碳合作优化策略

为解决多园区综合能源服务商参与综合能源市场和碳交易市场带来的利益分配和动态定价问题,该文提出一种新的多园区服务商合作交易框架。首先,设计阶梯式碳交易下多园区综合能源服务商合作运行交易机制,针对区域零售市场制定动态价格,以指导各园区服务商购能行为;其次,在新型电力系统的逐步构建下,根据新能源占比变化,完善碳配额与碳排放模型,并通过市场下阶梯式碳交易机制约束各园区的碳排放;最后,建立多园区服务商纳什议价模型,将所建模型分解为联盟成本最小化与电热交易支付谈判子问题,通过算例验证所提模型和方法能提高各园区参与联盟主动性,并有效降低各园区碳排放和总运行成本。     

吸收式制冷压缩CO2储能系统性能分析

提出了一种结合了吸收式制冷循环的压缩CO₂储能系统,该系统采用分流的方式,将一部分CO₂引流至二级压缩机,将压缩产生的热量提供给吸收式制冷循环,使其启动工作并提供冷量给主路CO₂,同时使用高压罐储存液态CO₂,从而提高系统的储能效率。此外,对该系统进行了热力学分析和多目标优化。结果表明：在设计工况下,吸收器、一级压缩机、透平和级后换热器的■损较大;本系统的储能效率随着冷凝压力、压缩机等熵效率和透平等熵效率的增加而提高,而储能压力的增大会使系统的储能效率降低;系统的最佳储能效率为68.70%,能量密度为0.153 kW·h/m³。     

基于S-CO2布雷顿循环的太阳能发电储能一体化系统性能分析

设计了一种以S-CO₂和石英石为储能介质、再压缩S-CO₂布雷顿循环为动力循环的塔式太阳能热发电储能一体化系统。基于Gensystem计算平台,建立了动力循环、太阳能集热系统、S-CO₂斜温层储热罐的数学模型,研究了集热系统性能和S-CO₂斜温层储热罐的储、释热动态特性。在此基础上,分析了一体化系统的热力性能和经济性能。结果表明：经过13次循环储、释热过程,斜温层储热罐出口温度趋于稳定。释热结束时,斜温层储热罐热流体出口温度下降了63 K,储热结束时,冷流体出口温度升高了46 K。与配置双储热罐的塔式太阳能热发电系统相比,一体化系统夏至日和冬至日日均发电效率分别提高了1.8%和1.7%,系统总投资降低了9.46%,平准化度电成本下降了9.45%,投资回收期缩短了1.8 a。     

考虑碳捕集和电转气的零碳园区综合能源系统经济调度

针对园区综合能源系统的多能耦合和零碳运行问题,提出一种考虑碳捕集和电转气的零碳园区综合能源系统经济调度策略。首先,分析园区综合能源系统架构,建立考虑碳捕集和电转气的电、热、冷、气多能耦合的园区综合能源系统模型;其次,综合核算园区生态碳汇、能源生产碳源等,提出适用于园区综合能源系统的零碳指标,以系统经济效益最优为目标建立零碳园区综合能源系统经济调度模型;最后基于不考虑碳中和约束、考虑碳中和约束及考虑碳捕集和电转气联合运行的3种场景,结合分时电价并采用改进粒子群算法对经济调度模型进行求解。结果验证了所提模型和方法的有效性,考虑碳捕集和电转气联合运行的方式可提高清洁能源的消纳率、降低系统运行的成本,同时实现园区综合能源系统的碳中和。     

我国分布式能源发展现状及展望

分布式能源具有清洁、低碳、高效等优点,是以新能源为主体的新型电力系统的重要组成部分,是实现能源体系“碳达峰、碳中和”的有效方式。为加快构建新型电力系统、尽早实现“碳达峰、碳中和”,有必要研究和了解现阶段分布式能源发展情况。通过分析当前我国能源结构和清洁能源发展形势,以及分布式光伏、天然气分布式和分散式风电三大典型分布式能源的发展现状,归纳了分布式能源发展五方面问题:发展有待协同、成本有待降低、消纳有待提升、技术有待创新、政策有待完善。在此基础上结合国家相关政策提出加大支持力度、做好科学论证、加强技术创新、推动市场交易和鼓励电网参与五方面建议,指出多能互补系统将是分布式能源高效利用的发展方向。     

Shrinkage of liquid CO2 droplets in water

The shrinkage rate of liquid CO₂ droplets in water at 3°C was measured by the use of high-pressure vessel placed in a constant-temperature room. The change of the diameter of the droplet was observed at pressures of 28 MPa and 35 MPa using a time-lapse video camera. Bromocresol green was employed as a pH indicator, and was effective in monitoring the profile of carbonic acid distribution. When a droplet of liquid CO₂ was injected, CO₂ hydrate immediately formed and covered the surface of the droplet. The diameter of the liquid CO₂ droplet reduced gradually at a rate of 5.0 × 10^?7 m/s. It is predicted, from the viewpoint of ocean CO₂ sequestration, that a thin film of hydrate will form at the interface of sea water and liquid CO₂, and that the hydrate film will greatly control the dissolution of CO₂ into sea water.