考虑电力系统灵活性的网-储联合规划

高比例可再生能源接入电网使得规划问题更加复杂。提出考虑电力系统灵活性的网-储联合规划方法。分析风电和光伏出力的相关性,采用蒙特卡罗方法生成大量可再生能源发电和负荷场景。基于k-means聚类算法对生成的场景进行缩减,并利用改进的遗传算法确定最优聚类数。通过斯皮尔曼系数筛选典型场景,构建考虑生成概率的典型场景集合。建立以提升灵活性、降低投资成本为目标的双层网-储联合规划模型,并采用灰狼算法迭代求解。算例分析结果表明所提网-储联合规划方案能够有效地提升电力系统灵活性,促进可再生能源消纳。     

基于数据挖掘的电力系统异常数据辨识与调整

为了保证电力系统的可靠运行,需要对系统中的异常数据进行检测辨识与调整。在数据挖掘领域,模糊C均值聚类法（FCM）在处理小量低维的数据挖掘时是有效的,但是面向电力系统的数据库的数据挖掘是要处理大量、高维的数据,这样FCM算法在时间性能上难以令人满意。文中基于采样技术对FCM算法进行改进,利用遗传算法对聚类结果进行优化,利用一种新的基于遗传优化的采样模糊C均值聚类算法FFGO（FuzzyFCMwithGeneticOptimization）,实现对异常数据的实时动态处理。     

基于改进PCM算法的冷热电联供系统优化配置

为提高CCHP系统的综合效益,提出一种基于改进PCM聚类算法的冷热电联供系统各电、热储能以及光伏装置容量最优配置模型,使得该系统的年折算投资成本、年运行维护成本最小,以及年CO2排放量最小。在传统PCM聚类算法基础上,使用熵权法以加权的形式引入PFS指标与Vp指标实现对聚类效果的综合评价,进而通过遍历的方法寻找最佳聚类数与模糊系数;构建了优化配置模型并以NSGA-Ⅱ算法完成求解;针对实际案例构建优化配置模型,并将改进PCM算法的聚类结果输入到模型中,经过对比分析验证了所提方法的可行性与有效性。     

计及火电深度调峰的高比例可再生能源电力系统日前优化调度研究

针对高比例可再生能源并网,提出含风、光、火、蓄的高比例新能源电力系统多目标日前优化调度模型。该模型考虑在火电机组深度调峰及频繁爬坡等新工况下的火电机组运行成本、污染物惩罚成本以及可再生能源弃电成本,以系统运行成本最低、风光出力最大以及净负荷波动最小为优化目标,采用NSGA-Ⅱ算法进行优化求解。通过对某典型日不同调度场景进行仿真计算,结果表明所建立的系统运行总成本计算模型能够兼顾该系统的经济、环保与消纳,所提出的多目标优化调度策略能够促进高比例可再生能源的消纳,缓解火电机组的调峰压力,降低系统运行总成本,指导电力系统火电灵活性改造,保证电力系统安全、稳定、经济运行。     

基于FCM-FM算法的光伏阵列故障诊断

工作于自然环境的光伏阵列故障频发,及时对故障进行定位和分类对于提高光伏电站运行水平具有重要意义。针对光伏阵列的常见故障类型（短路、开路、局部遮挡等）,基于运行数据提出无监督模糊C均值（FCM）聚类与模糊隶属（FM）算法相结合的光伏阵列故障诊断方法。论文首先对光伏阵列典型故障的产生机理进行分析并提取故障特征参数;然后,采用FCM聚类方法对光伏阵列典型故障样本数据进行分类,得到不同故障的聚类中心;最后,利用FM算法计算运行数据与聚类中心的隶属度,判定故障类型。基于数字模拟实验和实证测试,验证上述方法的有效性。分析结果表明,本文方法可有效判别光伏阵列的典型故障,诊断结果准确、可靠。     

考虑风光不确定性的综合能源系统容量-成本两阶段规划优化研究

针对综合能源系统规划面临可再生能源波动性强、出力不确定性等问题,文章提出了一种考虑风光不确定性的综合能源系统容量-成本两阶段规划优化方法。首先,运用拉丁超立方抽样生成基础风、光场景集,并基于改进的k-means算法进行场景削减;其次,以运行成本最低、碳减排最优、污染物减排最优构建多目标优化模型;最后,提出系统容量-成本两阶段规划优化求解策略,并选取南方某商业园区进行规划仿真。仿真结果表明,文章所构建的综合能源系统两阶段规划模型能够在保证系统经济性的同时兼顾环保性,并满足用户多种用能需求。     

考虑风电场景缩减的多区域综合能源系统容量配置

以冷-热-电联供为核心的综合能源系统(IES)能有效提高能源利用率和供能灵活性。文章针对大规模风电接入对IES规划和运行的影响,提出了一种考虑风电场景缩减的多区域综合能源系统容量配置方法。采用混合度量的改进k-means算法对风电历史数据进行聚类,判定聚类场景数目和聚类中心;在充分考虑热网损耗和延迟效应的基础上,建立包含热网管道、节点、换热器的详细热网模型;通过热网连接多个区域综合能源系统,建立以系统年投资成本、运行成本和弃风惩罚成本之和最小为目标函数的多区域综合能源系统容量配置模型。仿真结果表明,该模型能大幅降低设备配置容量和系统运行费用,提高风电消纳率。     

FCM-RVM预警模型在某重力坝典型坝段水平位移预测中的应用

针对大坝变形原型监测数据的非线性和影响因子的相关性问题,提出一种基于模糊C-均值聚类（FCM）和相关向量机(RVM)的组合建模方法。首先用FCM方法对影响因子进行相似聚类,然后运用RVM算法分别对每一聚类样本进行训练学习得到对应的RVM模型,其中RVM算法中的核参数采用改进的粒子群（PSO）算法寻优。将各组合算法用于某重力坝典型坝段水平位移的安全模型构建中,并与多种模型预测结果对比,结果表明,FCM-RVM预警模型的预测精度较高。研究结果可为类似工程的大坝变形预警提供参考。     

计及风光不确定性的风-光-光热联合发电系统中光热电站储热容量优化配置

传统新能源电站之间联合形式单一且未考虑风光出力不确定性,弃风、弃光现象严重。为此,提出了一种考虑风光不确定性的风-光-光热联合系统的光热电站储热容量优化配置策略,利用电转热技术使风光电站和光热电站有效耦合,明确联合系统框架与原理;采用改进拉丁超立方抽样方法抑制风光出力的不确定性。最后,构建基于风光出力典型场景的光热电站储热容量双层优化配置模型,并进行算例求解,结果表明所提方法显著降低了系统总投资与运行成本,提高了清洁能源消纳能力。     

基于优化聚类的组合风速短期预测

准确的风功率预测对电力系统安全、稳定运行具有重要意义,而风速预测是风功率预测的关键。文章提出一种基于优化模糊C均值(Optimal Fuzzy C means,OFCM)聚类的组合风速短期预测方法。首先,采用模拟退火遗传算法优化模糊C均值聚类算法的初始聚类中心;其次,基于优化模糊C均值聚类算法将初始风速属性样本数据进行分组;再根据不同风速样本组,运用极限学习机(Extremely Learning Machine,ELM)构建组合风速预测模型;最后,通过风速实测值与预测值的对比,验证了该方法的可行性。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。