考虑收益风险的梯级水电站群中长期合约电量最优组合模型

针对梯级水电站群参与不同时间尺度的合约电量交易时天然来水和交易电价的不确定性因素导致不同市场份额难以确定、水资源利用不充分及不同时间尺度电量分配不合理导致收益存在较大风险问题，提出了考虑收益风险的梯级水电站群中长期合约电量最优组合模型，该模型采用给定置信度下整个梯级发电收益风险最小为目标，其求解首先由多年来水数据生成随机月尺度来水过程，然后根据梯级水电站占市场比重不同模拟出三种电价函数，采用逐步优化和逐次逼近混合算法对电站出力和合约电量组合循环迭代求解。最后以西南地区某流域梯级水电站为例进行验证。结果表明，所提出的优化调度模型能够合理制定年度和月度双边合约电量申报策略，有效降低收益风险，为梯级水电站群参与不同时间尺度的双边交易市场提供可靠依据。     

考虑流量演进过程的丰水期梯级水电风险调度

丰水期梯级水电流域来水充沛,上下游水电站之间的流量演进过程对于水电站的优化调度具有重要影响。为了细致描述上下游出入库流量传播过程,结合槽蓄方程和水量平衡方程,运用马斯京根法建立了上下游流量的耦合关系,同时针对丰水期天然来水和市场电价的双重不确定性,综合考虑发电商的风险喜恶行为对调度决策的影响,构建了梯级水电风险调度模型,并利用混合整数线性规划法予以求解。算例结果表明,丰水期考虑河道流量演进过程的梯级水电优化调度模型精确性更高,在不同风险偏好下,可有效地平衡风险和发电效益之间的矛盾。     

考虑备用情况下的梯级水电站竞价策略研究

采用科学合理的竞价策略是赢得市场先机的重要先决条件。该文在考虑备用调用不确定性及梯级水电水力约束的基础上,以梯级水电站整体期望收入最大化为目标构建了梯级水电竞价策略模型,引入粒子群算法作为模型求解算法,并以四川省大渡河流域上的瀑布沟、深溪沟梯级水电站为算例,采用该文提出的模型算法进行验证,结果表明：承担备用任务的梯级水电在竞价过程中,受梯级水力约束的影响,梯级电站申报量最值与市场价格峰值出现时刻并不同步,但整体上市场价格高时较市场价格低时申报量更高;运用该文构建的模型能得到合理的优化调度竞价结果,能充分发挥上游电站的调节能力和下游电站的发电潜力,最大限度地挖掘梯级电站联合运行所产生的效益,在考虑备用调用不确定性下梯级期望总收入为2 469万元。     

基于分时电价的多年调节水库年末消落水位研究

针对梯级水库中多年调节水库年末消落水位优选问题,结合分时电价下梯级水库中长期发电优化调度的特点,建立了分时电价下多年调节水库年末消落水位优选模型,并应用协同进化遗传算法对模型进行了求解.乌江梯级水库实例计算结果表明,该模型与求解方法可靠、合理,为分时电价下梯级水库发电优化调度提供了理论计算依据.     

聚合商模式下电动汽车消纳风电研究

电动汽车协同新能源共同规划为新能源的充分利用带来新机遇。文章研究了聚合商模式下的电动汽车消纳弃风的调度策略;设计了聚合商、电动汽车车主、风电场三方共同获利的合作方法;提出了包含电动汽车的可信度和剩余电量的电动汽车可调度潜力评估方法;对参与聚合商充放电控制的电动汽车进行排序,建立了考虑风电出力不确定性的聚合商协同风电场消纳弃风的优化调度模型。该模型以聚合商收益最高为目标函数,在分析购电分时电价、电动汽车充电分时电价的基础上,结合各类基础参数对模型进行求解。文章以上海某区域为研究对象进行算例仿真,验证了所提策略既能使三方获利,又能取得消纳部分弃风和减轻电网负荷高峰的效果。     

基于自适应SMPC的梯级水-风-光互补系统多目标优化调度

为抑制风电、光伏的波动性,文章建立了梯级水-风-光互补系统的多目标优化调度模型,同时考虑了调度成本与水电出力波动性,提出了一种基于自适应随机模型预测控制的梯级水-风-光高效协调优化方法。该方法利用场景削减技术,进一步抑制风光出力不确定性,并采用自适应变权重方法自动调整多目标权重系数。文章比较了方法改进前、后以及梯级水电站数量对互补系统优化调度结果的影响。系统仿真表明,所提自适应（Stochastic Model Predictive Control, SMPC）方法,可有效抑制风电、光伏的不确定性与波动性,提高水电出力的可靠性与稳定性     

考虑源荷不确定性的分时电价动态修正机制研究

针对新型电力系统中可再生能源出力及负荷需求的不确定性造成源荷协调困难,导致难以制定合理的分时电价的问题,该文提出一种考虑源荷不确定性的分时电价动态修正机制。首先,根据可再生能源出力的波动性以及不确定性,建立新能源并网功率与并网电量偏差量化模型;其次,根据需求侧负荷的变化特征,结合可再生能源出力不确定性,通过多种不确定性因素影响条件的误差计算方法,建立电价概率密度模型。然后,根据负荷上报的用电量以及预报电价,建立考虑源荷不确定性的电力市场分时电价动态修正与优化模型,并采用粒子群算法进行模型求解。最后,通过实际运行数据仿真验证该文所提方法的有效性。     

不同电价政策下流域梯级水电站群长期优化调度

为定量分析、比较不同电价政策下流域梯级水电站群运营特点,结合发电侧市场开放后梯级水电站群发电计划制定的实际,考虑不同电价政策,以水电站群发电收益最大为目标,建立了长期优化调度模型,并采用粒子群算法求解模型.以我国西南某流域梯级电站群为例,探讨了不同电价政策对梯级电站群优化调度的影响.     

高水电比重系统随机电力电量平衡模型与算法

针对高水电比重系统中电力电量平衡问题,首先考虑利用典型周负荷曲线进行电力电量平衡分析,以更好地计及工作日和非工作日不同的负荷曲线对可调水电站库容及火电站开机的影响。为恰当考虑风电场和光伏电站出力的不确定性和波动性,建立了基于随机优化的随机电力电量平衡模型,从概率的角度更好地分析和衡量风光电站对电量平衡的贡献。为方便该模型的求解,对非线性的水电转换函数进行线性化处理,得到混合整数规划模型,采用CPLEX对模型进行求解。以某高水电比重系统作为算例进行仿真分析,验证了所提随机电力电量平衡模型与算法的正确性和有效性,从概率的角度定量分析了风光电站的电量贡献。     

水电厂年度合约电量的风险控制研究

针对电力市场环境下水电企业的合同电量确定及计划安排等问题,从水电厂商对预测径流和预测现货电价的风险态度出发,提出以风险价值(VaR)为风险量测方法,构建了考虑径流和电价的不确定性控制风险模型,并基于水电厂商风险控制目标确定年度合约电量.     

Contents in Volume 23,2014

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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.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

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.     

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。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.