Combined heat and power economic dispatch problem using the invasive weed optimization algorithm

Cogeneration units which produce both heat and electric power are found in many process industries. These industries also consume heat directly in addition to electricity. The cogeneration units operate only within a feasible zone. Each point within the feasible zone consists of a specific value of heat and electric power. These units are used along with other units which produce either heat or power exclusively. Hence the economic dispatch problem for these plants optimizing the fuel cost is quite complex and several classical and meta-heuristic algorithms have been proposed earlier. This paper applies the invasive weed optimization algorithm which is inspired by the ecological process of weed colonization and distribution. The results obtained have been compared with those obtained by other methods earlier and showed a marked improvement over earlier ones.     

Numerical simulation of the laminar hydrogen flame in the presence of a quenching mesh

Recent studies of J.H. Song et al. [1], and S.Y. Yang et al. [2] (see also references therein) have been concentrated on mitigation measures against hydrogen risk. The authors have proposed installation of quenching meshes between compartments or around the essential equipment in order to contain hydrogen flames. Preliminary tests were conducted which demonstrated the possibility of flame extinction using metallic meshes of specific size.Considerable amount of numerical and theoretical work on flame quenching phenomenon has been performed in the second half of the last century and several techniques and models have been proposed to predict the quenching phenomenon of the laminar flame system (see for example [3] and references therein). Most of these models appreciated the importance of heat loss to the surroundings as a primary cause of extinguishment, in particular, the heat transfer by conduction to the containing wall. The supporting simulations predict flame-quenching structure either between parallel plates (quenching distance) or inside a tube of a certain diameter (quenching diameter).In the present study the flame quenching is investigated assuming the laminar hydrogen flame propagating towards a quenching mesh using two-dimensional configuration and the earlier developed models. It is shown that due to a heat loss to a metallic grid the flame can be quenched numerically.     

Entropy production, efficiency, and economics in the thermochemical generation of synthetic fuels: II. The methanol water splitting cycle

The availability/heat penalty analysis described in our earlier paper [1] has been applied to the methanol-sulfuric acid water splitting cycle proposed by Schulten and Behr [2]. This four-reaction thermochemical process has been evaluated in terms of preliminary engineering design and economics by the Electric Power Research Institute (EPRI), the University of Kentucky and the CE-Lummus Co. [3]. The distribution of heat penalties induced by thermodynamic irreversibilities in the plant is shown, and the quantitative relationship among capital costs, production costs, heat penalties, and process efficiency is presented. The total thermal energy output of the nuclear reactor is the sum of the theoretical heat requirement and all the heat penalties in the plant. The costs, heat penalties and efficiency are also shown for the hybrid sulfuric acid process.     

供热机组变工况及其对经济性的影响

针对传统的热经济性分析的不足,利用循环函数法提出了一个新的特性参数－热量多耗系数。并运用该指标,对供热机组在变工况运行条件下运行经济性的变化进行了分析。结果表明,借助于该指标的变化,可直接获得热电联产节煤量分析结果。     

A new generalised correlation for predicting swirl flow pressure drops in a horizontal refrigerant 12 evaporator

This work is an extension of the earlier work [1] reported by the authors on correlating their swirl flow pressure drop data obtained in a horizontal R-12 evaporator. That correlation has been found to suffer when applied to more experimental pressure drop measurements obtained in wider ranges of parameters. Δp_s/Δp_p is found to be a weak function of flow velocity. A modified correlation has been suggested in this paper which is based on a large number of data points and wider range of inlet vapour quality and boiling number.     

减振算法研究及其在轴流压缩机叶片中应用

附加粘弹性阻尼材料是控制能源工程核心机械装置振动有效手段。有关的振动特征值计算较为复杂,但又特别重要。考虑装置阻尼特性在大范围内变化的可能性,为装置特征值的变化特性作出可靠分析,提出了具有统一计算格式的高阶摄动模型。通过对压缩机叶片的研究表明,该模型结果可靠,较易于计算程序实现,便于推广应用。     

Prediction of pressure drop during forced convection boiling of mixture of refrigerants 13 and 12

Pressure drop measurements during forced convection boiling of pure R-12 and mixture of R-13 and R-12 have been done inside horizontal tubes. The frictional component of the pressure drop has been found to be a function of mixture composition. The authors have successfully developed a correlation on the basis of C-S method, which has been found to give better agreement than an earlier reported method based on M-N correlation.     

Handling zero values in the logarithmic mean Divisia index decomposition approach

The Logarithmic Mean Divisia Index (LMDI) decomposition approach has many desirable properties. It has been recommended by Ang [2004a. Decomposition analysis for policymaking in energy: which is the preferred methods? Energy Policy 32, 1131–1139] for adoption in energy and energy-related environmental index decomposition analysis (IDA). A complication associated with this approach is the treatment of zero values in the data set. Several studies show that replacing the zero values with a small number gives converging results. In a recent paper, Wood and Lenzen [Zero-value problems of the logarithmic mean Divisia index decomposition method. Energy Policy, in press] argue that this strategy is not necessarily robust and recommend using the analytical limits proposed in Ang et al. [1998. Factorizing changes in energy and environmental indicators through decomposition. Energy 23, 489–495]. We compare these two strategies and extend earlier works by generalizing the analytical limits of LMDI.     

Three zone equilibrium and kinetic free modeling of biomass gasifier – a novel approach

Two zone equilibrium and kinetic free model proposed by the authors in their earlier work [Ratnadhariya JK, Channiwala SA. Two zone equilibrium and kinetic free modeling of gasifier. Proceedings of the 12th European Conference and Technical Exhibition on Biomass for Energy, Industry and Climate Protection. Amsterdam, The Netherlands; 2002. p. 813–816], offers gas composition, temperature profile and gasifier performance parameters for two zones. This model does not predict composition and temperature profile of pyrolysis zone, which is stated to be a precursor for gasification. Looking to this fact a three zone equilibrium and kinetic free model of biomass gasifier is proposed in the present work. In this three zone: first zone of the model is drying and pyrolysis zone combined together; second zone is oxidation zone; and the third zone is the reduction zone. Each zone has been formulated with: (i) reaction stoichiometry; (ii) constituent balance; and (iii) energy balance along with a few justifying assumptions. This model clearly provides an operating range of equivalence ratio and moisture content for the woody biomass materials. Further, this model facilitates the prediction of the maximum temperature in the oxidation zone of gasifier, which provides useful information for the design of the gasifier and selection of the material for the construction. The merits of the model lies in the fact that it is capable of handling predictions for all category of biomass materials with a wide operating range of equivalence ratio and moisture content in all of the three principal zones of the gasifier.     

Analysis of experimental data on diffuse solar radiation in Athens,Greece, for building applications

Proper design and performance prediction of solar energy systems requires accurate information on the availability of solar radiation. The diffuse-to-total radiation correlation, originally developed by Liu and Jordan, has been extensively used as the technique and provided excellent results, although it was latitude dependent and not universally applicable. Thus, diffuse fraction correlations of this type have been developed by few other authors and for different location. This paper presents an analysis of hourly diffuse radiation on a horizontal surface. Hourly pyranometer data from Athens, Greece, are used to establish relationships between the diffuse fraction and the clearness index k _T for hourly and daily values. The results of the proposed equations are then compared with earlier equations. For the urban conditions of Athens the developed correlation fit to the empirical data.     

12Cr1MoV和10CrMo910钢蠕变寿命研究的电阻法

在研究了湿度载荷对蠕变损伤的影响的基础上,对耐热钢蠕变形变提出了新的认识,建立了蠕变损伤与材料电阻特性变化之间的关系,提出了以材料电阻特性变化为主,综合显微组织结构特征及硬度变化的耐热钢材料寿命评定的综合评定方法。     

Using a strain based failure assessment diagram for creep–brittle materials

Recently, there has been considerable interest in studying creep crack growth in creep–brittle materials. For example, the methodologies for assessing creep ductile materials, using fracture mechanics parameters like C^* and C_t, have been extended to include creep–brittle materials [1]. This paper begins by examining these recent developments and outlines the difficulties in adopting these developments. An alternative approach is then proposed. This new approach leads from recent work proposed by the authors [2], where a strain based failure assessment diagram (SB-FAD) is used. Experimental results from a series of tests on a simulated heat affected zone of a low alloy steel are explored. The application of the methodology for assessing the initiation and growth of a defect in a creep–brittle material is also demonstrated.     

Lighting controls: Their current use and possible improvement

The use of automatic lighting controls to modify artificial lighting consumption, either to implement the concepts of Permanent Supplementary Artificial Lighting or to save energy, has been previously proposed by several authors. However, since little quantitative evidence of likely benefits exists, implementation of the proposals has been rare. the increased cost of energy has renewed interest and recent studies at the Building Research Station have attempted to: (a) decide if the use of photoelectric controls would save energy; and (b) define the situations where this might be done cost effectively. A [broad brush] picture of likely waste was obtained by a survey of about 200 offices, visited on at least five occasions each, over the course of several months. the illuminance at desk positions and the prevailing switching conditions were noted, and an estimate of waste was calculated by comparing the data with the known design illuminance. More detailed information of lighting use and apparent waste was obtained by [time-lapse photography] in seven installations; three offices and four teaching areas of different depths and occupancy patterns. Here, waste associated with excessive use during daylight hours and use during unoccupied periods could be isolated and savings predicted for the use of automatic photoelectric controls and time switches. The available hardware for such control has been surveyed and its cost effectiveness investigated in general terms for several types of installation. Predicted savings have been calculated using a simple model of available daylight and it is expected that analysis of more recent meteorological data will provide more precise estimates. the validity of using [daylight factors] as an effective control parameter in these calculations is also being investigated. The results of the studies outlined above are being assessed by installing control equipment in several real working interiors, including three of those originally monitored by [time-lapse] cameras. Energy consumption and user acceptability are being monitored and preliminary results on both counts are promising.     

Prediction of the dependence of KJC(T) on neutron fluence for RPV steels on the basis of the Unified Curve concept

A method is proposed that allows the prediction of the transformation of fracture toughness in the brittle–ductile transition temperature region as a function of neutron fluence for RPV steels. The method is based on the Unified Curve concept and a probabilistic local approach model proposed earlier by the authors as well as on physical analysis of the effect of impurities and carbide size on the local strength of a material. The results calculated with the proposed method are compared with available experimental data.     

食品冷冻干燥工艺的参数分析及其强化措施

针对目前国内保健食品冻干工艺的制定和食品冻干设备设计的要求,系统分析了食品真空冷冻干燥工艺的原理、系统设备组成及其主要工艺参数之间的关系,对如何强化冷冻干燥工艺过程进行了深入探讨,并提出了通过工艺方法提高冻干食品加工效率及质量的一些具体措施,为冻干食品生产企业制定食品冻干工艺和设计食品真空冻干设备提供了有力的参考依据.     

Carbon dioxide neutral, integrated biofuel facility

Algae are efficient biocatalysts for both capture and conversion of carbon dioxide in the environment. In earlier work, we have optimized the ability of Chlorella vulgaris to rapidly capture CO₂ from man-made emission sources by varying environmental growth conditions and bioreactor design. Here we demonstrate that a coupled biodiesel-bioethanol facility, using yeast to produce ethanol and photosynthetic algae to produce biodiesel, can result in an integrated, economical, large-scale process for biofuel production. Each bioreactor acts as an electrode for a coupled complete microbial fuel cell system; the integrated cultures produce electricity that is consumed as an energy source within the process. Finally, both the produced yeast and spent algae biomass can be used as added value byproducts in the feed or food industries. Using cost and revenue estimations, an IRR of up to 25% is calculated using a 5 year project lifespan.     

Land use competition for production of food and liquid biofuels: An analysis of the arguments in the current debate

This article analyses the current state of the debate over competition for land use, by means of an index of the main arguments in favor and against the production of liquid biofuels and the impacts on food production. Based on this index, an analytic framework is constructed to establish the causal relations indicated by the existing studies on this competition. We find that the emergence of agro-energy has altered the land use dynamic, albeit not yet significantly, with a shift of areas traditionally used to grow foods over to crops to produce biofuels. This has been contributing to raise food prices in the short run. However, it is probable that this is not the only factor determining this trend, nor will it last over the long run. The challenge is to conciliate the production of biofuels with the production of foods in sustainable form.     

Parametric analysis for a new combined power and ejector–absorption refrigeration cycle

A new combined power and ejector–absorption refrigeration cycle is proposed, which combines the Rankine cycle and the ejector–absorption refrigeration cycle, and could produce both power output and refrigeration output simultaneously. This combined cycle, which originates from the cycle proposed by authors previously, introduces an ejector between the rectifier and the condenser, and provides a performance improvement without greatly increasing the complexity of the system. A parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the cycle performance. It is shown that heat source temperature, condenser temperature, evaporator temperature, turbine inlet pressure, turbine inlet temperature, and basic solution ammonia concentration have significant effects on the net power output, refrigeration output and exergy efficiency of the combined cycle. It is evident that the ejector can improve the performance of the combined cycle proposed by authors previously.     

Development and simulation of dynamic control strategies for wind farms

The authors show that: (a) with reliable prediction of low variance in the wind velocity, modern wind farms have the wherewithal to produce regulated power in the next hour; (b) when the conditions for producing regulated power are not predicted, the wind farms may opt to use the tracking mode which tracks the slowly time-varying, non-turbulent component of wind power and (c) the proposed control system has the capability to divert some of the wind farm power to implement dynamic performance enhancement strategies, for system damping. The capabilities are demonstrated by simulations of a wind farm made up of 24 windturbine generators using one-hour-long wind velocity data.     

能量系统分析优化中排弃火用计价探讨

在火用分析及火用经济分析的基础上,说明了排弃火用与待回收火用的关系,就不同的回收情况,系统地研究了能量系统中排弃火用的计价问题;指出对于能量的逐级回收利用,传统的按物流的序贯分析计价方法并不适用于排弃火用的计价,基于能量系统双子系统模型,提出了当量计价的概念以解决排弃火用的计价问题。最后以催化裂化烟气能量回收方案的演变过程及排弃火用计价的变化表明了此计价方法的实际应用情况。