The heat-recovery power unit of a gas-piston mini cogeneration station

The specific features of the thermal operating conditions of the internal combustion engine and the design circuits of a mini cogeneration station’s heat-recovery unit are considered. The basic scheme of the heat-recovery unit’s thermal parameters automatic control system is proposed, the use of which makes it possible to maintain the design temperatures of coolants and heating agents (cooling liquid and oil, combustion products, and heat network water) during variations of the electrical and heat loads of consumers. The results from rig tests of the 450-kW(t) heat-recovery unit for a mini cogeneration station equipped with a YaMZ-8401 gaspiston engine are presented.     

The Electrical Aspects of Cogeneration System Design

Cogeneration and the reasons that it is a viable industry today are discussed. Both bottoming and topping cycles may be employed for cogeneration; however, the topping cycle is the major focus of current cogeneration projects due to its applicability in large cogeneration power plants. The effect and reasons for the Public Utility Regulatory Policies Act removal of many of the disincentives of cogeneration are discussed. The relative efficiencies of conventional and combined-cycle cogeneration power plants are compared in a typical example of a large cogeneration power plant currently under construction. Many considerations face the electrical engineer in the design of a cogeneration power plant. Many applications will be found in industrial plants and will utilize industrial thinking within the plant; however, many decisions will be influenced by conventional electric utility thinking, due to the interface with the electric utility in the switchyard. Basic discussion of the considerations required of the electrical engineer, including electrical system arrangement, integration of the new generation into the plant electrical system, short-circuit matters, one-line diagrams, generator characteristics, excitation systems, step-up transformer ratings and characteristics, auxiliary transformers (station service), distribution systems, and system grounding, is given for preliminary guidance in design.     

甲醇/电联产系统能耗特性

以一次能源消耗为统一基准推导了联产系统相对分产系统的相对收益、相对节能率和节能判据关系式。得到以化电比和联产系统效率表达的节能分区图,可以清楚地展示和比较国内外文献中多联产系统的节能效果。根据联产系统中合成气的不同利用途径,定义了联产气和非联产气,并据此建立了联产系统化电分摊的理论模型。以并联液相富CO一次通过多联产系统为例,对联产系统的节能原因进行了分析。结果表明：全系统的热量耦合是联产系统节能的主要原因。     

燃料电池在电动汽车中的应用前景

以石油燃料为动力的汽车,其尾气是空气污染的主要来源,以充电电池为动力的电动汽车是解决汽车尾气污染的途径之一.目前,由于充电电池贮能量比内燃机低而使电动汽车数量仍然很少.燃料电池是未来最有希望替代内燃机的汽车动力,它的运行效率高,能够使用甲醇、乙醇、天然气或氢气等非石油基燃料,还可以显著改善排气质量,减少大气污染.可用于电动汽车的燃料电池类型有磷酸型燃料电池、离子交换膜燃料电池和固体氧化物燃料电池.本文对上述燃料电池的原理和性能作了详细介绍,对世界各国的研究开发活动作了介绍.     

Harmonic resonance at a medium-sized industrial plant

Harmonic resonance is a concern for industrial plants because approximately 50% of the normal electrical load consists of computer equipment, switch mode power supplies and AC induction motor adjustable speed controllers. Due to the nonlinear characteristics of these loads, significant harmonic voltages and currents are produced on the electrical distribution system. Measurements were made with a harmonic analyzer at several locations in an electrical distribution system to quantify harmonic currents and voltages. The system impedance diagram, prepared from the system one line diagram, was used to model the electrical system and calculate power system natural frequencies. Calculations indicated harmonic resonance occurs near the seventh harmonic frequency depending on configuration of the electrical power system. The plant equivalent circuit was prepared for several harmonic frequencies to show the amplification of currents and voltages due to the effects of harmonic resonance. Calculations to determine network harmonics are presented using a simplified system representation in combination with traditional circuit reduction methods. The results of these calculations are shown to be valid by actual system measurement     

Hybrid fuel cells technologies for electrical microgrids

Hybrid systems are characterized by containing two or more electrical generation technologies, in order to optimize the global efficiency of the processes involved. These systems can present different operating modes. Besides, they take into account aspects that not only concern the electrical and thermal efficiencies, but also the reduction of pollutant emissions. There is a wide range of possible configurations to form hybrid systems, including hydrogen, renewable energies, gas cycles, vapour cycles or both. Nowadays, these technologies are mainly used for energy production in electrical microgrids. Some examples of these technologies are: hybridization processes of fuel cells with wind turbines and photovoltaic plants, cogeneration and trigeneration processes that can be configured with fuel cell technologies, etc. This paper reviews and analyses the main characteristics of electrical microgrids and the systems based on fuel cells for polygeneration and hybridization processes.     

Evaluation of the reduction in CO2 emissions by applying Micro‐Grid to home energy supply system

Dispersed generators such as wind power systems, photovoltaic systems, and cogeneration systems are expected to mitigate the environmental burden of energy consumption, and their installation has been promoted recently. Micro‐Grid is focused on as a method to solve some problems in a commercial electric power line when installing a large number of dispersed generators, and some demonstrative research on Micro‐Grid for large‐scale systems is being carried out now. Also, small cogeneration systems for houses, such as gas engines and fuel cells, are expected to improve CO₂ emissions. However, if the power and heat demand of a family are relatively small or are unbalanced, the cogeneration system does not operate effectively. The authors have studied the application of Micro‐Grid for home energy supply, and have developed a control system to solve this problem. The system achieves a reduction of CO₂ emissions and energy costs by sharing electric power and heat among some houses with cogeneration systems. This paper presents an outline of the newly developed system, and in particular describes the effect of the reduction in CO₂ emissions compared with a conventional energy supply method, and the case in which dispersed generators are installed in some houses and operate independently. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 19–27, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20879     

Results of bench tests of a gas-piston mini cogeneration station constructed on the basis of a YaMZ-240 engine

Results from bench tests of a gas-piston mini cogeneration station with efficient recovery of thermal energy are presented. The energy balance of the installation is obtained, and the concentrations of harmful impurities in the combustion products are measured. An algorithm of the automatic heat control system is elaborated.     

Cogeneration: Small Turbine-Generator Case Study

Cogeneration, simply stated, is the sequential production of two forms of energy, usually steam and electricity. Three factors have recently made the use of cogeneration in industry more advantageous than in the past. First, the high cost of energy has caused industry to turn to cogeneration as an economical alternative to escalating power bills. Second, the Public Utility Regulatory Policies Act (PURPA) requires utilities to offer qualified customers monetary incentives to use cogeneration, thus making cogeneration both efficient and profitable to that customer. Third, compact low-cost small (less than 1000 kW) turbine-generator hardware is now available. The installation of a small cogeneration system based on a back-pressure turbine-generator set is discussed. Topics covered include cogeneration background, type of system chosen, economic analysis, and physical installation. Particular attention will be devoted to the electrical interface required in the installation of this cogeneration facility.     

发电厂电力拖动系统的节能研究

随着厂网分开,发电企业市场化程度的加剧,电厂的发电煤耗、厂用电率已成为发电厂考核的重要指标,直接关系到电厂的经济效益和企业竞争力。现代发电厂的厂用电占发电总量的5％-10％,而电力拖动系统消耗的电量就占到其中的90％以上。分别从电动机供电电能质量、电动机选择及更换、电动机的改造、电动机监控和维护以及电动机运行角度出发,提出了电动机节能措施,最大程度地降低了电厂电力拖动系统的损耗,起到了良好的节能效果。     

Effects of Power Supply Variations on AC Motor Characteristics

Voltage level variations are shown to be only one of eight different types of voltage deviations which can affect motor characteristics. Each of these is discussed in relation to possible detrimental effects on operating costs or motor reliability. The timeliness of the paper is demonstrated, especially for continuous process and automated industries. Remedial measures, when indicated, are shown to cover a wide gamut from redesigning control systems to reappraising the electrical system one line diagram.     

Layouts of trigeneration plants for centralized power supply

One of the possible and, under certain conditions, sufficiently effective methods for reducing consumption of fuel and energy resources is the development of plants for combined generation of different kinds of energy. In the power industry of Russia, the facilities have become widespread in which the cogeneration technology, i.e., simultaneous generation of electric energy and heat, is implemented. Such facilities can use different plants, viz., gas- and steam-turbine plants and gas-reciprocating units. Cogeneration power supply can be further developed by simultaneously supplying the users not only with electricity and heat but also with cold. Such a technology is referred to as trigeneration. To produce electricity and heat, trigeneration plants can use the same facilities that are used in cogeneration, namely, gas-turbine plants, steam-turbine plants, and gas-reciprocating units. Cold can be produced in trigeneration plants using thermotransformers of various kinds, such as vaporcompression thermotransformers, air thermotransformers, and absorption thermotransformers, that operate as chilling machines. The thermotransformers can also be used in the trigeneration plants to generate heat. The main advantage of trigeneration plants based on gas-turbine plants or gas-reciprocating units over cogeneration plants is the increased thermodynamic power supply efficiency owing to utilization of the waste-gas heat not only in winter but also in summer. In the steam-turbine-based trigeneration plants equipped with absorption thermotransformers, the enhancement of the thermodynamic power supply efficiency is determined by the increase in the heat extraction load during the nonheating season. The article presents calculated results that demonstrate higher thermodynamic efficiency of a gas-turbine-based plant with an absorption thermotransformer that operates in the trigeneration mode compared with a cogeneration gas-turbine plant. The structural arrangements of trigeneration plants designed to supply electricity, heat, and cold to the users are shown and the principles of their operation are described. The article presents results of qualitative analysis of different engineering solutions applied to select one combination of power- and heat-generating equipment and thermotransformers or another.     

非平衡等离子体燃烧强化

为了引起我国对非平衡等离子体燃料强化技术研究的重视并促进该技术的发展,介绍了脉冲电晕放电和介质阻挡放电产生的非平衡等离子体对燃料或者可燃混合气活化作用的基本原理和特点,综述了国内外研究现状,并展望了其应用前景。     

溴化锂制冷在国华热电的应用及效益分析

推广使用热电联产机组的蒸汽、热水制冷技术,能够降低煤耗,提高能源的综合利用率。分析了热电联产机组的特性及不同季节的运行效率,据此提出热电企业适合增加非采暖季的热负荷,并介绍了国华热电分公司蒸汽制冷项目应用情况;阐述了热电联产机组蒸汽制冷技术的节能减排的社会效益。     

The prospects for using district-heating cogeneration stations in Russia

It is shown that the efficiency of district heating cogeneration systems should be improved by raising the fuel heating value utilization factor rather than their electrical efficiency. The drawbacks of using fuel cells and binary combined-cycle plants at cogeneration stations are pointed out. An advanced schematic arrangement of a district-heating cogeneration station is proposed.     

Energy Economics of a Modern Suspension Preheater Plant Compared to a Modern Plant Incorporating Cogeneration

The rising cost of fuel experienced over the past several years has caused the cement industry to look for more energy efficient systems for producing cement. Probably the most popular system has been the suspension preheater, frequently coupled with a roller mill, a flash calciner, or both. While these systems have yielded greatly improved fuel efficiencies, they have also contributed to higher consumption of electrical energy. This, coupled with the rapid rise in cost of electrical energy, has led to a renewed interest in cogeneration, wherein the heat contained in the kiln off-gases is used to produce steam to run turbine generators, thereby increasing the use of lower cost fuel energy while decreasing the use of higher cost purchased electric power energy. The production cost of a suspension preheater is different than for a plant utilizing cogeneration, so the production cost per ton of the two systems is compared, and the differences are used to determine the feasibility of cogeneration for a specific set of conditions. Two cogeneration cases will be examined. One is a plant utilizing generated power from waste heat only, all of which is consumed by the plant. The other is a plant which not only utilizes waste heat power but also produces for sale back to the utility company.     

A sensorless brushless dc motor system

This paper describes a brushless dc motor system without position or speed sensor. The brushless motor consists of a permanent magnet synchronous motor and a voltage-source inverter capable of controlling the amplitude and frequency of voltage. The rectangular-shaped stator current with a conducting interval of 120° (electrical) is controlled to be in phase with the trapezoidal back electromotive force. This results in producing maximum torque. Variable speed is achieved by adjusting the average motor voltage similarly to chopper control of dc motors. In this paper, two sensorless position detecting methods, i.e., an “indirect method” suited for the lower-speed range and a “direct method” suited for the higher-speed range are proposed. The combination of the two makes it possible to detect the rotor position over a wide-speed range. Furthermore, a speed-sen-sorless PLL control is proposed in applying the principle of the direct method. Experimental results obtained from a prototype brushless dc motor are shown to confirm the validity of the sensorless drive. The starting procedure of the motor also is discussed because it is impossible to detect the rotor position at a standstill.     

Designing and modeling a linear electric motor for vibration-technology machines

One industrial application of linear motors is as working-body drives of vibration-technology machines. Such drives allow manufacturing of equipment with very low energy consumption and material costs. This paper presents the results of research on substantiation of the prospects of application of linear electric motors as drive vibration-technology machines. The results of designing a linear dc motor are presented. This paper describes the design of the electric motor and its operation in the hold-down and vibrating modes. The main technical characteristics of the motor are given. Simulation of the electric-motor electromagnetic field based on symmetrical setting of the task for the Poisson equation was performed with a view to specifying and verifying the preliminary calculation data. The results of the calculations and simulations show that it is possible to create low-cost, manufacturable, and reliable electrical motors for a linear vibratory actuator.     

永磁无刷直流电机PWM调制方式研究

分析了永磁无刷直流电机电动运行时不同PWM调制方式对电枢电流的影响,得出了采用全桥载波时电流波动最小,转矩脉动最小的结论。又提出了一种能量回馈制动的方法,实现了电机制动时能量的回馈。     

热电冷联产系统的能耗特性

从系统基础能源消耗角度建立联产系统相对于分产系统节能判断关系式，并以实际热电机组为例进行计算验证，探讨了热电比、热效率、性能系数等参数对联产系统能耗特性的影响，研究发现：热电联产及在此基础上的热电冷联产的节能需满足一定的条件，相对来讲，冷电联供节能条件较热电联产更为苛刻。热电比、热效率和性能系数对联产系统节能影响程度明显不同；在联产系统中多效吸收机的应用并不总能使联产系统节能率增加，即使满足节能条件，对系统节能率的提升数量级也很小；热电冷联产系统相对于分产系统不一定节能，但从能的梯级利用原理讲，联产与分产系统相比火用 损的减少是绝对的，而这一部分火用 损的差值是联产的收益，也是热电联产的本质所在，据此建立了新的热电分摊理论模型。