Optimization of energy plants including water/lithium bromide absorption chillers

In this paper a methodology for the optimal integration of water/lithium bromide absorption chillers in combined heat and power plants is proposed. This method is based on the economic optimization of an energy plant that interacts with a refrigeration cycle, by using a successive linear programming technique (SLP). The aim of this paper is to study the viability of the integration of already technologically available absorption chillers in CHP plants. The results of this alternative are compared with the results obtained using the conventional way of producing chilled water, that is, using mechanical vapour compression chillers in order to select the best refrigeration cycle alternative for a given refrigeration demand. This approach is implemented in the computer program XV, and tested using the data obtained in the water/LiBr absorption chiller of Bayer in Tarragona (Catalonia, Spain). The results clearly show that absorption chillers are not only a good option when low‐cost process heat is available, but also when a cogeneration system is present. In this latter case, the absorption chiller acts as a bottoming cycle by using steam generated in the heat recovery boiler. In this way, the cogeneration size can be increased producing higher benefits than those obtained with the use of compression chillers. Copyright © 2000 John Wiley & Sons, Ltd.     

Proposal and analysis of a novel ammonia–water cycle for power and refrigeration cogeneration

Cogeneration has improved sustainability as it can improve the energy utilization efficiency significantly. In this paper, a novel ammonia-water cycle is proposed for the cogeneration of power and refrigeration. In order to meet the different concentration requirements in the cycle heat addition process and the condensation process, a splitting /absorption unit is introduced and integrated with an ammonia–water Rankine cycle and an ammonia refrigeration cycle. This system can be driven by industrial waste heat or a gas turbine flue gas. The cycle performance was evaluated by the exergy efficiency, which is 58% for the base case system (with the turbine inlet parameters of 450 °C/11.1 MPa and the refrigeration temperature below −15 °C). It is found that there are certain split fractions which maximize the exergy efficiency for given basic working fluid concentration. Compared with the conventional separate generation system of power and refrigeration, the cogeneration system has an 18.2% reduction in energy consumption.     

Cooling performance and energy saving of a compression–absorption refrigeration system driven by a gas engine

The prototype of combined vapour compression–absorption refrigeration system was set up, where a gas engine drove directly an open screw compressor in a vapour compression refrigeration chiller and waste heat from the gas engine was used to operate absorption refrigeration cycle. The experimental procedure and results showed that the combined refrigeration system was feasible. The cooling capacity of the prototype reached about 589 kW at the Chinese rated conditions of air conditioning (the inlet and outlet temperatures of chilled water are 12 and 7°C, the inlet and outlet temperatures of cooling water are 30 and 35°C, respectively). Primary energy rate (PER) and comparative primary energy saving were used to evaluate energy utilization efficiency of the combined refrigeration system. The calculated results showed that the PER of the prototype was about 1.81 and the prototype saved more than 25% of primary energy compared to a conventional electrically driven vapour compression refrigeration unit. Error analysis showed that the total error of the combined cooling system measurement was about 4.2% in this work. Copyright © 2006 John Wiley & Sons, Ltd.     

Modeling of ammonia absorption chillers integration in energy systems of process plants

A mathematical programming approach is proposed to study the integration of absorption chillers in combined heat and power plants. The aim of this work is to determine the economic viability of the introduction of ammonia absorption chillers in energy systems instead of using the more conventional compression cycles. This procedure selects the best refrigeration alternative taking into account both absorption and compression cycles. To select the most suitable refrigeration cycle for a given refrigeration load, it is not only necessary to model the performance of each cycle, but also to take into account the interactions between the energy system and the considered cycles, optimizing the performance of the global plant. This approach has been implemented in the computer program XV, and tested in an energy plant in the petrochemical complex of Tarragona (Catalunya, Spain). The refrigeration demands to be met are at 0 and −20°C. The results highlighted the benefit obtained with the simultaneous presence of ammonia absorption cycles and a cogeneration based energy plant.     

高压燃气调压器建模与仿真

根据重型燃气轮机的高压燃气调压器的工作原理,建立了能够描述调压器静态和动态特性的数学模型,并利用Matlab／Simulink软件建立了其仿真模型。通过数值仿真,分析了低压腔体积、弹簧弹性系数、皮膜面积等关键设计因素对燃气调压器静态和动态特性的影响。研究结果对燃气轮机燃气调压器的技术开发、设计和选型具有参考价值。     

M701F4燃气轮机“二拖一”联合循环热电联供系统的热电特性

为了提高能源利用效率,提高经济效益和环境效益,燃气一蒸汽联合循环热电联产系统已受到广泛的关注,目前国内大部分的联合循环机组均要求热电联供,为工业用汽或城市采暖提供蒸汽。本文介绍了东方汽轮机／三菱重工M701F4燃气轮机“二拖一”联合循环热电联供系统及其特点,分析了供热设计条件下该系统的热电负荷特性,供工程设计和电厂运行参考。     

A district heating system based on absorption heat exchange with CHP systems

In order to decrease the energy consumption of large-scale district heating systems with cogeneration, a district heating system is presented in this paper based on absorption heat exchange in the cogeneration system named Co-ah cycle, which means that the cogeneration system is based on absorption heat exchange. In substations of the heating system, the temperature of return water of primary heat network is reduced to about 25°C through the absorption heat-exchange units. In the thermal station of the cogeneration plant, return water is heated orderly by the exhaust steam in the condenser, the absorption heat pumps, and the peak load heater. Compared with traditional heating systems, this system runs with a greater circuit temperature drop so that the delivery capacity of the heat network increases dramatically. Moreover, by recovering the exhausted heat from the condensers, the capacity of the district heating system and the energy efficiency of the combined heat and power system (CHP system) are highly developed. Therefore, high energy and economic efficiency can be obtained.     

AE94.3A型燃气轮机进气冷却的应用可行性研究

对AE94.3A型燃气轮机燃气-蒸汽联合循环热力系统平衡进行研究进而发现,与同类型、同等级不同型号机组相比,AE94.3A型联合循环机组余热锅炉的排烟温度较高,排烟余热仍有进一步利用的空间。通过设计优化,扩大省煤器受热面,回收烟气余热加热给水,驱动热水型溴化锂制冷机制冷,用于机组满负荷调峰时的压气机进气冷却或厂房及办公区域空调供冷,对改善燃气轮机联合循环的运行性能,实现能源梯级利用,提高能源利用率和机组经济性运行起到了很大作用。     

燃气轮机在热电联产工程中的应用状况分析

燃气轮机是21世纪乃至更长时间内能源高效转换与洁净利用系统的核心动力装备.介绍了燃气轮机的发展现状及其在热电联产工程中的应用,简述了联合循环和简单循环燃气轮机电厂的基本组合方式,并列举了目前应用在热电联产工程中的几种主要的燃气轮机.阐述了燃气轮机相对于常规火电机组的优点,分析了影响燃气轮机在热电联产工程中推广的因素,并对我国燃气轮机的发展前景进行了展望.     

太阳能喷射/压缩复合制冷循环性能研究

研究了一种太阳能喷射/压缩复合制冷循环,由太阳能集热子系统、喷射制冷子系统及压缩制冷子系统组成,系统充分利用热电两种能源以及两种制冷方法各自的优点,优化喷射制冷子系统工作性能的同时,改善压缩式子系统的工作条件,从而提高复合制冷循环性能的同时节约高品位电能。采用性能较好的高蒸发温度式喷射制冷带走压缩机排气余热具有实际意义。通过数值模拟的手段分析系统性能及其主要影响因素,并优化工作条件。研究表明,与相同工作条件下的单压缩制冷循环相比,复合制冷循环工作日全天候运行时电力性能系数提升约为31.5%,节电优势显著。存在一个最佳的喷射子系统蒸发温度使得复合制冷循环性能系数达到运行工况的最大值。     

燃气—蒸汽联合循环机组轴系振动问题综述

本文对燃气—蒸汽联合循环机组轴系布置方案进行了详细研究,将其分为普通单轴布置轴系、带有SSS离合器(同步自动离合器)的单轴布置轴系、多轴布置中的燃气轮机轴系和汽轮机轴系4种类型。并且分析了4种类型与常规机组汽轮机轴系的区别,并通过对某联合循环电厂轴系的典型振动故障分析,讲述了此方面研究的重要性。本文从现场振动故障诊断和理论研究两个方面总结了近些年联合循环机组轴系振动的研究进展,提出带有SSS离合器的单轴布置轴系和多轴布置中带有SSS离合器的汽轮机轴系是今后的研究方向。     

Feasibility study of cogeneration in a plywood industry with power export to grid

Cogeneration is proved to be one of the promising energy management techniques, which offers an efficient method of producing electricity and useful thermal energy from a common source. In the present study various cogeneration options for a plywood industry in south India with power export is analyzed. It is found that the industry has a good potential for cogeneration. Three schemes such as steam turbine gas turbine and combined cycle are evaluated on the basis of Annualized Life Cycle Cost (ALCC). The steam turbine based cogeneration is found to be the best option as it has the least ALCC. The comparison was based on lean gas as fuel but the industry can save the fuel cost by utilizing the waste wood available which enhances the scope and economic feasibility of cogeneration. It is found that the proposed scheme can provide a tremendous saving in the annual operating cost compared to the existing facility with a payback period of 2.6 years.     

A district heating system based on absorption heat exchange with CHP systems

In order to decrease the energy consumption of large-scale district heating systems with cogeneration, a district heating system is presented in this paper based on absorption heat exchange in the cogeneration system named Co-ah cycle, which means that the cogeneration system is based on absorption heat exchange. In substations of the heating system, the temperature of return water of primary heat network is reduced to about 25°C through the absorption heat-exchange units. In the thermal station of the cogeneration plant, return water is heated orderly by the exhaust steam in the condenser, the absorption heat pumps, and the peak load heater. Compared with traditional heating systems, this system runs with a greater circuit temperature drop so that the delivery capacity of the heat network increases dramatically. Moreover, by recovering the exhausted heat from the condensers, the capacity of the district heating system and the energy efficiency of the combined heat and power system (CHP system) are highly developed. Therefore, high energy and economic efficiency can be obtained.     

替代燃煤小热电的F级燃气热电联产机组的选型分析

在对张家港市主城片区建设燃气热电联产机组替代燃煤小热电必要性分析的基础上,结合当地实际情况,阐述选择F级燃气—蒸汽联合循环热电联产机组的可行性,并对当前F级燃气热电联产机组的主流机型、性能和特点进行分析,进而提出燃气热电联产机组选型方案。分析认为,主机设备装机方案的选择,不仅要从机组的经济技术角度考虑,还要考虑整个机组运行高效、安全、可靠、灵活、供热连续等诸多因素,更要考虑投产后运行维护和检修费用,只有全面进行分析与比较,才能做出合理的选择。     

Exergy analysis,parametric analysis and optimization for a novel combined power and ejector refrigeration cycle

A new combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces both power output and refrigeration output simultaneously. It can be driven by the flue gas of gas turbine or engine, solar energy, geothermal energy and industrial waste heats. An exergy analysis is performed to guide the thermodynamic improvement for this cycle. And a parametric analysis is conducted to evaluate the effects of the key thermodynamic parameters on the performance of the combined cycle. In addition, a parameter optimization is achieved by means of genetic algorithm to reach the maximum exergy efficiency. The results show that the biggest exergy loss due to the irreversibility occurs in heat addition processes, and the ejector causes the next largest exergy loss. It is also shown that the turbine inlet pressure, the turbine back pressure, the condenser temperature and the evaporator temperature have significant effects on the turbine power output, refrigeration output and exergy efficiency of the combined cycle. The optimized exergy efficiency is 27.10% under the given condition.     

A method of improving the effectiveness of a mechanical vapour compression process and of its applications in refrigeration

The work proposes a thermodynamic method for increasing the effectiveness of the polytropic and adiabatic compression processes. The method is further used for improving the COP of the compression refrigeration cycles. The method theory is considered. A theorem proved here shows that ideal method application leads to the isothermal compression operation. The method application is illustrated by schemes running with single, two-stage and multi-stage compression, for the air conditioning, normal and industrial refrigeration. According to the proposal, the compression refrigeration should stimulate the compressor operation with high temperature discharge gas and the conversion of its heat into work, rather than using an additional compression work for limiting the discharge gas temperature, as it is happening today in the two-and multi-stage refrigeration. The schemes’ operation has been modelled. The model results emphasize a reasonable feasibility of the single-stage, but the three-stage and especially the two-stage compression are the most feasible, enjoying a great potential in the refrigeration COP increase, and therefore in the primary energy savings and carbon footprint reduction (～50–100% and more).     

Geothermal energy use in hydrogen liquefaction

We propose the use of geothermal energy for hydrogen liquefaction, and investigate three possible cases for accomplishing such a task including (1) using geothermal output work as the input for a liquefaction cycle; (2) using geothermal heat in an absorption refrigeration process to precool the gas before the gas is liquefied in a liquefaction cycle; and (3) using part of the geothermal heat for absorption refrigeration to precool the gas and part of the geothermal heat to produce work and use it in a liquefaction cycle (i.e., cogeneration). A binary geothermal power plant is considered for power production while the precooled Linde–Hampson cycle is considered for hydrogen liquefaction. A liquid geothermal resource is considered and both ideal (i.e., reversible) and non-ideal (e.g., irreversible) system operations are analyzed. A procedure for such an investigation is developed and appropriate performance parameters are defined. Also, the effects of geothermal water temperature and gas precooling temperature on system performance parameters are studied. The results show that there is a significant amount of energy savings potential in the liquefaction work requirement as a result of precooling the gas in a geothermal absorption cooling system. Using geothermal energy in a cogeneration scheme (power production and absorption cooling) also provides significant advantages over the use of geothermal energy for power production only.     

Optimization study of combined refrigeration cycles driven by an engine

In order to utilize the waste heat efficiently for a gas engine-driven heat pump running in a cooling mode, this paper studies two combined absorption/compression refrigeration cycles using ammonia and water as the working fluid. By analyzing the operating characteristics of the combined cycles that make efficient use of both the work and the heat output of an engine, this paper puts forward an optimal mathematical model with an objective function of the primary-energy ratio (PER). The model has been calculated for typical cooling applications. Analysis of the results indicates that optimization can make the combined cycle fully achieve the sought-after energy saving advantage. It was also found that the PERs of the combined cycles increase considerably compared with a conventional engine-driven compression cycle working with pure ammonia. The combined cycle, with two solution circuits, is the best.     

新型太阳能喷射与电压缩式联合制冷系统的研究

提出一种新型的太阳能喷射与电压缩联合制冷系统,其既可以利用太阳能喷射式制冷又可以利用电能驱动压缩式制冷,可提高太阳能与辅助能源的综合利用率。对该系统中以R141b作为制冷工质,采用斜盘式压缩机的辅助电压缩制冷系统进行了理论循环计算与实验研究。实验表明,该辅助电压缩制冷系统的性能系数达到2.53。与传统的辅助能源应用方式相比,该辅助电压缩式制冷系统能更高效地利用常规能源,提高新型太阳能喷射制冷系统的综合节能效果。     

Seasonal design and multi-objective optimization of a novel biogas-fueled cogeneration application

Switching from fossil fuels to biofuels is an effective option for small-scale power production and cogeneration systems. The target of the current study is to propose and investigate a novel seasonal combined cycle driven by a biogas-fueled gas turbine from thermodynamic and economic viewpoints. Regarding the high-temperature of the turbine's exhaust gases, an integration of Rankine and ejector refrigeration cycles is configured. The bottoming cycle is designated for winter and summer conditions, independently. Hence, a combined cycle capable of operating as a cogeneration system producing electricity/heating or electricity/cooling, individually, is designed. Moreover, a parametric study based on assessing the impact of key parameters on the essential variables and a multi-criteria optimization trough a genetic algorithm are performed to attain the facilities of the proposal. According to the results, the capability of the whole system in winter conditions is significantly higher than that for summer conditions due to the higher heating capacity. Also, the evaluated variables are more affected by change in the environment temperature in both seasons. Additionally, the optimal overall energy, exergy and levilized cost of products are calculated as 79.2%%, 45.6%, and 21.7 $/GJ for summer and 70.7%, 37.0%, and 17.6 $/GJ for winter, respectively.