Electricity Pricing for Natural Gas CHP Projects The Higher, the Better?

Regarding the state's policy that gives a higher on-grid electricity price to natural gas CHP (combined heat and power) projects, this paper studies the effect of it on the operation of those projects by theoretical analysis and a case study. It concludes that on-grid electricity price on the high side, compared to heat price, will lead power plants to produce more electricity but less heat, thus causing decrease of the plants' thermal eff iciency and harm to energy saving of the whole society.

Technical and Economic Aspects and Experience from 6 Years of Operating the Technology Using the Waste Heat from the Exhaust Gases of Heat Sources and 3 Years of Operating a Heating Plant in an Autonomous, Island Regime

This article is focused on technical and economic evaluation of more than 6-years experiences of operating the Waste Heat Recovery technology—the manner and system of flue gas processing generated in the combustion process in heat & power plants, cogeneration units, etc., which burn the gaseous fuel, primarily natural gas, or methane, biogas, geothermal gas, or other gaseous mixtures containing hydrogen. The solution proposes a more effective and non-traditional use of gaseous fuel for heating, the flue gases of which are processed in order to extract additional utilisable heat, with potential elimination of CO2 from them. Deploying of the heating plant in an island regime (OFF-GRID) enables definition of the benefits brought by the 3 years of operational experience and presents visions for the future offering the possibility to utilise the support energy services at the municipal as well as regional level.

Transforming Waste Heat into“Renewable Heat”

Introduction:The current worldwide electric power&heat&cool production has a negative impact on the environment by emissions and enormous leaks of low-potential waste heat.Transformation of unused industrial low power heat into“renewable heat”useful to enhance the efficiency of the system is essential and actual innovation in the field of worldwide environmental protection.By introducing and defining the terminology of low-potential,“renewable”,“green heat”has created a new,parallel category of research in the energy sector.Traditional co-generation systems produce heat for space heating and hot water and generate electricity.Moving to tri-generation allows growing demand for air conditioning for homes,offices and commercial spaces such as server rooms and switchboards to be met simultaneously or on a seasonal basis.Tri-generation,or combined cooling,heat and power,is the process by which some of the heat produced by a co-generation plant is used to generate chilled water for air conditioning or refrigeration.Usually an absorption chiller is linked to the plant to provide this functionality.The technical solution is related to the new efficient manner and system of simultaneous generation of heat/cold from multiple heat sources,which has not yet been known,but in practice required.New system also enables advantageous utilization of solar power in supporting of the cooling output.The innovative system can be operated also within the existing central heating distribution systems.

WHR （Waste Heat Technology） Method in Tri-generation Model

This paper is focused on description of cool production in using WHR （Waste Heat Technology） Technology-a new method of centralized production of heat by using the waste heat from generated exhaust gas, which has been in 2009 developed and operated by companies HELORO s.r.o, and COMTHERM s.r.o.

池式钠冷快堆堆内自然循环余热排出设计研究

基于装量功率比约为1 t/MW的较典型池式钠冷大功率快堆的堆内自然循环设计,采用ERAC程序,对两组4种不同事故余热排出系统(DHRS)输入条件下,反应堆在紧急停堆后堆内的自然循环余热排出特性进行分析。结果表明,从DHRS启用到其对堆芯产生显著冷却效应,需要较长时间,在千秒量级。在该段时间内,堆芯余热的排出依靠反应堆固有的热工流体安全特性。随后,在堆内关键温度上升到限值之前启用DHRS带出池内热量,使堆内关键温度处于下降趋势即可满足安全要求;相比将独立热交换器(DHX)布置在冷池,将其布置在热池时,热池温度及主容器壁温相对要低,这有利于主容器的温度控制,其效果要优于布置于冷池。另外,不同布置会对堆芯盒内、盒间流流量产生影响,但总体上对堆芯的冷却效应影响不大;池式钠冷快堆余热排出设计中,要充分利用固有热工流体安全特性,降低对DHRS的时效性要求。可以考虑将全部的DHX都布置在热池,并缩小设备体积、降低散热功率设计值,或在不降低安全性的前提下选用其他更经济便捷的有效方式等,以此大幅降低余热排出设备投入成本,降低反应堆运行成本,提高经济性。本文研究结果可为我国后续的商用快堆、一体化快堆等池式液态金属堆的堆内自然循环设计提供重要参考。

利用液化天然气冷能的冷热电联供系统热力分析与优化

为解决以甲烷作为燃料的固体氧化物电池余热利用、碳捕集以及液化天然气冷能利用问题,建立了一种新型的冷热电联供系统。该系统包括改进再压缩超临界混合工质布雷顿循环、跨临界CO_(2)回热朗肯循环和二级混合工质有机朗肯循环,对循环系统进行热力学分析、设备[火用]分析、经济成本分析,并利用遗传算法对系统参数进行多目标优化。仿真分析结果表明:提升改进再压缩超临界混合工质布雷顿循环的膨胀机入口压力、跨临界CO_(2)回热朗肯循环的膨胀机入口温度与二级朗肯循环中R14的质量分数可提升系统循环净功、热效率、[火用]效率并降低平均单位成本;在最优工况条件下,系统热效率、[火用]效率、平均单位成本分别为64.70%、47.85%、24.20美元/GJ。

基于双燃料原动机的天然气分布式能源方案设计

常规天然气分布式能源多选用以天然气为单燃料的陆用燃气轮机或燃气内燃机为原动机,常规应急电站多选用以柴油为单燃料的内燃机作为原动机。选取双燃料发动机为原动机,以天然气为能源开展相应的天然气分布式能源系统方案设计,从用户端各类能源的用能需求分析入手,以发电量最大化为原则,选取合适的余热转换技术,实现为客户提供最优化的供电、供冷和供热方案,能源综合利用率达到70%以上。验证了双燃料发动机作为天然气分布式能源的原动机,可以兼顾柴油机应急电站和天然气分布式能源的综合功能,为一种比较高效的能源利用方案,可以为后续实际工程应用提供指导。

Active-reactive power scheduling of integrated electricity-gas network with multi-microgrids

Advances in natural gas-fired technologies have deepened the coupling between electricity and gas networks,promoting the development of the integrated electricity-gas network(IEGN)and strengthening the interaction between the active-reactive power flow in the power distribution network(PDN)and the natural gas flow in the gas distribution network(GDN).This paper proposes a day-ahead active-reactive power scheduling model for the IEGN with multi-microgrids(MMGs)to minimize the total operating cost.Through the tight coupling relationship between the subsystems of the IEGN,the potentialities of the IEGN with MMGs toward multi-energy cooperative interaction is optimized.Important component models are elaborated in the PDN,GDN,and coupled MMGs.Besides,motivated by the non-negligible impact of the reactive power,optimal inverter dispatch(OID)is considered to optimize the active and reactive power capabilities of the inverters of distributed generators.Further,a second-order cone(SOC)relaxation technology is utilized to transform the proposed active-reactive power scheduling model into a convex optimization problem that the commercial solver can directly solve.A test system consisting of an IEEE-33 test system and a 7-node natural gas network is adopted to verify the effectiveness of the proposed scheduling method.The results show that the proposed scheduling method can effectively reduce the power losses of the PDN in the IEGN by 9.86%,increase the flexibility of the joint operation of the subsystems of the IEGN,reduce the total operation costs by $32.20,and effectively enhance the operation economy of the IEGN.

Analysis and Economic Evaluation of Hourly Operation Strategy Based on MSW Classification and LNG Multi-Generation System

In this study,a model of combined cooling,heating and power system with municipal solid waste(MSW)and liquefied natural gas(LNG)as energy sources was proposed and developed based on the energy demand of a large community,andMSW was classified and utilized.The systemoperated by determining power by heating load,and measures were taken to reduce operating costs by purchasing and selling LNG,natural gas(NG),cooling,heating,and power.Based on this system model,three operation strategies were proposed based on whether MSW was classified and the length of kitchen waste fermentation time,and each strategy was simulated hourly throughout the year.The results showed that the strategy of MSW classified and centralized fermentation of kitchen waste in summer(i.e.,strategy 3)required the least total amount of LNG for the whole year,which was 47701.77 t.In terms of total annual cost expenditure,strategy 3 had the best overall economy,with the lowest total annual expenditure of 2.7730×108 RMB at LNG and NG unit prices of 4 and 4.2 RMB/kg,respectively.The lower heating value of biogas produced by fermentation of kitchen waste from MSW being classified was higher than that of MSW before being classified,so the average annual thermal economy of the operating strategy of MSW being classified was better than that of MSW not being classified.Among the strategies in which MSW was classified and utilized,strategy 3 could better meet the load demand of users in the corresponding season,and thus this strategy had better thermal economy than the strategy of year-round fermentation of kitchen waste(i.e.,strategy 2).The hourly analysis data showed that the net electrical efficiency of the system varies in the same trend as the cooling,heating and power loads in all seasons,while the relationship between the energy utilization efficiency and load varied from season to season.This study can provide guidance for the practical application of MSW being classified in the system.

天然气冷热电三联产系统的应用分析

随着我国西气东输工程靖边—上海段管线于 2 0 0 3年 10月 1日向上海供气 ,天然气开始进入我国经济发达的东部地区 ,如何有效地利用西部天然气是一个至关重要的问题。为此介绍了具有很高的一次能源利用率的天然气冷热电三联产系统及其运行方式 ,还介绍了天然气冷—热—电联产系统在国外的应用情况 ,指出冷热电三联产系统是中国“西气东输”工程中应用天然气的理想方式 ,并具有很好的应用前景。

天然气热、电、冷联产系统及其在国内外的应用现状

阐述了天然气热电冷联产系统的几种常用运行模式 :燃气轮机 +余热型溴化锂冷热水机组、燃气轮机 +排气再燃型溴化锂冷热水机组、燃气轮机 +双能源双效直燃式溴化锂吸收式冷热水机组、燃气 -蒸汽轮机联合循环 +蒸汽型吸收式制冷机组及内燃机前置循环余热利用等。简要介绍了该系统在国内外的应用现状 。

不同自然冷却方式对光伏墙体性能影响的理论与实验研究

对有通风流道的光伏墙体和直接贴墙无通风流道的光伏墙体的性能进行比较 ,建立了各自的数理模型 ,并在香港建立了两种不同自然冷却方式的光伏墙体的对比实验台 ,通过实验与计算结果的比较 ,结果表明在香港地区这两种自然冷却方式的光伏墙体在发电性能差异不大 ,但室内得热方面相差较大。

一种基于低品位热源的LNG冷能回收低温动力系统

在分析LNG物理冷火用的基础上 ,提出了一种基于低品位热源的LNG冷能回收低温动力系统 ,并对影响系统循环效率的相关参数进行了研究。结果表明 ,在较低的热源温度下 ,系统的热效率和火用效率可以达到 30 %以上 ;对影响循环的主要参数分析表明 ,二次冷媒的冷凝温度及膨胀机进口压力对循环的效率影响很大。随着冷凝温度的降低及膨胀机进口压力的提高 ,循环热效率、火用效率都将有所提高。

天然气冷热电联供系统在贵州地区的应用案例研究

分析了贵州地区的气候特点,对贵阳市某大型公共建筑的冷、热、电及生活热水负荷进行了预测,针对发电并网不上网和发电上网两种情况,对燃气冷热电联供系统进行了优化配置和运行。两种方案均采用热泵型的冷热电联供系统,冬季在使排烟温度降至20℃左右的同时,回收部分浅层地热能,提高了系统的能源利用效率。以建筑原供能方案为比较基准,对两种方案进行了经济性和节能性评价。结果显示,两种方案的经济性相差不大;受贵州地区气候特点影响,建筑负荷匹配结构不利于冷热电联供系统的节能,如果发电可以上网,能使系统的节能性得到明显改善。

以液化天然气为冷源的超临界CO_2-跨临界CO_2冷电联供系统

为了提高超临界CO2布雷顿循环(SCO2循环)的低温余热回收效率,采用跨临界CO2循环(TCO2循环)作为底循环对再压缩式SCO2循环进行余热回收,并采用液化天然气(LNG)为冷源对工质进行冷凝,建立了以LNG为冷源的再压缩式SCO2-TCO2冷电联供系统,以同时输出电量和制冷量。对系统进行火用分析比较,并研究了关键热力参数对系统净输出功率、制冷量、系统热效率和系统火用效率的影响。结果显示:使用LNG作为冷源,降低了TCO2循环的冷凝温度,提高了低温回收热效率,系统的热效率(动力)在给定的条件下达到54.47%;提高LNG的入口温度,可以减小系统火用损;高温回热器换热效率增加,系统热效率和火用效率均增加;SCO2透平膨胀比增加,系统热效率降低,但火用效率增加;TCO2透平进口压力升高,系统热效率和火用效率均呈现先减小再升高后减小的变化趋势;随着冷凝温度升高,系统热效率降低,但火用效率先减小后增加。

影响我国分布式能源发展的因素分析

分布式能源(DER)系统因其具有可靠、高效、清洁、环保、配置灵活等优势而具有巨大的发展潜力,在国外已成为一种潮流,在我国发展却并不顺利。为此,采用逆推方法分析影响我国DER发展的主要因素。主要结论是:国家和社会是DER的主要受益者之一,因此政府应加大对DER的政策支持与直接投入;电力部门的既得利益受到威胁,因而希望电力部门自觉地"积极推动"DER的建设是不可能的;用户使用DER优先考虑的是经济性,但组成经济性的三大成本要素预期不容乐观:燃料市场价格波动与供应存在的不稳定性导致燃料成本具有不确定性,核心动力设备的国产化程度不高导致固定投资成本居高不下,用户环境的动态变化与技术支持的先天不足导致运行维护成本也不容小视。因此,推行DER项目,必须科学论证,总结经验,谨慎推广。

天然气分布式能源系统的能源综合利用效率计算

能源综合利用效率是评价分布式能源系统热经济性的重要指标,相关文件关于该效率的计算方法因不区分冷热电能品位而受到质疑。对两个承担常见负荷、采用典型动力设备的天然气分布式能源系统进行分析,并将其与系统实际的能源产量比较,发现该效率值对系统热经济性的评估不具客观性与合理性,认为将该效率指标与经济杆杠相结合的做法或将分布式能源系统集成与运行设计引导至错误方向。

含光伏的天然气冷热电联供园区微网能量优化调度

天然气冷热电联供园区微网集供冷、供热、供电和供气于一体,具有能源梯级利用的优势,能够有效地提高能源的利用率,减少污染物的排放.本研究针对天然气冷热电联供园区微网的能量优化调度问题,以最小运行费用为目标建立了天然气冷热电联供园区微网的多时段动态优化调度模型,考虑了供冷网、供热网、供电网和供气网的网络运行特性约束,以及储电、储冷和储热多种类型储能装置对微网调度的影响.并基于场景法建立了考虑光伏出力随机波动的园区微网能量优化调度模型,通过快速调节储能装置的储放能功率等措施来平衡光伏出力的不确定波动.以某个天然气冷热电联供园区微网为例,验证了所提出优化调度模型的正确有效性.计算结果表明,所获得的微网运行调度方案能有效节约能量消耗,降低微网运行费用;多种类型储能装置的协同运行能够更有效地降低微网的运行费用,并有利于平抑光伏发电的不确定波动.

高功率LED热管理方法研究最新进展

LED芯片结温的高低直接影响其出光效率、工作寿命和可靠性。在分析系统各个环节热阻的基础上,详细评述了高功率LED产品从芯片到系统级的热管理研究新动向,包括:自然对流冷却,采用压电风扇、电离方法所进行的强迫空气对流冷却,采用水、液态金属作为冷却工质的液冷方法,采用热管实现的相变冷却,采用热电片进行的固态冷却方案以及利用热电片对余热进行回收利用的热管热回收方案和液体金属冷却方法。并在上述基础上提出了发展更高功率密度LED热管理方法的关键科学问题。

冷热电三联供绿色能源项目的经济分析

介绍了国内外利用天然气发展冷热电三联供的概况,阐述了武汉中央商务区分布式能源站的“冷热定电”原则,确定了三联供系统方案的最低电价和最高气价.通过单双因素敏感性分析方法,论证了商务区冷热电三联供系统方案的经济可行性,为中央商务区采用冷热电三联供提供决策依据.