压缩空气储能透平滑压运行参数优化研究

针对绝热压缩空气储能系统中的透平滑压运行参数进行研究，以某项目100MW空气透平为例，介绍了储气方式和储气参数对空气透平的影响，提出了以单位质量发电量作为压缩空气储能透平性能指标的考核办法。对于全周进气加补气阀的进气调节方式，核算出了9.8MPa～3.7MPa滑压范围内各个补气阀开启点压力对应的单位质量发电量，通过对比确定最佳的补气阀开启点压力为7.3MPa,此时发电效率与纯补气方案相比提高2.7%,与纯节流方案相比提高12.6%,具有明显效率提升效果，对其它压缩空气储能透平进气调节方式选型具有明显参考意义。     

基于正交设计的压缩空气储能系统效率分析

根据压缩空气储能系统的结构特性,采用正交设计和数值模拟方法对压缩空气储能系统的压缩机绝热效率、级间冷却温度、储气室最低工作压力、回热度、膨胀透平绝热效率和燃烧室效率等6个参数进行实验设计和数值模拟,并对模拟结果进行效率分析.通过对实验结果的方差进行分析,得到设计参数对系统效率的影响程度.结果表明:在压缩空气储能系统中,压缩机绝热效率、级间冷却温度、回热度、压缩机绝热效率与级间冷却温度的交互作用、级间冷却温度与回热度的交互作用以及压缩机绝热效率与膨胀透平绝热效率之间的交互作用为影响压缩空气储能系统总过程效率的显著因素;在现有技术水平下,降低压缩机级间冷却温度和提高回热度是提高压缩空气储能系统效率的最佳选择.     

压缩空气储能系统的理论分析及性能研究

压缩空气储能技术和抽水蓄能技术是两种最具潜力的电能规模化储存技术。构建了四套压缩空气储能方案,结合热力学第一定律对高压储罐内压缩空气的温度与压力参数的变化规律以及不同储能方案性能进行了比较。研究结果表明,高压储罐在与环境换热较差时,高压储罐的充气过程会经历较为明显的温升现象。200 m3储罐以1.0 kg/s流速充气至10 MPa时,温升幅度为22.46 ℃,储气过程的温升现象降低了储罐的空气容纳能力。在压缩空气储能系统性能方面,四套储能系统的热耗位于4 100 kJ/kW·h至4 200 kJ/kW·h之间,系统效率位于52.30%与56.33%之间。在储能系统效率与对外输出电能总量指标上,高压储罐与环境之间换热性能较好的储能系统均要优于换热条件较差的储能系统。     

压缩空气储能系统释能过程动态调控

压缩空气储能被认为是最具有发展前景的大规模储能技术,而压缩空气储能系统运行过程面对的是储气室压力变化以及输入/输出功率变化的复杂工况.针对压缩空气储能系统变工况运行需求和节流阀减压调节膨胀机入口压力存在控制精度低、压力损失大等问题,本研究提出采用阀门组合与减压容器相结合的压力控制单元来调控膨胀机入口压力、满足输出功率需求,并建立了集成压力控制单元的10 MW蓄热式压缩空气储能系统热力学模型.在此基础上,研究了储释能过程压力、温度、质量流量、功率等关键参数随时间的变化规律,揭示了阀门组合与减压容器相结合的压力控制单元调控膨胀机入口压力的机理与效果.压力控制单元与节流减压方式相比,释能过程的总?损失减小1.56×108 J,储能效率提高0.24％,储能密度提高0.04 MJ/m3.结果表明,本研究所提出的压力控制单元可以平滑地调控膨胀机入口压力,对保障压缩空气储能系统稳定高效运行,提高系统综合性能具有重要的作用.     

两级填充床式压缩空气储能系统充放电行为研究

基于两级填充床式压缩空气储能系统运行原理,建立了压缩机、透平、填充床蓄热器及储气洞穴的非稳态分析模型,对两级填充床式压缩空气储能系统充放电行为进行了模拟,分析了系统在给定充电功率下的整体热力学性能和各部件的运行特性。结果表明：相比于完整充放电循环,在给定的充电功率下系统的充放电效率仅为54.33%,下降了约8.07%;受到储能功率的影响,压缩机的效率变化范围较大,仅有77.13%的电能转化为压缩空气的内能,而高/低压透平因为进口处空气温度逐渐降低而偏离设计工况导致效率下降;压缩机和透平的火用损之和占总火用损的81.51%。     

不同储气室和工质下AA-CAES+CSP系统运行特性研究

为了研究储气室和工质种类对带太阳能辅热的先进绝热压缩空气储能(AA-CAES+CSP)系统热力学性能的影响,基于空气和二氧化碳2种工质,以及恒温和恒壁温2种储气室,提出了4种运行模式,并利用Matlab软件进行数值模拟,比较不同模式下的系统性能差异,并研究了系统性能随关键设备参数和环境参数变化的规律。结果表明:当系统采用恒温储气室和二氧化碳时的循环效率和储能密度最高;循环效率和储能密度随着集热温度的升高而升高,但是集热温度过低的换热介质会冷却空气,降低空气做功能力,此时应切断辅热子系统;环境温度的升高会使循环效率和储能密度均下降;随着换热器效能的升高,4种模式下系统的循环效率均先升高后降低,但储能密度的变化规律不相同。     

大型空气压缩机变工况性能试验研究

压缩空气储能系统压缩机受系统自身特性影响,长期处于变工况运行状态。对某多级压缩空气储能系统大型空气压缩机变工况条件下级间性能开展试验研究,即利用压缩机管网特性试验平台,开展排气压力6.5～9.5MPa范围试验测试,对压缩机各级吸气和排气压力、吸气和排气温度、压缩机排气量、电机电流、电压等参数进行实时采集。通过对压缩机实时变工况下各项参数分析,具体研究压缩机的容积效率、循环指示功率、等温效率、各级压比分配和各级压损随出口负荷变化而变化的规律。研究结果表明:压缩机的容积效率基本不随工况的变化而变化,平均为0.96;循环指示功率随出口负荷的增加而增加;压缩机的多变效率从74.02%上升到78.14%,多变效率随着排气压力的增加而增加;低压级压比增大速度较快,易达到额定状态,高压级压比达到额定状态较缓;一～四级的相对压力损失基本保持不变,五级出口排气到集气汇管的相对压力损失随着出口负荷的增大而减小。     

进气温度和过量空气系数对乙醇均质压燃燃烧过程的影响

在一台经过改进的CA6110发动机上,进行了进气温度和过量空气系数对乙醇燃料均质压燃燃烧过程影响的试验研究．结果表明,在转速和供油量一定时,随着进气温度的升高,着火始点提前,燃烧持续期变短,压力升高率变大,缸内的最大燃烧压力变大,指示效率提高,平均指示压力升高．当进气温度一定时,随着过量空气系数的减小,着火始点提前,燃烧持续期逐渐变短,压力升高率变大,缸内的最大燃烧压力变大,指示效率增加．     

Design and thermodynamic analysis of compressed air energy storage system

压缩空气储能技术具有提升风能与太阳能等可再生资源电能质量的潜力,通过此项技术实现间歇性与不稳定性可再生电力的有效储存,进而在电网负荷高峰期以优质电力的形式稳定输出.结合热力学分析方法设计了储能功率56.58 MW,释能输出功率154.76 MW的压缩空气储能系统.在释能阶段透平机组配置上,参照GE 9171E燃机布置第二级透平入口参数,并以其812.41 K高温烟气余热提供第一级透平工质所需全部热量,无需为第一级透平配备专门燃烧器.在此思路下设计的压缩空气储能系统,热耗可降低至3783.96 kJ/(kW·h),储能系统的能量转换效率也高达56.11%.     

基于压缩空气储能的分布式能源系统热力学特性分析

为优化现有分布式能源系统集成方式,提高系统效率,提出了一种基于压缩空气储能的分布式能源系统,系统中压缩空气储能系统的压缩热以及膨胀透平的排烟余热可以通过热水换热器和吸收式制冷机为用户提供热能和冷能,同时,通过储气室和蓄热器可以调节系统的能量输出特性,进而满足用户负荷需求的变化。热力学分析结果表明:系统的一次能源效率为85.32%,效率为35.51%;从能量角度出发,系统对外输出的热量最多占总输出能量的42.64%,从能质角度出发,电能占系统输出总量的比例最高为64.27%。基于压缩空气储能的分布式能源系统具有较高的能源利用效率和较好的能量输出特性,为分布式能源系统的开发提供了新的思路。     

Thermodynamic analysis of a transcritical CO2 power cycle driven by solar energy with liquified natural gas as its heat sink

This paper proposes a transcritical CO₂ power cycle driven by solar energy while utilizing the cold heat rejection to an liquified natural gas (LNG) evaporation system. In order to ensure a continuous and stable operation for the system, a thermal storage system is introduced to store the collected solar energy and to provide stable power output when solar radiation is insufficient. A mathematical model is developed to simulate the solar-driven transcritical CO₂ power cycle under steady-state conditions, and a modified system efficiency is defined to better evaluate the cycle performance over a period of time. The thermodynamic analysis focuses on the effects of some key parameters, including the turbine inlet pressure, the turbine inlet temperature and the condensation temperature, on the system performance. Results indicate that the net power output mainly depends on the solar radiation over a day, yet the system is still capable of generating electricity long after sunset by virtue of the thermal storage tank. An optimum turbine inlet pressure exists under given conditions where the net power output and the system efficiency both reach maximum values. The net power output and the system efficiency are less sensitive to the change in the turbine inlet temperature, but the condensation temperature exerts a significant influence on the system performance. The surface area of heat exchangers increases with the rise in the turbine inlet temperature, while changes in the turbine inlet pressure have no significant impact on the heat exchanging area under the given conditions.     

Energy and exergy analyses of a CFB‐based indirectly fired combined cycle power generation system

Combined cycle configuration has the ability to use the waste heat from the gas turbine exhaust gas using the heat recovery steam generator for the bottoming steam cycle. In the current study, a natural gas‐fired combined cycle with indirectly fired heating for additional work output is investigated for configurations with and without reheat combustor (RHC) in the gas turbine. The mass flow rate of coal for the indirect‐firing mode in circulating fluidized bed (CFB) combustor is estimated based on fixed natural gas input for the gas turbine combustion chamber (GTCC). The effects of pressure ratio, gas turbine inlet temperature, inlet temperatures to the air compressor and to the GTCC on the overall cycle performance of the combined cycle configuration are analysed. The combined cycle efficiency increases with pressure ratio up to the optimum value. Both efficiency and net work output for the combined cycle increase with gas turbine inlet temperature. The efficiency decreases with increase in the air compressor inlet temperature. The indirect firing of coal shows reduced use with increase in the turbine inlet temperature due to increase in the use of natural gas. There is little variation in the efficiency with increase in GTCC inlet temperature resulting in increased use of coal. The combined cycle having the two‐stage gas turbine with RHC has significantly higher efficiency and net work output compared with the cycle without RHC. The exergetic efficiency also increases with increase in the gas turbine inlet temperature. The exergy destruction is highest for the CFB combustor followed by the GTCC. The analyses show that the indirectly fired mode of the combined cycle offers better performance and opportunities for additional net work output by using solid fuels (coal in this case). Copyright © 2009 John Wiley & Sons, Ltd.     

An integrated system for thermal power generation,electrical energy storage and CO2 capture

This work reports a newly proposed system for electrical energy storage. The new system combines a direct open nitrogen (cryogen) expansion cycle with a natural gas‐fuelled closed Brayton cycle and the CO₂ produced in the system is captured in the form of dry ice. Thermodynamic analyses are carried out on the system under the baseline conditions of 1 kg s^?1 natural gas, a combustor operating pressure of 8 bars and a cryogen topping pressure of 100 bars. The results show that the exergy efficiency of the proposed system is as high as 64% under the baseline conditions, whereas the corresponding electricity storage efficiency is about 54%. A sensitivity analysis has also been carried out on the main operating conditions. The results indicate that the baseline performance can be enhanced by increasing the gas turbine (GT) inlet temperature, decreasing the approach temperature of the heat exchange processes, operating the combustor at an optimal pressure of ～7 bars and operating the cryogen topping pressure at ～90 bars. Further enhancement can be achieved by increasing the isentropic efficiency of the GT and the liquefaction process. The results of this work also suggest that the power capacity installation of peak‐load units and fuel consumption could be reduced by as much as 50% by using the newly proposed system. Further work is suggested for an economic analysis of the system. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermodynamic analysis of a new combined cooling, heat and power system driven by solid oxide fuel cell based on ammonia-water mixture

Although a solid oxide fuel cell combined with a gas turbine (SOFC-GT) has good performance, the temperature of exhaust from gas turbine is still relatively high. In order to recover the waste heat of exhaust from the SOFC-GT to enhance energy conversion efficiency as well as to reduce the emissions of greenhouse gases and pollutants, in this study a new combined cooling, heat and power (CCHP) system driven by the SOFC is proposed to perform the trigeneration by using ammonia-water mixture to recover the waste heat of exhaust from the SOFC-GT. The CCHP system, whose main fuel is methane, can generate electricity, cooling effect and heat effect simultaneously. The overall system performance has been evaluated by mathematical models and thermodynamic laws. A parametric analysis is also conducted to examine the effects of some key thermodynamic parameters on the system performance. Results indicate that the overall energy conversion efficiency exceeds 80% under the given conditions, and it is also found that the increasing the fuel flow rate can improve overall energy conversion efficiency, even though both the SOFC efficiency and electricity efficiency decrease. Moreover, with an increased compressor pressure ratio, the SOFC efficiency, electricity efficiency and overall energy conversion efficiency all increase. Ammonia concentration and pressure entering ammonia-water turbine can also affect the CCHP system performance.     

Performance analysis of an industrial waste heat‐based trigeneration system

The thermodynamic performance of an industrial waste heat recovery‐based trigeneration system is studied through energy and exergy efficiency parameters. The effects of exhaust gas inlet temperature, process heat pressure, and ambient temperature on both energy and exergy efficiencies, and electrical to thermal energy ratio of the system are investigated. The energy efficiency increases while electrical to thermal energy ratio and exergy efficiency decrease with increasing exhaust gas inlet temperature. On the other hand, with the increase in process heat pressure, energy efficiency decreases but exergy efficiency and electrical to thermal energy ratio increase. The effect of ambient temperature is also observed due to the fact that with an increase in ambient temperature, energy and exergy efficiencies, and electrical to thermal energy ratio decrease slightly. These results clearly show that performance evaluation of trigeneration system based on energy analysis is not adequate and hence more meaningful evaluation must include exergy analysis. The present analysis contributes to further information on the role of exhaust gas inlet temperature, process heat pressure, ambient temperature influence on the performance of waste heat recovery‐based trigeneration from a thermodynamic point of view. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparative exergoeconomic analyses of the integration of biomass gasification and a gas turbine power plant with and without fogging inlet cooling

Inlet cooling is effective for mitigating the decrease in gas turbine performance during hot and humid summer periods when electrical power demands peak, and steam injection, using steam raised from the turbine exhaust gases in a heat recovery steam generator, is an effective technique for utilizing the hot turbine exhaust gases. Biomass gasification can be integrated with a gas turbine cycle to provide efficient, clean power generation. In the present paper, a gas turbine cycle with fog cooling and steam injection, and integrated with biomass gasification, is proposed and analyzed with energy, exergy and exergoeconomic analyses. The thermodynamic analyses show that increasing the compressor pressure ratio and the gas turbine inlet temperature raises the energy and exergy efficiencies. On the component level, the gas turbine is determined to have the highest exergy efficiency and the combustor the lowest. The exergoeconomic analysis reveals that the proposed cycle has a lower total unit product cost than a similar plant fired by natural gas. However, the relative cost difference and exergoeconomic factor is higher for the proposed cycle than the natural gas fired plant, indicating that the proposed cycle is more costly for producing electricity despite its lower product cost and environmental impact.     

Energetic and exergetic performance analyses of a combined heat and power plant with absorption inlet cooling and evaporative aftercooling

In this paper, exergy method is applied to analyze the gas turbine cycle cogeneration with inlet air cooling and evaporative aftercooling of the compressor discharge. The exergy destruction rate in each component of cogeneration is evaluated in detail. The effects of some main parameters on the exergy destruction and exergy efficiency of the cycle are investigated. The most significant exergy destruction rates in the cycle are in combustion chamber, heat recovery steam generator and regenerative heat exchanger. The overall pressure ratio and turbine inlet temperature have significant effect on exergy destruction in most of the components of cogeneration. The results obtained from the analysis show that inlet air cooling along with evaporative aftercooling has an obvious increase in the energy and exergy efficiency compared to the basic gas turbine cycle cogeneration. It is further shown that the first-law efficiency, power to heat ratio and exergy efficiency of the cogeneration cycle significantly vary with the change in overall pressure ratio and turbine inlet temperature but the change in process heat pressure shows small variation in these parameters.     

应用溴化锂吸收式制冷技术提高燃气轮机电站发电效率的研究

对燃气轮机进口的空气进行预冷,能够提高发电机组的输出功率。与蓄冷方法相比,使用燃气轮机－蒸汽联合循环电站余热锅炉低压蒸发器的一部分蒸汽为热源,利用溴化锂吸收式制冷机制取冷源,冷却燃气轮机进口处的空气,以提高发电机组的输出功率,该方法技术可行,经济效益显著。     

The effect of elevated inlet air temperature and relative humidity on cogeneration system

The effect of elevated inlet air temperature and relative humidity on a gas turbine (GT) cogeneration system performance was investigated. The analysis was carried out on a GT of a capacity 171 MW at ISO condition, which is integrated with a dual pressure heat recovery steam generator (HRSG), the cogeneration system had been tested under Kuwait summer climate conditions. A computational model was developed and solved using engineering equation solver professional package to investigate the performance of a dual pressure GT‐HRSG system. The suggested HRSG is capable of producing high‐pressure superheated steam at 150 bar and 510°C to operate a power generation steam turbine cycle, and a medium pressure saturated steam at 15 bar to run a thermal vapor compression (TVC) desalination system. In this research, the influence of elevated inlet air temperature and relative humidity on the energy assessment of the suggested cogeneration system was thoroughly investigated. Results indicated that operating GT under elevated values of inlet air temperatures is characterized by low values of net power and thermal efficiency. At elevated inlet air temperatures, increasing relative humidity has a small positive impact on GT cycle net power and thermal efficiency. Integrating the GT with HRSG to generate steam for power generation and process heat tends to increase energy utilization factor of the system at elevated inlet air temperatures. Increasing inlet air temperature plays a negative impact on power to heat ratio (PHR), while relative humidity has no effect on PHR. Copyright © 2009 John Wiley & Sons, Ltd.