机械蒸汽压缩机模型及其与风力发电机耦合模拟研究

机械蒸汽压缩海水淡化是一种很有前景的消纳风能的方式,其中的压缩机是这种能源利用方式的核心部件。建立了离心式蒸汽压缩机数学模型,研究了压缩机性能参数间的关系,重点探讨了压缩机输入功率及吸气蒸汽参数与压缩机流量、压比和转速间的关系,并通过耦合风力发电机模型,研究了定压比条件下,压缩机流量和转速在风力发电机随机功率变化时的响应曲线。结果表明,风力发电机驱动的机械蒸汽压缩机需要辅助能源来保证在较小的风力发电机输入功率情况下,压缩机能稳定运行在非喘振区。对于额定功率为160 k W的压缩机,在压比2.4条件下的最小输入功率为50 k W。     

亲水/吸水改性下管式海水淡化器性能研究

设计一种表面亲水改性并包裹吸水材料的单效管式海水淡化器。探讨亲水/吸水改性强化淡化器热质传递的机制,并进行定温和定功率加热实验研究,获得淡化器表面亲水/吸水改性后的产水性能。实验结果表明:动态实验条件下,最佳进水速度为460 m L/h;淡化器的产水率与运行温度呈正线性关系,其中运行温度为80℃时,复合管产水率达255.6 m L/h,相比光滑管提高24.9%;定功率(100 W)加热12 h时,复合管的累计产水量和性能系数分别为1493.2 m L和0.78,相比于光滑管提高44.4%。     

多效鼓泡蒸发太阳能海水淡化系统的稳态实验研究

基于鼓泡蒸发和空气载湿气液相平衡机理,设计并实现了一台具有五级四效性能的鼓泡蒸发式太阳能海水淡化系统,对该系统的稳态产水性能进行研究,给出系统在特定的运行温度和压力环境中,不同鼓气量下各效的产水率、耗电当量及经济性能系数。实验结果表明,系统采用多效鼓泡蒸发技术并对各级采取鼓气量的优化组合措施,可提高系统的产水率。当各级载气流量分别为570、570、570、450L/h时的,装置的淡水产率为1.668L/h,GOR值为2.77,折算单位产量能耗4.93kWh/t,该点为装置的经济性能系数最高的工况点。     

漂浮式聚光升膜多效太阳能蒸馏器的性能研究

提出一种漂浮在海面上进行淡化产水的聚光升膜多效太阳能蒸馏器，该淡化装置包含一个抛物面聚光镜和多个垂直布置的蒸发-冷凝单元。采用吸水芯作为蒸发器，利用毛细吸力使海水形成上升的液膜，有效减少了加热损失。建立理论模型分析装置内部的传热传质过程。通过实验研究不同运行参数对装置温度、产水量和比能耗的影响。室内稳态研究结果表明，当太阳辐照度为900 W/m²时，蒸馏器内部温差为56.9℃，产水率可达到2.64 kg/(m²·h)。在户外平均太阳辐照度为603.7 W/m²的条件下，装置一天产水量为5.3 kg/(m²·d)，日平均比能耗为1591.6 kJ/kg。     

多效增湿除湿太阳能海水淡化装置的性能试验

文章提出了一种具有规模灵活、操作简单、维护运行成本低廉、易于和可再生能源结合等优点的新型多效增湿除湿太阳能海水淡化装置;介绍了装置的结构和运行原理,进行了海水运行温度、进水流量等影响产水性能的参数的实验研究。研究结果表明,装置产水量随进水流量和运行温度增加而增大,当进水流量为906 kg/h时,装置产水量达到58.14 kg/h。该多效增湿除湿海水淡化系统具有较大的性能提升空间和广阔的应用前景。     

低温多效蒸馏海水淡化水热电三联产系统经济性分析

对于凝汽式机组,提出采用低真空运行后的高温排汽作为低温多效蒸馏海水淡化的热源,实现水电联产.在此基础上,冬季利用一部分汽轮机排汽用于对热用户供暖.电厂在低真空运行模式下的热力计算采用矩阵法并基于弗留格尔公式进行变工况计算.低温多效蒸馏海水淡化系统的数学模型采用等温差法建立,并同时建立了制水成本的经济性计算模型.根据计算结果分析了低温多效蒸馏海水淡化系统的蒸发器效数、供热负荷、蒸发器传热系数和制水成本之间的关系,并得出了影响制水成本的主要因素及其敏感性分析.     

顺流流程多效蒸馏海水淡化系统的热力学分析

建立了顺流进料流程低温多效蒸馏海水淡化系统的热力过程数学模型;考虑了过程中物性变化和压力损失引起的传热温差变化,计算分析了在相同淡水产量下,蒸发器效数、末效蒸发器蒸发温度、加热蒸汽温度和浓缩比变化时,造水比、冷凝器海水流量、蒸发器总传热面积的变化规律.结果表明:蒸发器效数对系统性能有显著影响;末效蒸发器蒸发温度和加热蒸汽温度对蒸发器总传热面积影响较大;浓缩比在一定范围内,系统热力性能最优.     

柴油发电机组废热驱动的海水淡化系统分析

利用海岛柴油发电机组排出的废热驱动低温多效海水淡化装置实现水电联产,节约能源并为缺水海岛提供价格低廉的淡水。根据柴油发电机组工作参数,设计了一套低温多效海水淡化系统,经热力和换热设计计算确定该系统的主要结构参数。并在不同的发电机组负荷下,对系统的产水率、喷淋密度、浓缩比等参数进行了模拟计算,其研究结果可为实际的海岛水电联产系统的设计和运行提供参考。     

应用人工神经网络(ANN)分析热泵型海水淡化系统产水特性

利用人工神经网络来模拟仿真热泵型海水淡化系统的性能。以空气入口干球温度和湿球温度、预冷器进口冷却水温度、预冷器出口冷却水温度、海水喷淋温度作为输入参数,建立了海水淡化系统产水(淡水)模型。对建好的神经网络模型经训练学习后,用来模拟预测预冷器和蒸发器的产水值,并且与数值模拟产水值、实验产水值进行了比较,误差较小。表明利用人工神经网络(ANN)建立的热泵型海水淡化系统仿真模型取得了满意的结果。     

低温多效蒸发海水淡化系统不同进料方式的热力学分析

应用Aspen Plus软件,建立了平流、顺流、逆流三种进料方式的低温多效蒸发海水淡化工艺流程,并进行了流程模拟,模拟结果与文献[6]进行了对比,验证了所建工艺流程的可靠性和流程模拟的准确性。在加热蒸汽质量流量和热力压缩机引射率相同的情况下,应用等温差分配法对三种进料方式海水淡化系统进行模拟计算,获得了造水比和比传热面积与蒸发器效数、浓缩比、效间温差和进料海水温度之间的关系。研究结果表明:蒸发器效数对系统的热力性能有显著影响,当效数较少时,采用平流进料方式较为合适;增大浓缩比可以提高造水比,且比传热面积变化不大;当浓缩比较大时,可采用顺流进料,以降低结垢风险;增大效间温差,会降低逆流进料方式的造水比,但会增加平流和顺流的造水比;提高进料海水温度可以提升系统热力性能,但进料海水温度受末效二次蒸汽温度的限制。     

Experimental study on laboratory scale Totalized Hydrogen Energy Utilization System using wind power data

The renewable energy source like wind energy generates electric power with intermittent nature. Hydrogen energy system can help to solve the fluctuation problem of the wind power. Totalized Hydrogen Energy Utilization System (THEUS) consists of a Unitized Reversible Fuel Cell (URFC), a hydrogen storage tank, and other auxiliary components. Wind power is inherently variable; the URFC will be subjected to a dynamic input power profile in water electrolyzer mode operation. This paper describes the THEUS operation and performance at different variations in intermittent wind power. The performance of the THEUS was evaluated in water electrolyzer and fuel cell mode operation. The stack efficiency, system efficiency, and system efficiency including heat output from the URFC were presented at each operation. The total efficiency of the URFC and THEUS were also investigated. The maximum total efficiency of the URFC and THEUS were 53% and 66%, respectively.     

Theoretical and experimental studies of water injection scroll compressor in automotive fuel cell systems

A water injection scroll compressor to supply clean compressed air to an automotive fuel cell system is researched. The water is used as both the lubricant and coolant in the compressor. A thermodynamic model of the water injection scroll compressor considering leakage and heat exchange for use with an automotive fuel cell system was developed using the conservation of energy and mass equations and the equation of state. The results show that the scroll compressor has nearly isothermal compression when injecting water in it. Increasing the compressor rotation speed increases the discharge loss and the volumetric efficiency of the scroll compressor. The difference between the calculated power and the isothermal power increases as the compressor rotation speed rises, which means the efficiency of the compressor decreases. Increasing the flow rate of water injected increases the indicated isothermal efficiency and decreases the discharge temperature. Under the condition studied, the mass flow rate of water has the greatest effect on the discharge temperature.     

Economics of off-shore/on-shore wind energy systems in Qatar

This work presents an assessment of the potential and economical feasibility of adopting off-shore/on-shore wind energy as a renewable source of energy in Qatar. An analysis is presented for the long term measured on-shore wind speed (1976–2000) at Doha International Airport. A similar analysis is presented for the measured off-shore wind speed at the Qatari Haloul Island. For the on-shore measurements, the average annual wind speed (at 20 m height) was found to be about 5.1 m/s. On the other hand, for the off-shore measurements at Haloul, the average annual wind speed was found to be about 6.0 m/s. This result indicates the suitability of utilizing small to medium-size wind turbine generators, efficiently. Such generators can be implemented for water pumping and to produce sufficient electricity to meet vital, limited needs of remote locations, such as isolated farms, which do not have access to the national electricity grid. An economical assessment is presented which takes into consideration the interest recovery factor, the lifetime of the wind energy conversion system (WECS), the investment rate and operation and maintenance costs. The results indicate that the cost of electricity generation from the wind in Qatar compares favorably to that from fossil fuel resources. The feasibility of utilizing off-shore wind turbine systems to meet the power requirements of the island of Haloul and possibly provide additional power for nearby on-shore areas is discussed.     

独立式海上风电制氢工艺设计

  目的  文章旨在为充分利用深远海优质的风资源,解决海上风电的弃风问题以及对未来新能源船舶提供一种可能的海上氢气燃料供给方式。  方法  论述了一种依托于独立式海上平台的海上风电耦合海水制氢技术的工艺流程,主要对关键设备——质子交换膜电解水制氢系统、氢气压缩机、氢气储罐及部分辅助设备的工艺设计问题进行阐述,简略说明了制氢平台的控制方案,并且对其经济性进行了初步分析。  结果  从工艺设计的角度对海上风电制氢平台上的设计仅在较为前期的阶段,关键设备的供应链市场处于发展初级时期且大部分供应商未进军海工市场,表明现今海上浮式制氢的工程设计到工程化还不成熟且可再生能源制氢经济性较差。  结论  目前,海上风电还无法做到平价上网,海洋风电耦合氢能应用还需要一个长期过程,进行工程试验是大规模工程化的前提。     

Variable structure strategy to avoid amplitude and rate saturation in pitch control of a wind turbine

This work proposes the application of a recent compensation technique for input constraints avoidance to the pitch control of a wind turbine. The pitch angle actuators commonly present a hard limit on their rate of change together with the natural amplitude saturation, and a dynamics during their unconstrained operation that can be modeled as a first-order linear system. This dynamic behavior of the pitch actuator requires a particular design of the compensation method, which is based on variable structure systems to avoid both amplitude and rate input saturation by means of an auxiliary loop. The developed methodology reduces the pitch actuator activity necessary to regulate the generated power around its nominal value when facing sudden wind gusts. Another interesting feature of the proposal is that it allows the operator to fix conservative bounds for the actuator speed operation in order to increment the structural robustness of the wind turbine and to extend in this way the service life of the energy system. The effectiveness of the proposed strategy is evaluated by simulation results in an autonomous wind energy conversion system for water pumping with a brushless double feed induction generator (BDFIG).     

风氢耦合系统能量管理策略研究

针对风力机出力的波动性和并网弃风问题,采用风力机/电解槽/燃料电池/超级电容的风氢耦合发电系统及其能量管理控制策略。针对风氢耦合发电系统的12种运行模式,提出一种能量管理控制策略,确保在各个控制单元的作用下,能量协调流动于各个子单元间。能量管理控制策略不仅使风氢耦合发电系统出力可控,而且平抑了直流母线电压波动,平滑了上网功率。通过Matlab/Simulink软件进行仿真研究,验证了风氢耦合发电系统的能量管理控制策略的有效性,提高了风电消纳能力。     

Integration of wind turbine with heliostat based CSP/CPVT system for hydrogen production and polygeneration: A thermodynamic comparison

In this study, two wind-solar-based polygeneration systems namely CES-1 and CES-2 are developed, modeled, and analyzed thermodynamically. CES-1 hybridizes a heliostat based CSP system with wind turbines while CES-2 integrates heliostat-based CPVT with wind turbines. This study aims to compare the production and thermodynamics performance of two heliostat based concentrated solar power technologies when hybridized with wind turbines. The systems have been modeled to produce, freshwater, hot water, electricity, hydrogen, and cooling with different cycles/subsystems. While the overall objective of the study is to model two polygeneration systems with improved energy and exergy performances, the performances of two solar technologies are compared. The wind turbine system integrated with the comprehensive energy systems will produce 1.14 MW of electricity and it has 72.2% energy and exergy efficiency. Also, based on the same solar energy input, the performance of the heliostat integrated CPVT system (CES-2) is found to be better than that of the CSP based system (CES-1). The polygeneration thermal and exergy efficiencies for the two systems respectively are 48.08% and 31.67% for CES-1; 59.7% and 43.91% for CES-2. Also, the electric power produced by CES-2 is 280 kW higher in comparison to CES-1.     

Influence of two systematic parameters on the geothermal heat pump system operation

In order to match the output capacity of a geothermal heat pump system (GHPS) with the actual load requirement, research has been carried out in finding the influence of two systematic parameters, the water flow rate inside the condenser and the compressor input frequency on the GHPS operation. Experiments are done on a small-scale GHPS at the water flow rate ranging from 0.054 kg/s to 0.174 kg/s and the frequency from 30 Hz to 55 Hz. The analysis of the experimental data reveals the relationships among the compressor frequency, the water flow rate and other important parameters such as coefficient of performance (COP), heat capacity and compressor power input. The conclusions in the paper can serve as some guidance to the load adjustment of GHPS.     

Assessing high wind energy penetration

In order to convincingly promote installing wind power capacity as a substantial part of the energy supply system, a set of careful analyses must be undertaken. This paper applies a case study concentrated on assessing the cost/benefit of high wind energy penetration. The case study considers expanding the grid connected wind power capacity in Praia, the capital of Cape Verde. The currently installed 1 MW of wind power is estimated to supply close to 10% of the electric energy consumption in 1996. Increasing the wind energy penetration to a higher level is considered viable as the project settings are close to ideal, including a very capable national utility company, Electra, a conventional power supply system based on imported heavy fuel and gas oil, and favourable wind conditions with an estimated annual average of 9.3 m/s at the hub height of the wind turbines. With the applied case study assumptions, simulations with WINSYS over the lifetime of the assessed wind power investment show that investments up to 4.2 MW are economically viable. The economic optimum is found at 2.4 MW reaching an internal rate of return of almost 8% p.a. This 2.4 MW of wind power would, together with the existing wind power, supply over 30% of the electric consumption in 1996. Applying the recommended practices for estimating the cost of wind energy, the life-cycle cost of this 2.4 MW investment is estimated at a 7% discount rate and a 20 year lifetime to 0.26 DKK/kW h.