10MW太阳能热气流发电系统结构优化与成本分析

针对太阳能热气流发电系统烟囱超高、集热棚超大的特点,基于太阳能热气流发电系统的流动与传热模型,预测了10 MW太阳能热气流发电系统的基本几何结构,建立了太阳能热气流发电系统各关键部件、整体系统的造价模型及发电成本模型.通过计算和对比10 MW系统各种几何结构型式的系统造价,获得了经济上较为合理的结构型式,并分析了影响集热棚、烟囱及系统总造价的主要因素,提出了降低系统造价的方法.结果表明,该方法经济、可行.     

太阳能热气流发电系统的传热与流动数值分析

建立了集热棚、烟囱以及多孔蓄热层的太阳能热气流发电系统传热与流动数学模型,分析了太阳辐射对蓄热介质的蓄热特性的影响.计算结果表明,在太阳辐射为200～800W/M2的范围内,随着太阳辐射的增强,蓄热介质的蓄热比例先减小后增大;烟囱底部的最小相对压力显著减小,流动速度增大;系统内空气的温升增大,蓄热介质表面的温度也显著升高.     

太阳能烟囱发电系统非稳态传热问题及性能分析

建立了包含蓄热层的太阳能烟囱发电系统非稳态传热数学模型,研究了集热系统特性和蓄热层的增温效应,结果表明:蓄热层表面温度、气流温度、集热棚板温度相互影响,随时间有较大波动;气流温升主要发生在气流入口至集热棚半径1/3处,蓄热层表面温度沿径向逐渐升高,在集热棚出口段有明显下降;集热棚板、蓄热层底部及四周是系统热量损失的主要地方;系统运行非稳定期,在没有太阳辐射时,深层蓄热层不参与向气流放热过程,而是继续从浅层蓄热层吸热,浅层蓄热层贮存的热量并不全向气流传递。系统运行平稳期,蓄热层底层的温度趋于定值;理论发电功率的变化趋势与气流温度随时间变化趋势一致。     

太阳能热气流发电系统的热力性能分析

对太阳能热气流发电系统的热力学性能进行了分析,建立了系统的热力学循环,进一步分析了系统的实际循环效率和理想循环效率,对不同规模的太阳能热气流发电系统的热力学特性进行了计算比较.结果表明:大规模太阳能热气流发电系统相应的标准布雷顿循环效率、理想循环效率以及实际循环效率分别为:35%,10%～25%和0.9%～2.0%.分析结果为太阳能热气流发电技术的设计与商业应用提供理论参考.     

多孔介质太阳能集热组合墙的耦合传热与流动分析

针对接触型和分隔型多孔介质太阳能集热组合墙系统,分析了太阳辐射及环境温度变化时,组合墙内传热与流动变化.多孔介质太阳能集热组合墙中,多孔介质起半透明隔热体和蓄热体的作用.多孔介质集热层的孔隙率、粒径、材料热导率和多孔介质集热层在组合墙中的位置对系统的采暖效果影响较大.     

太阳能热气流发电系统的热力性能分析

对太阳能热气流发电系统的热力学性能进行了分析,建立了系统的热力学循环,进一步分析了系统的实际循环效率和理想循环效率,对不同规模的太阳能热气流发电系统的热力学特性进行了计算比较。结果表明:大规模太阳能热气流发电系统相应的标准布雷顿循环效率、理想循环效率以及实际循环效率分别为35%,10%～25%和0.9%～2.0%。分析结果为太阳能热气流发电技术的设计与商业应用提供了理论参考。     

太阳能热气流发电流道优化分析

以西班牙太阳能热气流电站为原型进行数值模拟,得出了太阳能烟囱内的速度场、压力场和温度场分布;研究了集热棚坡度、分流板高度和弧度等因素对系统发电性能及涡轮机位置的影响。研究结果表明:集热棚坡度增加时,烟囱的抽吸作用增强,空气流速增加,有利于提高太阳能热气流发电的输出功率;当集热棚坡度约为0.5°时,其作用最为明显,对于提高系统发电性能最为有利;增加分流板有利于气流发电站的优化,当分流板高度略微高于集热棚高度时,优化效果较好;分流板弧度越小,越有利于系统的优化;集热棚坡度对涡轮机位置有影响,改变分流板的几何因素对涡轮机位置没有影响。     

太阳能槽式集热系统动态传热特性

采用数值模拟方法研究了太阳能槽式集热系统的动态传热特性.建立了管内流体的一维传热模型,并进行了检验,计算结果与实验结果符合较好.采用该模型,该文首先分析了恒定辐射强度下,集热特性受入口温度、环境温度、流体质量流量以及风速的影响规律.然后,研究了辐射强度变化情况下的出口参数动态变化特性.得出:集热管出口温度的变化由于热惯性的影响滞后于辐射强度的变化,对于短期的辐射强度波动,出口温度变化较小,系统可不考虑加入额外的能量.对于全天辐射强度变化,集热管出口温度受辐射影响较大,尽管可忽略短时辐射强度波动的影响,但为维持系统正常运行,蓄热或额外的燃料供应是必须的.     

风压对太阳能热风发电系统的影响分析

根据太阳能热风发电系统的工作特征,以内蒙古乌海金沙沙漠太阳能热风发电系统为模型,模拟计算了不同形式的太阳能热风发电系统;对比不同系统内的气流分布,研究讨论了风压对气流流动和气流速度大小的影响。模拟结果表明:半圆形集热棚系统更具优势,其利用率较高,塔囱底部的平均气流速度可达24.38 m/s。该研究分析为乌海金沙沙漠太阳能热风发电站的建设提供了技术指导。     

太阳能热风发电技术及其应用

在太阳能热气流发电的基础上增设进风口,形成了利用太阳能和风能的太阳能热风发电系统。建立了太阳能热风发电热动力稳态数学模型,通过此模型可判断出发电系统的稳定性,并可解出热风风速、集热棚出口温度及稳态数学模型的其它参数。文章介绍了太阳能热风发电系统的实际运行情况,运行结果与数学模型计算结果相吻合。理论分析和运行实践表明,提高塔筒高度、加大塔筒内外温差、增加集热棚的太阳能吸收率、增大集热棚面积系数及风力发电机组的风能利用率,是提高太阳能热风发电量的途径。     

大型太阳能烟囱发电站热力分析与计算

利用热力学方法建立太阳能烟囱发电系统中集热棚、烟囱及风力透平的热气流能量转换过程的理论模型及求解方法.鉴于太阳能烟囱发电站的大尺寸特征,采用一维假设建立热气流传热模型,使用龙格-库塔方法对非线性能量方程进行数值求解.对集热棚直径3 600 m,烟囱高950 m,设计功率100 MW的大型太阳能烟囱发电站进行分析与计算,给出了该电站的风力透平轴功率随质量流量和太阳辐射强度变化的规律,为风力透平机组提供热力气动设计参数,为大规模开发利用太阳能提供借鉴.     

Three-dimensional CFD analysis for simulating the greenhouse effect in solar chimney power plants using a two-band radiation model

The greenhouse effect in the solar collector has a fundamental role to produce the upward buoyancy force in solar chimney power plant systems. This study underlines the importance of the greenhouse effect on the buoyancy-driven flow and heat transfer characteristics through the system. For this purpose, a three-dimensional unsteady model with the RNG k–ε turbulence closure was developed, using computational fluid dynamics techniques. In this model, to solve the radiative transfer equation the discrete ordinates (DO) radiation model was implemented, using a two-band radiation model. To simulate radiation effects from the sun's rays, the solar ray tracing algorithm was coupled to the calculation via a source term in the energy equation. Simulations were carried out for a system with the geometry parameters of the Manzanares power plant. The effects of the solar insolation and pressure drop across the turbine on the flow and heat transfer of the system were considered. Based on the numerical results, temperature profile of the ground surface, thermal collector efficiency and power output were calculated and the results were validated by comparing with experimental data of this prototype power plant. Furthermore, enthalpy rise through the collector and energy loss from the chimney outlet between 1-band and two-band radiation model were compared. The analysis showed that simulating the greenhouse effect has an important role to accurately predict the characteristics of the flow and heat transfer in solar chimney power plant systems.     

Chimney shape numerical study for solar chimney power generating systems

A large number of researchers have paid great attention to solar chimney (SC) power generating technology, but only a few have studied the chimney configuration. Taking a 10 MW SC system as an example, the physical and mathematical models illustrating the fluid flow, heat transfer and output power features of the system are established. Based on constraints such as equal chimney bottom section area or equal chimney surface area, the impact of several sizes of three different chimney configurations upon the chimney outlet air temperature and velocity, system output power and efficiency is analyzed and the influence of the height‐to‐diameter ratio (H/D) of the cylindrical chimney on system performance is studied as well. After a comprehensive analysis of system output power and efficiency, it is proved by the numerical simulation that the cylindrical chimney would be the best choice among the three basic configurations, whose optimum H/D value ranges from 6 to 8. Copyright © 2011 John Wiley & Sons, Ltd.     

Numerical simulation of the solar chimney power plant systems coupled with turbine

Numerical simulations have been carried out on the solar chimney power plant systems coupled with turbine. The whole system has been divided into three regions: the collector, the chimney and the turbine, and the mathematical models of heat transfer and flow have been set up for these regions. Using the Spanish prototype as a practical example, numerical simulation results for the prototype with a 3-blade turbine show that the maximum power output of the system is a little higher than 50 kW. Furthermore, the effect of the turbine rotational speed on the chimney outlet parameters has been analyzed which shows the validity of the numerical method advanced by the author. Thereafter, design and simulation of a MW-graded solar chimney power plant system with a 5-blade turbine have been presented, and the numerical simulation results show that the power output and turbine efficiency are 10 MW and 50%, respectively, which presents a reference to the design of large-scale solar chimney power plant systems.     

Evaluation of operational control strategies applicable to solar chimney power plants

Numerical simulations are carried out to study the performance of two schemes of power output control applicable to solar chimney power plants. Either the volume flow or the turbine pressure drop is used as independent control variable. Values found in the literature for the optimum ratio of turbine pressure drop to pressure potential vary between 2/3 and 0.97. It is shown that the optimum ratio is not constant during the whole day and it is dependent of the heat transfer coefficients applied to the collector. This study is a contribution towards understanding solar chimney power plant performance and control and may be useful in the design of solar chimney turbines.     

Analysis of some available heat transfer coefficients applicable to solar chimney power plant collectors

A solar chimney power plant consists of a translucent collector which heats the air near the ground and guides it into the base of a chimney at its centre. The buoyant air rises in the chimney and electricity is generated through one or more turbines in or near the base of the chimney. Various studies about solar chimney power plant performance have been published. Different calculation approaches with a variety of considerations have been applied to calculate chimney power plant performance. In particular, two comprehensive studies are relevant, namely those of (Bernardes, M.A.d. S., Voß, A., Weinrebe, G., 2003. Thermal and technical analyses of solar chimneys. Solar Energy 75, 511-524; Pretorius, J.P., Kröger, D.G., 2006b. Solar chimney power plant performance. Transactions of the ASME 128, 302-311). The paper compares the methods used to calculate the heat fluxes in the collector, and their effects on solar chimney performance. Reasons for the discrepancies between the predictions of the two models are given. In general the Pretorius model produces higher heat transfer coefficients and higher heat rate fluxes for both the roof and for the ground surfaces. The two approaches lead to very similar air temperature rises in the collector and thus, similar produced power.     

太阳烟囱发电系统及其固有的热力学不完善性分析

简述了太阳烟囱发电系统的工作原理，指出根据浮力产生的压强差的不同计算方法将得到不同的性能评价。基于这种发电系统的创始人Schliach给出的一个30MW的算例，计算了太阳集热棚和烟囱组合的第一定律效率及集热棚和烟囱各自的第二定律效率。说明太阳烟囱发电技术实质上是太阳热发电，受热力学定律的制约。虽然太阳集热棚的效率相当高，但其第二定律效极低，比第一定律效率低一个量级。由于作为热发电系统热源的热空气的温度很低，这就导致了即使在理想的条件下系统的发电效率也较难大于1％     

太阳能烟囱制冷系统的研究

通过分析制冷系统和太阳能烟囱热气流发电系统的技术和特点,提出了太阳能烟囱制冷系统.将太阳能烟囱系统与制冷系统相结合进行制冷,可实现制冷不用电.该系统由烟囱、集热棚、蓄热层、涡轮机、开启式制冷压缩机、冷凝器和变速器等组成.介绍了太阳能烟囱制冷系统的结构特点、工作原理以及系统相关参数的计算方法.分析结果表明,太阳能烟囱制冷系统结构简单,运行维护方便,制冷不用电,无污染,具有良好的环境效应,可根据环境温度改变压缩机运行转速调节供冷负荷,能有效解决热带及沙漠地区的供冷及供电问题.     

一种新型的太阳能发电技术

对迄今为止有关太阳能热气流发电技术的研究成果进行了全面的综述,其中包括作者在该领域的最新研究进展：太阳能热气流发电系统的热力学循环,HAG效应,带有蓄热层的系统以及带有透平的系统耦合数值模拟等,并对下一步的研究工作进行了展望。