太阳能烟囱发电系统的CFD模拟研究

太阳能烟囱发电技术是一项综合应用温室效应技术、烟囱技术及风力涡轮发电技术于一体的太阳能发电新技术,是实现大规模开发和利用太阳能的一种新途径.采用计算流体动力学(CFD)方法对太阳能烟囱发电系统的速度场、压力场和温度场进行了数值模拟.结果表明:在其它条件不变的情况下,集热棚周边高度对系统的发电功率没有影响;太阳能烟囱直径存在一最佳值,使发电系统输出的发电功率最大.     

太阳能烟囱发电装置的集热棚集热效率分析

在太阳能烟囱发电系统中,集热棚是影响其发电效率的关键部件之一.为了提高太阳能烟囱发电系统的发电效率,对系统中集热棚集热性能的各种影响因素进行了分析,模拟计算了集热棚的集热效率.     

太阳能烟囱发电新技术

介绍了一种太阳能烟囱发电新技术。太阳光辐射透过太阳能集热棚，加热集热棚下面的地面，被加热的地面与集热棚内的空气进行热量交换，使其温度上升，被加热的空气上升并进入与集热棚中部相连的烟囱，在烟囱内上升气流推动涡轮发电机旋转、发电。整个太阳能烟囱发电技术的能量转化以及效率可以从三个部分来分析：通过集热棚太阳能转化为空气热能，通过烟囱将热能转化为动能，通过涡轮发电机将动能转化为电能。另外，总结了太阳能烟囱发电技术的优缺点，指出它是一种适合于我国西部地区的一种能源开发新途径。     

基于集热影响系数d的太阳能烟囱集热效率分析

针对呼和浩特地区太阳辐照资源,以太阳能烟囱为研究对象,在呼和浩特地区应用太阳能烟囱进行可行性分析。太阳能烟囱在定集热棚半径定壁温条件下,对不同集热棚倾角进行数值模拟计算,引入集热影响系数d,对集热棚内流场努赛尔数(Nu)进行分析,比较不同倾角下温度场、压力场、速度场、集热效率。研究表明,集热棚集热影响系数d存在最大值,在不同集热棚倾角下,集热棚内温度场、压力场、速度场变化较大,集热效率存在最大值。认为在定集热棚半径条件下,集热棚倾角选取10°作为呼和浩特地区太阳能烟囱集热棚倾角更经济适合。修正了以往国内外太阳能烟囱集热棚倾角的选取方法。     

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。     

荒漠中的发电站——太阳能烟囱发电站

一前言 太阳能烟囱发电技术是通过集热棚吸取太阳热能使棚内空气温度升高,根据烟囱的原理,在烟囱内将形成强大的气流,利用这股气流形成的风力驱动风机,带动发电机发电。太阳能烟囱发电系统主要由透光的采光大棚、烟囱及风力涡轮机构成,如图1所示。     

集热棚半径和涡轮压降对太阳能热风系统性能的影响

研究了太阳能热风系统中涡轮压降和集热棚半径对系统功率的影响,并对流动方向上集热棚内温度的分布情况进行了分析.结果表明:结构确定的太阳能热风系统存在使系统功率最大的最佳涡轮压降;在涡轮压降不变的情况下,系统功率随集热棚半径增大到一定程度后将不再增大,即无限制地增大集热棚半径是无意义的,指导工程运用时不能仅通过增大集热棚半径来增大系统功率;增大涡轮压降能在一定程度上加快空气的温升速率、提高空气最终温度以及降低系统的做功潜能.     

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。     

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.     

Feasibility study of a solar chimney power plant in Jordan

A solar chimney power plant system is theoretically designed for future erection in Jordan. Analytical analysis of the system is simulated by mathematical software. The actual values of solar irradiation in Jordan are used in the simulation to predict the power output of the solar chimney power plant. The output results of the maximum (inlet) values of velocity, pressure, and mass flow rate of air versus the chimney height variation are obtained. Furthermore, the electrical power output and the efficiency of chimney versus chimney height variation were determined. For a solar collector diameter of 40 m and a chimney diameter of 3.5 m, the maximum power output (85 kW) was obtained for a chimney height of 210 m.     

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.     

Simulation of a pilot solar chimney thermal power generating equipment

A pilot experimental solar chimney thermal power generating equipment was set up in China. A simulation study was carried out to investigate the performance of the power generating system based on a developed mathematical model. The simulated power outputs in steady state were obtained for different global solar radiation intensity, collector area and chimney height. By intercomparison, it is found that the simulated power outputs are basically in agreement with the results calculated with the measurements, which validates the mathematical model of the solar chimney thermal power generating system. Furthermore, based on the simulation and the specific construction costs at a specific site, the optimum combination of chimney and collector dimensions can be selected for a required electric power output.     

一种新型的太阳能热气流发电系统

提出了一种螺旋集热型太阳能热气流发电系统,建立了该系统的流动与传热特性数学模型.数值模拟结果表明,与西班牙太阳能热气流试验电站相比,在烟囱出口流动与传热特性参数及输出功率相同情况下,螺旋集热型太阳能热气流的集热棚半径减少了25%,占地面积减少了44%,具有较明显的经济性和商业优势.     

太阳能热风发电系统的性能分析及研究方法

阐述了太阳能热风发电系统的研究进展.对影响该系统性能的主要因素———集热棚、空气涡轮机及烟囱的特性进行了分析,并根据这些影响因素探讨了太阳能热风发电系统的研究方法及关键问题.给出了部分研究结果,说明对太阳能热风发电系统的研究还需深入,提出应加快商用电站的建设.并指出:在发展太阳能热风发电系统时,应综合考虑荒漠治理、农作物种植及海水淡化处理等.     

Numerical analysis on the influence of ambient crosswind on the performance of solar updraft power plant system

The solar updraft power plant system (SUPPS) is a novel kind of solar thermal application, which uses the fluid buoyancy of the chimney effect to achieve output power. To investigate the impact of a strong ambient crosswind on the system output power through the collector inlet and chimney outlet, numerical analysis on the performances of a SUPPS identical to the prototype in Manzanares, Spain which is exposed to the external crosswind with different velocities is carried out in this paper. A geometrical model including the SUPPS and its outside ambience is built and the mathematical models to describe the fluid flow, heat transfer and output power of the whole system are further developed. The pressure, temperature and velocity distribution of the air in the ambience and SUPPS together with the output power of the SUPPS are analyzed. The numerical simulation results reveal that ambient crosswind has influence on the performance of the SUPPS in two ways. On one hand, when the ambient crosswind is comparably weak, it will deteriorate the flow field and reduce the output power of the SUPPS. On the other hand, it may even increase the mass flow rate and output power if the crosswind is strong enough.     

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.     

Performance evaluation of solar chimney power plants in Iran

The solar chimney power plant is a simple solar thermal power plant that is capable of converting solar energy into thermal energy in the solar collector. In the second stage, the generated thermal energy is converted into kinetic energy in the chimney and ultimately into electric energy using a combination of a wind turbine and a generator. The purpose of this study is to evaluate the performance of solar chimney power plants in some parts of Iran theoretically and to estimate the quantity of the produced electric energy. A mathematical model based on the energy balance was developed to estimate the power output of solar chimneys as well as to examine the effect of various ambient conditions and structural dimensions on the power generation. The solar chimney power plant with 350 m chimney height and 1000 m collector diameter is capable of producing monthly average 1-2 MW electric power over a year.     

Performance analysis of conventional and sloped solar chimney power plants in China

The solar chimney power plant (SCPP) has been accepted as one of the most promising approaches for future large-scale solar energy applications. This paper reports on a heat transfer model that is used to compare the performance of a conventional solar chimney power plant (CSCPP) and two sloped solar chimney power plants (SSCPPs) with the collector oriented at 30° and 60°, respectively. The power generation from SCPPs at different latitudes in China is also analyzed. Results indicate that the larger solar collector angle leads to improved performance in winter but results in lower performance in summer. It is found that the optimal collector angle to achieve the maximum power in Lanzhou, China, is around 60°. Main factors that influence the performance of SCPPs also include the system height and the air thermophysical characteristics. The ground energy loss, reflected solar radiation, and kinetic loss at the chimney outlet are the main energy losses in SCPPs. The studies also show SSCPPs are more suitable for high latitude regions in Northwest China, but CSCPPs are suggested to be built in southeastern and eastern parts of China with the combination to the local agriculture.