| Solar chimney power system (SCPS) is a thermal system that is suitable for large-scale power generation. There are vast desertified regions, high-fall mountains, abundant available solar radiation, and large diurnal temperature in Western China where SCPS has large potential of application. However, the energy conversation efficiency of SCPS is low, its investment is large, and its safety is not good. By now, any commercial power plant has been not built up. Further study on fundamental problems and application of SCPS can be performed. It is significant to develop cost-effectiveness SCPS adapting to the local topography in Western China to supply energy.The dissertation is studying SCPS and its application in Western China and divided into the following two sections.The first section: A testing prototype of SCPS is built and the experimental and theoretical investigations of SCPS are performed.A testing prototype of SCPS is designed and built in China, which has a collector 10 m in diameter and a chimney 8 m high. Experimental investigation of SCPS is performed. The results show that the temperature of air increases along a radius from the inlet to the outlet, the velocity of air firstly decreases and then increases, the temperature of air decreases with heights in the chimney, the temperature rise in the collector reaches more than 20 K in a sunny day and 10 K in a cloudy day, a temperature inversion occurs around the chimney outlet in the morning and its duration decreases with higher solar radiation, and temperature inversion will block the operation of SCPS.The problems of the models modeling the flow and heat transfer in SCPS include compressibility, convective heat transfer between the flow and the ground, pressure drop coefficient, turbine efficiency, simulation using commercial computational fluid dynamics (CFD) software. As for the above problems, three numerical simulation models are developed to simulate the flow and heat transfer in SCPS. A 3D code is written in C based on SIMPLE algorithm. This code written can be free adjusted by the researcher. The CFD programme Fluent is re-developed by introducing functions of accurate density and buoyancy, which improves the inaccuracy of simulation using the buoyancy models automatically included in CFD programmes where some crucial assumptions are made. A'1+1'dimensional compressible flow code is written by Matlab. In the model, natural and forced convection effects is considered for convection between the air flow and the ground and that between the air flow and the collector roof, flow resistance in the collector and chimney, and the pressure drop and temperature drop at the turbines are included, the ambient pressure and temperature changes with heights. This model has few assumptions and is more realistic, which solves the above problems of other models modeling the flow and heat transfer in SCPS.All the modes are validated by the comparisons of the simulation and the measurements or the calculation using the authoritative model. The deviation of the simulated results using the re-developed buoyancy model and the results using the buoyancy models (i.e. Full buoyancy model and Boussinesq model) automatically included in CFD programmes in a proposed 1500 m high solar chimney is estimated. The results show that Full buoyancy model and Boussinesq model give 42% and 33% times more power respectively than our model. Then, the influence of different solar radiations and dimensions on the power output are analyzed by using the'1+1'dimensional compressible flow code, respectively. The results show that the power capacity of SCPS increases with the increase in solar radiation, chimney height, or collector diameter.The second section: Adapting to the special topography in Western China, various solar chimney thermal systems are proposed, economic analysis of large scale SCPS and its influence on local climate are performed, respectively.A concept of solar chimney groundwater pumping is first proposed and the solar chimney groundwater pumping system (SCGPS) is designed. The feasibility and economics of the use of small and mediumsmall scale SCGPS for driving to pump groundwater for drinking and agricultural use are discussed. The results show that the small and mediumsmall scale SCGPS has large potential at the remote villages where grid electricity is not reached and wind is plain. The relation of driving power capacity of SCGPS and its service scope and the depth of groundwater is investigated. The performances of three combined power systems with mountains are investigated. The performances of the three combined power systems with high mountains are analyzed by comparing their efficiency, building difficulty, investment, safety and the likes. The efficiency of the sloped collector system is the highest. The efficiency of the sloped collector system with 45°inclination mountain-side is about 40% more than, and the efficiencies of the sloped chimney system and tunnel chimney system with 15°inclination mountain foot are about 20% more than the classical system at the same latitude. It's concluded that compared to the classical reinforced concrete SCPS, the three combined power systems with high mountains are more available and has potential of reaching high height for'chimney', good safety and low investment..Force equilibrium of floating solar chimney is established. The influence of wind velocity and net buoyancy of chimney on the power capacity of large scale floating solar chimney power system (FSCPS) are discussed. The analyses show that the optimal condition for floating solar chimney power system is that annual wind velocity is below 3.5 m/s at the ground level. Economic analyses of FSCPS are performed by using the developed economic model including the carbon credits. The results show that the minimum electricity price of more than 200 MW FSCPS under financial incentive of soft loan is less than 0.58 yuan/kWh, which is competitive with coal-fired plant.Flow and heat transfer of the plume from the gigantic chimney in the cross-section atmosphere are simulated. Viewpoint that the gigantic solar chimney is likely to affect the local climate is presented. The influences of chimney height, relative humidity, and wind velocity on the potential precipitation area and precipitation strength are analyzed. Environmental and economic benefits of increasing chance of precipitation around the large scale FSCPS are analyzed. It is concluded that higher chimney, bigger relative humidity of atmosphere, bigger velocity of wind increased the potential precipitation area and precipitation strength. In addition, latent heat produced in condensation process helps rise of plume by heating the plume.The investigation in this dissertation would provide the theoretical basis for the design and construction of solar chimney power plant in Western China, to some extent. |
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