Development and performance investigation of a novel solar chimney power generation system

Abstract

South Africa has limited reserve electricity resources and many parts of the country have limited access to electricity. Predictions suggest South Africa will have a serious electricity allocation problem in the very near future, and current rolling blackouts in many of our cities can attest to the looming problem. The energy crisis in South Africa has highlighted the need to increase electricity generation capacity and to search for alternative energy sources. Solar chimney plants could form part of the solution in the near future in South Africa to create additional power. Solar radiation energy is abundant in South Africa, while wind sources are limited mainly to coastal regions. Presently, wind turbine technology is more efficient than solar voltaic cells. This study develops a wind generation system in areas where wind is absent. A solar chimney power plant is expected to provide remote areas in South Africa with electric power, or complement the current electricity grid. Solar energy and the psychometric state of the air are important to encourage the full development of a solar chimney power plant for the thermal and electrical production of energy for various uses. A solar chimney power plant consists of a greenhouse roof collector, and the chimney is located at the centre. The chimney is used to direct and vent the low density air through a wind turbine which in turn converts the air enthalpy into mechanical energy. The main advantage of a solar chimney system lies in its low maintenance cost, the simplicity to operate and the durability of the system. Research of a design within the South African context and particularly on increasing the effectiveness of the solar chimney power plant technology is lacking. Several simulations were performed to find the optimum design configuration to focus the research. The results from the simulations were used to design the best configuration for a pilot plant. * Symbols : A : Area, m2 b : Breadth, m C : Circle diameter, m Cair : Heat Capacity of air = 0.0342, J/kg K Cv : Heat Capacity of air at a constant volume, J/kg K E : Energy, J Ek : Kinetic Energy, J g : Gravity acceleration = 9.81, m/s2 h : Height, m L : Height of straight chimney, m m : Mass, kg m : Mass flow rate, kg/s P : Pressure, Pa P : Atmospheric pressure, Pa PE : Potential Energy, J Pel : Electrical Power, W/m2 Q : Flow rate, m3/s r : Radius, m Rair : Air constant = 287.058, J/Kg K s : Square diameter, m T : Temperature, K V : Velocity, m/s Wturbine : Power of turbine, W Greek symbols : ρ : Density, kg/m3 η : Efficiency, % γ : Specific heat ratio Subscripts : 1 : Inlet of the solar collector 2 : Inlet of the wind turbine/outer of the solar collector 3 : Inlet of solar chimney/outlet of the wind turbine 4 : Outlet of solar chimney