Timothy J. Chiaverini
One of the more innovative but simple solar power systems is the solar chimney, a passive ventilation system or power generation system that is powered by the sun and buoyant force. A simple schematic for a solar chimney power system was proposed by Schlaich in 1978, and the system proved successful through the operation of a 50 kW pilot plant in the early 1980s.
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The simplicity of the design and the physical principles of the system's operation are based on the process of convection.
The solar chimney structure is constructed with three main components: structures to gather air and heat water, the cylindrical or prism shaped "chimney" and a turbine. The three components work together like a greenhouse. The sun heats the water and air, in essence jumpstarting the process of thermal expansion. The warmer air is collected inside the chimney which accelerates the process of convection, and airflow is created. This airflow turns turbines. Its working principle is that direct and diffuse solar radiation heats a large body of air in the collector, which is then forced by the laws of physics (warm air rises and creates a convective flow) to move up the chimney as warm wind, driving the turbines to generate electricity.
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Of course, hotter air escapes through the mouth of the chimney.
This amazingly simple, clean and renewable system modeled after natural phenomenon converts solar energy to heat energy, then heat energy to kinetic energy, and finally kinetic energy to electric power. The surplus of kinetic and heat energy provides the gravitational buoyant force that completes the cycle.
A prototype of a solar chimney built in Manzaranares, Spain is 195 meters tall. The solar collector for the chimney is 240 meters in diameter. Measurements show the solar chimney warms the air by approximately 17 degrees and creates airflow through the chimney at a speed of 12 m per second. The system puts out 50 kilowatts of electricity.
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