SolarMission Technologies (OTC: EVOMY.PK, ASX: EVM.AX) and its Australian subsidiary, EnviroMission Limited produced this 5 minute video about its early pilot plant in Spain. It is an older video (2000) but gives a basic understanding of the solar tower concept. The designs have changed and technologies added, but it gives an introduction to the solar tower concept.
The power plant consists of a very large glazed solar collector with a chimney in the center through which the hot air generated in the collector rises. The hot air wind drives turbo-generators located at the base of the chimney. The floor of the collector absorbs heat during the daytime and release the heat during the night, so that the power is produced on a continuous basis. Cold air enters the collector, with an upward sloping ceiling, from its outer perimeter, is heated and rises through the tower at 50 feet per second (15 meters per second)