A solar updraft tower is a large-scale solar power plant (30-200 MW) for regions of the earth that are rich in sunlight.

Solar updraft towers generate electricity from solar radiation: the sun heats the air under a large translucent collector roof. Because of the density differential created between the warm air in the collector and the cooler ambient air, air flows radially into an open-ended tube arranged vertically at the centre of the collector roof and rises within it. The airflow drives turbines installed at the base of the tube and generates electrical energy.

The essential components of a solar updraft tower are the collector, the turbine and the chimney.

The collector in a solar updraft tower resembles a greenhouse: a covering made of glass, synthetic material or foil admits a maximal amount of solar radiation that heats the air beneath the collector. The warmed and lighter air then flows in the direction of the tower tube and is naturally driven upward.

The turbine is propelled by the tube’s rising air that was warmed in the collector. The jacketed turbines are very similar to the more common water turbines and were jointly developed with the cooperation of water turbine manufacturers.

For a large-scale solar updraft power plant, a tower of up to 1000 m high is required. From a technical standpoint, this is nothing more than a very tall natural draft cooling tower. In a 1000 m tower, the wall width ranges from approx. 1 m at the base to 0.3 m at the midsection, at which point the width remains constant. So-called “spoke wheels”, which are mounted horizontally, stabilize the tower while minimizing costs and optimizing air flow. We hold the patents for these spoke wheels and their assembly.

Investment costs for a solar updraft tower are significantly higher than for a fossil fuel power plant; however, operating costs for a solar power plant are considerably lower as there are no costs for combustibles.

The initial investment requires full amortization and interest payments. As a result, high interest rates and the low cost of combustibles mean that solar power is more expensive than energy from power plants that burn fossil fuels. However, with low interest rates and long amortization periods, it becomes cheaper. When financed at a low interest rate (< 6%) and with a 40-year amortization period, electricity generation costs can be reduced to as low as 0.06 €/kWh.

Large-scale facilities can thus make a significant contribution to the global, clean and cost-efficient supply of energy.