SA firm plans 400MW solar tower

The solar tower, named Greentower, would be 1.5 kilometres high and 280 metres in diameter and will work by causing an updraft to the drive turbines, generating 400 MW of electrical power.

Air within the solar tower is heated in a large circular greenhouse-like structure, and the resulting convection causes the air to rise and escape through the tower. The moving air drives turbines, which then produces electricity.

Hahn & Hahn managing director Alan Dunlop said Tuesday that the project has gained the nod from the Namibian government adding that national power utility is partially funding a feasibility study.

Dunlop said that the base of the tower will incorporate a 37-km2 greenhouse, in which cash crops can be grown.

The greenhouse will be used to develop soil humus to transform barren land to fertile soil that retains moisture and nutrients to enable rapid plant propagation.

Dunlop says that studies have shown that plant-linked humidity does not reduce the uplift in the tower by which the turbines are driven, and even represents a store of latent energy that can be drawn on after sunset.

Water for the plants in the greenhouse can be supplied by desalinating sea water or purifying groundwater, using known technology and a supply of energy, which is only a small fraction of the energy generated.

Solar tower technology has been slow to develop over the years. Between 1979 and 1989, a German engineer is reported to have designed a solar tower 200 metres high, which was built in Spain and financed by a grant from the German government.

The tower ran trouble free for eight years, producing 50 kW of electricity until it was decommissioned.

However, despite the attractiveness of the power project, a senior government official said that Namibia currently need committed investors and not speculators adding that the electricity supply situation remains dire.

Joseph Iita, permanent secretary in the Ministry of Mines and Energy, said that government is not aware of the proposed solar tower adding that ‘fly-by-night’ investors were flooding government with applications for energy generation projects.

“We have so many offers but we are only prepared to work with serious investors and despite so many investors showing interest in the field of energy generation, we haven’t seen any project taking off,” Iita told national daily New Era.

Iita also said that government had not made any commitment to fund the ambitious solar power project.

August 2008
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