Green tower not all hot air

Green tower not all hot air

CLIMATE CHANGE and the need for alternative energy sources in southern Africa have led experts to develop a new technology to produce electricity with a so-called green tower.

The tower is more than one kilometre high and collects hot air sucked up through its chimney, causing large turbines at its base to rotate and generate power. A group of German and South African engineers and university professors gave a day-long presentation to local engineers, technicians and energy experts of the Green Tower Project on Friday.According to Prof Wilfried Kraetzig, a smaller model plant was run successfully in Spain for seven years.”A proper green tower power plant of 400 megawatt electricity needs to be 1,5 km high and 280 metres in diameter – but nowhere in the world has such a high structure ever been built,” he admitted.To collect sufficient hot air, a circle of 37 square kilometres with glass panels – which are heated by the sun during the day – would have to be constructed around the tower base.They would not lie on the ground, but would be about on a three-metre-high platform.”Underneath it one can grow large-scale vegetables and grapes, since the total roofed area would cover 3,7 hectares like a huge greenhouse,” his colleague, Professor Reinhard Harte, added.”Growing flowers for export and fish farming (aquaculture) would also be a possibility,” he said at the presentation.At the tower base 32 turbines would be installed and driven by the “hot air” to generate electricity.If constructed in the Namib Desert, close enough to allow for a pipeline to the Atlantic Ocean, seawater can be extracted and desalinated to allow large-scale agriculture like crop farming.According to Harte, all these diversified activities would create some 25 000 jobs.One solar chimney project would cost about 600 million euros (N$6 billion), including a turbine manufacturing plant and a glass factory to produce the thousands of glass panels needed for the collector platform.This is roughly the same cost as the envisaged Kudu gas plant near Oranjemund – the Kudu project has still not materialised, as prices for power exports have not been agreed on with buyers.According to Jens Stinnes of Green Tower Ltd, based in South Africa, Namibia has lots of space and up to four such towers could be constructed over the years, generating 1 600 MW of electricity, half of which could be exported to help alleviate the power crunch southern Africa is experiencing.”The lifespan of each plant would be 160 years and the electricity selling price is calculated at 15 Namibian cents per kilowatt hour,” Stinnes said.This is cheaper than the price at which NamPower buys electricity from Eskom in South Africa, which is around 17,4 cents.NamPower boss Paulinus Shilamba said the diversified uses of the unique project would be an enhancement for Namibia’s economy.”The possibility to desalinate sea water and use it for agricultural irrigation projects, apart from establishing aquaculture or fish farming, makes the green tower power project very interesting,” Shilamba said at the presentation.”Constructing a 1,5-kilometre-high tower – a venture never carried out before – is however risky,” he told The Namibian on Friday.The chief technical advisor to NamPower, Reiner Jagau, suggested that a feasibility study should first be conducted to see if such a project was economically viable.”However, it might take quite a few years to build and once completed, we must make sure there is not an over-capacity of electricity, because quite a few power projects are going to be constructed very soon in our neighbouring countries,” Jagau said.A group of German and South African engineers and university professors gave a day-long presentation to local engineers, technicians and energy experts of the Green Tower Project on Friday.According to Prof Wilfried Kraetzig, a smaller model plant was run successfully in Spain for seven years.”A proper green tower power plant of 400 megawatt electricity needs to be 1,5 km high and 280 metres in diameter – but nowhere in the world has such a high structure ever been built,” he admitted.To collect sufficient hot air, a circle of 37 square kilometres with glass panels – which are heated by the sun during the day – would have to be constructed around the tower base.They would not lie on the ground, but would be about on a three-metre-high platform.”Underneath it one can grow large-scale vegetables and grapes, since the total roofed area would cover 3,7 hectares like a huge greenhouse,” his colleague, Professor Reinhard Harte, added.”Growing flowers for export and fish farming (aquaculture) would also be a possibility,” he said at the presentation.At the tower base 32 turbines would be installed and driven by the “hot air” to generate electricity.If constructed in the Namib Desert, close enough to allow for a pipeline to the Atlantic Ocean, seawater can be extracted and desalinated to allow large-scale agriculture like crop farming.According to Harte, all these diversified activities would create some 25 000 jobs.One solar chimney project would cost about 600 million euros (N$6 billion), including a turbine manufacturing plant and a glass factory to produce the thousands of glass panels needed for the collector platform.This is roughly the same cost as the envisaged Kudu gas plant near Oranjemund – the Kudu project has still not materialised, as prices for power exports have not been agreed on with buyers.According to Jens Stinnes of Green Tower Ltd, based in South Africa, Namibia has lots of space and up to four such towers could be constructed over the years, generating 1 600 MW of electricity, half of which could be exported to help alleviate the power crunch southern Africa is experiencing.”The lifespan of each plant would be 160 years and the electricity selling price is calculated at 15 Namibian cents per kilowatt hour,” Stinnes said.This is cheaper than the price at which NamPower buys electricity from Eskom in South Africa, which is around 17,4 cents.NamPower boss Paulinus Shilamba said the diversified uses of the unique project would be an enhancement for Namibia’s economy.”The possibility to desalinate sea water and use it for agricultural irrigation projects, apart from establishing aquaculture or fish farming, makes the green tower power project very interesting,” Shilamba said at the presentation.”Constructing a 1,5-kilometre-high tower – a venture never carried out before – is however risky,” he told The Namibian on Friday.The chief technical advisor to NamPower, Reiner Jagau, suggested that a feasibility study should first be conducted to see if such a project was economically viable.”However, it might take quite a few years to build and once completed, we must make sure there is not an over-capacity of electricity, because quite a few power projects are going to be constructed very soon in our neighbouring countries,” Jagau said.

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