Solar tower

A solar tower is a power station with renewable energy, built so as to channel the air heated by the sun in order to actuate turbines to produce electricity. The concept was invented by the German engineer Jörg Schlaich.

Principle

The tower is in fact only a Cheminée. The Air, under a gigantic Greenhouse, the “collector”, placed all around the central chimney, is heated by the Sun and is upwards directed by Convection, the air volume displacement allowing Turbine S located at the mouth of the chimney to produce electricity. Its operation is based on a simple principle: the hot air being lighter than the cold air, it rises.

The principal advantages of this technology are: little of maintenance necessary, a simple mechanics, and exemption from payment of the rays of the sun. Moreover, like the ground under the collector, truffle of water pipelines, stores heat the day to give again it the night, the system is operational almost 24 hours a day. The only difficulty is the starting investment.

An alternative which consists in laying down the tower with mountainside is also being studied. The principle remains the same one: a vast collector located at the level of a plain, and a conduit which emerges in altitude, allowing to benefit from the difference of Température. Since it is not a question of a chimney drawn up in the middle of the collector, but of a conduit laid down with mountainside, its installation and its possible disassembling can be considered more easily. The project could for example apply to mountainous areas like the island of the Réunion.

History

Many researchers in the world presented various projects of solar tower.

The first is incontestably a Spanish soldier, Colonel Isidoro Cabanyes, which in 1903 proposed a model of solar tower in the review Energía eléctrica .

One can also quote the French physicist Bernard DUBOS who proposed into 1926 to exploit a vertical wind produced by a large tube installed on the side of a mountain.

One of the first representation of a solar tower was written in 1931 by a German author: Hans Günther.

Between 1940 and 1960, French Edgard Nazare, after having observed several swirls of sand (dust devil) in the Saharan south, and to have measured of them the characteristics thanks to its declination compass-azimuth reading device of pocket, imagined dipositif completely revolutionary: the tower with depression, now called tower with vortex. It is in 1956 qu ' it deposited its first patent in Algiers. This patent was redeposited in Paris on August 3rd, 1964 under number 1.439.849 (statement 983.953). It was a question artificially of generating a swirling atmospheric ascent in a kind of turn in the shape of conduit of Laval and of recovering of it part of energy by means of turbines.

In 1975 the Canadian engineer Louis Mr. Michaud published his project Vortex Power Station in the bulletin of the American company of meteorology. It was also a question of generating a swirling atmospheric ascent, but in a cylindrical tower.

But it is not that in 1981 qu ' a first solar prototype of chimney was actually built in Manzanares (Spanish city with 150 kilometers of Madrid) under the direction of German engineer Jörg Schlaich, and thanks to the funds of the German Ministry of research and technology. It was not of a tower with vortex but about a simple solar chimney, 5 times less powerful (with equal height). This chimney measured 194 meters for a power of 50kW and functioned until 1989. It was stopped because of a cost of the kilowatt-hour, five times higher than a traditional thermo plant.

Lastly, it is on October 8th, 1985 that Russian George Mamulashvili deposited his patent N° 1.319.654 for a project comparable with the tower with vortex called Vertical Aeorothermal Power Station .

In more precise terms, the Anglo-Saxons indicate the technology of the solar chimney by: " Individual Flow Upwind System" and the technology of the tower with vortex by: " rotational flow wirling system".

Projects

The Australian project

A project of solar tower, called Project of Buronga, planned for 2010, is currently developed in Australia by the Enviromission company. The chimney would have 990 Mètre S height, 70 meters of Diamètre. The power station would provide 200 megawatt S of electric output. It is about one of the most ambitious projects of planet for the production of alternative energy: a factory with renewable energy which provides 4 times less power than a small engine Nucléaire (200 MW compared with 915 MW for a Pressurized water reactor) while being surer and cleaner.

The capital cost is approximately 400 million Euro S.

To counter the effect of ovalization of the tower (which would as easily fold up it on itself as wet a paper cylinder posed on a table, considering its incredible lightness), the company of engineering SBP, person in charge of the project, had the idea to place in the tower at regular intervals of the structures of maintenance resembling the ray S of a Roue of Bicyclette. They decrease only by 2% the Speed of the air.

The solar tower would provide one kilowatt-hour nearly a third less expensive than those provided by the solar panels, but still five times more expensive than electricity with the coal, which accounts for 95% of the production in Australia. Tourists could visit the tower, in order to still significantly reduce the price of the kilowatt-hour. The culture of Tomate S within the collector is also considered.

Specifications of the project

chimney a 990 height m (3281 feet) materials composite
a collector 7 km in diameter, is 38,5 km 2 of glass and plastic.
Temperature of the air heated in the chimney: 70 °C.
Air velocity in the chimney: 15 m/s (54 km/h).
32 turbines.
produced Energy: 200 megawatts, 7 times less than a modern Nuclear reactor (Chooz = 1500 MW per engine), but to provide in electricity approximately 200 enough; 000 residences.
This project can appear incredible but its originators say it realistic. The feasibility studies by the German office of engineers SBP, based with Stuttgart, come to a end. This solar tower would thus be built by the EnviroMission company in the desert of News-Wales of the South, in the county of Wentsworth. If the financing is found, its construction should start before 2010.
With the breaking news, EnviroMission launches out in the development of a first smaller and less expensive version (50 MW) with a prestressed concrete chimney high strength. One worries all the same about the slowness of the project to the sights of the concerned sums and the already joined together investments.

The Spanish project

Another project of solar tower, designed to expire before 2010, if the financing is found, is currently developed in Spain in the locality of Fuente el Fresno, a village of the Province of Ciudad Real. Work should be carried out in collaboration with the Spanish companies Campo 3 and Imasa, and the German company Schlaich Bergermann. This 750 meters height tower would be consequently highest of this kind in Europe.

Specifications of the project

a chimney of 750 m in height.
a collector of 3 km of diameter, covering 350 hectares, of which 250 hectares could be used for the vegetable culture under greenhouse (tomatos).
Air velocity in the chimney: 43 km/h.
Power of the installation: 40 megawatts, is the demand for electricity of approximately 120.000 people.
Cost of the project: 240 million euros, that the partners hope to join together in 2007.
In complement of this energy production, the project would also allow the installation of equipment of telecommunication and monitoring against the fires, and should take on a tourist aspect by envisaging an access to the public.

Other projects

There exist currently two construction projects of solar tower: a tower in the shape of Conduit of Laval by the Sumatel French company in Savoy which already built in 1997 a model of 6 m in height and plans to pass to 60 m or more, and the cylindrical tower of 500 m in height quoted above. With equal height, the powers planned for these two projects are very different and the experimental model, built by Sumatel on the site of Ebullient in the Antilles, is not strictly speaking a solar tower, because it draws its calories from a geothermal field and not from the sun.

For a possible tower of 500 m, Sumatel announces more 1500 MW whereas the australo-German project advances the figure of 50 MW. This difference in performance is explained by the difference in height of the exploited atmospheric phenomenon. The French process makes it possible to generate an atmospheric swirl which can reach 20 km in height, whereas the process australo-German is satisfied to exploit the effect of pulling with a simple chimney. A such waterspout or a tornado, the virtual chimney of 20 km in height has a pulling, therefore an output, much more important than a human construction, even very great height. In both cases the Lois of Carnot are respected. The difference in temperature between the low and high layers of the atmosphere is simply much more important in the French project. The Nazare inventor, and with him the Sumatel company, estimates that it is starting from a tower of 300 m minimum which one can hope for to generate a swirl of 20 km height and to obtain the announced powers. Contrary to the tower australo-allemande, the French tower is used only to start the atmospheric phenomenon.

Homonymy

A solar tower is also an scientific instrument to examine the sun: Solar tower of Meudon.

See too

References

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