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II] The caracteristics of the offshore wind turbines and the futur projects. b)Example: Offshore wind turbines in Denmark. c)The project of offshore wind turbines in Dunkerque. d)Can the offshore wind turbines always produce energy? III] Positives and negatives things. a)Positive things. b)Negative things. c)Conclusion.   I] What are the offshore wind turbines and why are they usefull?______________________________________________________________ To begin the word offshore means an exploitation in the sea, like electric or oil exploitation. The offshore wind turbines consist of put wind turbines on the sea to produce electricity, the systeme is approximatly the same as the onshore wind turbines. The offshore wind turbines are usefull when the population density is high or when there is not enough place on the territory. Around the farm there are marks to protect the boats when there is fog or rain. There are some problems with the offshore wind turbines, the principal one is the low production, the number of wind turbines must be high to have a good production. Several country want to build offshore wind turbines for the reason it is an ecologic way to make electricity and the landscapes are not dammage by the onshore wind turbines. The offshore wind energy actually is competitive with other power generating technologies. The production of the total of the world is 5.1012 kWh. II] The caracteristics of the offshore wind turbines and the futur projects.______________________________________________________________ a) Construction of offshore wind turbines To build the offshore wind turbines we use a floating crane. It's a kind of boat with a crane to construct them .  This ship is also called the «ship with legs» because 4 sorts of legs stabilize the boat when a wind turbine is built . 
 The cost of this kind of construction is higher but the wind is higher too in the sea so the production is better. Some offshore wind turbines have an electrical crane to be able to remplace the major parts without a floating crane. The areas where the offshore wind turbines are put are between 10 and 40 km and the water depths is between 5 and 11 meters for environmental reasons. There are two ways to construct wind turbines: The first consits of fixing the wind turbines by concrete blocks. This solution is not very usefull when the depth is high and the costs are high too but they are easy to build. Or we can use metallic structure to anchor in the wind turbines.  This solution is more usefull, because with this one the wind turbines can be built with a bigger depth and the metallic structure is more resistant than the concrete blocks. When the offshore wind turbines are placed, the current is bring back by cables. The futur projects: The scientists have few projects to upgrade the offshore wind turbines. The first project to build the offshore wind turbines is to use floats, this sort of construction will be usefull because the offshore wind turbines will be able to be build with a big depth so everywhere in the sea. There is another way to use the offshore: build what can be called «offshore water turbines». It is the same process than the offshore wind turbines but the blades are in the water and use the marine current. Some countries are very interested in the offshore energy and they want to build offshore wind turbines together in the Northsea like Denmark, England, Belgium... b) Example:Offshore wind turbines in Denmark The population density in Denmark is high and the territory is rather small so the offshore wind turbines are very usefull. This is why the bigger offshore farm is in Denmark. It's the Nysted offshore wind farm. There are 8 rows with 9 turbines each. For information the 72 turbines product a total of 165.5 MW. Some numbers:-In 1995 a farm was created. The wind farm is composed by 10 offshore wind turbines. -In 1998 they want to build 750MW offshore wind power divided in five different farms. -In 2002 and 2003 the Denmark increases their farms, one of 158 MW and another of 160 MW. -The Danish government wants the offshore production to represent 40% of the Danish electricity consumption in 2030. c)The project of offshore wind turbines in Dunkerque There are not offshore wind turbines in France althought there are many onshore wind turbines. This project is the first in France and it will produce 90 MW. The wind turbines will be placed at 10 km of the coast. The Dunkerque's has many avantages: the North of the France is windy, the Dunkerque's area has a good depth... This project results of an association between Total and Shell. It is a human and technologic challenge. But there are some problems: a lot of ship cross the Northensea so an accident can happend, and in 2004 a wind turbine in Dunkerque fell down because the wind was too high. The fishermen disapprove this constructions because the offshore wind turbine's noise disturbs the ecosystem. d) Can the offshore wind turbines always produice energy? The wind conditions are better in the sea, the wind is also higher. But sometimes the wind is too high so the wind turbines must be stopped, if they are not stopped they can be destroyed. Sometimes the wind is not enough high but it is rarer than the first. In this situation the wind turbines are not usefull so they do not turn. III] The positive and negative things______________________________________________________________ a)Positive things: The offshore wind turbines are more ecologic than the other power stations. It is usefull when the territory is small. Production is higher than the onshore wind turbines. b)Negative things: The electricity production is not very important compared with the power stations. The offshores' construction cost is higher than the classic wind turbines. The cost of the maintenance is high. c)Conclusion. The offshore wind turbines are an ecologic way to produce electricity but the cost of construction and maintenance is high and the electricity production is rather low.  sources: windpower.org total.com vestas.com wikipedia.org by FISHER Harrison & THUILLIER Baptiste |