HEROSE is working full out on the corresponding products in order to make them proof against sea water. This is a challenge for a technology which will play a key role in the new energy mix.
When everything is complete, the off shore wind parks will provide one sixth of Germany‘s electricity requirements. This is certainly an ambitious plan. Up to now, 130 off shore wind parks with a total of almost 9000 rotors have been applied for in the German Bight area. None of these are yet complete. Although there is a small test field “Alpha Ventus” to the north of Borkum and the rotor area “Baltic 1″ in the Baltic, these are near to the coast. Further out, where the “resource of the North” (German Minister of Transport Peter Ramsauer) blows particularly strongly, only one off shore manufacturer has dared to go – for various reasons: In 2010 construction of “Bard 1″ started – a gigantic rotor garden with 80 turbines, each with an output of 5 megawatt. In total, the nominal output of “Bard 1″ will be 400 megawatt, which corresponds to the electricity needs of more than 40,000 households. According to the Bard spokesman Andreas Kölling, up to now 25 of the 80 rotors have been built and construction should be complete at the beginning of 2013.
A series of transformers are necessary in order to feed the electricity which is generated out at sea into the landbased electricity grid. For example, at “Bard 1″ the three-phase electric voltage from the total of 80 wind energy plants is increased from 33 kV to 155 kV and transferred to the neighbouring converter platform “BorWin 1″, from where it is transferred to feed-in points on land via a submarine cable. To perform this task efficiently, the electrical voltage from the offshore generators is changed several times before it reaches the consumers. For example, in the course of its journey of several hundred kilometres to the urban and industrial centres the electricity is transformed to high voltages of 380 kV. In the urban centres, the electricity is reduced to medium voltage and fed into the regional grid networks. Distribution transformers close to the consumers finally produce the normal mains distribution voltage of 400 volt.
The offshore market is also extremely interesting for HEROSE. The Bad Oldesloe company has long been a supplier of valves for the transformers which are in normal use on land. Here, the valves are primarily used in the oil circuit. The proportion of energy products in the total sales is still below 10 %, however, this will be greatly expanded by further developed and newly developed products.
The first product for offshore use is a seawater-resistant gate valve with the type designation 09320. The difference to the standard product: a special bronze alloy which is resistant to corrosion by salt water is used for the housing and the internal components. At present HEROSE is preparing further products for use out at sea, for example the type 03199 outlet valve. In order to test the material under conditions which are as near as possible to real life, an extensive salt-spray test is being carried out in cooperation with a well-known transformer manufacturer. HEROSE Manager Dirk Zschalich: “With regard to offshore application we are also demonstrating the strong commitment which our customers can expect from us.” Initial experience has shown that transformers for offshore wind energy plant are subjected to completely different stresses that in wind energy plant close to the coast. Wind and seawater attack the material much more severely than we thought. Transformers out at sea must be as maintenance-free as possible, because in the worst case a transformer breakdown can mean that the entire wind park is shut down for up to a year.
A downtime of one year? That is a rather optimistic estimate. Offshore transformers are cooled with up to 40 tons of oil. This oil must first be drained off before repairs can start. This is out at sea, where weather conditions can make it impossible for access with ships for weeks at a time. If it turns out that the damage cannot be repaired, a new transformer has to be ordered, built and installed. This alone takes an average of twelve months. Generation of electricity out at sea is a decisive factor in the future energy revolution. For example, according to the policy of the EU heads of government, renewable energy will cover 20 percent of consumption by 2012. At the same time, emissions of greenhouse gases are to be reduced by 20 percent and energy is to be used 20 percent more efficiently.
Photo: Alpha Ventus, Bard 1