Friday, May 09, 2008
Breaking Wind in Ireland part 3
Big Wind in Ireland
More on the E126
The E-126 tower in Emden is 131 m high and consists of 35 concrete sections manufactured by WEC Turmbau Emden GmbH situated on the South Quay in Emden. Due to the 14.5 m diameter at the tower’s base, the first eight segments are divided into three parts for transport purposes. 22 of the segments are half-divided, and the other five are in one piece. The top segment supporting the nacelle is made of steel.
The tower walls are up to 45 cm thick, a new record for ENERCON. And a total of 110 m³ of concrete were used to build the tower. Since the ground along the silty banks of the Ems River is quite soft, a total of 64 fifty-six-centimetre thick piles measuring an average of 25 m had to be rammed into the ground to support the foundation. Another 1500 m³ concrete and 180 t of reinforcing steel were used in the foundation.
Enercon have a second E-126 directly next to the first one on the Rysumer Nacken. Both turbines are part of a research and development project in which Enercon will be testing various storage systems in combination with the multi-megawatt wind turbines. More E-126 are planned to follow: One turbine is to be erected at the DEWI-OCC test site in Cuxhaven this fall. In 2008, five other turbines are scheduled to be installed – in Georgsfeld near Aurich, in Hamburg Altenwerder and in Estiennes in Belgium.
Generator and Inverter
Because the Enercons have no gearbox the turbine blades attach directly to the annular generator which is housed at the widest part of the nacelle.
As with smaller wind turbines, the Enercon series use inverters instead of synchronous generators, that is to say, a separate controller that converts the irregular current generated into smooth AC for the grid. This also means the rotor can run at more optimum and/or varied speeds. The Enercon does not have to shut off at a predetermined wind speeds, it simply throttles back by feathering the blades and it can continue to generate power although at a lower production rate. Then, when the wind is more favorable, it goes back into full mode.
Why build such big wind turbines? Money, that’s why!! Building big is generally cheaper per unit of production. To install say three 2 megawatt turbines, you have to have to build three sets of massive foundations, Transport the parts for 3 turbines, utilise three separate teams of workers and three cranes. After the installation there are 3 machines to maintain, and three times the parts to fail. One big one, while more expensive initially, works out costing less in the end. Another reasons for having high capacity turbines is that a wind farm of say 6 large turbines looks a lot better than one with 24 smaller turbines.
Birds and Noise
Some people are concerned about birds being killed by wind turbines. With the really big ones, this is very unlikely indeed as they rotate at only 12 rpm. In other words, it takes about 5 seconds to complete one revolution. Any bird that flew into that would have to be blind and stupid.
As for noise, the big Enercons will be less noisy than some other makes. This is due to two factors, 1. They don't have gearboxes. The gearbox in a turbine makes a noticeable whine. and 2. The blade design makes less wind noise.
Enercon in Ireland?
Today, I briefly spoke to Kevin O’Donovan of SWS Natural Resources who told me that the company are installing some Enercon turbines in Ireland in a current project. I will have more on that in a later post. SWS have an open policy and have invited me to attend the installation of some new turbines in Kerry. I look forward to that event, and be sure I will have my camera with me.