Developer turned turbine maker

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Only one EHN 1.3 MW turbine is up and running so far, but Energía Hidroeléctrica de Navarra (EHN) -- until now only a developer of wind plant and not a turbine manufacturer -- says it will have 21 up and running by the end of the year. The only 60/1300 unit yet built went on-line at the Aizkibel wind station in Navarra in October, but it is the first step of a strategy to give EHN a better understanding of the technology on which its wind power development business is based, says company head Esteban Morrás.

There are two main reasons for the strategy: "First, to be in a position to negotiate the best technological solutions. Second, to know exactly the costs involved in manufacturing enabling us to negotiate margins. Then, if we don't receive the product we want in the conditions we want we will be in a position to supply our own technology," says Morrás.

Much depends on the prototype's performance, though EHN says it is pleased with results so far, claiming production to have reached a total of 1.8 million kWh up to June 12. "Pretty good considering it's still undergoing tests and adjustments," says EHN's José Arrieta.

The main technological challenge is to adapt inherited turbine design and technology -- mostly coming from Northern Europe -- to Spain's specific conditions, explains the company's Miguel Nuñez. "In Denmark, Holland and Germany, the terrain is flat and the winds are considered horizontal," he says. "In Spain we install turbines up mountains where considerable variations in wind speed and direction occur. For such conditions EHN considers a more robust design is needed to compensate for the increased loads upon the machine." Nuñez also points out that increased robustness is limited by cost effectiveness, making it another major challenge to optimise the cost-performance ratio.

Given such criteria, the innovative factor of the machine rests in the sum of a whole series of small adjustments in design, components and materials, rather than any single radical break with existing technology. Such details include a double bearing for the main drive shaft, with a standard support at the rotor end and a second support before entering the gear box. Nuñez explains that the idea behind this is to reduce the direct forces upon the gear box caused by gusts.

The turbine incorporates variable pitch and variable speed technologies. Amongst the prototype's most immediately outstanding features are the fact that subsequent machines will generate at 12,000 volts. The prototype operates at 6000 volts. Nuñez explains that the reason behind the high voltage is to enable direct connection to a single plant substation rather than having to install a transformer in each tower, which not only increases the overall investment requirement but also implies energy losses.

The prototype, with a 60 metre rotor, is designed to meet Germanischer Lloyd specifications for winds over 8 m/s and EHN has applied for certification. The company will build one other prototype for Class I winds and then plans to put up a pre-series of 20 Class III turbines with 70 metre rotors in the smoother conditions of its Peña Blanca plant, also in Navarra. The Class I turbine kicks in at wind speeds of 4 m/s, reaches rated power at 13 m/s and shuts down at 25 m/s, while the Class III machine will operate in winds as low as 2.5 m/s, reaching rated power at 11 m/s and shutting down at 18 m/s.

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