Turbines of the year: Onshore turbines 3MW-plus

WORLDWIDE: Rapidly growing sector in mature markets, especially in low- and medium-wind-speed areas

Enercon E-141… prototype is now field testing


GOLD Enercon E-141

The 4.2MW direct-drive E-141 EP4 features a record 141-metre rotor diameter (onshore) and is Enercon’s first IEC IIIA turbine.

It is the second model of a new modular 4MW platform designed for 30-year operating life. Two 4.2MW E-126 EP4 prototypes for IEC IIA were installed earlier this year. A total of 140 units is planned for 2017.

The E-141 flagship is fitted with new-generation slender segmented composite blades, aimed at optimised manufacture, transport-logistics and installation, that build technologically on the blades first introduced for the E-115.

The inner blade is identical for both EP4 models and manufactured by a wrapping process with aerodynamic add-ons. The outer blade is new and state-of-the-art, and both are mechanically joined on-site.

Enercon gives much consideration to optimised airflow around the characteristic egg-shaped nacelle, and tip winglets are standard fitting. The company claims superior aerodynamic performance compared with conventional similar-size blades.

Shared features include the drivetrain configuration, and structural and external nacelle components. Innovative elements include a split (180-degree) electrically-excited synchronous air-cooled generator, and individual electro-mechanical adapter units incorporating a complete pitch module.

The new modular concrete-steel hybrid tower concept with reduced foot base and hub heights up to 159 metres aims at reduced manufacturing costs, easier assembly and higher overall flexibility.

SILVER Vestas V136-3.45MW

The latest Vestas V136-3.45MW model with 3.6MW power mode now released for IEC IIB, is expected to become a powerful contender in low- and medium-wind-speed markets. \

The turbine comes with a  high-torque gearbox, new in-house designed slender 66.7-metre rotor blades, and in-house large diameter steel towers (LDST) with hub heights up to 166 metres.

The 3MW platform was introduced in 2010 with the V112-3.0MW. Its conventional non-integrated drivetrain is also applied offshore. Today’s versatile platform has five 3.45MW versions with different rotor sizes for various wind classes. In 2013 Vestas raised platform rating to 3.3MW and switched from PMG to IG.

BRONZE GE 3.4 – 137

GE’s latest 3.4MW 3.4-137 low-wind 3MW platform extension has competitive specifications and is the result of continuous product evolution since 2003.

The initial 2.X series evolved into the 2.5MW 2.5-100 (original 2.5XL) model fitted with PMG. With the 2.85-103 introduced in 2013, GE switched back to DFIG across the 3MW platform.

The unusual drivetrain concept comprises a compact main shaft and two bearings directly integrated in the cast main chassis, plus a non-integrated gearbox.

Claimed benefits of the perhaps undervalued drivetrain concept are that only "pure" rotor torque enters the gearbox, and rotor-induced axial forces are fully absorbed because there is no free play.