Each company brings to the table its current 5MW offshore turbine technology, know-how, experience and assets. One ambitious plan is to combine technological knowledge to accelerate the development of a next-generation 8MW turbine.
Areva's 5MW M5000 low-speed turbine technology was developed and patented by German engineering consultancy Aerodyn during 1996/7. This unique turbine development created a new hybrid-drive category in-between conventional high-speed geared and gearless direct-drive technology.
Key features of the M5000 drivetrain include a 1.5-stage planetary gearbox, a 150-rpm permanent magnet generator (PMG), and a single rotor bearing integrated together in one load-carrying cast structure. Still rare and unusual today is the use of slow-rotating slide, or journal, bearings in the gearbox.
A consequence of the fully integrated drivetrain design is that complete nacelle exchange is required in the event of a major drivetrain mechanical failure. While this may be expensive, the claimed benefit is that all main components are new, with 100% operating lifetime expectancy.
The intellectual property and assets of the Areva Multibrid M5000 moved from the designer to two other turbine manufacturers before Areva acquired 51% of the shares in 2007 and the remainder in 2010.
Four M5000-116 onshore turbines, including a prototype of the current 5MW model have been installed since 2004, followed by six more offshore turbines installed in 2009 at Alpha Ventus in Germany. These offshore models are technically comparable but have the characteristic large offshore nacelle. Another 120 of the M5000-116 are currently being installed in two German North Sea offshore wind projects, bringing total installations at the end of 2014 to 130 units.
Last year Areva installed an upgraded M5000-135 offshore prototype at an onshore location, with the increased 135-metre rotor diameter aimed to achieve a higher yield and reduce the cost of energy. This model is set to cover the period until a proposed 8MW turbine is ready for market launch.
The development of Gamesa's initial G128-4.5MW lightweight onshore turbine dates back to 2003 and a prototype was installed in 2009.
This innovative turbine model features segmented rotor blades with a 128-metre rotor diameter and a pioneering semi-integrated, tube-shaped medium-speed drivetrain. The solution developed together with gearbox designer ZF Wind Power comprises a housing that supports the main shaft plus two bearings, while providing flange connections to a two-stage planetary gearbox and PMG.
One main advantage of this approach is that it virtually eliminates the risk of misalignment. It also enables individual component exchange and up-tower repair — a growing trend in offshore wind — inside the nacelle in the event of gearbox or generator failure.
The G128-4.5MW was further developed to 5MW power rating, and among the differences are a higher gearbox ratio and faster rotating generator (490rpm).
The G128-5.0MW is available for both onshore and offshore application. For the G128-5.0 offshore model, a prototype of which was installed last year at an onshore location in the Canary Islands, Gamesa developed a single-piece blade in-house, offering an unchanged 128-metre rotor diameter.
The turbine's low 270-tonne head mass is claimed to enable its use with cost-effective monopile foundations even in greater water depths. There are a total of 16 G128-4.5MW turbines installed, and one G128-5.0MW offshore prototype.
Areva's M5000-116 has a clear advantage over the Gamesa models, with many more installed and therefore a stronger test base, and this could serve as a key asset for the joint venture when translated into offshore bankability. It comes as no surprise then that the joint venture will continue to market Areva's latest M5000-135 turbine. Somewhat confusing, however, is the explicit reference to an "enhanced 5MW generation turbine to be developed in the short-term, benefiting from the full potential of Gamesa's multi-megawatt cutting-edge technologies".
The company has confirmed that the Gamesa G128-5.0MW and G132-5.0MW sister models will be focused on onshore markets, where the company already enjoys promising prospects, including a framework agreement for 57 units.
Technologically, both 5MW serial turbines differ significantly, particularly in terms of drive technology and associated serviceability characteristics. It is therefore not easy to see immediate synergies especially in blending the best of both technologies and the individual products. However, substantial added-value benefits will be offered by combining resources in additional fields.
Next step up
Each company had already announced that it is working on a more powerful next-generation offshore model. Areva aims at an 8MW turbine with 180-metre rotor diameter and a competitive 520-tonne head mass. Gamesa is planning to develop a medium-speed turbine in the 7-8MW range, but has not released a similar degree of detail yet.
Considering the early stage of both individual projects with many options still undecided, joining forces
could substantially boost the pace of product development and product industrialisation in parallel.