Wind technology is set for a giant leap with Alstom's 1.43 GW French
offshore contract, involving its massive Haliade 150 turbines.
LONDON --
What are the challenges involved in serial production of the new
generation of huge offshore wind turbines? So far nobody really knows,
as Vestas' plans for a 7 MW turbine are on hold until 2014, and Siemens'
6 MW SWT-6.0 and Alstom's 6 MW Haliade 150 are both still in the
testing phase. After winning the French tender for 1.43 GW, Alstom plans
to roll out its monster turbine by scaling up its prototype
manufacturing facility in St Nazaire, France using lessons learned from
automotive manufacturing.
A visit to the turbine
The Haliade 150 sits at land’s edge in Le Carnet, in France’s
Loire-Atlantique region, on a site that was planned as a nuclear
facility in the 1970s but later abandoned. The Le Carnet site was chosen
partly because it is geologically similar to the submarine environment
where the turbine will eventually be installed; the coastal soil is
essentially sand, said Frederic Hendrick, vice president for offshore
wind. And the wind conditions at Le Carnet closely resemble those in the
North Sea.
The Haliade tops a 75-metre tower, a 25-metre jacket foundation and
monopiles driven 30 metres into the seabed. The foundation sits
partially above ground, ‘onshore but installed as if it was at sea,’
explains Hendrick. The turbine was installed at the site in February
2012 and has begun its 18-month testing phase.
‘In offshore wind, size matters,’ says Hendrick. And offshore
turbines don’t get bigger than the Haliade 150; its only current
competitor, Siemens’ SWT-6.0, was designed to be super-lightweight,
while the Haliade is massive.
Before you see it you know the turbine is big; you even know it’s
very, very big. But you don’t really have a sense of just how big it is
until you stand under it, with you and your car and the nearby trees and
buildings all dwarfed by its sheer height and size, and feel the
WHOOMP-WHOOMP-WHOOMP as its blades turn. The Haliade’s rotor is 150.8
metres in diameter, the blades are 73.5 metres long, and the turbine’s
sweep is 17,500 m
2. The turbine and its support structure boast a combined total weight of 1500 tonnes; the nacelle alone weighs 360 tonnes.
Hendrick believes in going big. ‘The size of the rotor is key,’ he
says. ‘A bigger turbine leads to a better electricity price.’ Alstom
claims that the Haliade can generate up to 40% more electricity per kg
of material used in its construction than today’s offshore wind
turbines, and that it will yield 15% more energy annually than other 6
MW turbines due to its larger rotor swept area and lighter blade,
developed in conjunction with LM Wind Power. (Siemens claims that its
SWT-6.0, with a 75-metre super-lightweight blade and a towerhead mass of
slightly lower than 350 tonnes, will lower energy costs through ease
and speed of installation.)
Onshore, the turbine accounts for 80% of total CAPEX for a wind
project. Offshore, the turbine accounts for 35%, while the rest of the
cost involves the connection to shore, installation, and O&M. During
the design phase Alstom calculated the total cost of foundation,
installation and maintenance against the cost of electricity, and
arrived at 150.8 metres as the ideal rotor size for the Haliade.
‘If the wind speeds were lower, we could have gone for a 5 MW
machine,’ says Hendrick. Wind speed at the Le Carnet site is around
eight metres per second. ‘If they were higher, we would have gone for 7
MW – 8 MW.’
Design
Siemens places its mega-turbine components in the nacelle rather than
in the tower. The company claims this facilitates pre-testing and
pre-commissioning, potentially making installation quicker and easier,
reducing power losses by transporting medium-voltage rather than
low-voltage solutions, and making it possible to use lighter, cheaper
copper cables.
Alstom, explains Hendrick, is moving in the opposite direction and
putting components in the tower. He says having components in the tower
is ‘better for commissioning’: before the Haliade’s tower was
commissioned, 80% of the necessary connections were already made. He
also says that when performing maintenance ‘you will be happy it’s all
in the tower, at the bottom’. Commissioning accounts for just a few days
in a turbine’s life, says Hendricks, while ‘O&M is the next 20
years’.
Almost all of the Haliade’s equipment is located on the first three
levels of the tower. At the very top there is a helipad, from which
maintenance personnel can gain access. Nearly all necessary maintenance
can be performed from inside the machine; only bolt-tightening must be
done outside. And there is a reinforced beam so that workers can lift
the transformer down and bring it through the door. The transformer
weighs two tonnes, and so does the crane installed to lift it.
The Plant
A short drive inland from Le Carnet, we meet Pascal Girault, plant
manager at Alstom’s St Nazaire turbine manufacturing centre. Girault has
a background in managing manufacturing plants for large automotive
suppliers, and he brings experience in process automation for mass
production. His previous positions included production centre manager,
process & methods manufacturing manager, and plant director for
companies making engine parts.
Alstom’s plant at St Nazaire is a temporary pre-series workshop; the
company plans to expand into serial production in 2014, by which time it
expects to build four separate manufacturing facilities for nacelles,
generators, blades and towers in different French locations (the tower
and blade facilities are planned for Cherbourg, and are expected to be
operational in 2015). The nacelle factory is the only facility that is
currently operational, and it currently manufactures the entire turbine.
The company predicts that each factory will produce 100 units per year.
An additional engineering and R&D centre is planned for the Pays de
la Loire region.
Hendrick explains that ‘there was too much stress on internal
resources to start four factories in one year; better to do it in two
batches.’ Transport was a major issue in the company’s decision to build
the factories in different locations: there is less constraint in
manufacturing the blades and towers than in making the generators and
nacelles because the latter are easier to transport longer distances to
the site. Generators for the first two turbines – the test model
installed at Le Carnet and a second one currently in production – were
made in Nancy in the northeast of France, but while this solution,
involving transport to St Nazaire by canal and sea, might be viable in
the short term, Hendrick says that in the long term ‘it’s not a good
idea’. A generator production facility is planned for the St Nazaire
area, to be built by Alstom’s partner GE Power Conversion (formerly
Converteam).
Since many of the Haliade’s components will be located in the tower,
the Cherbourg factory will assemble towers rather than fabricate them.
‘Where the metallic part of the tower will be made, we don’t know,’
Hendrick says, ‘but because of the internals in the tower, assembly is
sensitive from a quality point of view.’
Alstom says that once it is scaled up to full production the St
Nazaire facility will produce about 15 machines per year, with
approximately 20 days spent on producing each machine. The temporary
plant is expected to produce roughly 40 turbines before serial
production begins at a permanent facility.
Employees work in two shifts. The 3000 m
2 work space is
divided into 15 stations manned by six people per station – no more,
explains Girault, because of safety regulations. Currently 12 people
work in the St Nazaire factory; by March 2013 a staff of 40-50 (half of
which will be assembly workers, the other half engineers and
technicians) is planned, and by 2014 the facility is expected to have a
staff of 100.
Assembly
The Haliade’s nacelle is put together along an assembly line, in a
dynamic construction process akin to the way automobiles are made.
Girault explains that it takes 2.5 days to manufacture one nacelle.
Production takes place on a transport platform. A ‘multi-wheeler’
wagon moves the entire assemblage from one station to the next. The
generator is moved with a hydraulic crane and is eventually bolted onto
the nacelle.
Assembly begins with the turbine’s central block, which forms the
interface between tower and nacelle. The central block contains the
direction drive system, including a direction bearing. The central block
also includes the helipad.
Next the intermediate block is fitted to the permanent magnet
generator. The two blocks are then fitted together, ready to receive the
rotor, and then the blades are fitted to the rotor.
At the end of the production process, parts are placed in a storage
and logistics area before shipping. Blades, towers, nacelles and other
parts sit to wait for installation close to the site.
A ‘self-improving system’
Girault terms his production process a ‘self-improving system’ and a
‘never-ending improvement loop’. His goal is a process akin to Toyota’s
‘lean system’ for auto manufacturing (also known as Toyotism). Lean
manufacturing focuses on generating value for the end customer while
requiring as little work as possible from the employees. Its principles
are increasing efficiency, decreasing waste, and using empirical methods
to decide what matters, rather than uncritically accepting pre-existing
ideas. Lean manufacturing is widely viewed as building on earlier
efficiency systems, such as Fordism, and taking them forward.
Girault believes in empirically testing his production process.
Turbine assembly is broken down into discrete tasks which are timed, and
then timed again to see if their duration can be reduced. The workers
keep track of timing on a large wall chart which records how long it
takes the assigned number of workers to do a particular job and is
updated after each task is completed.
Girault conducts weekly audits on safety, quality, activity and
logistics in order to streamline the process; employees are also
encouraged to suggest areas for improvement and awards are given for
workable ideas. For example, one employee suggestion that was adopted
was integrating an ‘octopus’ tracking intelligence module, which
monitors machines and processes, into the workshop; another suggestion
was to fix mirrors to the underside of the generator in order to see
whether there are workers near it.
Alstom’s engineering and R& D centre in Barcelona has designed
detailed documentation for training purposes, which Girault hopes will
make assembling a wind turbine ‘as easy as putting together furniture
from Ikea’.
Rules and procedures applicable to serial production have been
applied from the first unit produced in St Nazaire; Girault believes
this will make subsequent commercial production easier to implement. In
this way the current production facility is also a testing facility: it
is constantly testing and refining the manufacturing process in which it
is engaged.
Eventually Girault hopes that Alstom’s four French factories, planned
to initially manufacture the 240 Haliade turbines to be installed from
2016 onwards as part of the French tender, will all benefit from the
lessons learned at St Nazaire.
A big future
Hendrick believes that the Haliade 150 will be ‘the turbine for the
coming decade’. He doesn’t believe that offshore turbines will get much
larger because of limits linked to the size of installation vessels. And
rotational speed is key: higher tip speeds can result in blade erosion
in a saline offshore environment. Also, if rotational speed is reduced
in order to get more power, ‘you’ll have enormous torque’, explains
Hendrick. So will there be 15 MW-20 MW turbines? ‘I don’t believe it,’
he says. But the Energy Research Centre of the Netherlands’ 2011 Upwind:
Design Limits and Solutions for Very Large Wind Turbines report found
that 20 MW turbine designs should be achievable if some key innovations
can be developed, and GE Global Research has already begun work on
developing a generator for 10 MW-15 MW turbines. If turbines grow ever
larger, innovation in manufacturing, assembly and transport will be
increasingly necessary.
http://www.renewableenergyworld.com/rea/news/article/2012/09/mega-turbines-poised-for-serial-production?page=2
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