Design limits and solutions for very large wind turbines

Results
Subtask A: Reference wind turbine and cost model
As reference wind turbine an NREL 5 MW model - was
used (see [1]) and improved. An overall framework for
an optimal design of wind turbines was formulated,
taking up-scaling and cost modelling into account [2]
and [3]. The approach is based on a life-cycle analysis
including all the expected costs and benefi ts throughout
the lifetime of the wind turbine (wind farm).
The cost model was developed for wind turbine upscaling
up to 20 MW. These wind turbines are expected
to have a rotor diameter of approximately 250m
and a hub height of 153m. A theoretical framework for
a risk-based optimal design of large wind turbines was
formulated. Three types of formulation were made: 1)
a risk / reliability-based formulation, 2) a deterministic,
code-based formulation and 3) a crude deterministic
formulation. These formulations are described in
[2] and [3].
In the third formulation (crude, deterministic), generic
cost models are given as a function of the design
parameters using basic up-scaling laws adjusted for
technology improvement effects. There, the optimal
design is the one which minimises the levelised
production costs. The main design parameters are: the
rotor diameter, the hub height, the tip speed and where
the wind turbines are placed in relation to one another
in wind farms. In a more detailed approach, the crosssectional
dimensions (such as the geometry of the
blade or the tower), the O&M strategy, or more refi ned
input parameters can be included. External design
parameters are fi xed regarding the size of the wind farm
(in terms of MW capacity and / or the geographical area
covered by the wind farm), the wind climate including
the terrain (mean wind speed and turbulence), wave and
current climate (offshore), water depth, soil conditions
and distance from land (or nearest harbour).
The cost model is based on a life-cycle approach
including all capitalised costs. The main up-scaling
parameter is typically the rotor diameter. The cost
model is basically formulated as function of this
design parameter using an up-scaling factor with an
up-scaling exponent (typically 3) and a time-dependent
technology improvement factor.
Subtask B: Integral design approach methodology
UpWind addresses the full life-cycle of the large-scale
wind turbines of the future, including the technical and
commercial aspects. However, non-technical disciplines
do not use any kind of model that is compatible with
the technical disciplines. There is a strong need for
new design paradigms that are able to account for both
technical and non-technical disciplines within the same
framework so that manufacturing, transport, installation
and O&M procedures become design parameters
rather than constraints. A new design approach was
proposed in UpWind. This approach is based on the
principles of systems engineering and features elements
of Multi-disciplinary Design Optimisation (MDO),
Knowledge Based Engineering (KBE) and Mono-disciplinary
Computational Analysis Methods (MCAM).
The approach requires knowledge on the design processes
of the wind turbine and their subsystems to be
captured and written down. The wind turbine technologies
currently applied are in this approach, as well as
those being studied and developed within the UpWind
project. The captured knowledge is analysed and translated
into knowledge applications through KBE. These
applications address the following areas of the design:
Design limits and solutions for very large wind turbines
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