Environmental Engineering Reference
In-Depth Information
that include a monopile or raft confi guration. Figure 40 relates the relative size of
the required monolithic foundation dimensions relative to their respective towers
for some representative turbines from the 10-turbine analysis group. Turbines in
excess of 5
7 MW require excessive monopile depth or raft outer diameter, thus
further supporting the thesis for multiple smaller foundations and multi-legged
towers for larger turbines.
−
4.7.3 Offshore foundation
A signifi cant amount of research is underway for offshore foundations, and many
designers are attempting to leverage experience with offshore foundations in the
oil and gas industry. Currently, two types of offshore foundations have been used
with success in the wind industry - gravity and monopile. The gravity foundation
was more common in the past, but it is more expensive and has a much larger
footprint. More common today is the monopile foundation, which has a very small
footprint and can be used for somewhat deeper water installations (up to about
30 m water depth).
As turbines become larger and near-shore locations become less available, the
industry may need to look towards installations in deeper water. Many different
types of foundations are being explored for these applications, such as different
types of trusses, multiple legs and even fl oating foundations stabilized by ballasts
and cable anchored to the seabed or lake bottom.
5 Special considerations in MW WT design
5.1 Continuously circling back to value engineering
The proportion of how total project cost is divided amongst the turbine, BOP,
developer, and transportation costs vary as turbine rating is increased. Table 4
shows the breakdown in total project cost for a 100 MW WPP with fl at terrain using
a nominal technology MMW WT. Multiple trends in the proportions of project cost
can be observed as the turbine rating is varied.
Table 4: Major cost breakdown for an onshore WPP.
Wind Power Plant “all-in” cost fraction (total = 100%)
Rated Net Power
Turbine
BOP
Developer
Transportation
[MW]
[%]
[%]
[%]
[%]
2.0
63.6%
25.0%
7.3%
4.1%
4.0
66.3%
22.5%
6.8%
4.4%
6.0
67.8%
20.9%
6.3%
5.0%
8.0
68.7%
20.4%
5.9%
4.9%
10.0
68.6%
20.5%
5.8%
5.2%
100MWWPP; Flat terrain w/easy access & good geotechnical; Nom technology MMWWT price;
10% BOP cont. inclusive. Number of loads determined by weight (no dim considerations) Larger
components assumed capable of multiple loads.
Search WWH ::
Custom Search