Summary
There are growing incentives to develop offshore wind farms. As with the
early oilfield developments of 1900 to 1920, most of the wind developments to
date have extended onshore designs and construction techniques to shallow
waters. It is time to apply what we in the offshore oil and gas industry have
learned to arrive at truly fit-for-purpose offshore solutions for wind-farm
development.
This paper describes the needs of a typical wind farm and how these differ
from those of a typical offshore oil and gas project. It draws on recent AMEC
experiences in the design and installation of offshore wind turbines in Europe
and studies performed in Houston.
Information and expertise exists within the current oil and gas industry to
allow safe and economical designs of offshore wind farms in depths where
bottom-supported structures are economical choices. Consideration of the
following, however, will lead to different solutions: each installation may
require 100 or more structures, the ratios of axial loads to lateral loads are
much lower, torsion loads are considerable, and rotating blades will have
significant dynamic effects. A proper design must take into account economics
of scale (“design one, build 100”) and assembly-line-type planning for
component fabrication, transportation, assembly, and installation.
The methods and application of technologies successfully used by the
offshore oil and gas industry can advance the development of offshore
wind-energy projects. The tremendous amount of expertise, data, design
technology, and construction knowledge accumulated by the offshore oil and gas
industry has the potential to aid a great leap forward for wind energy. While
future research and data collection can help optimize the designs, there is no
need to further delay projects by waiting on these results.
Introduction
The supply of energy is a topic of interest to people of every nation in the
world. Usually the discussion begins by modifying the word “energy” with words
such as “cheap,” or “renewable,” or “clean,” or any of a myriad of modifiers
that place some level of restriction on the supply of the energy. Inevitably,
there is an argument against the siting of new energy sources. The public
perceives a negative impact from the sight of large stacks associated with
coal-fired power plants, domed concrete containment buildings associated with
nuclear-fired power plants, large oil tanks behind earthen containment berms
for oil fired power plants, and large dams blocking a natural stream for
hydroelectric power plants. Visions of terrorist attacks, industrial
explosions, environmental pollution, and so on, can be easily conjured up by
those opposed to development. It makes no difference whether the impact is real
or perceived.
Wind energy, however, brings to mind an 18th-century European windmill of
the Don Quixote variety, or a small propeller turning slowly on top of a steel
column on a west Texas hilltop or across the plains of mid-America. What could
be more picturesque? What could be more benign? Wind has become an icon for
cheap (maybe), renewable (certainly), and clean (obviously) energy.
Activists who are opposed to these projects argue about noise pollution and
land use. This is not a problem in the American West, where land is cheap and
plentiful and neighbors are far removed. However, population density and the
demand for energy is greatest on our coasts, where land is expensive, neighbors
are close, and rich, potentially powerful people are concerned about the views
from their expensive shore houses.
Offshore, where it is possible to use large floating construction equipment
and where the noise generated by the blades is less of a factor, new, more
economical, larger wind turbines are possible. Wind turbines with 126-m
diameter rotors producing 5 MW of electrical power are already available for
offshore applications.
As was the case with the oil and gas industry, which began on land and
advanced offshore approximately 50 years ago, it is now time for wind farms to
move offshore. There are several advantages that are immediately apparent, even
to structural engineers: no neighbors, no hills, no trees, and lots of wind. As
the wind farms move into deeper waters, they can be made to largely disappear
from sight.
The next major advance in wind power will be to take what 50 years of
offshore oil and gas experience has taught us about offshore structures and
facilities and use that knowledge as a basis for developing a new generation of
wind turbine support structures. To the offshore engineer who has labored and
battled offshore fabrication, installation, operation, and maintenance for
these 50 years, this question is a no-brainer. Not only can one move wind power
offshore, but the technology is available to advance beyond what is now
accomplished onshore to larger turbines and greater possibilities.
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
5 February 2007
- Meeting paper published:
30 April 2007
- Revised manuscript received:
23 July 2007
- Manuscript approved:
29 July 2007
- Version of record:
20 December 2007
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