Page 92 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

Offshore Wind Chapter | 4 85

FIG. 4.2 Global installed capacity of wind power, 2002–16 [3].

much less than onshore projects. Also, offshore wind farms are a good source
of electricity for coastal cities; around 40% of the global population lives in the
coastal zone. Some analysts predict that much of the future development of the
wind industry will move towards offshore wind farms [4], because there will
be much less capacity to install wind farms on land (e.g. lack of suitable land
near coastal cities). Therefore, the offshore wind industry is gradually becoming
an important part of the global energy mix. In some regions of the word (e.g.
the northeast region of the United States), offshore wind is the most promising
renewable energy resource, compared with other types of renewables (e.g. wave
and solar).
A major consideration in the design and construction of offshore wind
farms is water depth. Up to now, the majority of wind farms have been
built in relatively shallow waters—typically less than 30 m water depth. The
substructure of offshore wind turbines can be considered as the most limiting
factor in the development of offshore wind projects. Fig. 4.3 shows the trend in
the design of substructure for offshore wind turbines. In shallow water zones,
simple monopile support structures can be used. As water depth increases to
transition zones (less than 60 m in depth), more complex supporting structures
such as Jacket or Tripod are required (Fig. 4.4). In deep waters (more than
60 m), floating structures are used to support wind turbines. Whilst building a
substructure for offshore wind turbines in shallow water is a proven technology,