Types of offshore structures for generating energy

The generation of energy – in particular the sustainable generation of energy – is perhaps one of the greatest challenges facing the modern world.

There is probably very little debate about our continuing need for energy, but the big questions centre on just how it might be generated. In this respect, some of the last remaining, largely untapped resources are the vast oceans of the world.

The various types of offshore structures required to generate such energy, however, are all likely to involve considerably complex and sophisticated marine engineering solutions. Typically these require a multi-disciplinary approach drawing upon the relevant expertise in several branches of engineering, including:

• civil;

• geotechnical;

• hydrogeology;

• hydrology; and

• environment.

It is hardly surprising, therefore, that even amongst marine engineering specialists it may be difficult to find companies equipped to design and build offshore structures for generating energy. One of the few, for example, is the Australian company, Ausenco.

Types of offshore structure

There are three principal types of offshore structure, depending on the source of the energy to be generated:

Wave energy

• just as the term suggests, this requires offshore structures capable of capturing the latent energy of ocean waves. It is a concentrated form of wind energy since wind energy is transferred into the power of the waves;

• the engineering challenges in constructing offshore structures for capturing wave energy typically include the reduction of wave movement on the structure itself, and “inverse engineering” solutions to maximise the motion of the waves through wave energy converters capable of producing electrical energy;

• it is estimated that there is a global capacity of exploitable wave energy equivalent to that of 200 large power stations;

Tidal energy

• marine turbines may be used to capture tidal energy. Such turbines are not dissimilar to those used to propel ships through the water, but reverse engineering instead allows the turbines to generate rather than consume energy;

• one of the important characteristics of tidal energy is that it tends to be more predictable than wave energy, although it is by its very nature far more localised – requiring different offshore structures and engineering solutions;

Offshore wind energy

• this is currently probably the most widely used source of offshore energy, and may be captured either by floating or fixed offshore construction;

• amongst the most common engineering problems concerning offshore wind parks are their installation, mobility, maintenance, hazards to shipping and impact on fishing and bird life;

• in these and in most other instances of offshore structures for energy generation, environmental impact assessments play a key part in obtaining the necessary permission for their operation.

Generating energy offshore

Although the potential for generating sustainable energy offshore is considerable, in many respects the engineering challenges remain at a relatively early and untested stage. Companies with the necessary expertise in the design and installation of the required offshore structures, therefore, are few and far between.