What is marine renewable energy?

Sheringham Shoal Offshore wind farm
Sheringham Shoal Offshore wind farm
Marine renewable energy is the power harnessed from the wind, waves and tide and is typically regarded as an abundant, inexhaustible and non-polluting resource that can play a significant role in combating climate change. What the development of many new energy plants in the sea with all the associated construction work and boat traffic that they will bring is far from clear for marine wildlife, including cetaceans.

Spurred on by the growing global energy crisis and to meet requirements to reduce greenhouse gases derived from burning fossil fuels, governments around the world are investing in new renewable energy technologies and much of this development is going on out at sea.

There are a number of ways that renewable energy can be derived from the marine environment, including lesser known technologies such as ocean thermal energy - where the energy is generated from temperature differences at varying depths - and salinity gradient energy where the energy is generated from the difference in the salt concentration between seawater and river water. Yet there are three main forms of renewable energy that are currently generating energy and which are being predominantly developed, these are offshore wind farms, tidal power and wave power.

Of all marine renewable energy, offshore wind farms have been experiencing the swiftest development. Their rapid expansion continues across Europe in particular. Until quite recently, offshore wind farms have mainly been in near-shore waters, within approximately 5 km of the coast. Now very large developments are planned further off the coast and in deeper waters, deep water concepts have huge potential due to stronger winds further from shore.

Tidal power can be subdivided into two categories: Tidal stream power is produced from the horizontal movement of water in a current and usually harnessed by using completely submerged turbines; tidal range power is produced from the vertical movement of water in the rise and fall of the tide and usually harnessed by using barrages.

Wave energy is generated from the waves that are formed by winds blowing over the sea’s surface. The power of the waves depends on the speed of the wind, its duration and the distance it travels over the water (its fetch). Other determining factors are the sea depth and interacting tides. The most powerful waves are created by strong winds over a long fetch, such as those along the western coasts of Europe, South America and Australia. The main disadvantages to wave power are the variability and poor predictability of waves.

These developments are likely to be the most intensive engineering interventions in the UK's coastal waters in the next decade and, as such, attention needs to be given to their environmental impacts on cetaceans and other marine wildlife.

There have been some investigations into the impacts of marine wind farms on harbour porpoises in Europe but as wave and tidal devices are still relatively new, little is known about their potential impacts on these and other marine species.

One of the places that wind farms are being developed at great pace is in the UK and large scale developments, covering thousands of square kilometres are now planned, but data on the likely impact of this expansion on the 28 cetacean species found in UK waters are lacking, or at best limited. However, the available information, including inferences drawn from the impact of other human activities in the marine environment, indicates a significant risk of negative consequences, with the noise from pile driving highlighted as a major concern.

WDC believes the impacts on marine wildlife, not only cetaceans, should be taken into account, not only from the moment of submitting proposals, but from the point of conception. We believe that these impacts should be implicit in the design, rather than farther down the developmental line, and that a device that has not been developed accordingly should not be given the consents to be deployed.