Renewed interest

Illustration of marine turbines

Illustration of marine turbines

23 January 2015 by Paul Bell

The UK's rich marine renewable energy resources are driving an exciting area of innovation. Paul Bell explains how understanding the potential environment consequences will be critical to the success of the industry.

During 2014 and 2015, the first arrays of tidal turbines are expected to be installed in UK waters, and plans for the first commercial arrays of wave energy devices are well advanced.

The UK is rich in marine renewable energy sources. We have excellent tidal energy potential with a number of regions of strong tidal currents and others with large tidal ranges. Much of our surrounding ocean, especially the west coast, is exposed to the full force of Atlantic waves. This resource wealth has stimulated innovation, with dozens of designs for marine energy devices coming out of UK universities and small businesses.

Now large multinational companies are investing in or buying devices that have been successful in ocean tests and prototypes are giving way to the first commercial installations, backed by established marine industry and energy companies.

It's a fast-moving sector and the UK academic community and industry are working hard to tackle the challenges it presents. Where are the greatest concentrations of energy and how much is harvestable? What forces should the devices be designed to survive and how can we minimise the costs and risks of operating in such extreme environments? What effects will energy-harvesting devices, individually and cumulatively, have on the environment?

I lead a project called FLOWBEC - FLOW and Benthic ECology 4D - which is studying how currents, waves and turbulence at tide and wave energy sites influence the behaviour of marine wildlife, and how the presence and operation of energy devices could affect that behaviour - whether they might deter wildlife, for example, or perhaps attract certain species by replicating the foraging conditions they prefer.

The environmental challenge

Before we can understand what effects energy devices might have, we need to understand the undisturbed environment. This means studying conditions at the sites and the behaviour of the wildlife that is present there.

The standard way of measuring waves and currents, with wave buoys and sonar current meters, is problematic in some of the more extreme conditions as there's a high risk of equipment being damaged or lost. Tidal sites present a further challenge as the effects of headlands, tidal channels and shoals mean measurements at a few points may not give an accurate picture of conditions across the whole site.

FLOWBEC sonar frame being prepared

FLOWBEC sonar frame being prepared for lowering to the seabed at the European Marine Energy Centre tidal test site, Orkney. The OpenHydro tide turbine test platform is top right.

One answer is to use remote-sensing techniques, using radar, cameras and satellites to map the ocean from vantage points on shore, the air or from space.

FLOWEBEC uses two types of radar to map tidal currents and waves at study sites - a ship's radar at the European Marine Energy Centre in Orkney, and a longer range High Frequency (HF) Doppler radar that covers the Wave Hub site in Cornwall. The quality of the results often depends on local conditions at the time, but having the equipment out of the water means it's much easier to operate and maintain, and can give you almost immediate access to the data rather than having to wait for an instrument to be recovered from the sea.

We use many techniques to study the animals themselves, some remote and some very much hands-on. Observations from the shore or a boat are complemented by underwater measurements using sonar to track wildlife such as seals, diving birds and fish, and shore-based radar to track birds in flight. Radar can also pick up larger marine species like whales when they are at the surface although they can be difficult to distinguish from the background 'sea clutter'.

Other related projects, such as RESPONSE and QBEX, also tag and track individual animals. Larger tags can transmit data via satellite, radio or phone networks, but we usually have to rely on the smaller ones, from birds and fish, being returned by a member of the public once it's been separated from its host or the animal has been captured.

Tagging is proving invaluable for observing animal behaviour over longer periods. We're already seeing that individual animals of the same species tagged at the same location may behave in very different ways, so it's really important that we gather information on sufficient numbers for all the species affected to make sure we capture these natural variations in behaviour.

Concurrent observations of wildlife above the surface (radar, visual) and below the surface (sonar) made by the FLOWBEC team show the advantages of this approach when combined with environmental information such as tidal currents, turbulence and sea surface roughness derived from radars or computer simulations. We are starting to understand the way different species of marine wildlife use their perception of the physical environment to decide where and when to forage for food and what conditions they prefer to avoid - factors which vary depending on species.

Our research programme, and others like it, are also highlighting how much we still have to learn about marine wildlife, as there is often relatively little information available about the presence and behaviour of marine animals either individually or collectively at potential development sites.

The UK's renewable energy resources are undeniably important, and worth harvesting provided the benefits outweigh the costs. The environmental effects may be hard to measure but if we are going to move to low-carbon electricity in a responsible way we need to be sure we are not solving one environmental problem by creating a new one.

The good news is the need to understand and mitigate the environmental effects of marine renewable energy is driving innovation in tools and methods that will support industry and the environment.

Harvesting marine energy

The Atlas of UK Marine Renewable Energy Resources uses tide and wave models and a variety of observations, such as tide-gauge and wave-buoy measurements, to produce detailed regional descriptions of potential marine energy resources in UK waters. The atlas guides policy and planning decisions and some of the most promising UK sites have been leased to developers for testing and commercial energy extraction.

Energy is harvested by an array of turbines designed to generate electricity through the action of waves or currents.

The large areas, extreme conditions and relative inaccessibility of many potential sites mean we may need to find new ways to make the best use of the energy they generate; electricity cables to shore may not always be practical or affordable, and once the power is brought to the shore the electricity grid may not be suitable for exporting the generated power. Ways around this include using the energy on-site or at least locally to make high-energy-cost products, fuels such as hydrogen, or to produce fresh water by desalinating sea water.

Dr Paul Bell is based at the National Oceanography Centre in Liverpool and leads the NERC/Defra-funded FLOWBEC project with participants from a consortium of eight universities and research centres and a number of industry partners.