Wave Energy Converters are critical for combating the global climate crisis by enabling us to produce electricity from the oceans and seas. However, these devices can also impact their surrounding environments. In order to balance renewable energy development with environmental protection, more targeted research is needed on the extent of these impacts.
A time lag in environmental research
Great advances have been made in recent decades in developing new technologies that harness the energy of the oceans and turn it into electricity to power our lives. Since the 1970s, a variety of Wave Energy Converters (WECs) have been designed, some of which have been tested in real life scenarios. This type of research and development is crucial in our drive to reduce fossil fuel use and to provide energy security in the global climate crisis. However, there is a mismatch between the four decades of WEC development and the corresponding one or two decades of research focussed on the environmental impact of WECs. More environmental research has been conducted on tidal devices than WECs because there are more tidal devices operating globally. WEC development has not reached the same level of technical convergence and most research that exists is based on a single (usually prototype) device. Therefore, we must supplement our understanding of WECs with data from analogous industries, such as tidal energy and offshore wind.
This time lag in environmental research has meant that we are much further ahead in terms of WECs’ technological development compared to our understanding of the environmental impacts of this technology. At the same time, protecting the environment has emerged as a critical priority in the face of climate change and a biodiversity crisis, and therefore balancing renewable energy development with environmental protection is a challenge that must be navigated.
What do we know about WECs and the environment?
A decade or so of research on both WECs and Tidal Energy Converters (TECs) has revealed that the highest environmental risks are related to the turbines’ moving blades (tidal only), the possibility of marine life coming into contact with mooring lines, anchors or foundations, power export cables, and the resulting emissions from any of these parts.
The six most studied impacts are underwater noise, collisions, electromagnetic disturbances, habitat change, tidal modifications and water quality impacts. Between them, these impacts have the potential to cause changes throughout the entire marine environment, from individual animals (e.g. a whale or dolphin colliding with a turbine) to whole populations and ecosystems (e.g. habitat removal during the commissioning phase).
The six most studied impacts
Underwater noise is the most commonly researched impact, which is usually caused by WECs’ moving parts, but can also occur during deployment and decommissioning phases. It affects a range of animals but especially cetacean species (whales and dolphins), as it interferes with their ability to communicate, thereby impacting all aspects of their lives.
Physical interactions and collisions with the devices are also of concern for cetaceans and for fish, which can collide with or become entangled in devices.
Electromagnetic disturbances are disruptions of the Earth’s natural Electro-Magnetic Fields (EMFs). Within the marine environment, the Earth’s geomagnetic field is the predominant EMF, but electric fields (known as bioelectric fields) are also naturally emitted as a result of biochemical, physiological and neurological processes within organisms. These can be disturbed when the power generated by a WEC is transported via a cable network. Animals and oceanic fish species that use EMFs for navigation and migration are particularly sensitive to these disturbances.
Habitat change and loss is caused by the installation of cables, infrastructure moorings, electrical hub moorings, vessel anchoring systems and anchor deployment during the commissioning and decommissioning phases of developing installation sites. A number of devices could lead to an overall footprint spanning hundreds of square kilometres, and it is important to consider the nature of the surrounding habitat being lost or altered in the context of the surrounding area on a local, national and in some cases international scale.
Wave or tidal modifications are changes in wave or tidal patterns. At present, most research efforts on environmental impacts have focussed on tidal installations, and many have been modelling studies. Modelling studies have also comprised the majority of research on the impact of WECs on wave or tidal modifications, which may be a significant factor in understanding the hydro-sedimentary impacts of WECs in the future. For example, WECs have been shown to have a probably negligible impact in terms of wave height or wave direction, and any effects are not likely to extend beyond the close vicinity of the “array” itself, which can comprise up to 100 WEC devices. However, another study that modelled a scenario involving 200 individual WEC devices (often called a “farm”) off the coast of Hawaii predicted that processes such as sediment deposition, as well as wave and circulation properties, would be significantly impacted by WECs.
Water quality can mainly be affected by substances such as fuels, lubricants and coolants, which are used as hydraulic fluids and/or for painting. While little research has been conducted on the impact of lubricant spillages from tidal turbines or WECs, a study on wind energy devices suggested that water quality may be impacted during the operational phase due to the risk of spillages of grease and lubricants (which are essential to the operation of any type of turbine) and the use of anti-fouling paints. For example, spillages could occur in conjunction with turbine breakdowns (although such breakdowns are considered to be rare). Water quality may also be affected by sedimentation during the construction phase.
Other potential environmental impacts
In addition to the seven impacts listed above, there are a number of other potential environmental effects that require considerably more research:
- entrapment,
- entrainment,
- pollution,
- hydro-sedimentary effects,
- energy extraction,
- artificial reef generation,
- altered seafloor,
- changes in flood.
Although publications may not explicitly mention these impacts as frequently, some of them are closely linked with the seven more commonly cited impacts. For example, hydro-sedimentary processes and changes in flood are linked to tidal and wave processes; entrapment and entrainment are related to collision; and altered seafloor is linked to habitat loss and change.
Staying positive
It isn’t all bad news however, and WECs can also have perceived positive impacts, such as the so-called reef effect, wherein marine animals are attracted to submerged structures. This effect has long been exploited by commercial fisheries, and Marine Renewable Energy (MRE) installations have been shown to create potential habitats for fish and other marine animals. In fact, these structures can also prevent the most destructive bottom-trawling activities, and can therefore function as de facto Marine Protected Areas (MPAs) – this is called the reserve effect. Such positive effects should also be considered in order to get a holistic picture of the impact of these structures.
Going around in circles?
While research has provided us a picture of the broad range of possible impacts, it is not yet specific or detailed enough to help guide the development of WECs or of their components. This has created a circular problem: without more environmental information, it is difficult to design devices and deploy them in a way that minimises environmental impacts. However, without devices being deployed and monitored in the real world, we cannot increase our knowledge of environmental impacts. Gaining permission to deploy novel devices without environmental data accompanying them is a particular challenge, and the huge advances in the design and laboratory testing of novel WEC technologies are therefore offset by the difficulties in gaining the necessary deployment permissions.
Learning by doing: realistic solutions to move forward
There are a few things that we can do to help us to progress in this important field.
First, although research does not link specific impacts directly to particular WEC components, minimising environmental impacts should remain an overarching goal during design and testing. Although the data is still at a relatively coarse level, it does highlight the most significant potential impacts, and these should be taken into account from an early stage where possible. Furthermore, we should continue to test in established test centres across Europe that already have an environmental baseline, thereby increasing the likelihood of detecting environmental changes.
Second, we need to be open to adapting and changing our approach as information increases, and we need to undertake risk assessments so that we can deploy and test devices, even in the absence of robust environmental data. These are principles called Adaptive Management (AM) and Risk-Based Approaches (RBAs).
Finally, when devices are deployed, it is essential that robust monitoring programmes be set up, in order to collect data on impacts, and thus improve our understanding over time.
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