Large scale interactive coupled modelling of environmental impacts of marine renewable energy farms

For the UK to fulfil its energy demand and renewable commitments by 2020, it is recognised by the Government that it will be necessary to have a significant input from marine renewable resources, both wave and tidal. This will require the deployment of arrays of large numbers (>50) to provide electrical energy on a commercially viable basis. Such arrays would potentially extend along many kilometres of UK coastlines. While limited work has been carried out into the potential environmental impact of single devices, the impact that arrays may have on the flow-field together with possible resulting effects on marine ecosystem processes is unknown. Forecasting the hydrodynamic changes resulting from array installation is difficult but is a core requirement of the industry; considerable effort is being put in to this field by commercial and academic research groups. Ecological surveys and studies to investigate ecological effects are time consuming and costly and are generally reactive; a more efficient approach is to develop 2 and 3D linked hydrodynamic-ecological modelling which has the potential to be reactive and to allow forecasting of the effects of array installation.

Arising from this background, the overall aim of the project is to demonstrate the ability to numerically model the change in ambient hydrodynamics resulting from the installation of wave and tidal device arrays and to couple the model output to associated ecological models to allow prediction of associated changes in benthic habitats and dynamics, plankton growth and fish communities.

To achieve this aim the proposal incorporates a series of objectives based on the exploitation of different modelling approaches using both 2 and 3D modelling. The software to be used will include (i) MIKE, a family of modelling tools developed by DHI which is widely used by the majority of marine consultants in the UK. The package includes the associated Ecolab ecological processes model which is widely used in Australasia for a range of environmental assessments especially in the coastal zone. (ii) Other high resolution hydrodynamic models such as Fluidity-ICOM and GOTM and (iii) the ERSEM ecological model which will be linked to output from the hydrodynamical models in (ii). Models in (ii) and (iii) are all widely recognised within the research community. A major novelty of the project is that it will thus make use of a range of readily available commercial and open source software. This approach will allow two main goals to be achieved: (i) Demonstration that output and results are not model specific and (ii) the development of open source tools will have the potential for the research approach to be enjoyed by the wider community.

The proposal fully recognises the complexity of ecological processes. An initial objective of the project will therefore be to parameterise the relevant biological processes, especially relating to benthic detrital dynamics, plankton growth and fish population dynamics, in order to effectively run a coupled hydrodynamic-ecological model. These parameterisations will then be tested to give realistic results with respect to inter- and intra-annual variation of tidal and wave climate conditions without the presence of any Marine Energy Converters (MECs) before application to situations involving array deployments. Special focus will be given to the potential positive effects of array deployments arising from the changes in the hydrodynamics and establishment of no-fishing zones.

The importance of the work will be the value of this ground-breaking R & D for end-users, spanning the commercial developers of marine energy devices, environmental consultants and the regulatory authorities. The project has been designed specifically for use by all sectors of the industry in order to accelerate the development of marine renewable devices by allowing forecasting of the environmental consequences of array deployments.

The outcomes of the project will principally benefit the UK marine renewable energy industry, particularly the commercial developers of marine energy device arrays, marine environmental consultants and national marine regulatory authorities. There will also be certain wider benefits to the general public primarily through optimising environmental sustainability and impact reduction against the urgent need to encourage the development of marine renewable resources.

The UK is, arguably, at the forefront in the development of marine renewable energy devices and arrays. However, with the deployment of any such devices there will always be a cost to the environment. Establishing the resulting change to the environment is not easy owing to the complexity of the factors contributing to the change including, for example, the specific design of the wave or tidal energy devices to be used, the design of the array and local physical and environmental influences. In addition the complexities of the marine ecosystem make it particularly challenging to carry out convincing observations. At present observational programmes are usually based on monitoring carried out before and following the installation of the device: such an approach is reactive in nature. It is much more desirable to take a pro-active approach which has the potential to allow forecasting of environmental consequences.

The impact of the project will be maximised by employing a modelling approach. Application of the model to proposed device array sites will allow forecasts to be made of the effects of the array on two main ecosystem components, the benthos and the fisheries. This in turn will allow predictions to be made of the device array on the economics of local fishing industries and on the effects on biodiversity and stability of the indigenous benthic communities. This will be of considerable assistance to national regulatory bodies and others in the drive to establish limits to ecosystem modification associated with commercial marine energy extraction. In a broader context the outcomes of the study will provide a solid component for the development of a national protocol for the marine renewable energy industry in relation to the environment. The establishment of such standards would be a major boost to the industry by shortening the consultation process on environmental acceptability of such schemes.

The project will also benefit the marketing base of the UK marine renewable energy industry by allowing developers to offer a more integrated management package to potential customers. The attractiveness of the model to be developed will be enhanced by its flexibility allowing a range of environmental parameters of local interest to be incorporated in the model as required. Development of the model, especially the ecological component, will be assisted by liaison with DHI, Denmark; the extensive international links of this company will enhance the impact of the project internationally. Underpinning the overall model are two state-of-the-art hydrodynamic sub-models which reflect the UK lead in the field of flow prediction in the vicinity of marine energy device arrays: this again will enhance the impact of the project by providing greater confidence to potential customers.

The benefits arising from the project will be realised at the end of the project and beyond. However essential foundations for gaining the full impact benefits will be laid over the course of the project: this will be done through an Advisory Forum and through wider contacts.

While the PDRAs employed for the project will be focussed on the hydrodynamic and ecological modelling, they will receive training in knowledge exploitation and will be expected to participate actively in establishing working links with end-users.