Wave and tidal power generation is currently receiving significant attention from a number of sources. With many commentators pointing out that the industry is where wind power was at least 15 years ago – at the bottom of a very steep curve of adoption – there is a flurry of activity that is set to accelerate development in the sector at a rapid pace.
It is easy to understand why there is such profound interest. In the UK alone, The Carbon Trust estimates that the UK could capture just under a quarter of the global marine energy market – worth up to £76bn by 2050, generating over 68,000 jobs. The analysis, the most in-depth of its kind, found that total marine energy capacity in the UK could be 27.5GW by 2050, capable of supplying the equivalent of over a fifth of current UK electricity demand to the grid.
More immediately SSE Renewables and Scottish Power Renewables have signed lease agreements to develop sites, which ‘represent potential for up to 600MW of capacity and a step change in the industry’. £6.4m in funding from the European Regional Development Fund was recently confirmed for Tidal Energy to manufacture its 1.2MW DeltaStream device for deployment in Wales.
Against this backdrop of a huge prize for the taking, there are some specific technical challenges to be overcome. Firstly there are the challenges of developing and installing large scale machinery in one of the most hostile environments on the planet.
Then there are the more familiar concerns such as reducing the cost of manufacturing this equipment and maximising its yield. Lastly there are of course environmental concerns to be addressed.
Issue 1: Turbine Design
There are many different types of turbine design. Though these systems suit different needs they all face the same issues as a result of the unchartered, hostile underwater environment. The tidal streams that can create this power are necessarily fast and the forces exerted on the blades, support structures, mountings and the drivetrains can be immense. As a result there is a high incidence of failure and high maintenance costs.
Simulation software – specifically mechanical and stress analysis simulation – can predict the physical stresses on the various components of the turbine – the blades, gear box, drive train and support structures. This can then provide compelling evidence for the selection of one design over another based on its likely resilience.
As well as being long lasting, the turbines must extract as much energy as possible from the tidal streams. Fluid dynamics simulations can predict the energy yield from a turbine design, and also the pressure loading on the turbine components, which is required by the stress analysis simulations.
These simulations can be used to guide the optimisation of the turbine components and assess the impact of design changes (that may range from increased costs and delayed installation to drastically improved yields or more resilient equipment) and help to increase the likely ROI of the entire installation.
Issue 2: Turbine placement
Turbine placement is also a critical factor. The depth of the water will define many aspects of a turbine design – though as a rough guide turbines are suitable for water of around 20-50m deep.
However, assuming a given design and even a given location, there are then issues of how to place the turbine to best capture tidal energy, reduce installation costs and minimise interaction effects.
Simulation is critical here as it is not an option to move the turbines in-situ just to assess the best position or least interactive site. Building on the mechanical and CFD assessment of the design itself, simulation can first show the most cost effective options for installation.
The technology can then look at the interaction of the turbines across the entire installation and give an estimate of the output a given configuration or placement will yield. And of course, different configurations can then be compared. Critically this is all done before committing resources.
This mixture of stress analysis and fluid dynamics simulations means that expensive prototypes that can cost millions and take months to develop and test can be avoided. It also means that improvements in design can be tested and ‘verified’ in the virtual environment before resources are committed.
Simulation can demonstrate the dynamic development of stress on the underwater structure and show the likely output of a given field of turbines, as well as highlighting the interaction effects of different configurations. This information is critical in developing a realistic, cohesive business case for the investment in wave and tidal power generation.
Simulation is not limited to these commercial factors. It can also help minimise environmental disruption – be this disturbance to fish stocks or the damage caused by scouring of the sea bed. In the UK this is critical as many of the turbine sites are in Scotland where the fisheries industries are a vital source of employment.
On the global scale, there has been concern that inserting turbines into the tidal streams responsible for regulating the temperature of the earth may have detrimental impact. Simulation offers a critical insight into these changes and can help ensure that the development of a new turbine field does not damage existing economies and employment.