Foundation costs represent approximately twenty per cent of the total cost of monopile turbines, of which a significant proportion relates to scour protection. Minimising erosion (scour), protecting foundations and cables, reducing operation and maintenance costs and increasing the overall asset life are key to the early design stage of offshore developments.
The use of sophisticated hydrodynamic modelling, as well as physically testing equipment, gives developers a much clearer picture about how their wind farms will work in real situations, saves costs later and extends the life of the project.
The cost savings gained from understanding scour can reduce or even eliminate the need for scour protection around the foundations. In fact, savings usually hugely outweigh the cost of the upfront research. For instance, a recent study by HR Wallingford showed that for a development of 80 turbines scour protection costs could be reduced by £50k per turbine, resulting in a CAPEX saving reduction of around £4 million.
A recent example of this kind of research is the physical model testing of a potentially revolutionary new offshore wind foundation designed by Offshore Wind Logistics and Construction (OWLC), known as the Gravity Tripod. The company is working with Offshore Design Engineering (ODE), DNV-GL, Cambridge University, HR Wallingford and the Offshore Renewable Energy (ORE) Catapult to test and certify the new offshore wind foundation concept.
The gravity tripod is being tested using one of the world’s largest hydraulic facilities. Housed at HR Wallingford, the fast flow facility is 75m long x 8m wide and contains a 1m deep sediment pit. The flume has been specially equipped for the offshore wind sector and features include the ability to generate a unique combination of waves and strong currents, key to accurately testing scour protection.