Successful demonstration wind farms have proved that wind energy technology is capable of operating economically in harsh offshore environments. However, the next generation of offshore wind farms will be installed on a larger scale ranging from 50-100 MW. Continued successful development and improved economic value of offshore wind energy requires careful design and planning. In 1999 a Research Requirements Workshop was held as part of the UK's Offshore Wind Energy Network series (Watson, 1999). Main recommendations (for resource and economics) were:
Detailed prediction of the wind resource - relationships between onshore measurements and coastal winds out to 30 km, improved models (incorporating turbulence, gusts and diurnal and longer term variations) and linking wind and waves
Prediction of extreme environmental conditions - use of existing data and relationships between extreme wind and waves
Wind forecasting - improved models for coastal areas and evaluation of current techniques
Areas requiring further research include:
Improved wind resource estimates particularly in coastal areas which are difficult to model. This should include accurate prediction of vertical wind speed and turbulence profiles. Resource and loading predictions are required on long-time scales for economic and fatigue assessments and variations on short-time scales are required for forecasting and for improved maintenance scheduling. Further development of methods to forecast wind power output up to several days ahead (see e.g. (Hutting and Cleijne, 1999), (Landberg, 1998)).
Evaluation and prediction of wake impacts on power output and loads for large wind farms. Although monitoring at Vindeby has provided useful data on offshore wakes, significantly more research is required to develop models which can predict wake development in the lower turbulence environment offshore where atmospheric stability variations will be more important. Additionally there are very few data for large wind farms (onshore or offshore) so there is considerable uncertainty.
Reduction in down-times. Access to offshore turbines for maintenance can be difficult leading to the potential for increased down times. This can be minimised both through careful design of mooring facilities, providing helicopter access, good predictions of offshore weather allowing better maintenance planning by innovative design solutions (Pedersen, 1998) and preventative maintenance and development of smart wind farms which include component monitoring to predict component failures.
Optimised design criteria to further understanding of complex wind/wave relationships and for assessment of combined wind-wave loads (Kuhn et al., 1998). Calculation of extreme wind and wave events and their recurrence periods is also required.
Optimisation of design of the major components such as foun dations and towers to increase lifetimes. Use of lighter materials for some components (e.g. blades) such as carbon or glass fibre may provide less expensive but more productive and durable wind turbines. See section CA-OWEE 2.1.
Energy storage and transmission solutions to weak grid or loss in transmission problems (see e.g. (Gardner et al., 1998), (Grainger and Jenkins, 1998). See section CA-OWEE 2.2.