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Future Trends

Future trends are outlined in the following sections.

BLADE AND ROTOR DESIGN

• New aerofoil design;
  
• Improved aerofoil shapes, variable chord distributions and variable twist distributions, such that the overall performance of SWT can be improved significantly;
  
• Noise emission reduction. Noise is still a constraint in certain countries on the further expansion of wind energy.  The current trend towards integrating SWT closer to populated areas and on buildings enhances this problem. Several design parameters can change, such as aerofoil shape, tip speed and angle of attack, but modifying design parameters always means compromising between noise reduction and optimal performance;
  
• Low Reynolds number aerodynamics.  The Reynolds number is an important parameter in fluid mechanics, and tends to be lower for SWTs.  Low Reynolds numbers make the problem of aerofoil design difficult because the boundary layer is much less capable of handling an adverse pressure gradient without separation.  Thus, very low Reynolds number designs do not have severe pressure gradients, and therefore the maximum lift capability is restricted;
  
• Deforming blades;

• New materials such as thermoplastics (nylon);
• New SWT regulation methods in order to avoid the use of furling systems.  Furling systems are unattractive because of the high acoustic noise emission and vibrations when the SWT furls. New cheap, reliable pitch systems may be developed; and
  
• Magnetic bearings to reduce losses in small wind turbines.

GENERATOR

• Solutions for cogging torque reduction, such as asymmetric poles; and
  
• Low rotational speed SWT, based on hybrid planetary gear and PMG.

MANUFACTURING SPECIALISATIONS

• Blade manufacturers: new methods based on, for example, pultrusion process and filament winding;
• Open-use power electronics - Power converter capable of working in both stand-alone and grid-connection mode; and
  
• Light tower manufacturing.

CONCENTRATION OF MANUFACTURERS

Standardisation, Legislation and Characterisation:

• Wider use of existing standards;
• Further development of standards; and
  
• Commonly-accepted means to characterise performance.

OFF-GRID

• Storage technologies;
• Improved sizing tools;
• Improved understanding of hybrid systems and W/D systems;
• Wider offer of components (sizes, manufacturers);
• Communication protocols; and
  
• New applications.

GRID CONNECTED

• Interconnecting power electronics;
• Communication protocols;
• Standardised interfaces (‘plug & play’ devices); and
  
• Simpler, more uniform and better-understood technical requirements of network operators.

UNDERSTANDING OF WIND RESOURCE IN AREAS WHERE SWTs ARE INSTALLED

• Near buildings;
• On buildings; and
  
• Within buildings (building-integrated).