The team is led by the University of Virginia and includes Sandia National Laboratories, the University of Illinois, the University of Colorado, the Colorado School of Mines and the National Renewable Energy Laboratory. Corporate advisory partners include Dominion Resources, GE, Siemens and Vestas Wind Systems.
Sandia's previous work on 13MW systems uses 100m blades on which the initial Segmented Ultralight Morphing Rotor (SUMR ) designs are based. While a 50MW horizontal wind turbine is well beyond the size of any current design, studies show that load alignment can reduce peak stresses and fatigue on the rotor blades, reducing costs and allowing construction of blades big enough for a 50MW system.
Most current wind turbines produce power in the 1 to 2MW range, with blades about 50m long, while the largest commercially available turbine is rated at 8MW with blades 80m long.
Todd Griffith, lead blade designer on the project, said: "Offshore installations are expensive, so larger turbines are needed to capture that energy at an affordable cost."
Griffith added: "Conventional upwind blades are expensive to manufacture, deploy and maintain beyond 10 to 15MW. They must be stiff, to avoid fatigue and eliminate the risk of tower strikes in strong gusts. Those stiff blades are heavy, and their mass, which is directly related to cost, becomes even more problematic at the extreme scale due to gravity loads and other changes."
He said the new blades could be more easily and cost-effectively manufactured in segments, avoiding the unprecedented-scale equipment needed for transport and assembly of blades built as single units.
The exascale turbines would be sited downwind, unlike conventional turbines that are configured with the rotor blades upwind of the tower.
The load-alignment of the SUMRs is bio-inspired by the way palm trees move in storms. The lightweight, segmented trunk approximates a series of cylindrical shells that is designed to bend in the wind while retaining segment stiffness. This alignment is said to radically reduce the mass required for blade stiffening by reducing the forces on the blades using the palm-tree inspired load-alignment approach.
Segmented turbine blades have a significant advantage in parts of the world at risk from severe storms or hurricanes, where offshore turbines must withstand wind speeds over 200mph. The blades fold and align themselves to the direction of the wind to reduce cantilever forces on the blade through a trunnion hinge near the hub that responds to changes in wind speed.
At lower wind speeds, the blades spread out more to maximise energy production
The research on the extreme-scale SUMR is funded by the Department of Energy's (DOE) Advanced Research Projects Agency-Energy programme.
