'From wind to torque with the Smart Rotor' describes the focus in our wind energy research. DLR researchers are using their expertise, derived among others from DLR's extensive aeronautics research work, to produce more efficient, quieter and lighter wind power plants.
In a helicopter, the dynamic lift is generated by the air streaming against the rotor blades. We have gained knowledge about this process down to the smallest detail at DLR. The physical laws for this also apply in reverse, when existing air flow drives a wind turbine to efficiently generate electricity. Whether on land or offshore, wind turbines in Germany and around the world are among the most important technologies for the sustainable supply of energy. To extend the energy obtained from wind, a significant increase in efficiency is required for wind turbines. At the same time, the wind turbines must become quieter than before and the costs of production and maintenance should also be reduced.
Involved are the DLR Institute of Aeroelasticity, the DLR Institute of Aerodynamics and Flow Technology, the DLR Institute of Propulsion Technology, the DLR Institute of Composite Structures and Adaptive Systems, the DLR Institute of Flight Systems, the DLR Institute of Atmospheric Physics and the DLR German Remote Sensing Data Center (DFD).
Rotor design (aerodynamics, aeroelasticity, structure, production)
Experts assume that individual wind power plants will in the future have a power output of up to 20 megawatts. To enlarge a wind turbine to the extent required for this, assuming its current structure would be maintained, the engineer would need to increase the individual rotor blades to more than 100 metres in length and, weighing in at over 100 tons, they would be much too heavy. Conventional rotor blades are also not sufficiently rigid for this; it would not be possible to safely maintain the required minimum distance between the blades and the tower. For the performance class that we are currently aiming for, the profiles, structures, construction methods and materials used have to be amended.
We develop rotor blades using a high proportion of carbon-fibre reinforced plastics (CFRP), which are five times more solid and rigid than the standard material reinforced with glass fibre. The effects of wind loads on the structure and materials are examined at the aeroelasticity research department. Composite design can provide greater stability for the rotor blades. At the same time, automated production processes can reduce manufacturing costs.
With an intelligent structure, sensor technology and controls, rotor blades would not need to be throttled even in the case of strong, gusty winds. At DLR, we are making a contribution to this field by developing so-called smart blades, for example through adaptive rotor blades and rotor blades capable of rotating with a so-called droop nose. We work using both numerical simulations and wind tunnels for experiments that are unique in Europe. The necessary test infrastructure is jointly provided with partners in the Research Alliance for Wind Energy so that every important aspect of wind energy can be examined.
Aeroacoustics and sound
The expansion of wind farms on land is increasingly leading to problems of public acceptance, regarding the matter of noise, for example. We are therefore not only looking into how to calculate sound fields produced by wind energy installations and their transmission, but also researching the design of more efficient, low-noise rotor blades as well as noise reduction measures.
Wind potential and wind-field characterisation
DLR competency in wind energy also comes from the fields of atmospheric research and remote sensing. Using satellite data and ground-based systems, we are working on even more accurate forecasts for wind speeds at the sites of individual installations and wind farms. These forecasts help the operators of wind farms and networks to optimally control their installations and accurately predict the power supply to the grid. Using optical scanning systems, so-called lidar systems, the wind currents and their interactions can be recorded within an entire wind farm. This is also a precondition for a better understanding of the aero-acoustic behaviour, and contributes to an improvement in noise protection for the resident population. Using a long-term series of wind speeds, investors can better assess various locations for wind farms.