Aircraft wings that change their shape in flight can help to protect the environment

Aircraft wings that change their shape in flight can help to protect the environment. Simulation of a flex module. Credit: © Fraunhofer IFAM

A top priority for any airline is to conserve as much fuel as possible -- and this helps to protect the environment. The EU project SARISTU aims to reduce kerosene consumption by six percent, and integrating flexible landing devices into aircraft wings is one step towards that target. Researchers will be showcasing this concept alongside other prototypes at the ILA Berlin Air Show from May 20-25.

Airport congestion has reached staggering levels as some 2.2 billion people a year take to the skies for business or pleasure. As their numbers grow and more jets add to pollution in the atmosphere, the drawbacks to the popularity of flying become obvious. This has encouraged airlines, aircraft manufacturers and researchers to pull together to reduce airliners' kerosene consumption and contribute to protecting the environment. One effort in this direction is the EU's SARISTU project, short for Smart Intelligent Aircraft Structures.

Landing flaps that change their shape

While birds are able to position their feathers to suit the airflow, aircraft wing components have so far only been rigid. As the name suggests, landing flaps at the trailing edge of the wing are extended for landing. This flap, too, is rigid, its movement being limited to rotation around an axis. This is set to change in the SARISTU project. "Landing flaps should one day be able to adjust to the air flow and so enhance the aerodynamics of the aircraft," explains Martin Schüller, researcher at the Fraunhofer Institute for Electronic Nano Systems ENAS in Chemnitz. A mechanism that alters the landing flap's shape to dynamically accommodate the airflow has already been developed by the consortium partners. Algorithms to control the required shape modifications in flight were programmed by ENAS, in collaboration with colleagues from the Italian Aerospace Research Center (CIRA) and the University of Naples.

The mechanism that allows the landing flap to change shape can only function if the skin of the landing flap can be stretched as it moves, a problem tackled by researchers from the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen. "We've come up with a silicon skin with alternate rigid and soft zones," reveals Andreas Lühring from Fraunhofer IFAM. "There are five hard and three soft zones, enclosed within a silicon skin cover extending over the top."

The mechanism sits underneath the soft zones, the areas that are most distended. While the novel design is noteworthy, it is the material itself that stands out, since the flexible parts are made of elastomeric foam that retain their elasticity even at temperatures ranging from minus 55 to 80 degrees Celsius.

Four 90-centimeter-long prototypes -- two of which feature skin segments -- are already undergoing testing. Does the mechanism work? Are the forces being transferred correctly? These are questions for upcoming tests in the wind tunnel. Scientists will be showcasing the prototype at the ILA Berlin Air Show from May 20 -- 25.

Maneuverable wingtips

A single improvement won't be enough to cut kerosene consumption by six percent. Since a variety of measures are needed, scientists from Fraunhofer IFAM are participating in a second subproject focusing on the wingtip. Here the SARISTU consortium has developed a tab that forms part of the wing tip and changes shape during flight to keep air resistance as low as possible. Any gap between the flap and the fixed aircraft wing would cancel out any positive effect. "This led us to develop an elastic connecting element, and this work already covers everything from the chemical makeup to the process technology and manufacture of the component," says Lühring. Like the landing tab, this component retains its elasticity at temperatures ranging from minus 55 to 80 degrees Celsius, and it easily copes with the high wind speeds involved. Researchers will be showcasing the prototype at the ILA Berlin Air Show.

Funding

This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 284562.

Source: Fraunhofer-Gesellschaft

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Wave energy integration costs should compare favorably to other energy sources

The Ocean Sentinel has been deployed off the Oregon Coast, one of the nation's first wave energy testing devices. Credit: Pat Kight, Oregon Sea Grant

A new analysis suggests that large-scale wave energy systems developed in the Pacific Northwest should be comparatively steady, dependable and able to be integrated into the overall energy grid at lower costs than some other forms of alternative energy, including wind power.

The findings, published in the journal Renewable Energy, confirm what scientists have expected -- that wave energy will have fewer problems with variability than some energy sources and that by balancing wave energy production over a larger geographic area, the variability can be even further reduced.

The variability of alternative energy sources is one factor that holds back their wider use -- if wind or solar energy decreases and varies widely, then some other energy production has to back it up, and that adds to the overall cost of energy supply.

"Whenever any new form of energy is added, a challenge is to integrate it into the system along with the other sources," said Ted Brekken, an associate professor and renewable energy expert in the College of Engineering at Oregon State University.

"By producing wave energy from a range of different sites, possibly with different types of technology, and taking advantage of the comparative consistency of the wave resource itself, it appears that wave energy integration should be easier than that of wind energy," he said. "The reserve, or backup generation, necessary for wave energy integration should be minimal."

This estimate of the cost of integrating wind energy indicated that it would be 10 percent or less than the actual charges being made for the integration of wind energy. Energy integration, however, is just one component of the overall cost of the power generated. Wave energy, still in the infancy of its development, is not yet cost competitive on an overall basis.

Wave energy is not now being commercially produced in the Pacific Northwest, but experts say its future potential is significant, and costs should come down as technologies improve and more systems are developed. This study examined the hypothetical addition of 500 megawatts of generating capacity in this region by 2025, which would be comparable to approximately five large wind farms.

Another strength of wave energy, the study suggested, is that its short-term generation capacity can be predicted with a high degree of accuracy over a time scale ranging from minutes to hours, and with some accuracy even seasonally or annually.

The Pacific Northwest has some of the nation's best wave energy resources, and as a result is home to the Northwest National Marine Renewable Energy Center, supported by the U.S. Department of Energy.

Wave energy in the region is expected to spur economic growth, help diversify the energy portfolio, reduce greenhouse gas emissions and reduce transmission losses, the study noted.

Source: Oregon State University

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