Sight unseen?

of research in sustainability involves something that can’t be seen or even held. but it can be harnessed. And that’s why Charles Meneveau’s research on wind energy just received a grant from the National Science Foundation (NSF) under their newest funding category, Energy for Sustainability. “Wind farms are springing up everywhere,” says Meneveau, the Louis M. Sardella Professor in Mechanical Engineering. “Worldwide, about $23 billion was invested in wind farming equipment in 2006 and it’s expected that total installed capacity will double by the end of the decade. The potential is enormous.” Meneveau estimates that 3 million giant wind turbines operating at an average power generation of 1 megawatt each could enable wind energy to become our country’s only energy source. Spaced every half a mile, the turbines would cover a square measuring approximately 900 miles on each side (e.g., most of the Midwestern states between the Mississippi and the rockies). “Of course this isn’t going to happen,” he concedes, but, he adds, “the estimate at least gives us a sense of the massive scale of our energy consumption.” With wind energy on an “upsweep,” Meneveau, post-doc raul Cal, and co-investigator Luciano Castillo of rensselaer Polytechnic Institute, propose to use the NSF funding to study the interactions between wind farms and the atmosphere. “Wind turbines extract kinetic energy. They slow the wind down, but perhaps increase turbulence in their wakes; this in turn may affect evaporation from the ground, and, honestly, we’re not sure what else happens when wind farms are implemented on a massive scale,” says Meneveau. And what Meneveau ultimately plans to produce is only slightly less ethereal than the wind itself: more accurate computer models that could inform us about the relationship between wind and wind turbines— models that would help environmental planners with the placement of turbines to create maximum energy extraction with minimal negative impact on the environment. In order to develop these models, Meneveau and collaborators will use “toy” turbines to collect detailed fluid dynamic measurements of the air velocity between and behind turbines. These model turbines, each about five inches tall, are being installed in the Corrsin wind tunnel in Maryland Hall. “We’ll make the invisible turbulent motions of air visible by using advanced laser-based measurement methods. Microscopic particles floating in the air will be illuminated, digitally photographed, and these images can be analyzed computationally. This will enable us to deduce the instantaneous velocity field,” Meneveau explains. “Wind energy is just one of several options to be developed. If wind farms are to be implemented on a massive scale, we need to improve our tools to predict their interactions with the environment in the lower atmosphere,” he says. “That’s what we’re after.” Sight Unseen