One of the key principles of green energy, is the reuse of energy that would otherwise be lost using conventional methods. A current example of this, employed in some hybrid gasoline/electric vehicles, is regenerative braking — the recapturing of energy used to slow down the vehicle. To witness a second example of this, at least in the future, we may only have to go as far as the closest freeway, if some proposed energy capture concepts successfully move from the drawing boards to the freeway billboards — more correctly, the freeway barriers themselves.
According to an article in Engadget published 30 April 2007, a number of recent student designs have suggested that freeways and other major roadways could be retrofitted with turbines designed to capture the wind energy generated by passing vehicles. These designs include turbines built into any of the three planes defined by a roadway: the crash barrier that separates opposing traffic, the sound barrier separating the roadway from the adjacent community, and the overhead area that up until now has only been utilized for freeway overpasses, walkways, elevated rail crossings, and navigation signs. Small wind turbines built into a crash barrier, would be primarily powered by vehicles in the fast lane, whereas turbines built into a sound barrier, would be closest to the slow lane. Overhead wind turbines would be powered primarily by large trucks.
The idea is that the wind energy captured would be transmitted into the local power grid, for use by the community, light rail system, and "intelligent billboards". However, one question that can only be answered by computer simulation or actual aerodynamic testing, is whether or not these wind turbines would perhaps increase air turbulence through which the vehicles must power themselves, thereby negating any wind energy captured. (An analogy would be a bicycle light that draws power from the movement of the corresponding bicycle wheel, and slows down the rider a bit.) But intuitively this does not appear to be a problem, since the turbines would not be generating any sort of headwind. So where does the lost energy currently go? It takes the form of faster air speeds close to roadways, i.e., air molecules moving at greater velocities, a.k.a., heat.
While this innovative thinking is commendable, and the amount of wind energy currently lost is likely quite considerable, the future of these projects will face some barriers (no pun intended), including fabrication costs, installation costs, and, especially for turbines built into crash barriers, repair costs — for whenever a motorist becomes excessively distracted by a so-called intelligent billboard.
We can only hope that the system planners and designers are intelligent enough to skip the billboards and use all of the energy for more critical purposes. Or, even better, leverage the enthusiasm and creativity of this next generation of green industrial designers, and have them figure out how to completely do away with the freeway, and go straight to light rail or other, far more efficient transportation methods.