More wind than we thought?

A new study of the global potential for wind-generated electricity (Lu et al. 2009) concludes that windmills can meet the world’s energy demand with plenty of power to spare.

The open access paper in the Proceedings of the National Academy of Sciences claims that a global network of windmills operating at 20% of capacity could produce 2,470 exajoules (EJ) — about five times the current commercial energy consumption of the planet (~500 EJ). The latest estimate is much higher than the first evaluation of global wind power (Archer and Jacobson 2005), which estimated a similar network’s output at 443 EJ.

The paper’s state-by-state analysis of the potential for wind power in the US offers some surprises. The area where wind generation looks like a feasible alternative to fossil fuel power has grown dramatically. The old US-Department of Energy map (right) shows places like Kentucky, Tennessee, and Mississippi as blank slates of white with no real potential for wind power. The new analysis (below) colors these states yellow, and concludes that each of them could replace their fossil fuel consumption entirely with wind power and have energy to spare.

Building the windmill network necessary to realize this potential would be a massive undertaking. Each turbine in the network would have the capacity to generate 2.5 MW, with blades 100 m in diameter, perched on a 100 m tower. Windmills even larger are already in use. The video below shows one such windmill — the Enercon E-126 — which has a diameter of 126 m and a capacity of 6 MW.

It would be wonderful to see thousands of windmills eliminate fossil fuel consumption, but a network of such gigantic structures could have some pretty substantial environmental impacts of their own. The paper discusses the possibility that large-scale wind harvesting could alter atmospheric circulation and reduce temperatures at higher latitudes. It doesn’t mention the potential effect on birds and bats, already hit hard by habitat loss, but this article claims that large turbines are actually less dangerous to our flying friends than little ones. When I watch the slow rotation of the large windmills in the video I can see why.

While contemplating wind mega-projects, it’s also interesting to imagine what could be done at the micro scale. Large wind turbines tend to be much more efficient than small turbines. Small windmills don’t even harvest enough energy to pay back the energy used in their manufacture.

Humdinger Wind Energy is a recent start-up proposing an interesting solution. Instead of small wind turbines, Humdinger proposes vibrating belts for micro-scale wind harvesting. They even offer instructions to make your own windbelt, using about $5 worth of commonly available materials.

Perhaps more of our farms should be harvesting wind, in addition to sunlight.