Tuesday, May 1, 2012

Wind craze

I recently fell upon a discussion on a wind energy forum. Someone was trying to figure out how much power he would be able to generate if somehow he could tap into the jetstreams of the uper-atmosphere. Now, initially, most people react with astonishment and scepticicm when they hear such ideas - and I'm writing today to tell you that those people would be right! A back of the envelope analysis reveals the cold (or shall I say hot) truth.

A small sized wind generator raised into the upper atmosphere would not only be facing a problem just having it float in the air, but the power would most likely never get to the ground.

Using the thickest cable on the American Wire Gauge (A measure of cable thickness) reveals that we would lose over 16% of the power to so-called "resistive heating" in the cable. Now, this would be acceptable if the copper-cable wouldn't weigh almost 10 metric tonnes, or the same as two large Boeing 747 jet engines!

 The smaller the cable, the lower the weight obviously but also the higher the power loss. The cut-off point comes at around AWG5 (The weight only HALF a jet engine) where the power loss would surpass 100%. 

Now remember, I'm not saying that we should not experiment with new ideas or concepts. The point I'm trying to make here, is that sometimes we get so focused on being innovative that we get our heads stuck in the clouds (pun intended) and forget the basic facts and physics that surround us. There are plenty of down-to-earth ways we can be innovative today: Google has been experimenting with investments in flying wind turbines, and they have succeeded fairly nicely with low-altitude flying wind turbines such as this.
 
So, sure there a probably ways we can think about concepts like these in a plausible way, low-weight superconductors, microwave transmission and so on, but let's focus on the low-hanging fruits of sustainable and renewable development for now. Space-beams, and jetstream wind can wait a little longer.

Makani's prototype flying wind turbine.