My doctor, who knows that I understand physics and renewable energy in particular, asked me today what I thought about wind turbines on boats.

I explained that, since boats need their own ways to generate electricity, what is called “small wind” may make sense. Most ships have diesel-powered generators, and that’s an option for smaller craft as well, and solar is not an attractive option because of the small area.

Doctors generally don’t have time to kill, but he asked me further about small wind, to which I explained:

Because the area of a circle is proportional to the square of the radius, big is better.  If you can build a turbine with a radius 100 times larger than a small one, you’re going to generate 10,000 time more power.

Because the power generated by a turbine is proportional to the cube of the wind’s velocity, if you can site a turbine in wind conditions that are 10 times those on your rooftop, with trees and other buildings slowing the wind down, you’re going to generate 1000 times more power.

So, as usual, the answer resides in physics and math. 1000 times 10,000 is 10 million, which is why we see huge turbines on structures that lift huge turbines high above the ground, and it’s why the small wind industry has essentially disappeared.

If you don’t understand elementary school math and high school science, and you have money to burn, the investment offered at left may be right for you.

Rooftop Wind