Tuesday, May 19, 2009

Power From Wind

I think it might be a good idea to look at how a wind generator's output varies with speed. Wind power varies with the cube of wind speed. That is basic physics. No way around it that we know of.

So let us look at some wind turbines. Typical are turbines that start generating power at wind speeds of 2.5 meters per second and max out at wind speeds of 16 meters per second or 20 meters per second. First let us convert that to miles per hour to get a feel for the speeds involved.

2.5 m/s = 6 mph
16 m/s = 36 mph
20 m/s = 45 mph

Now let us look at output.

If you consider 2.5 m/s minimum output then at 16 m/s maximum output the max/min ratio is 262. At 20 m/s the max/min ratio is 512.

Or consider a wind blowing at 90% of maximum turbine rating. Output is 73% of maximum. At 80% output is 51% max. At 70% it is 35%. At 60% it is 22%. At 50% it is 12.5%. At 40% you are down to 6.4%. At 30% you are down to 2.3%. At 20% you are at less that 1%.

Economically it is probably useless (other than to impress the rubes) to design wind turbines that can handle max/min ratios more than 5 or 6 to 1. And from a practical stand point useful effectiveness is actually in the 2 to 1 range.

So it is not just having wind. You really need a very stiff breeze to generate useful power. I think our experiment with deploying massive amounts of high cost wind power are just about over. If the costs come down that improves the situation some. But not a lot.

Evidently Mr. Obama and his Green friends have never run the numbers.

Inspired by Glasgow Looking To Freeze In The Dark

Cross Posted at Classical Values

1 comment:

LarryD said...

Washington DC ought to replace its evil coal fired power plant with a benevolent wind powered facility. Work out a schedule for the replacement and shutdown the old plant on the switch over date.

I suspect the reality bite marks on Congress, the courts, the bureaucracy, and the DC reporters pool would be harsh.