Friday, August 17, 2007

Anti-Wind Site Uses Fuzzy Math

When will they get the basic math right?

From an anti-wind blog comes this excerpt:

Dominion and Shell WindEnergy Inc (owners of the company, NedPower Mount Storm LLC) have announced the first phase of their project - 82 turbines producing 164 megawatts, or enough electricity for 41,000 homes - is under construction at a site near Dominion's Mount Storm Power Station. It is scheduled to begin operation in the fourth quarter of 2007 (see -

Notice this a [sic] "nameplate" capacity rating - and typically wind turbines produce only 25% of rating - so that means 10,000 homes in reality - at a cost of 82 turbines @ $2M each = $164M, which is $16,400 per home.

Well, oops, no, that's wrong. The company already allowed for the difference between nameplate rating and average production in calculating the number of homes.

The math goes like this: 164 MW = 164,000 kilowatts (kW). Reasonably expectable average production is actually more like 33%, not 25%. 164,000 kW x 8760 hours in a year X .33 = 474 million kWh (caveat: this is my estimate, not an official projection from Shell WindEnergy). The average household uses a little over 10,000 kWh annually, so a figure of 41,000 homes seems reasonable.

(I'm told that this sort of distortion has also been quite popular in the Palm Springs, Calif., area, where anti-wind groups insist that the statement by wind developers that one megawatt of wind generates electricity equivalent to that used by 250-300 homes should be further reduced by two-thirds. Wrong.)



KM said...

The confusion begins with the statement describing "82 turbines producing 164 megawatts". That is their nameplate capacity, but, as you note, they will be producing at a rate of perhaps only 33% of that: 55 MW.

Both sides should be more careful.

Tom Gray said...

Good try, Eric, but the anti-wind post purports to expose a misrepresentation about the number of homes. In that context, I think a slightly higher standard of care is called for.