That is a good measure too. Thanks for clarifying. Retired physics professor Howard Hayden has used it for several years as the fundamental measure of all kinds of alternative power. Total power (all forms) usage in the US divided by land area yields 0.4 W/m². If we used ALL our land to produce energy, that is what would have to be achieved as yearly average. We need somewhere to live and grow food. A figure of 4 W/m² says 10% of land area would be required. I don't know if we would really stand for that, but it is a production threshold where alternative energy starts to make sense. It is a formidible threshold.
--- On Sat, 9/5/09, Stan Jakuba <[email protected]> wrote: From: Stan Jakuba <[email protected]> Subject: [USMA:45743] Re: [Fwd: Energy and power] To: "U.S. Metric Association" <[email protected]> Date: Saturday, September 5, 2009, 8:47 PM Taken out of context, it was not clear that the W/m² refers to the land. It is meant to be reflective of the section of the Earth's surface that is occupied by the towers to the max practical density. The larger the propeller, the larger the radial and axial distance between adjacent towers. Thus the 1 W/m² is universal and it comes from wind farms in operations, not prognosis. Big difference. The 1 W/m² is the measured, NET output of the sites that had operated long enough (several years, preferably) to provide annual averages. The largest number I ever saw was 1.25 - the best location. Many more sites must be yielding less than 1 W/m² The paper is about the land area for a watt of power form various sources. And although the land occupied by the wind farm can potentially be used for growing something (not cities, though) that is a different subject. Stan
