Archer and Jacobson comment: Kenneth Perry suggests that wind turbines interfere with nature’s beauty. We believe, though, that the correct comparison is not with nature’s beauty but with the visual, health, and climate impacts of coal, natural gas, and nuclear power plants (see, for example, http://www.fotosearch.com/photos-images/coal-burning-plant.html), which is what wind turbines would be replacing. No one wants to add a new facility of any type to the landscape, but so long as society demands energy, it must come from somewhere. Coal, natural gas, and nuclear power all have visual and health-risk externalities that we believe exceed those of wind power.
Frits de Wette contends that the intermittency of wind makes power management of a wind-energy-dominated grid risky. This is true when wind farms are not linked together in an organized manner through the transmission grid, but not true if they are. We have shown in a new study that interconnecting up to 19 wind farms several hundred kilometers apart converts an intermittent wind resource to one that produces about one-third of its electric power at the same reliability as the average US coal-fired power plant—which has a 12.5% outage rate. Remaining electricity can be firmed with hydroelectric, geothermal, solar, or other power. The website for Red Eléctrica, which operates Spain’s electric power system (http://www.ree.es/ingles/i-index_de.html), further shows, as an example, that linking most of Spain’s wind farms through a common grid would eliminate minute-by-minute fluctuations that occur at a single wind farm.
Whereas older wind turbines produce capacity factors of 20% to 25%, modern turbines (for example, producing 1500 kW, with 77-meter blades and 80-meter hub height) placed where mean annual wind speeds exceed 6.9 m/s at hub height have capacity factors greater than 35%. The Galveston project will generate approximately 40% of 150 MW, or 60 MW of electric power. California’s electric power from fossil-fuel sources could be replaced by 6280 5-MW turbines offshore or onshore in wind speeds greater than 8.5 m/s. This is only 3.3 times the current number of smaller turbines in California. We believe wind can provide a large portion of electric power and energy if wind farms are sited and interconnected in an organized way.
Terry Goldman suggests that large-scale wind farming will cause significant bird loss. Statistics suggest otherwise. According to the Bird Conservancy, the 15 000 existing US wind turbines kill 10 000 to 40 000 birds per year, which compares with 50 million US bird deaths per year due to transmission towers and 200 million worldwide due to avian flu in 2005. Extrapolating to 5 million 5-MW turbines needed to satisfy all electric power and energy needs worldwide gives 3 million to 13 million bird deaths per year, much less than transmission towers in the US alone.
With respect to wind speeds, 5 million turbines must have a much smaller effect than the hundreds of millions of buildings that also slow down winds. Whereas turbines will slightly slow horizontal winds, they will increase vertical turbulence, enhancing convection, cloud formation, and rainfall and reducing pollution in areas where high pressure traps pollution near Earth’s surface.
