Seite - 121 - in Water, Energy, and Environment - A Primer

8.4.2 Windenergy Windenergy is avariable (intermittent) renewable energy source that can be used as an energy saver for fossil-fuel-powered generating systemswhen thewind is blowing, but requires some kind of storage of excess wind-generated electricity if it is to supplyelectricityatother times.Water reservoirs associatedwith hydropower dams can serve as a natural ‘storage battery’ for variable wind (or variable solar) as hydroelectric generators haveshort response/startup timesandoffer flexibilityas towhen water can be released to the generators from reservoir storage. The combination of wind and hydropower thus provides a system capable of firming up power availability evenwhen the wind is not blowing, and reducingwater releaseswhen thewind isblowing. However, this hybrid system has its limitations. It works extremely well as long as the wind component is not too large and the variations can be handled by the hydropower system’s flexibility. When wind generation gets too big, that flexibility no longer exists (or becomes increasingly expensive) and excess wind energy must be utilized elsewhere. The US Department of Energy’s Pacific Northwest Smart Grid Demonstration, underway in five Pacific Northwest states, is exploringoptions for addressing this growingproblem. 8.4.2.1 Onshorewind Wind farmsconsist ofmany individualwind turbines,which are connected to the electric power transmission network (see Figure 8.11). TheWhitelee,commissionedin2009, in thesouthofScotland, isoneofEurope’s largestonshorewindfarms. Itwasbuilt in two stages to reach its current configuration: 215 turbines (140at 2.3 MW, 69 at 3 MW, 6 at 1.67MW) with a maximum capacity of 539 MW. Wind energy is Scotland’s fastest-growing renewable energy technology, reflecting the fact that Scotland is Renewableenergy 121