Critical lengths of grade in highway design for wind farms

Wind energy as a power source is an attractive alternative to fossil fuels. Globally, an increasing number of wind farms is being planned and constructed. The conditions of highway design indexes for wind farms are unique, and the current design standards are not appropriate for determining the necessary critical lengths of grade. The relative vehicle parameters for aerogenerator transportation are investigated in detail, and the typical design vehicle for aerogenerator transportation is selected. The dynamic characteristics, such as acceleration and deceleration performances, are analysed based on the nominal dynamic, kinematic and operating characteristics of the typical vehicle on wind farm grades and terrain elevation. This study proposes a formulation to obtain the relation between speed and distance travelled for heavier design vehicles, from which speed-gain and speed-drop curves are calculated and drawn. In addition, the total accumulative speed–distance profiles with different gears are also combined. Through an extensive calculation, this paper also provides practitioners with design tables for the maximum critical length of typical design vehicles for large aerogenerator transportation under full load and 80 t load. The research results can serve as a reference for aerogenerator transportation highway design and construction and are helpful for related highway geometric design guidelines.