sentences:  This has led to a variety of proposals for "partially self-erecting wind turbines" that, for a given available crane, allow taller towers that put a turbine in stronger and steadier winds, and "self-erecting wind turbines" that can be installed without cranes.Currently, the majority of wind turbines are supported by conical tubular steel towers.These towers represent 30% – 65% of the turbine weight and therefore account for a large percentage of the turbine transportation costs.