In the Millennium Mill, the cap and sails will be turned to face directly into
wind and the area of the sails adjusted under computer control according to wind direction
and strength, and will rarely require human intervention except for maintenance and
repairs. The electricity required by the computers and other mill functions will be
generated by the mill itself. The cloth sails work on the roller blind principle to
achieve changes in area.
Changing the sail area
The streamlined leading edge of the sail is hollow apart from the main
structural member at the front, and contains two servo-driven rollers. Sailcloth
is rolled
onto one, and a rope outhaul on the other. Variable amounts of sailcloth can be drawn
backwards out of the leading edge to increase the sail area in lighter winds or drawn back
onto the roller to decrease the area in stronger winds. The cloth is guided and restrained
by the channelled ribs which extend back from the leading edge. The outhaul ropes operate
around pulleys at the outer ends of the ribs.
