including shaft 31 worm gear 32 and spur gear 33 the latter of which is secured to a flange 34 the flange 34 in turn is secured to an end plate 35 of the mirror 20 the gear 33 and flange 34 are journaled for rotation in a stanchion 36 secured to the cradle 15 operation of the motor contained in the box 30 causes rotation of shaft 31 and rotation of the mirror assembly 20 a suitable insulating bearing 40 allows rotation of the assembly 20 about the fixed receiver tube 25 without significant loss of thermal energy to the cradle 15 the receiver tube 25 is insulated as shown in fig1 by encircling insulation such as 11 2 inch thick foam insulation covered by resin bonded glass fiber skin the shaft 31 extends continuously along the module and engages each of the mirror assemblies through reduction gear assemblies 34 g 34 of the type shown in fig8 as shown in fig1 the gear assemblies are gimbal mounted to accommodate any slight mis alignment between the shaft 31 and the mirror assemblies it has been found that such gimbaling is not required and the mounting arrangement of fig8 has been found to be fully satisfactory as mounted on cradles 14 and 15 and driven by the common shaft 31 all collector assemblies 20a d turn in synchronism about their respective axes a d driven by the common motor the motor is operated at a speed to provide one revolution of the collector assemblies per day this.