Design of the developed Mini-Mirror Array (MMA)
In a still running project such an alternative heliostat design was developed in cooperation between SIJ, IZM and DLR. The resulted design (fig. 3) of a longer development time consists, instead of the typical huge construction with large mirrors, of an array of numerous small parallel arranged mirrors.
The array has a filigree movement system with a cost-effective design and it is driven by small actuators that are adjustable by computer program on a linked pc. This mirror array is imbedded in a box with a transparency cover and a plane design to guarantee low wind loads.
Fig. 3. (Left side) Sketch of the first realised test version of the MMA with the parallel mirror array affiliated with each other
by an agile, crossed stick stage for movement.
Fig. 4.: (Right side): A model of the mechanical system that interlinks and moves the mini-mirrors.
The first built test device (see figure 4, and 5) of the newly developed MMA has a reduced number of only 25 small mirrors (around (10 x 10)cm) to keep the heliostat at a suitable size. The mirrors are made of light, thin glass (thickness 2mm) and placed in an adequately large box of (60 x 60)cm to ensure a free movement in all directions. Future MMAs could be around (2 x 2)m with several hundred mirrors. The box is covered with a highly transparent solar glass generally for photovoltaic modules and the glass has a special coating reducing reflection losses of the sunlight.
