New-Tech Europe Magazine | Aug 2018

operating system. Other considerations were also taken into account when building the prototype of the entire heliostat system. A product's weight is a measure of its production costs: the heavier the item, the higher the cost. In a heliostat, the size of the mirror directly affects the weight of the entire structure. Small heliostats therefore seem to be most promising in the long run. This is especially true if they don't come with the traditional high wiring cost, as the number of wires required for small heliostats is the same as for big heliostats. Thus, it was decided to build a small prototype with a mirror of only 8m2 in area, compared to a typical heliostat mirror area of up to 115m2. Simplified manufacturing and assembly TMC spent some time trying to come up with a way of manufacturing the frame and mounting the mirror on the frame that would make these tasks simple to perform, with easily accessible resources, and for a low cost. Laser cutting can be used to cut a wooden framework that contains a concavity. 3D printing can be used to make mounting pins that are glued on the back of the mirror on one side, and screwed in place on the other side of the mounting pin to create a sandwich- facet (see Figure 5). The laser-cut frame is placed in between a wooden board on the back side and the mirror on the front side. As the 3D printed mounting pins are glued to the back side of the mirror and have a threaded side sticking out of the wooden board, this simplified construction will be held in place tightly when screwing the 3D printed nuts on top of the mounting pins -- sandwiching the laser-cut frame in between the mirror facet at the front, and the wooden board at the back. When doing so, nuts should be screwed on evenly so as to distribute the load, ensuring

Figure 5: Experimenting to find the right tension for the mounting pins. By tightening the nuts, the mirror is forced into the concave shape of the wooden frame.

concavities (see Figure 6). Once all nuts are tightened accordingly, the concave mirror is placed on top of the metal structure to complete the heliostat. All that's left is adding the PV cells to the front side so that the heliostat doesn't need anything else but the sun.

the mirror follows the concavity of the laser-cut frame. By changing the tension on the screw, the mirror can be tensioned on the concave wooden frame to shape it as needed. Experimenting with different tensions, such as screwing it on as tight as possible, can result in some weird

Figure 6: The final result is a cost-efficient heliostat that can be made with easily accessible resources.

New-Tech Magazine Europe l 19