New-Tech Europe Magazine | Aug 2018

TRINAMIC Motion Control (TMC), and the German Space Agency (DLR). The University designed a wireless communication system to reduce cabling cost, and simplify CSP plant deployment and scalability. This is the meshed network HelioNode that connects individual heliostats and lets them communicate with the cloud. TMC designed the HelioEBMU (energy and battery management unit), a decentralized control unit with low energy consumption, using a photovoltaic (PV) energy supply with battery storage. The DLR provided TMC with three different drive systems to develop a final version based on its experience in testing these three. This final version is a simple rim drive system, the HelioDrive, that reduces overall weight while simplifying production. The rim drive system Heliostat designs can be divided into three types: those using a linear drive system, a swivel gearbox, or a rim drive system. Rim drives are cheaper than swivel gearboxes and have several advantages over linear actuators. One is that all drive train components have a high efficiency rating, compared to solutions based on slew drives or lead screw linear actuators. The rims work as levers for the drivers, allowing small, cost-efficient motors to move the big frames. Small motors are cheaper to build and also cheaper to ship, lowering the price of the overall heliostats, especially for countries without the means to build engines themselves. To move the rims, several methods were investigated, including winch wheel drive systems, chain gear systems, and systems using a belt drive. Previous experience with winch wheel drive systems proved that mounting thesesystems is complex. Furthermore, the scaling-up potential for larger

Figure 1: Structure of the AutoR (autonomous rim) drive heliostat.

cables. In addition, as an intermediate gear is needed, the cost is high. Chain gears are precise, but only when there is constant tension on the chain. Even then, the polygon effect prevents the heliostat from turning into position in one constant movement. Using a belt drive to move the rims proved to be a cost-efficient method. Mounting the belt to the rim with springs, the belt stays tensioned throughout the

heliostats is low. This is because, for larger heliostats and higher loads, cables of a larger diameter would be needed. This, in turn, would lead to a bigger diameter of the winch wheel, which would reduce the gear reduction ratio. An alternative could be to use more cables of a smaller diameter. But this would complicate the mounting of the drive system, which is already not very simple with its existing two

Figure 2: Closeup of the driver and machined rim.

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