As noted in Section 2.4, the energy yield can be increased above that obtained with a fixed installation using single – or dual-axis trackers. Relative to peak nominal power, solar generator energy yield can be increased by around 10 to 25% with a single-axis tracker and by around 25 to 40% with a biaxial system; of course, the number of full-load hours increases accordingly (see Section A8.3, Figure A.11 and the examples in Sections 10.1.9-10.1.12). However, solar trackers are subject to size limitations for reasons of wind load. Hence larger-scale installations are subdivided into a series of around 1 to 50kWp tracked arrays into each of which an inverter can be integrated. Various vendors sell mounting systems for biaxial solar trackers.
Single-axis trackers have less complex mechanisms, but also provide less in the way of additional energy. Solar trackers with rods that are horizontally mounted in the north-south direction and that rotate from east to west over the course of a day allow for an approximately 10 to 12% annual energy gain in Central Europe [4.16]. Such a tracker was integrated into a 6.3 MWp ground-based PV installation in Muhlhausen, Germany (see Figure 4.59), where tracking is realized in a relatively straightforward manner, using rods that are attached to the various arrays.
Single-axis trackers yield better power gains if their rotation rods face southwards. A rod oriented 30° to the south provides a 20% energy gain in Central Europe and somewhat more in Southern Europe [4.16]. Figure 4.60 displays a rooftop solar tracking system.
Figure 4.61 displays a mechanically robust construction for the dual-axis trackers integrated into the solar generators at the Berlin R&D Centre of Solon AG. In this solution each of the tracked 6.5-9 kWp solar generators (area ~ 50 m2) integrates an inverter. A 12 MWp installation that integrates 1500 such elements (known as Solon Movers) has been in operation since 2006 at Solarpark Erlasee near Arnstein,
Figure 4.59 Each of the arrays that make up this 6.3 MW solar generator in Miihlhausen, Germany, integrates a single-axis tracker. These mechanisms are mounted in a north-south orientation on horizontal rods that rotate from east to west over the course of the day in accordance with the path of the Sun. This also helps to prevent winter snow accumulation (Photo: Power Light GmbH)
Germany (see Figure 4.62), and numerous other Solon Movers have been installed since (see, inter alia, the installations described in Sections 10.1.9-10.1.11).