NORD Drivesystems has supplied over 700 SI-series UNIVERSAL worm gear units to align solar panels at the Rodenäs Solar Park located in Northern Germany. Each gear unit is controlled to drive a 16m2 solar panel to precisely track the sun at a rate of 4 degrees every 15 minutes.
Maximum EfficiencyFor this demanding application it was decided to use two worm size 63/31 gears connected in series.
By driving the panels, rather than permanently fixing their position, some 25% to 30% more electricity can be generated – this method is particularly suited to locations like Germany where sunlight levels necessitate the need for maximum efficiencies.
The Nord SI-series gear units operate round the clock, tracking the sun by day and returning the panels to a start position in readiness for sunrise the next day. They are completely exposed to the elements with summer and winter temperature extremes, and up to Force 10 winds causing unpredictable load conditions and no tolerance for position loss.
Everything revolves around this technology
For this demanding application it was decided to use size 63/31 double worm gears – two worm gears connected in series. When the gear units start up, there are extremely high radial loads on the drive shaft bearings. The compact design of the NORD unicase gear unit housing with generously dimensioned drive shaft bearings is well placed to handle the peak loads. The housing design also includes the facility for universal installation, allowing the drive units to be easily integrated into the solar tower structure.
To meet the demanding environmental conditions, the drive units have double corrosion protection. Firstly, the highly corrosion-resistant aluminium housing and secondly a special paint provides even better protection against the harsh climate.
In order to ensure reliable operation, especially at sub-zero temperatures, the gear units are filled with synthetic oil. The high efficiency gear units are designed so that they can produce a large torque with a relatively low motor power.
A further advantage of the worm gears is the self-locking effect which eliminates changes in position due to the effects of high wind conditions. The NORD solution offers many advantages compared with other drive types which are available on the market. With these types, further mechanical intervention such as braking is required in order to counter the force of the wind and prevent the tower from turning. In addition, the braking system often requires a heating system necessary to prevent the brakes from freezing up in the winter. Such components add both cost and complexity to the application.