Innovative turf care concept set in motion

Demag drive technology moves LED lighting system

Demag drive technology moves LED lighting system

The Demag modular drive system provides RHENAC GreenTec AG with the right mobility solution for an innovative turf care concept. Demag geared motors, wheel blocks and frequency inverters move a 190-tonne structure consisting of steel and electric elements at 12 m/min. In figures, 2,755 LED light modules and more than 200,000 LED lights supply the 7,000 m2 pitch area with turf grow light. Innovative technology for an award-winning pitch in professional football.


Many innovative companies are active in green technology. For RHENAC GreenTec AG in Hennef (Sieg), this is particularly true and quite literal. With innovative developments and products under the RHENAC Sports LED brand, RHENAC ensures that plants can grow and thrive well by exposing them to artificial (and energy-saving) light. For more than ten years, the company has relied on CLS (Complete Light Spectrum) light technology, which has been adapted to this application with many years of scientific support. It is the only plant grow light system in the world that can create a flexible light spectrum for sports turf and even mimic sunlight. This light technology not only performs its task better, but also consumes significantly less energy than previously used light sources.

As a result, RHENAC has established one of the leading positions in the market for plant grow lights, has numerous patents in this field and builds complex system solutions for light and irrigation – including for football stadiums. A lot is expected of grass in stadiums. It should be particularly green and resistant to football studs on the day of the match, and of course grow evenly. The mobile and highly automated RHENAC light systems support greenkeepers.


How can an LED light system be positioned over a 7,000 m² turf, moved across the entire area and thus evenly supply the turf with the required light? It goes without saying that the system should not touch the 70-metre-wide green area. The system also needs to be stored as efficiently as possible during rest periods.

The two portals in front of the multifunction arena in Gelsenkirchen
The two portals in front of the multifunction arena in Gelsenkirchen

The RHENAC developers in Gelsenkirchen have come up with a solution that does precisely this. The system consists of two identical portals with main girders made of steel. With a total weight of 190 tonnes, they span the entire width of the football pitch and travel at a speed of more than 12 m/min on rails over the turf. Twelve fold-out B-girders and six infinitely adjustable C-girders, each equipped with around 1,400 LED light modules and a total of more than 100,000 LED lights, can each illuminate a total of 3,500 m², or half of the football pitch. Another special feature: the operating height of the portals can be raised from 1.5 meters (in working position) to up to 4.65 meters (in resting position) to allow buses to pass underneath. This means that the concrete surface, which otherwise provides the pitch with sufficient light outside the arena, serves as an additional car park.  

RHENAC GreenTec AG uses LED lights to provide even illumination of the turf.

Part of the task for the developers was to find the right drive concept. The drives include: precise synchronous travel when moving the 190-tonne and 80-metre-long bridge, as well as reliability in all ambient temperatures and adverse weather conditions – a very demanding requirement profile.


When looking for such a drive concept, the best place to look is obvious when you look at the portal: the basic structure is similar to that of a “lowered” portal crane. The Demag DRS wheel block system was developed as a drive concept for cranes and as a universal component for application solutions. Since then, the wheel block system has proven itself with its reliability and rugged design, and has been used in many applications over the years.

The basic concept of the wheel block: heavy duty travel wheels, which are integrated into a robust and compact housing, can be combined with various electric and geared motors as well as frequency inverters from the Demag modular drive range. For the turf grow light system presented here, Demag engineers recommended wheel blocks of size DRS 400 with a travel wheel diameter of 400 mm and a load capacity of 30 t in combination with compact Demag angular geared brake motors.

16 Demag DRS 400 wheel blocks transport the heavy portals.

The ratio of the weight of the portals (190 tonnes) to the drive power (16 x 3 kW = 48 kW) shows the high efficiency of this rail-mounted drive system. This is underlined by the energy efficiency class IE2 of the speed-controlled Demag electric motors, which have been specially developed for such applications. The multi-layer coating with two-component water-based paint keeps the azure blue geared motors rust-free even under adverse weather conditions in outdoor use.

Demag geared motors ensure powerful and infinitely variable speeds.

The eight drives per portal are synchronised via the frequency inverters, which can also apply a very high torque from standstill and thus ensure smooth start-up and operation.

Special features

From the extensive range of options Demag offers for wheel blocks, the RHENAC and Demag engineers opted for precisely fitting torque brackets and a rail cleaning set on each wheel block.

Rail sweepers are a useful option for Demag DRS wheel blocks when used outdoors.

One of the special features of the RHENAC turf grow light system is the fact that it is installed together with the entire turf in or on a mobile tub, which enables the entire turf to be moved out of the stadium and back in again. This turns the stadium into a multi-purpose arena, and the turf is both protected and maintained (without the shadow cast by the stands). This is also implemented with Demag drive technology. The club, together with the greenkeepers, has already received an accolade for the award-winning pitch.

Three questions to Werner Günther, sales engineer responsible for the project with RHENAC GreenTec AG and the multifunction arena in Gelsenkirchen

Werner Günther, Demag sales engineer

Demag: Mr Günther, what were the initial requirements you received from your project partner?

Werner Günther: As a first step, I received a document with the technical parameters to set in motion two portals for lighting and watering sports pitches. The dead weight of a portal was designed to be 80,000 kg. This colossus needed be moved at a variable speed in a range of 0.8 to 20 m/min over a distance of 120 m.
The special feature was that the portals were to be operated outdoors and calculated with a surface area of 320 m² that is exposed to the wind. The portals needed to be able to operate even in stronger winds with a force of 6 Beaufort. The trailing cable resistance was 2,000 N at the first request. That’s how it all started. In the end, the total load had more than doubled due to theoretical icing to a static load of 192,000 kg.

My notes on the project at the time

Demag: What product features are particularly noteworthy in the drive solution for the portals?

Werner Günther: The use of proven drive technology components. The drive concept performs reliably in all weather conditions. We ultimately decided to use 16 Demag WUE80QD drives with ZBE 100 B4 B050 brake motors to drive 16 Demag DRS 400 wheel blocks during project planning and implementation. The wheel blocks have end connections and accessories, such as rail sweepers. Two Demag frequency inverters are responsible for infinitely variable speeds in the desired speed range of 0.8 to 20 m/min.
The Demag SCU safety control system was integrated by the RHENAC engineers into the higher-level control system and, for example, independently prevents collisions between the two portals during operation.

Demag: Did this project involve any unusual requirements?

Werner Günther: The track gauge of the portals with a span of over 80 m per bridge was particularly noteworthy. The skewing tolerance of max. 1 m must not be exceeded during operation. This requires a high level of synchronisation accuracy for both travel units.

In addition, outdoor operation in itself naturally places high demands on the components. Demag components are designed for operation in temperatures down to minus 20 degrees Celsius and must also cope with ambient conditions such as heat, humidity, ice and snow.

For safety reasons, it is important to know that people are moving over the turf while the portals are moving. The safety requirements for the control system are correspondingly high. In order to meet the safety requirement, eight safety laser scanners are used to monitor operation and transmit information to the Demag SCU safety control system.

Throughout the project, our team worked together with RHENAC GreenTec AG, but also with the other suppliers that made this project possible. From steel builders to hydraulic engineers and control system builders. Good planning and coordination were essential and made this project in Gelsenkirchen a special one.

The Demag modular drive system also demonstrates the variety of options it offers to provide reliable travel solutions to meet specific requirements.