Bearing up to solar challenge
November 1st 2008

Rapidly growing technology company, Conergy, uses components from igus to ensure that its new solar tracking system runs maintenance-free for long periods – even in extremes of weather

SolarOptimus tracking is fitted to the latest Conergy photovoltaic systems. The twin drive systems are controlled by an astronomical algorithm which increases the production efficiency of eco-friendly energy. The system has the task of always optimising the alignment of the photovoltaic generators; The company says investment pays off for the operator because energy production can be increased by more than 30% by twin-axis tracking systems.

In Northern Europe, this optimum position detection always moves to the brightest spot in cloudy conditions. In Southern Europe, where the sky is often cloudless and there is a high brightness level, a system that keeps the photovoltaic modules at a right angle to sunray incidence on the basis of astronomical data is more effective.

During development of the frame system, the main focus was on durability and maintenance freedom, since the systems are often set up in remote areas without any on-site personnel. For this reason, the developers consciously eliminated complex drive systems, preferring to use components that have a straightforward but high quality design.

This applies to both the motors and the bearings.

Bernd Krabbe, project management for the SolarOptimus development, comments "We explained our requirements to several suppliers of bearings systems and asked for their solutions." It had to be considered that the set-up locations for the solar systems are often very dry, with high levels of sand and fine dust. Another factor is the very wide temperature spectrum across which the bearings have to work.

All bearing points of the SolarOptimus are equipped with igus products. On the main axes of the frame systems, which are about 20m long, iglidur plastic bearings ensure low friction and maintenance-free operation. The built-in solid lubricant of the high performance polymer ensures that no lubricants have to be added. This is a precondition for the long service life of the bearing under the given conditions.

With iglidur G, Conergy is using the 'allrounder' among the numerous iglidur materials, which is suitable for pivoting and rotary movements at low to medium speed. These bearings are said to operate in dirty, dusty conditions without any problem.

To reduce the strain on the drive systems, Conergy used linear bearings in the adjustment systems. DryLin linear plain bearings guarantee the exact linear motion of the axes. The dryLin W bearing slides on a hard anodised aluminium rail profile, the combination gives low-friction running without 'stick/slip' effects. igus adapted the mounting plate for the moving components to meet the requirements of the Conergy developers. Sand and dust have no effect on the bearing; debris is simply pushed away by a snowplough effect without affecting the gliding properties.

igubal rod end bearings are used for the couplings which link the solar module carriers together. These connecting parts absorb high forces, have good damping properties and are said to weigh five times less than conventional metallic bearings.

Even if there is fine or coarse dust present, there is no danger of seizing or blocking, and integrated solid lubricants ensure low friction with maximum abrasion resistance.

The drives of the module frames, which are responsible for the north-south alignment, apply a force of 6800N; the drive of the main frames for east-west tracking 10 000N. Speed is low at max.

4mm/s, and the drive is moved through a maximum of one revolution/day.

Nevertheless, high demands are made on wear resistance because the environmental conditions affect all components. igus carried our a series of tests for Conergy, and had abrasive sand flown in from Southern Spain, where the first SolarOptimus systems have been installed.

Results showed that even under conditions that are rougher than in reality, the igus bearings did not have to be replaced over the entire calculated service life of the Solar Optimus. This applies to the UV resistance of the plastic as well as the wide temperature range and humidity.

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