Economical plain plastic bearings make wind power plants more attractive to private investors
Only a few years ago small wind turbines were manufactured using simple mechanical design and control technology. Today this has evolved into increasingly high-tech products which compare well with larger systems. Currently small wind turbines are used mostly for the power supply of houses, geographical measuring stations or on boats, to support heating systems and feed power into home grids. Going beyond that, experts predict a prosperous future for wind energy in electricity production in developing countries. The “Antaris 2.5” small wind turbine looks set to have a great future – profiting both technically and economically from the igus® polymer plain bearings.
Heyde Windtechnik, located in Dippoldiswalde, Germany, was founded in 2001 and is dedicated, among other things to the production of rotor blades and accessories for small wind turbines. In addition, the complete system “Antaris 2.5“ is offered. This system has a nominal output of 2.5 kW for battery charging, can be used for wind heating as a supplement to solar heating, and to feed power into the home electricity system. In good wind conditions, it is possible to practically halve energy costs for a single family home. In addition to this, there are many applications for small wind turbines in developing countries.
“I wanted to develop a system that is robust, can withstand storms, is free from maintenance, and, especially, is quiet,” says company founder and Managing Director Michael Heyde, who designed the “Antaris 2.5“. ”This is especially important near residential areas, where other systems could not fulfil all these conditions. Naturally it should also be able to withstand all climatic conditions – from Greenland to the Sahara – and work safely even in major storms like Kyrill, which hit Germany in 2006.”
In order to achieve this safety in storms, a special mechanism was designed: the entire generator of the “Antaris 2.5“ system tips with the rotor upwards like a helicopter. This greatly reduces the surface the wind can hit and restricts output. The tip bearings of the rotor were selected from the range of igus® plain plastic bearings. Also, the unit uses flange bearings from the igubal® self- aligning range.
Maintenance – free and economical
Designers can select from a complete range of self-aligning igubal® bearings: rod ends, clevis joints, flange, spherical, and pedestal plain bearings. Self-aligning bearings are easy to fit, adjust to any angular movement, and can in many cases replace special housings. For standard plain bearings there is a spherical ball made of iglidur® W300, a material which gives the lowest friction values in dry operation and has a very low stick-slip tendency, especially important at low loads and for very slow movements. The housing is made of igumid® G, an impact resistant Polymer with long fibre reinforcement. Igubal® products work without problems even under difficult conditions and have excellent corrosion resistance allowing use in damp or wet environments. The igubal® range can be used at temperatures ranging from -30 to +80 °C and do not even need a seal in the case of extreme dirt contamination – regardless of whether it is fine dust or coarse particles. The bearings are used technically dry and have very good vibration damping characteristics in addition to being insensitive to dirt. The lightweight and compact bearings also save costs in two ways: they are inexpensive to purchase and need no maintenance saving both installation and maintenance costs. This final point was the deciding factor for their use in the “Antaris 2.5“ small wind turbine.
Self-lubricating effect as decisive criterion
The secret to the success of igus® products in contrast to traditional bearings, which have a hard shell with a soft coating, is that all iglidur® plain bearings consist of high performance polymers, further improved through the use of precisely adjusted reinforcement materials and solid lubricants. The traditional approach using polymer coated steel can suffer extreme failure due to the sliding layer migrating under heavy loads, edge pressure or vibration. The igus® plain bearings, iglidur®, do not suffer from this as the solid lubricants are mixed homogenously throughout the wall thickness, therefore the lubricant cannot be pushed out of the way when the shaft starts to move.
The individual components of the bearing material are also adjusted to each application, resulting in a range of materials customised perfectly for each application. igus® engineers develop more than 100 polymer compounds every year, testing them in over 3,500 trials and have built up a comprehensive database of the tribological characteristics of the polymer over many years – knowledge that benefits the customer in the long run. In order to find the right bearing for every application, the user can make use of the igubal® expert system. Here it is possible to select from various kinds of loads – radial/axial as well as static, cyclic, and dynamic. The expert system uses this data along with other information to calculate the bearing wear and the theoretical lifespan.
The positive characteristics of the igubal® flange bearings made the decision easy for Michael Heyde to use polymer bearings. “There are mass produced flange bearings made of metal, but these often need to be lubricated, because they corrode, or are too expensive for small wind turbines. I have not been able to find any comparable bearing to the maintenance-free, corrosion resistant, and economical igubal® bearings that has the right mix of characteristics.” In addition, they are easy to fit and are UV resistant. According to the experience of Heyde, the igus® bearings ensure the tipping function even in extreme storms with over 150 km/h wind speed.
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