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 — and now plastic bearings from igus are helping to make the most of the technology
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.
As an example, plastic bearings manufacturer igus cites the ‘Antaris 2.5’ small wind turbine from Heyde Windtechnik of Dippoldiswalde, Germany, as looking set to have a great future – profiting both technically and economically from the use of igus polymer plain bearings. This turbine has a nominal output of 2.5kW 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 practically to halve energy costs for a single family home.
“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. The unit also 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.
Housings are 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 +80degC 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
One 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.
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 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.
