Cleff windscreen heaters
Mode of operation and variants
The beginnings of window heating
The need to clear windows of ice and snow was recognised in the early years of automotive engineering. The first solutions were mechanical, such as manually scraping off ice with special tools or using windscreen wipers in combination with antifreeze. Real progress in windscreen heating development began in the 1960s, when the first heated rear windows were integrated into European production vehicles in particular. Ford was one of the pioneers, launching the first heated rear window in 1969. The technology consisted of fine, electrically conductive wires embedded in the glass surface. This development represented a huge step forward, as it considerably simplified the manual defrosting of rear windows.
While mainly rear windows were heated in the 1960s, applications expanded to include windscreens in the 1970s and 1980s. The integration of heating wires in windscreens was technically more demanding, as the driver's view could not be impaired. The wires therefore had to be extremely thin. During this time, other variants of windscreen heaters also came onto the market, such as heating foils that were applied to the inside of the windscreen. This method also made it possible to offer retrofits for existing vehicles. Such heating systems also began to be integrated into buses and trains in order to increase travelling comfort and safety in cold and damp regions.
In the 1990s, a further technological leap was made with the introduction of metal oxide coatings. These conductive coatings offered several advantages over traditional heating wires: they were invisible, offered more even heat distribution and reduced the impact on the optical quality of the pane. This technology made it possible to efficiently heat even large panes in buses, trains or ships without significantly affecting the weight or structure of the glass. In addition, manufacturers began to pay more attention to energy efficiency at this time, as vehicles became increasingly electrified. The requirements for window heaters changed, particularly with regard to energy consumption and integration into vehicle electronics.
Since the 2000s, window heaters have become increasingly intelligent and efficient. With the advent of electronic controls, it has become possible to develop heating systems that are only activated when they are actually needed. Sensors now automatically recognise when the windscreen heating needs to be switched on, for example when the temperature drops or the humidity inside the vehicle increases. This saves energy and extends the service life of the systems.
Window heaters are now used in a wide variety of vehicle types - from cars, buses and trains to inland waterway vessels - and the development of windscreen heating is continuing in the direction of multifunctionality. Modern window heaters are often equipped with UV protection, sun glare protection and sound-absorbing properties. This is particularly important in electric vehicles, where energy saving and comfort play a central role.
In the future, even lighter, more efficient and more environmentally friendly technologies are likely to be used. These include windows with improved insulating properties that can not only be heated, but also reduce the vehicle's energy consumption through thermal insulation.
Why are window heaters so important?
A major problem in all climatic conditions is the formation of moisture, ice or condensation on the vehicle windows. This can lead to impaired visibility, which not only jeopardises driving comfort, but above all safety. The main task of a window heater is therefore to keep the window surfaces free of frost, fog and moisture.
Tasks of the window heaters
Dehumidification: Condensation often forms on the inside of the windows, especially in the colder months. Window heaters prevent the windows from misting up and thus ensure a clear view. De-icing: In winter, ice or frost can form on the outside of the windows. Window heaters melt this ice quickly and efficiently so that the windows do not have to be scraped clear manually.
How do the window heaters work
The way the windscreen heater works can vary depending on the vehicle type and technology, but the basic principle is similar for all versions: the windscreen is heated by introducing thermal energy and thus remains free of ice and condensation.
Electrical conductor layers: One of the most commonly used methods is the integration of fine, barely visible heating wires into the glass layers. These wires are so thin that they do not impair visibility. When current flows through these wires, the glass pane is heated evenly. This is a common technology, particularly in buses and trains.
Coating technology: Another modern solution is the use of conductive metal oxide coatings that are applied to the surface of the glass. These coatings work in a similar way to heating wires, but generate heat through electrical voltage without having any visible elements in the glass. They offer the advantage of even heat distribution over the entire surface of the pane.
Infrared heating: Some window heating systems work with infrared rays that radiate heat through specially developed heating foils or panels. This technology is often used for particularly large glass surfaces, such as those found on inland waterway vessels. It provides rapid heating and is energy-efficient.
Different versions of window heaters
There are different types of window heaters depending on the vehicle type and application:
Windscreen heating: This type of heating is particularly important for the driver's area. In trains or buses that also drive in extreme weather conditions, the windscreen must be free of snow, ice or condensation at all times. The heating wires or coatings ensure that the windscreen is cleared immediately, thereby offering maximum safety.
Side window heating: Heated side windows play an important role, especially in buses and trains, when passengers want to enjoy the view or the crew have to perform special tasks, e.g. work on the track bed. Here, the windscreen heating not only ensures passenger comfort, but also provides a better view to the outside and therefore increased safety.
Special solutions for inland waterway vessels: Ships travelling on inland waterways often have special requirements, as they travel on open water surfaces both in fog and at extreme temperatures. Large, heated glass windows are often used here.
Additional features: Modern window heating systems from Cleff can also integrate additional functions, such as UV protection or tinting, which reduce the heating of passenger areas. This ensures greater comfort and saves energy at the same time, as air conditioning systems do not have to work as hard.
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Challenges in the development of window heaters
The development of window heaters is a complex task that requires technical expertise and precision. Cleff attaches particular importance to the following challenges:
Energy efficiency: window heaters must be powerful enough to heat the window quickly, but also efficient in terms of energy consumption so as not to put unnecessary strain on the vehicle's batteries or generators.
Weight: In public transport in particular, the additional weight of heated windows must be minimised so as not to increase fuel consumption. Light but stable glass layers with integrated heating technology are crucial here.
Durability: windscreen heaters must be extremely robust in order to function reliably for many years, even in continuous operation. The mechanical loads, weather influences and vibrations require particularly durable materials.
