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Smart Glass could reduce AC loads

German parts giant Continental used the recent Consumer Electronics Show in Las Vegas to demonstrate its latest work in “intelligent glass control” – or self-dimming window glass – which could have a major impact on the HVAC sector by reducing the load on the vehicle’s air conditioning unit.

Continental intelligent glass control
Continental intelligent glass control

Continental claims the latest technology allows it to insert special films into the glass and which can change their transparency – when on the move, or when parked – through electronic control signals. 

As well as safety benefits brought with improved driver visibility, the intelligent tinting system – which brings “selective, incremental darkening” of the side and rear windows – also has obvious advantages in terms of occupant comfort and vehicle environmental performance.

According to the head of Continental’s body and security business unit, Andreas Wolf, the new films can reduce solar radiation more effectively than with other technologies, which means “we can keep the heat out of the the vehicle and significantly reduce the interior temperature”.

In taking a load off the air conditioning unit, vehicle manufacturers could therefore install smaller, lighter and more energy efficient HVAC systems, and could potentially do away with sun visors and other components such as mechanical blinds, further reducing weight.

“Our calculations have shown that the CO2 emissions are reduced by a good four grams per kilometre thanks to these measures, thus increasing the range of electric vehicles by around 5.5 per cent,” Wolf says. 

While auto-dimming windows have been available for some time – using films in which embedded particles can be aligned when a voltage is applied, allowing the use of targeted window darkening – Continental claims that the technology has, up until now, only been feasible in the roof area and therefore limited to a small number of high-end vehicles. 

The test vehicle shown at CES, however, demonstrates the intelligent activation of “suspended particle device” film technology for a broader surface area including the windscreen and the side and rear windows. 

Due to legal requirements, the technology was initially only shown in the permitted area of the sun visors. But that has not stopped Continental pushing for change with the film technology it claims is ready for production. 

Wolf explains that the latest technology is based on embedded particles which arrange themselves randomly when unpowered and darken the window from outside, while retaining transparency from the inside to the outside. 

“If a voltage is applied, the particles systematically align themselves in parallel, so that the window becomes permeable to light in both directions,” he says. “The connection to the vehicle system enables the windows to lighten automatically when you approach the vehicle with a key or smartphone.”

The company admits the film is “still rather cost-intensive”, particularly for mid-range vehicles with large glazed areas. It also acknowledges that there are other alternatives to film technology, such as liquid crystal polymers or “electrochromism”. The latter uses the ability of molecules and crystals to change their optical properties under the influence of an electric field or a current flow. 

As each of these technologies must be electronically controlled, Continental says the crux of the matter is in the software and the intelligent connection to the vehicle system. 

In other words, “control is what counts most”.

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