One of my favourite things about this job is hearing how the products that I write about are used in the real world. Normally these are in popular applications, such as datacentres and EV powertrains, but occasionally one pops up that is totally unique. Recently, I talked to Vicor, and its customer, BetterFrost, about one such application.
We take many things for granted, and never try think of a better way of achieving them. Tasks like de-icing wind shields. A hot air blower, often in combination with heating elements in the glass, does a decent job, and that technique has been used for many decades, but could that be improved?
BetterFrost was founded specifically to answer that question. The company’s CEO, Derrick Redding explains, “internal combustion engines used to have plenty of waste heat. It's still inefficient to flood a surface with heat, even if you posses an almost unlimited supply. EVs don’t have that natural heat source, and today’s hybrid and ICE engines are getting so efficient they can't generate enough waste heat, so they're having to use secondary heaters.”
He continues, “our technology came from the ice lab at Dartmouth College of Engineering. One physicist there studied the way ice bonds on the surfaces and the best way to release it, using the least amount of energy. His key insight was to only melt the 0.1mm think interfacial layer, and then the ice will release. The most efficient way to achieve that is to pulse power to control how heat penetrates the surface and goes no farther than that interfacial lair.”
To achieve this, BetterFrost uses the transparent conductive oxide layer that is already integrated into the screen to provide infrared-reflecting properties. Unlike the resistance wires in a rear screen, the film is invisible and heats the whole surface evenly. The layer is heated using high power pulses, which confines the heat to the interfacial layer. This is impossible to achieve at lower power levels. The frequency of the waveform shifts continuously as the surface warms, and it must be precise enough not to crack the glass. The voltage used can vary from 48V up to the battery voltage.
Testing has shown that measured against the FMVSS 103 defrost standard, the system uses 95–96% less energy than conventional air defrost, and 98–99% in commercial vehicles. An Alaskan test cleared a two-square-metre wind shield in 80 seconds, while the truck's own air defrost took 51 minutes. The same technique can also be used for demisting on the move. This is important for EVs that fog up far more readily than ICE vehicles.
BetterFrost was assisted by Vicor in getting the design up and running. Current is supplied through bus bars and connected in the same way as resistive heating. A compact Vicor step-down converter feeds the bus bars. BetterFrosts main contribution is the software that controls the pulses, along with assisting OEMs through specification, prototyping and validation.
