Volvo has filed a patent with the European Patent Office proposing a novel method to reduce aerodynamic drag and improve efficiency by heating a vehicle’s window surfaces. Using the existing interior heating system, the warmed windows lower the density of the boundary layer of air moving over the car, leading to reduced drag, enhanced fuel or energy efficiency, and a higher top speed.
Targeted Heating for Optimal Aerodynamics
Reducing the density of air in a vehicle’s boundary layer decreases aerodynamic drag, and Volvo proposes achieving this by heating the car’s window surfaces. Heating the entire outer surface is impractical due to high energy demands, but Volvo’s innovative approach uses the vehicle’s existing HVAC system to warm only the windows. This targeted heating reduces drag, resulting in improved efficiency, lower fuel consumption (or energy use in EVs), and a higher top speed, making it a practical and beneficial solution.
Warm-Weather Limitations of Volvo’s Concept
We have questions that are not addressed in Volvo’s patent, for example, how the windows would be heated. In cold weather, the HVAC system blows hot air onto the windows to defog them and to keep the cabin warm, but this might heat the glass unevenly. A rear window (and some windshields) have electric heating elements in them that heat the glass uniformly, but instead of making use of free powertrain heat like the HVAC system, these heaters are power-hungry, reducing the advantages of the lower aerodynamic drag.
Volvo has not addressed how it proposes to heat the windows uniformly without incurring losses that might negate the advantages. And in warmer weather, the glass would have to be heated electrically, since the heater won’t be running and isn’t needed. At the moment, Volvo’s idea seems good in theory, but various questions would have to be answered satisfactorily for it to prove its worth in practice.
