Aerodynamics' Influence on Performance in Human-Powered Vehicles for Sustainable Transportation 2024-37-0028

The issue of greenhouse gas (GHG) emissions from the transportation sector is widely acknowledged. Recent years have witnessed a push towards the electrification of cars, with many considering it the optimal solution to address this problem. However, the substantial battery packs utilized in electric vehicles contribute to a considerable embedded ecological footprint. Research has highlighted that, depending on the vehicle's size, tens or even hundreds of thousands of kilometers are required to offset this environmental burden. Human-powered vehicles (HPVs), thanks to their smaller size, are inherently much cleaner means of transportation, yet their limited speed impedes widespread adoption for mid-range and long-range trips, favoring cars, especially in rural areas. This paper addresses the challenge of HPV speed, limited by their low input power and non-optimal distribution of the resistive forces. The article explores dissipation sources from rolling resistance, aerodynamics, ground slope and inertia for various vehicles, emphasizing the increasing significance of aerodynamic resistance for HPVs. In fact, it is here shown that, for classical non-enclosed bicycles, aerodynamic resistance is typically higher than rolling resistance. Enclosed HPVs, specifically velomobiles, are then proposed as a solution. Their low drag results in a distribution of the various dissipation sources more similar to that of a car than that of a bicycle. Furthermore their use in tandem for long rural trips is particularly efficient, exceeding the 40 km/h threshold with only 75 W/rider and negligible battery consumption. Urban trips, with heavy traffic, may favour non-faired bicycles over velomobiles. However, the latter remain valuable in average to low traffic conditions and offer a decisive advantage when the weather conditions are non optimal. This analysis contributes insights into optimizing the design and efficiency of HPVs, showcasing velomobiles as a promising solution for sustainable and efficient transportation, alternative to cars.