Compressed Air Vehicles

Abstract

In the face of the climate crisis, petroleum dependence, and volatile gasoline prices, it is imperative to explore possible opportunities in unconventional alternative-fuel vehicles. One such option is the compressed air vehicle (CAV), or air car, powered by a pneumatic motor and onboard high-pressure gas tank. Although proponents claim that CAVs offer environmental and economic benefits over conventional vehicles, the technology has until recently not been subject to a rigorous analysis. This study characterizes the potential performance of CAVs in terms of fuel economy, driving range, carbon footprint, and fuel costs and examines their viability as a transportation option as compared with gasoline and electric vehicles. Subjects of analysis include energy density of compressed air, thermodynamic losses of expansion, CAV efficiency on a pump-to-wheels and well-to-wheels basis, and comparisons with gasoline and electric vehicles. Results show that although the CAV is a bold, unconventional solution for today's transportation challenges, it is ultimately not workable, and compares poorly with gasoline and electric vehicles in all environmental and economic metrics. Further, applications of the CAV are severely constrained because of its limited driving range. The results from this study, including the analysis of energy density and expansion losses, may be used to identify future opportunities for CAV applications. The pump-to-wheels and well-to-wheels methodology contained here establishes a framework for evaluating future CAV designs.