Note: To magnify any graphic, click once or twice on it.1. Background 1a. Residence Time of Mass Element in Reservoir In descriptions of material flow, residence time refers to the average length of time a molecule spends in a container. For a container that is simultaneously filled and emptied, the steady state molecular residence time […]
Various methods of determining the energetic performance of vehicles were described and compared. Earlier work emphasized maximum vehicle power and theoretical performance limits, and characterized the vehicle or payload in terms of weight. Energetic economy was calculated here as the payload mass times distance moved divided by thermal energy used. This economy was multiplied by average speed to yield an energetic performance parameter that was expressed in seconds, using SI units. The differential form of this parameter was twice the useful payload kinetic energy divided by thermal power expenditure. This ratio of fundamental quantities was shown to be inversely proportional to a performance parameter originally defined by Gabrielli and von Karman in 1950. A transportation matrix was developed, describing how vehicles are most commonly used in terms of speed, energetic economy, emissive economy, payload mass and energetic performance. Vehicles with the highest level of energetic performance have efficient powerplants, high payload to gross mass ratios, or reduced friction with the surrounding environment. For steady state conditions, energetic performance was shown to equal twice the residence time (or storage time) of an infinitesimal fuel energy element as payload kinetic energy. General application of energetic residence time as a measure of emissions leveraging and thermodynamic reversibility was proposed.
Energy flow analysis reveals an extremely cost-effective strategy to personally address global climate change by reducing transportation related carbon dioxide emissions. The specific recommendation is to ride an electric bicycle, rather than drive an automobile, as frequently as one is comfortable doing so. Human powered vehicles are typically less effective abatement means, due to greenhouse gas emissions associated with human food production, delivery, storage, preparation and waste. Presentation format is graphical and non-mathematical.