Relocating automated shuttles during the day can cut fleet size requirements by up to 26 percent, finds analysis.

The model, which seeks to optimize fleet sizes for single-passenger automated electric vehicles, also found that vehicle-relocation efforts could also cut the number of required charging stations in half.

Date Posted
04/23/2019
Identifier
2019-B01365
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Joint Fleet Sizing and Charging System Planning for Autonomous Electric Vehicles

Summary Information

Autonomous vehicles are expected to significantly alter the way that cities approach transportation. Because they do not require an operator, they would likely be significantly cheaper to run, but more expensive to purchase. They are also anticipated to provide significant benefits in efficiency and emissions reduction, both of which may be magnified by also converting from conventional to electric engines. Such Automated Electric Vehicles (AEVs) would even be able to route themselves to charging stations, allowing for still more efficient operations.



While such technology is still a significant distance from being actualized on a meaningful scale, it is possible to consider and proactively address some key business model concerns. This paper, funded by the US Department of Energy Vehicle Technologies Office, seeks to define a fleet-sizing algorithm and to understand optimal charging-system planning.



By optimizing both of these factors, an AEV-based system can minimize the down-time of waiting for vehicles to adequately charge and return to their route, as well as avoiding unnecessary fleet expenditures for redundant vehicles.



The researchers created a network model and performed a mathematical analysis to understand how theoretical AEVs would behave given certain environmental parameters. This knowledge was then applied to a case study with a 25-node network and approximately 15,000 trips per day. Three benchmarks were used for comparison to evaluate the efficacy of the researchers' proposed strategy: MinTime, where AEVs always chose the most direct routes to their destinations, MinOperations, where AEVs chose the route that minimized the operation cost, and NoRelocation, where vehicles were not relocated by an operator throughout the day.



The analysis found that a total of 2,500 AEVs and 300 chargers were needed to meet the demand of 15,000 trips per day. This means that each AEV can complete 6 rides and each charger can fuel 8 AEVs on average.

The analysts' proposed model is the most beneficial for both passenger and goods transportation. It reduced investment costs by 4.4 percent for passenger transportation and 8.8 percent for goods transportation.

The MinTime strategy, because it disregards operational costs, caused an increase in total costs of up to 8.1 percent, depending on how dominant of a cost factor electricity was. However, the model found planning results similar to those of MinOperation.

MinOperation performed overall similarly to the analysts' proposed model, with similar operational costs. However, the analysts' model has an up-front investment cost that is approximately 5 percent lower than the MinOperation model.

Analysis of the NoRelocation model found that services that did not relocate AEVs over the course of the day required approximately 26.5 percent more vehicles in their fleets. At the same time, the number of required chargers nearly doubled, representing an investment cost that is approximately 41 percent higher than the optimized model.

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