Elsevier

Applied Soft Computing

Volume 67, June 2018, Pages 519-528
Applied Soft Computing

Location optimization for multiple types of charging stations for electric scooters

https://doi.org/10.1016/j.asoc.2018.02.038Get rights and content

Highlights

  • A Multi-Objective Particle Swarm Optimization for location-allocation problem.

  • The characteristics consider the population density and land cost.

  • The compound site selection considering recharging station and battery exchange station for e-scooter.

Abstract

The difference between traditional scooters and electric scooters is the convenience of refueling and charging process. Designing a complete infrastructure system is a necessary step if efforts to promote e-scooters are to meet with success. This study discusses the optimal location problem of locating charging stations—which is generally considered a location-allocation problem. There are two types of charging stations: charge stations and battery-exchange stations. The only one model in determining the location of either type of station tends to decrease the traditional utility compared to compound model traditional as this method tends not to set stations where they would serve the greatest number of customers. In addition, population density and land cost should be taken into account in determining where stations are set. We, therefore, propose a method that accounts for differences in population density and land cost in order to solve a multi-objective problem with maximum utility at minimum cost. A mathematical model is developed in which constraints pertaining to capacity and distance are considered. To find an optimal parameter for Multi-Objective Particle Swarm Optimization (MOPSO), generational distance (GD), maximum spread, spacing, and diversity metrics are applied. Finally, we research an angle-based focus method and determine the extent to which stations would be used in order to determine the optimal proportions of charging stations and battery-exchange stations. Moreover, according to the analysis we found that the installed ratio model of BES/BCS (Battery-exchange stations/Battery charging stations) is 6:5 in the downtown area and 1:6 in the outskirts of high population density areas. Besides, the BES/BCS ratio model is 1:13 in the downtown and only BCSs are installed in the outskirts of the low population density area.

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A Multi-Objective Particle Swarm Optimization for location-allocation problem is developed to minimize total cost and maximize service capacity considering land price, service distance, and installation capacity at each station.

Introduction

About 15 percent of manmade carbon dioxide comes from cars, trucks, airplanes, ships, and other vehicles. Reducing transportation emissions, therefore, is one of the most critical steps in fighting global warming. Environmentally friendly means of personal transportation such as electric cars, e-scooters, and electric bikes are among the solutions available and have become the subject of increasing attention as global warming has worsened. In particular, e-scooters may constitute a viable form of transportation given that they create less pollution than fuel scooters do [1]. However, in order to promote e-cars, e-scooters, and e-bikes effectively, it is necessary to consider not only the performance and efficiency gains associated with the power trains used in these vehicles but also the customer’s experience.

There are two issues in regard to determining the location of BES/BCS systems: station type and station location. According to Wang and Lin [2], the main purpose of facility planning is that of determining the locations of multi-type stations, i.e., those that combine BES and BCS systems to that customers can access various stations and convenient battery refills. You and Hsieh [3] identified number, location, and type as three key parameters for stations that are necessary to consider in planning BES/BCS systems. They also concluded that location and station type should be given the most weight when stringent cost limitations are involved. Two cost limitations are discussed in the present study: the land cost of the location and the installation cost of battery-refill systems. Undoubtedly, the land cost is a fundamental issue to address in the location-allocation problem. Doong, Lai, and Wu stated that final location decisions are affected by various land costs associated with candidate areas. It should be expected, therefore, that land cost together with the installation costs of the two battery-refill systems, BES and BCS, are matters of great concern in location-allocation decisions. When only one type of battery-refill system is used at a station, however, the extent to which that station used can be expected to be limited.

In the present investigation, our goal is to understand the optimal facility location decision in regard to the highest numbers of times a station is used of the refill system. A hybrid refill system allocation in various land cost conditions can provide an optimal solution to the problem presented by the short battery life of e-scooters and the inconvenience of refilling, thereby providing a foundation for increasing the sale and use of this form of transportation.

This paper only focuses on the locations and allocations of battery-exchange station (BES) systems and battery-charging station (BCS) systems for e-scooters. Although charging and battery-exchange stations could provide services to almost all types of electric mobility devices, the assumptions and problems should be studied separately. The objective is to maximize the cover rate of electric scooters’ customers instead of other types of electric mobility devices such as vehicles and bicycles, because maximum distance acceptable to customer for various mobility devices are different. For example, electric vehicles may have longer acceptable distance than electric scooters. Furthermore, the socket outlet, and required voltage are substantial different in electric mobility devices. The required power loading for the charging and battery-exchange stations is relatively small comparing to general electric cars. Charging electric scooters requires a regular household outlet of 115VAC, 15A, and produces about 1.5 kW, and the charge time is 7–30 h depending on battery size. Usually electric scooters prefer to have the battery-exchange service or overnight charging requirements. On other hand, electric vehicles require 230VAC, 30A two pole, and produces about 7 kW to charge a mid-sized electric vehicle in 4–5 hours. In this case, candidate locations such as convenient store, supermarket, and malls have the capabilities of setup the extra charging services using regular household outlet.

In the present study, we review the literature on the location-allocation problem, present a Multi-Objective Particle Swarm Optimization (MOPSO) algorithm, describe the design and verify our mathematical model and algorithm, and analyze the critical parameters and Pareto-optimal front. We also provide a conclusion and suggest directions for future research.

Section snippets

Related work

Cooper defined the location-allocation problem in terms of the need to provide goods or services to satisfy a spatially dispersed demand. Based on this definition, in regard to the subject of the present study, when there is a demand for battery-refill services at a large number of widely dispersed sites, it is usually impossible to provide the service everywhere. Therefore, it is necessary to engage in a process of decision-making aimed at effecting optimization in a continual way under cost

Mathematical model

The problem considered in the present study can be described as follows. There are i customer nodes and j charging stations, and each of the latter is located in either a high- or a low-price area. The objective is to minimize the total cost of setting charging stations and to maximize the total number of customers served.

ICustomer nodesi={1,2,,|I|}I
JCharging stationsj={1,2,,|J|}J
AAreaa={1,2,|A|}A

Parameters:

dijaDistance from customer i to charging station j in area a
PaLand cost of area a

Model evaluation

In this section, we describe how we implemented the mathematical models and verified the algorithm coding. The generational distance (GD), maximum spread (MS), spacing (S), and diversity metric (Δ) were used to determine the optimal learning factor with the MOPSO algorithm. The optimal learning factor was inputted into the algorithm to explore the generated Pareto front by using a dual-objective PSO. The front solution was analyzed in three stages: stage 1, which involved a case analysis of

Conclusion and future research

In this study, a multi-objective MILP model for the location-allocation optimization problem by applying the PSO algorithm was proposed. The location and allocation decisions are optimized in reference to minimum total cost and maximum service capacity as two objectives and in reference to land price, service distance, and installation capacity at each station as the limitations. This study used Ilog Cplex 9.0 to develop the mathematical optimization model as a comparison to the PSO algorithm.

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