Modeling electric vehicles

Transportation Optimization supports the definition of transportation assets as electric vehicles. You define these vehicles and their charging requirements using the following input tables:

• Electric Vehicle Battery Definitions – Use this table to define vehicle batteries, their capacity, energy consumption per distance and charging options.
• Battery Charging Option Definitions – Define battery charging speed in terms of C-Rate. The C-Rate for a given charger-battery combination is the number of batteries that can be fully charged from 0 to 100% in one hour. You can also define the fixed and variable costs for charging.
• Charging Option Assignments – Use this table to associate batteries, charging options and sites where batteries can be charged.

You then populate the Battery column in the Transportation Assets input table using the batteries defined in the Electric Vehicle Battery Definitions table. Assets that include a battery are assumed to be fully charged at the start of the route. When they visit a charging station (a site with the appropriate Charging Option Assignment), the battery can be recharged.

When a battery is charged at a site, the time required to charge the battery is counted as service time for the asset driver. If you have populated the Service Time Cost in the Rate table, the cost incurred is added to the battery charging cost and is included in the final route cost.

Defining electric vehicle batteries

The Electric Vehicle Battery Definitions table is where you create the specifications for the batteries that can be used in Transportation Assets. You specify the battery capacity in kilowatt hours, the consumption rate per distance unit, and the actual distance unit to be used. This information determines the distance range for the vehicle before the battery needs to be recharged. For example, if the Battery Capacity is 100 kWh, the Per Distance Consumption Rate is 1 kWh and the Consumption Rate Distance Basis is MI, then the range of the vehicle is 100 miles. The range is also affected by the Maximum Capacity, the Minimum Charge Percentage and the Maximum Charge Percentage of the battery.

Defining battery charging options

Battery charging options allow you to define how quickly batteries can be charged. The Charging Speed is in terms of the number of batteries that can be charged in one hour. The charging options also provide costing options - the Fixed Cost is incurred whenever the charging option is used, while the Variable Cost is incurred for each unit of charge using this charging option. These costs are reflected in the Activity Cost in the Route Details table, which shows the sum of Fixed Cost and Variable Cost incurred during the charging round. Additionally, if Service Time Cost is populated in the Rate table, service cost is incurred as the battery is charging and is included in the Service Time Cost in the Route Summary table. The final charge cost is added to the Route Cost in the Route Summary table.

Assigning battery charging options

The Charging Option Assignments table defines which charging options are available at a given site, and which batteries can be charged at that site using the specified charging option.

Requirements:

• For an asset with a Battery selected to be used, there must be at least one Charging Option Assignments record for that battery. This ensures that vehicles with electric batteries can receive charges in the solution.
• When an asset has Round Trip set to "Yes", and discharges before reaching its domicile, then it will stop at a different charging station to charge if possible. By default, every time the asset comes back to its origin, it is charged to the maximum capacity irrespective of how much charge remained at the end of the route.
• In the case of fleet optimization, the asset domicile must have charging options assigned so that the asset can recharge whenever it returns to the domicile before starting another route.