Managed electric vehicle (EV) charging balances vehicle energy needs and site energy control objectives. Managed charging can ensure that fleet vehicles are properly powered when needed, while reducing unnecessary burden on the site's building infrastructure and supporting a more reliable and resilient grid.
In the case of federal fleets, managed charging can have two distinct connotations:
- Networked or "smart" electric vehicle supply equipment (EVSE) units that can adjust power levels or shift charging sessions.
- Human planning to optimize charging and reduce EVSE deployment needs. This solution can be less expensive but may require drivers to program their vehicles to charge according to agency policy.
No matter which type of managed charging is chosen, human ingenuity and flexibility is necessary in any networked or non-networked EVSE approach. The benefits of managed charging can range from reducing on-site equipment upgrades, maximizing the value of local generation, harnessing lower time of use (TOU) rates for EV charging, or providing grid services.
Managed Charging with Smart EVSE
Smart EVSE, capable of providing managed charging services, are designed with sophisticated features that often require a network connection. The graphic above outlines common types of EVSE features, as detailed in the National Renewable Energy Laboratory's Electric Vehicle Supply Equipment Tiger Team Site Assessment Findings from Army Facilities report. Certain EVSE can also share power from a single circuit and power two EVSE simultaneously. This strategy can reduce the need for service panel replacements or other electrical upgrades and only reduces power to a vehicle when both ports are occupied, to conserve load.
EV charging can be controlled by a separate controller or at the service panel, or in conjunction with smart, solid-state breakers that do not need to be manually reengaged. These solutions can convert the simplest EVSE units into a smart charging solution. Networked EVSE may also aid by reporting energy consumption and billing privately owned vehicles for workplace and visitor charging.
Managed Charging through Human Planning
Managed charging through human planning works with basic EVSE (without data controls) and with networked EVSE. The building manager, energy manager, and fleet manager can coordinate to schedule vehicle charging during lower TOU rates, which can save the site money, or schedule charging during hours when the grid electricity mix is cleaner, which can allow for further site decarbonization. For example, if electricity costs $0.20/kWh from 6:00 a.m. to 12:00 a.m. and $0.05/kWh from 12:00 a.m. to 6:00 a.m., the EVSE could be set to charge starting at 12:00 a.m. However, if a vehicle needed to drive at 2:00 a.m., then the fleet and building managers would have to communicate to ensure that human planning for managed charging met the fleet and site needs.
Most utilities charge a demand rate for the most energy consumed in a 15-minute period over the course of a month. To avoid all vehicles charging at the same time, networked chargers can set EVs to start charging at different points in time (e.g., 1/3 of the EVSE units begin charging at 5:00 p.m., 1/3 begin at 10:00 p.m., and 1/3 begin at 3:00 a.m.). Actual optimal timing will depend on other facility loads and fleet needs. Fleet managers should work with facility managers to set charging times. More detailed information about managed charging can be found in the FEMP ZEV Implementation Guide for Federal Agencies.