With new electric school bus technology comes new charging opportunities.
As electric vehicles, including electric school buses, become more common, charging technologies are evolving to offer a range of additional benefits to going electric – above and beyond the standard air quality, climate and economic benefits. Managed charging and vehicle-to-everything/V2X, described below, are two charging technologies with the potential to provide value to electric school bus owners and operators.
An Overview of Charging Technologies
Three broad categories of charging technologies relevant to school bus electrification are:
- Unmanaged charging, in which vehicles are plugged into a charger, and energy flows from the electric grid to the vehicle at the greatest power level possible. Charging takes place at any time with no regard for its impact on the electric grid.
- Managed charging (or “V1G”), in which the time and power level of charging are controlled to maximize benefits to the customer and the electric grid.
- Bidirectional charging (or “Vehicle to Everything/V2X”), a two-way energy flow in which batteries are charged and later discharged using a bidirectional charger.
What is Managed Charging?
Managed charging is the proactive, controlled charging of electric vehicles in a manner that is beneficial to the customer and electric grid either by shifting the time or power level of charging. Managed charging can be broken into two types:
- Passive – relies on influencing customer charging behavior via incentives, guided communications, or varying electricity costs based on time of charging. Most often, these price signals are done through Time-of-Use (TOU) rates that are highest when energy is the most expensive to generate.
- Active – relies on signals from the electric utility or aggregator to a vehicle or charging station to manage charging activity. An example of this is demand response (DR) in which the utility will communicate to program-enrolled customers through varying means (phone call, email, text, etc.) to reduce charging to relieve electricity generation shortfalls or to increase charging to take up excess energy often from renewable generation.
Managed charging can allow for cost savings for customers, remotely scheduled operations, renewable energy integration and reduced energy usage.
The Benefits of Managed Charging
Managed charging can produce benefits for customers and the electric grid. Depending on how it is implemented, managing charging can support various goals, including:
- Cost Savings for Customers – With managed charging, electric vehicle charging can take place outside of peak demand periods, when energy is being used by the most customers, which often results in lower rates and/or an electricity bill credit.
- Remote Scheduled Operation – Managed charging can be done remotely or at planned intervals, allowing operators and drivers to be absent during the actual charging session, which often lasts several hours. This is especially important with electric school buses because the most opportune time for charging is often overnight when staff is unavailable.
- Renewable Energy Integration – Electric vehicles can charge when there is peak renewable energy production for sources like solar and wind. This can increase the overall output of renewable energy by reducing instances of curtailment, in which renewable energy production is intentionally decreased below maximum output to match demand.
- Energy Use Reduction – Electric vehicle charging can be delayed or shifted to avoid electricity outages when available energy supply does not match anticipated demand. Reducing energy use (load) can also help reduce greenhouse gas emissions through avoidance of having to start up less efficient and more polluting generators, called peakers, to meet these shortfalls. Moreover, these peaker units are often located in disadvantaged communities.
Why Managed Charging and Electric School Buses?
Electric school buses are well positioned to deliver on the many benefits of managed charging:
School Districts Save Money
Managed charging offers school districts and other school bus operators the opportunity to charge when electricity prices are lower, saving precious funds that – in the case of school districts – can be repurposed for other critical student needs. This can help school districts make the financial case for electric school buses.
Duty Cycles & Large Batteries Enable Renewable Energy Storage
Electric school buses and their high-capacity batteries are a perfect fit for storing renewable energy – whether it’s on-site renewable generation from devices like solar canopies or utility-scale renewable energy – as the buses have long periods of time sitting unused.
The Scale of the U.S. School Bus Fleet
Managed charging of electric school buses could have positive impacts on the grid, especially given the scale of the overall fleet. If all the nearly half a million school buses in the United States were to be upgraded to electric or repowered, the result would be over 60 GW of new load on the electric grid – requiring massive upgrades in generation, transmission and distribution capabilities and costs which are passed along to customers through electricity rate increases. Managed charging represents one of the most cost-effective strategies to mitigate negative effects from increasing electric vehicle loads on the electric grid, potentially deferring some electric grid investments and avoiding high electricity prices when charging. For example, having electric school buses charge overnight moves the load away from the peak to a period when electricity demand is the lowest.
What is V2X?
V2X stands for vehicle-to-everything, an all-encompassing energy technology concept in which an electric vehicle is viewed as a mobile battery, and stored energy in the vehicle can be discharged for some benefit.
V2X can be applied in different ways depending on the end use. Four applications are described in the chart below.
|Vehicle-to-Building/Home (V2B/H): Stored energy is discharged to a building or home, usually to provide backup power or avoid peak energy use demand charges.||Vehicle-to-Grid (V2G): Stored energy is discharged beyond the site meter out to the greater electric grid with the purpose of mitigating peak energy demand and/or for compensation of the site owner.|
|Vehicle-to-Load (V2L): Stored energy is discharged to provide power for some other energy load, such as powering construction equipment or other independent energy consuming devices.||Vehicle-Grid-Integration (VGI): Charging and discharging of the vehicles is done in coordination with grid demand to work as a grid asset.|
The Benefits of V2X
V2X technologies offer a variety of benefits to vehicle owners and grid operators. These include:
- Grid Flexibility – V2X services provide grid operators with an on-demand source of power which can be utilized during high energy demand periods, either directly providing energy back to the grid or temporarily satisfying end use power requirements of a building, home, or other load.
- Opportunities for Compensation – Vehicle owners, such as school districts and other operators, can be financially compensated for the V2X services they provide to the electric grid. This may come in the form of an electricity bill credit to offset other electricity consumed at the site.
- Emergency Preparedness – In times of emergency, there may be electric utility power outages or power disconnects, but V2X services can supply back-up power for shelters, homes, command centers, and other locations.
- Support of Renewables – V2X enables more efficient use of energy from renewable resources by storing excess renewable energy when it is abundant and releasing that energy when it is not.
V2X can enable grid flexibility, opportunities for compensation, better emergency preparedness and support for renewable energy.
Why V2X and Electric School Buses?
While the use of electric school buses to store energy and discharge it back into the grid or a building is in an early stage, the characteristics of electric school buses make them strong candidates for V2X applications. Here’s why:
Predictable Operating Schedules
School buses typically have early morning and afternoon routes, Monday through Friday, during the school year.
Electric school buses and V2X can easily be used during evening peak demand periods or the summer season when the buses are available for grid services like demand response and balancing electricity supply and demand.
Large Battery Capacity
A typical electric school bus has a battery between 100-200 kWh, providing plenty of usable capacity for different V2X services.
Benefits for School Districts
Even in the absence of official compensation avenues, electric school buses and V2X can provide numerous benefits to school districts and transportation contractors, including reduced electricity charges and renewable energy integration.
As mobile power units, electric school buses can provide backup power during emergencies and power outages at schools or remote locations like emergency response command centers.
3 Design Considerations for Electric School Bus V2G Programs
Utilities in a diverse range of locations across the United States have launched electric school bus V2G pilot programs. We have catalogued these early efforts and offer three design considerations for Electric School Bus V2G programs:
- Does the program prioritize an equity-first approach when selecting partners and locations?
- Does the program consider new rates to enable school bus electrification and V2G applications?
- Does the program help drive community resilience?
Read our full post on V2G design considerations for details.