Flipping the Switch on Electric School Buses: Infrastructure Planning and Solutions: Module 1 (Text Version)

This is a text version of the video for Flipping the Switch on Electric School Buses: Infrastructure Planning and Solutions: Module 1.

Welcome to Part 5 of the Flipping the Switch on Electric School Buses series where we will discuss electric school bus infrastructure planning and solutions. The Flipping the Switch series contains a number of parts on electric school bus technical assistance. This is currently where we are at in the series. In the upcoming parts we will discuss infrastructure planning and solutions, vehicle in-use performance, training for both drivers and technicians, and then finally cost factors. Part 5 of the Flipping the Switch Series: Infrastructure Planning and Solutions consists of two modules. Module 1, which is the module we're talking about today, provides an overview of electric school bus charging infrastructure interconnection challenges and solutions, including utility structure, grid and facility considerations, and possible interconnection solutions. Module 2 will discuss electric school buses and provides an overview of vehicle-to-grid barriers and opportunities.

Now, let's get started with Module 1 of Infrastructure Planning and Solutions: Interconnection Challenges and Solutions. Similar to other electric vehicles, the energy needs for a battery electric bus will be primarily provided by the grid. The electric grid provides power to buildings, vehicle chargers, and other loads through a series of distribution equipment, such as substations, transformers, and conductors or wires. In order to provide customers with the power they need, utility companies must design each of the elements in this system to be capable of supporting the highest power demand. The highest power demand is sometimes referred to as the coincident load, which is defined as the point at which the sum of all loads is the highest. The coincident can sometimes be a result of home running its air conditioning at the same time the EV in the garage is charging up. The sum of these two loads would be referred to as the home's coincident peak. The same concept is applied to the utility grid when determining the capacity requirements for substations and transformers. In the event a building's peak load increases as a result of the installation of new EVSE, nearby grid infrastructure may need to be upgraded to support this higher load. To learn more about EV charging and coincident peaks, please refer back to the Part 4, Charging Infrastructure.

Some equipment upgrades such as the installation of wiring and circuit breakers are required for all EVSE installations. Each new EV charger must be installed on a dedicated branch circuit, which means there must be a circuit breaker for every EVSE. These breakers will be installed in service panels throughout the facility and are often separated into primary and secondary panels to organize different loads such as lighting and air conditioning. In the event the primary panel needs to be upgraded to support larger loads, the EVSE installer will need to contact the local utility to determine if a new meter and upgraded electric service needs to be installed. In the event a new electric service is required to support a larger peak demand, the utility company may also have to upgrade some of their distribution equipment. Most often these upgrades include the installation of higher capacity service lines or a larger transformer. The transformer is designed to step down the medium voltage from the primary line to the low voltage delivered to the facility through the service wires. The installation of these upgrades is typically managed by the local utility. However, the financing of these upgrades can vary by location. Some utilities offer an upgrade stipend to customers that may cover some or all of these expenses. In other cases, these costs might be passed on to the customer with the option to have some or all of these costs reimbursed if the site's energy consumption increases by an agreed upon amount. It's important to reach out to the electric utility early in the process of installing EVSE to understand the implications of service upgrades and any possible programs that may be available.

When new EVSE is installed that exceeds the nearby grid capacity, something must be done to maintain a safe and reliable interconnection to the grid. Although the most obvious solution is to upgrade the equipment that is at a risk of overloading, it's not always the fastest or most cost-effective solution. It's important to consider other options such as managed charging or distributed generation that could mitigate the facility's peak demand. Equipment upgrades such as installing new transformers and service drops can delay the installation of EVSE and increase installation costs at locations where the utility passes these expenses on to the customer. However, smart EVSE are sometimes capable of managing EV loads in a way that reduces peak demand. This can be done through the implementation of a power ceiling where EV charging will either be delayed during peak power concerns or power will be reduced in conjunction with the fleet's charge session requirements. These systems can often be paired with distributed energy resources such as solar photovoltaics or energy storage systems to avoid the reduction of EV charging power during a peak demand event while maintaining operations within the limitations of nearby grid equipment.

An example of this type of managed charging solution is deployed at the National Renewable Energy Laboratory's employee parking garage. NREL recently expanded its workplace charging program from 36 to 108 EVSE ports. This new equipment created the risk of a 720 kW coincident charging peak if all EVSE were operating simultaneously at full power. This would've exceeded the capacity available in the nearby distribution transformer and many of the garage's service panels. In order to avoid upgrading all of this equipment, NREL employed a managed charging program that limits the peak charging capacity for all these EVSE within the limitations of the transformer and service panel. This system requests users input their desired miles of range and how long they will be parking at the garage. This tells the managed charging system how much energy their vehicle requires and when their charge session must be complete. The system then monitors the local grid conditions and facility loads to ensure EV charging operations are maintained within the site's limitations and each user receives the energy they requested.

In summary, the electric grid is designed to be capable of supporting the largest coincident peak among the sum of all loads. The installation of new EVSE may impact facility- and utility-owned equipment. These impacts may require upgrades which can be costly and delay installations. However, those upgrades can be mitigated through the use of managed charging or through the installation of DER.

Thank you for listening. That concludes Module 1 of Part 5 of the Flipping the Switch Series: Electric School Bus Infrastructure Planning and Solutions. To complete the modules in Part 5 of this series, continue on to listen to Module 2 where we will discuss electric school buses and the possibility for vehicle-to-grid. As a reminder, you can find all the content for the Flipping the Switch on Electric School Buses series including each part of the series and associated modules, as well as handouts with the summary of information and links to all the resources mentioned today on the Alternative Fuels Data Center's Electric School Bus page.