How States Are Building High-Powered EV Charging Centers
The National Electric Vehicle Infrastructure program will help increase the number and availability of electric vehicle fast-charging stations along highways and primary roads.
As states help establish a national network of high-powered electric vehicle (EV) charging stations, they are determining how to build them in areas where electric grids have limited capacity.
Electric vehicle charging station in rural Pennsylvania. Image used courtesy of PA DCNR
Battery-supported charging stations can overcome the constraints of existing grids. States or companies could add stations as more drivers turn to EVs.
Filling the EV Charging Gaps
The federal entity supporting the effort is the National Electric Vehicle Infrastructure (NEVI) program. This U.S. Department of Transportation project was administered through the Federal Highway Administration. NEVI aims to support the buildout of an accessible, convenient, equitable, and reliable national charging network. NEVI primarily supports direct current fast charging (DCFC) on designated EV corridors. This includes the interstate system and other roads, like critical rural freight corridors, which provide access to primary highways. The U.S. Department of Energy (DOE) assists by researching EV power consumption patterns and public charging needs.
DOE research shows ports along travel corridors tend to be in demand during peak travel hours between 1 and 4 p.m. Demand drops off through the evening. The lowest use occurs in the pre-dawn hours.
DCFC demand tends to be highest between 1-4 p.m. and lowest before dawn. Image used courtesy of Energetics
“The federal government is funding a backbone of consistent DCFC across the entire country. States have the local knowledge needed to implement the specifics of fast-charging along their electric vehicle corridors,” Tom McCarran, a researcher at DOE’s National Renewable Energy Laboratory in Golden, Colorado, told EE Power.
Planning for Actual EV Charging Needs
NEVI seeks to add EV charging stations on interstate highways and other major corridors every 50 miles. The program aims to address numerous issues, including ensuring adequate charging coverage across the country and guaranteeing capacity in high-utilization areas like dense metropolitan zones. NEVI must also make sure that ports remain reliable and easy to use.
A DCFC station can require as much grid capacity as the average high school. Many remote areas along interstates lack the capacity to provide this much power. NEVI requires that, at minimum, each charging station funded by the program must have four 150-kW ports. Some sites may have more than four ports. The total number depends on the station’s expected power use.
Given current EV technology and EV charging curves, it could be unusual for a station location to experience requests for 150 kW from every port at the site simultaneously. EVs do not charge at their peak rate for an entire charging session. Depending on the state of charge in an EV battery, most charging sessions quickly ramp up to their peak rate and then taper off as the battery gets more fully charged.
“You can see how most sessions are between 10 and 40 kWh. An EV with a 250-mile range might have roughly a 65-kWh battery in a small car up to a 100-kWh battery in a pickup truck or large SUV. So many motorists are topping up a bit instead of filling up when they stop to charge,” McCarran said.
Most DCFC EV charging sessions draw between 10 and 40 kWh. Image used courtesy of Energetics
The underlying problem in constructing the charging station network is that, historically, some rural areas had little need for a high-capacity grid. Expanding the capacities of these grids to support the power needs of corridor DC fast chargers takes time. It is also expensive. Since the demand for charging drops overnight, upgrades could be mitigated with on-site energy storage systems.
Typically, the entity that requests an upgrade to a grid bears the cost of improving it. NEVI alleviates this problem by providing up to 80 percent of the costs for a charging infrastructure buildout. The federal government’s share for NEVI projects is 80 percent. A state or private entity can fund the remaining costs.
The Potential of DCFCs
DCFC can deliver between 50 and 350 kW, charging most EVs in 15 to 45 minutes. Battery-supported DCFC chargers can be a cost-effective way to add charging capacity where the grid has a low output.
McCarran said DC fast chargers on highways can potentially promote EV use.
“When you’re on a road trip in an EV, you want charging stops to be brief and convenient. DC fast chargers make that possible,” said McCarran.
A battery-supported DCFC could meet demand when the grid alone could not. Image used courtesy of NREL, DOE
Cost can be an issue. A DC fast charger costs between $25,000 and $150,000 per unit, depending on the power output. The total sum of construction, installation, and grid upgrades often exceeds the equipment cost.
Still, DC fast chargers make it easy to meet demand when the daily travel for a vehicle exceeds the vehicle’s rated range. They also help when a driver has to charge during short periods, like a mid-route lunch break.
“These mid-route charging events are more challenging to predict. The DC fast-chargers at these sites require more power to ensure drivers can resume their trip as quickly as possible,” Jesse Bennett, research engineer at the National Renewable Energy Laboratory, told EE Power.
For example, say a school football team traveled on the highway to play in another city. The vehicles to transport the team, the cheerleaders, the band, parents, and fans might all want to charge EVs simultaneously. Batteries can enable the installation of more fast chargers at the charging station. This would help more parties get back on the road quickly.
Installing battery-supported stations is also becoming a cost-competitive option because battery prices are declining.
“EV technology keeps improving, which results in falling battery prices and increasing EV adoption. As public charging demands grow, states may want to consider how the capacity needs from these energy storage systems could increase over time,” Bennett told us.
Assessing EV Charger Needs
One of the ways that states are measuring the potential for EV charging station use is by monitoring traffic exiting venues like NASCAR raceways. The goal is to see how many EV drivers want to charge a vehicle when many vehicles leave an area at once.
Local and regional transportation planners may have unique data and expertise to inform charging deployment strategies.
“State governments can decide how to plan charging stations for concerns like emergency evacuations. We are working on tools to specify energy storage for a given level of charging demand. States have the data, experience, and authority to plan for their traffic patterns,” said McCarran.
In mid-October, states began to break ground on NEVI-funded charging stations.
Ohio was the first state to lead the charge with a NEVI-funded charging center at the Pilot Travel Center along Interstate 70 at U.S. Route 42, west of Columbus. The station will have DC fast chargers installed by EVgo.
Going forward, states and other recipients of funds from NEVI will share data about charging station use, reliability, and cost information with the federal Joint Office of Energy and Transportation. The Joint Office will then be able to share this information with entities that build charging stations. This will help the entities ensure the projects align with similar efforts across the U.S.