Overview: The article gives an overview of the problems that commercial electric vehicles face when they are charging at public charging stations. It also suggests smart ways to solve these problems.
To catch up on Rakesh Kumar's previous article in this series on the challenges in charging commercial electric vehicles, follow the link below:
Challenges in Charging Commercial Electric Vehicles - Part 1
Part 1 deals with the challenging issues faced by commercial electric vehicles in return-to base-model charging infrastructure.
Public Charging Infrastructure Related Challenges
Public charging infrastructure is one way that commercial electric vehicles (CEV) could be charged. There are certain difficult problems with charging CEVs while they are on the road at public charging infrastructure. On a technical and financial level, these problems could affect the people who run the charging infrastructure and the people who run the fleets. The discussion of these difficult problems follows.
Daily Operational Schedules
Commercial trucks operate according to daily operational schedules that correspond to daily business hours and offer prompt and consistent service to their customers. Several commercial vehicles operate under strict time constraints, making it impossible for them to stop their journeys to recharge their batteries. In order to avoid any disturbance to their operational schedules, some fleet operators prefer to charge their vehicles while they are on the road at spots where cars are routinely stopped during lunch breaks, between two shifts.
Hence, the placement of public charging infrastructure must be coordinated with the duties and situated near their final destination and parking location at all times. Still, because commercial vehicles have different destinations and routes to get to where they need to go, there may not be enough public charging infrastructure at some destinations and parking spots. Also, if these vehicles are charged during peak hours, this could limit how much power can be used at charging stations.
These rules would probably mess up the schedules of commercial vehicles because it would take a long time to charge them, they would have to wait longer than expected, and they would have to travel a long way to get to charging stations. Because of this, the process of charging CEVs at public charging stations should be timed to match the driving cycles of these vehicles.
Utilization Rates of Charging Infrastructure
The percentage of time that a charging station is actually giving out electricity is shown by its utilization rate. The revenue from charging infrastructure depends on how many kWh of electricity are sold per unit of time. A charging station with a low rate of use is likely to not be capable of earning sufficient revenue to pay for itself. So, a charging station needs to maintain a high enough utilization rate by increasing the number of charging events and decreasing the amount of time a vehicle is plugged in idly to a charging station.
A high rate of public charging infrastructure use can take advantage of economies of scale and lower the costs of running charging infrastructure like demand charges. As shown in Fig. 1, fast charging in the Midwest, the high rate of charging station use per day spreads the demand charge over many charging events, which reduces the effect of the demand charge on the total electricity bill. This makes it easier for utilities, automakers, and infrastructure providers, among other groups, to work together to increase the number of public charging stations.
Fig. 1. Impact of a high utilization rate per day on spreading demand charges over many charging events. Source: IEEE Access
To make the most of the money spent on transformers and utility service upgrades, the charging infrastructure should be set up with more charging stations. If you do it this way, the capital costs of the charging infrastructure will lead to higher profits as the number of users grows. To sustain a high level of utilization, any given infrastructure that has more chargers must host more charging events. Thus, the use rate of newly added charging stations must be at least equal to that of current stations.
To meet charging needs across a wide area, it is important to put public charging infrastructure in the best places possible, taking into account the different locations and times that CEVs work.
Charging Cost of Commercial Vehicles
Electric companies employ time-of-use (TOU) tariffs. This means that the price of electricity goes up when more people are using it. This is a good way to move the charging load of light-duty EVs to times when the grid isn't as busy. But commercial vehicles don't have the same freedom to change how they are charged based on TOU tariffs. As commercial vehicles usually follow set schedules during business hours, it can be very expensive to charge them on the road, during lunch breaks, between shifts, or after an early shift due to TOU tariffs.
In the past few years, many researchers have looked into real-time tariffs, which take into account the higher levels of distributed energy resources that are connected to the grid, as a way to reduce the effects of peak grid load. Real-time tariff information can make it possible to lower the cost of charging commercial vehicles while they are on the road. But because some commercial vehicles have to stick to strict schedules, these tariffs may also make it more expensive to charge them.
So, a smart charging system is needed to coordinate the process of charging commercial vehicles on the road in a way that lowers the cost of charging these vehicles and keeps them running on time.
Stability Limits of the Grid System
Due to the high power capacity of public charging infrastructure for commercial vehicles, especially heavy-duty vehicles, electrical networks at infrastructure locations must be able to supply enough power to charge the vehicles. Also, the effect of a charging infrastructure on the performance of electrical networks needs to stay within stable limits, especially when residential loads are at their highest.
Smart Strategies for Charging Infrastructure in Public Spaces
To solve the problems listed above, you have to plan the process of charging CEVs at public charging stations. These vehicles can get a full charge or a partial charge at different charging stations along their route, depending on the vehicle's operational schedule and TOU electricity tariff.
According to the operational schedules of commercial vehicles, each customer along the route of a driving cycle should be served for no more than a certain amount of time. This limit affects the amount of time that commercial vehicles can spend charging at each charging station. Also, the following parameters affect the maximum time for charging:
- Waiting time in the queue because of potential congestion at charging stations. The amount of time it takes to charge at a charging station is limited by the waiting time.
- Location of charging station based on a truck's daily route. Electric trucks will have to take a detour to reach stations that are far from the main route, which will cut into the time they have to charge.
- Charging time is affected by the charging power rate of the charging stations. Electric trucks take less time to charge at stations with high power rates than at stations with low power.
- High-power charging stations usually have higher charging prices, so there should be a trade-off between reducing the time it takes to charge and increasing the cost of charging based on how the vehicles are used.
- Depending on where the charging station is along the route, an electric truck may run out of power before it gets to a charging station. So, practical charging stations that can be used to charge commercial vehicles need to be put in places where an electric truck's current SOC can reach them.
Summarizing with Key Points:
- The shift to electric vehicles is crucial for reducing greenhouse gas emissions and mitigating climate change.
- Public charging infrastructure is essential for the widespread adoption of electric vehicles and reducing reliance on fossil fuels.
- Technical and financial challenges must be addressed to make public charging infrastructure viable for commercial EVs.
- Smart planning of the charging process, including time-of-use tariffs, can help overcome these challenges.
- Collaboration between utilities, automakers, infrastructure providers, and governments is key to expanding public charging infrastructure and promoting the adoption of electric vehicles for a sustainable future.
This blog post is part of a full research article from IEEE Access.
The featured image is courtesy of Midjourney.
