Overview: Many challenges are faced when charging electric vehicles at potential charging infrastructure. The challenging issues with charging commercial electric vehicles at charging stations are discussed in this article.
Return-to-base model charging infrastructure and public charging infrastructure are two potential techniques for charging commercial electric vehicles (CEV). For operators of business fleets and grid systems, charging commercial electric vehicles (EV) poses difficult technical and financial challenges. The adoption of medium- and heavy-duty electric trucks (ET) by many commercial companies may be restricted by these issues. In this article, challenges regarding return-to-base model charging infrastructure are discussed in detail.
Return-to-Base Model Charging Infrastructure Related Challenges
The vast majority of business operations employ a "return-to-base" strategy, whereby high-power charging infrastructure is installed at their commercial facilities (depots, yards, industrial micro-grids, etc.) to allow the full charging of electric trucks (ET) after working hours, such as overnight or in between shifts. The activities of the commercial truck fleet are distributed both spatially and temporally, and there aren't enough appropriate public charging stations.
1. Upgrading of Electric Power Infrastructure
CEVs can be charged using the return-to-base approach at their commercial facilities; hence, these vehicles must have large-sized batteries to cover the necessary daily driving distances before returning to their charging point. In order to charge these vehicles, high-power charging infrastructure must be established at certain locations. As a result, the peak power demand at areas where medium- and heavy-duty CEVs charge will rise significantly. This will have a substantial effect on the electrical network assets at these locations.
Peak power requirements for the simultaneous charging of light-duty passenger cars and CEVs at a commercial location are shown in Fig. 1. It can be seen that 66 kW of power is needed to charge 20 passenger light trucks, but 20 medium- and heavy-duty CEVs being charged at the same time with 11 kW and 50 kW chargers would put a load of 220 kW and 1 MW on the electrical infrastructure. Furthermore, as demonstrated by the example of 50 heavy-duty trucks, if more CEVs are charged in commercial areas, the peak demand may rise to 3.5 MW and rise significantly if quicker charging is needed.
Fig. 1. Peak power demands for simultaneously charging various EVs and CEVs fleets. Source: IEEE Access
Particularly during residential peak load hours, this high power consumption could put a strain on the local electrical distribution network, which is where electricity is delivered to customers. While light-duty passenger EVs now dominate the market, there might not be enough incentives for distribution networks to improve their infrastructure in order to quickly fulfill the demand for electric trucks. As the market for electric trucks reaches a certain size, the cost-benefit analysis and business case will undoubtedly influence the choice of infrastructure improvements.
In order to handle the rising use of ETs within a commercial fleet, the electrical power network facility and the local electrical distribution network must be improved. Yet, the large initial expenses of upgrading the electrical infrastructure of commercial structures may make it hard to expand the use of electric vehicles in fleets. A local electrical distribution network upgrade also presents difficulties for the power industry due to the high cost and lengthy time required for the upgrade.
2. Peak Demand Charge and Electricity Bill
Commercial and industrial electricity rates are used to charge commercial infrastructure for the electricity they use. These rates are mostly made up of a per-kWh energy charge and a per-peak-kW demand charge. These demand charges are based on how much power (in kW) is needed at any given time during the month (usually every 15 minutes). These rates are a way to find out the estimated cost of the generation needed to meet the peak demand of commercial businesses.
Fig. 2. Sample peak demand charges from selected metropolitan areas across the USA. Source: IEEE Access
As shown in Fig. 2, these demand charges vary a little bit by region and a lot by commercial facility. Also, some utilities charge higher demand fees in the summer than they do in the winter. For some businesses, the cost of meeting peak demand may be more than 50% of their monthly electric bill. If CEVs are charged without being managed at their parking spots, which also buy electricity for other uses on the same contract, peak demand charges at these spots could go up by a lot.
This increase in demand charges depends on whether the peak demand of the parking location's base load matches the peak demand of the total charging load of CEVs. Fig. 3a shows that if the peak demand of the charging load and the peak demand of the base load are the same where CEVs are charged during business hours, the demand charge of the total charging load is added to the demand charge of the aggregate load. The unmanaged peak demand charge scenario in Fig. 3a can be very expensive, making it impossible for businesses to add charging infrastructure to their buildings. As shown in Fig. 3b, peak demand does not happen at the same time when CEVs are being charged outside of business hours. So, the demand charge for the aggregate load would be less, or it could even be zero.
Fig. 3. The increase in peak demand of the facility: a) the facility’s base load coincides with the peak demand of the total charging load of CEVs, and b) the two peak demands do not coincide. Source: IEEE Access
3. Operation Conditions of Facility and CEVs
At some commercial facilities, charging ETs solves some operational problems caused by the facility's participation in incentive-based demand response programs, which are meant to get commercial customers to cut back on their energy use during times of high demand. This decrease in demand has an effect on the facility's peak demand during the charging period.
Also, charging some CEVs can be hard because they have to follow special work schedules while they are parked. According to these schedules, ETs need to be moved away from charging stations for some tasks (like washing and loading the goods for the next day) before leaving the facility. These operational schedules affect both the charging load profile of ETs and the availability of ETs for the charging process. So, this needs to be taken into account when ETs are being charged at commercial facilities, which affects the capacity of the charging infrastructure at these places.
4. Deterioration of Battery Health
In the return-to-base charging strategy, CEVs can only be charged at their business location during certain times, such as overnight or after shifts. So, CEVs must be charged at their places of business so that they can do their daily transport jobs without worrying. But the way CEVs are charged and discharged when using the "return-to-base" strategy could be bad for the health of battery banks.
Depending on daily work, CEV batteries may need to be discharged to a deep level often so that they can do their transport jobs perfectly before going back to where they are charged. Also, their batteries might have to be kept at a high level of charge at their facilities for a long time before they can be used in transport missions. CEV’s charging and discharging processes can hurt the health of a battery, which could shorten its life cycles and limit its maximum capacity. This would mean that ETs could only drive a shorter distance each day.
Summarizing with key points:
Some of the takeaways from the article are as follows:
- Two possible methods for charging CEVs are return-to-base model charging infrastructure and public charging infrastructure.
- Upgrading of electric power infrastructure, peak demand charge and electricity bill, operation conditions of the facility and CEVs, and deterioration of battery health are common challenges in return-to-base-model charging infrastructure.
- High residential peak power consumption and increased charging of CEVs can strain the local electrical distribution network. Yet, the high costs of updating electrical infrastructure may make companies' adoption of electric vehicles difficult.
- If CEVs are charged without being monitored during residential peak hours in commercial infrastructure, which also buys electricity on the same contract, peak demand charges get doubled, which reflects in the electricity bill.
- Operational schedules have an impact on both the electric truck charging load profile and the availability of the vehicle for the charging process.
- CEV batteries may need to be depleted deeply during work and held at a high charge for a long time before they can be utilized in transport missions. The "return-to-base" approach for charging and discharging CEVs may damage battery banks.
This blog post is part of a full research article from IEEE Access.
The featured image is used courtesy of OPEN AI.
Check out the next article in this series to know about the challenges and solutions to charging Commercial Electric Vehicle charging.
