In a paper to be presented at the Australian Transport Research Forum by University of Queensland researchers Thara Philip, Dr Kai Li Lim, and Jake Whitehead, empirical data on real-world driving and charging patterns of 239 electric vehicles across Australia is analysed. As Tesla is the only car manufacturer that widely allows application programming interface (API) access and 80% of electric vehicles sold in Australia are Teslas, they formed the most accessible research pool.
One of the concerns answered by the research was about the effect on the grid. I have previously written about this, but only from anecdotal evidence. The University of Queensland (UQ) team provides insights that are supported by academic rigor. I was pleased that the conclusions were similar.
According to the International Energy Agency (IEA), “EVs are projected to account for anywhere between 2 to 4 percent of total electricity demand in 2030, compared to 0.3 percent today.” So, “To support grid stability and plan for future infrastructure upgrades, it is essential to predict the electricity demand by EVs in the future accurately.”
Data collected included “distance driven, location, energy consumed during a trip, charging duration, time of charging, charging location, battery state of charge (SoC) at start and end of charging event, location of charging.”
Concerns about residential charging coinciding with peak hour and stressing the grid were allayed by the data. Home charging was the preferred option, particularly of female drivers [Lee et al. (2020)], while non-home charging was necessary for dwellers in high density housing.
Real-world data are needed to inform those managing the grid and planning upgrades. If we overestimate the aggregated charging demand of EVs, it could lead to unnecessary upgrades at a high cost.
Observed self-managed charging behavior indicated that EVs are plugged in at midday, charging at work or from home solar. It should be noted that some workplaces also have solar. The research team noted that “Charging utilisation is lowest at 7:00 am and 7:00 pm, which coincides with morning and evening peak tariffs, as noted with the decrease in charging events from 4:00 pm onwards. Conversely, low power consumption is observed in the morning and evening peak periods.”
Most charging events were top-up charges. The assumption that EV drivers let their charge dwindle to almost nothing and then charge to 100% is not accurate. It is expected that the impact of EV charging on the grid is likely to be minimal for the foreseeable future.
The data show that a small number of drivers chose to charge at peak hour (4–8pm). Why? Some possible reasons include charging at the end of a trip or preparing for a long trip the next day. Thus, the vehicle would need to be charged over a longer period of time. Perhaps these drivers had no access to off-peak charging or may live in rental accommodation and have no control over their electricity supply. However, demand per EV in the 6pm peak period across the entire grid (i.e., including both home and public charging) is estimated to average only a 219W increase in power.
The research identifies two peak EV charging times — middle of the day and overnight. These align well with renewable generation from solar and wind.
Those EV owners who have solar panels and a battery prioritize their own generation to power the home during peak hour. Fast charging infrastructure is used by those travelling longer distances.
“Importantly, this study highlights that many EV owners are already taking advantage of off-peak electricity tariffs and solar power to charge their EVs. During the evening peak, EVs appear only to be increasing power demand by an average of 250 W per vehicle (home and public charging combined). This is minimal compared to increases caused by other electrical appliances during the same period and suggests that fears of EVs placing a significant burden on the electricity grid in the short term are likely overplayed and undoubtedly premature. However, this does not remove the need for planning future smart charging programs that support and further encourage these existing, positive charging behaviours.
“Looking to the future, it will be imperative to support renters in being able to shift charging events away from the evening peak period through greater access to off-peak tariffs and dedicated home charging infrastructure. Continuing to increase awareness of the economic benefits of charging during off-peak periods may also help to shift the minority of charging events occurring during the evening peak electricity period.”
The data demonstrate that far from presenting a significant risk to the grid, EV owners are already managing their charging in a responsible manner. Encouraged by tariff reductions, they charge mostly from the grid outside of peak periods. If they have solar, they charge from the excess energy generated in the daytime.
Thank you, UQ, the sky is not falling.
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