Why should we focus on building the network of AC charging stations instead of DC?

Published in

tau-blog

4 min readJul 1, 2019

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Availability and comfort play an important role in charging of electric vehicles. If the driver has to walk more than 1 km to charging station, most likely he is not very happy about it.

Argument 1: Average range per day

According to the research made by insurance company HUK-Coburg, nearly half of the cars doesn’t travel more than 250 km in one day. During research which lasted for 8 months, HUK-Coburg studied 25 million trips on the total distance of 6800 circumnavigations.

Today, most of the electric car models already can go beyond 250 km without the need in recharging their battery.

According to the estimations from the study, 47% of electric vehicles have reached 250 km only in 2 days. Remaining 53% have traveled for the distance of more than 250 km only once during the time of study from January to August 2018 and only one percent of that remaining part made trips with this range daily. Which means that only 0.53% of all drivers need fast charging stations on daily basis.

Argument 2: Most charging stations are used only 30% of the time

Category 1. Around 70% of drivers charge their vehicle at home, mostly in the evening or at night. Taking that into account we can conclude that 70% of drivers can potentially rent their charging station during the time period from 9 am to 5 pm.

Category 2. The remaining 30% of drivers charge their vehicle at work or at public charging stations. 12% daily. 15% 3–5 times per week. 10% 1–2 times per week.

Category 3. Drivers who do holiday traveling. Let’s assume once a month.

People from category 1 can provide an access to their charging station to people from category 2 and 3.

The similar situation is being observed in the US. For 85% of e-car drivers charging their vehicle at home is the most convenient option.

In this case DC charging station is not needed because the driver spends time working or visiting friends/family for the time of more than 6 hours, which even with 3.6 kW charging station will be enough to add additional 100 km of range to electric vehicle.

Argument 3: Amount of parking places to charge vehicle

Typical distribution of parking places of cars at night in Germany (source: fraunhofer)

As can be seen from the infographic above:

Town with less than 5 thousand inhabitants — 95% of population has garage or parking place (i.e. around 7.52 million people).
Town with 5 to 10 thousand inhabitants — 93% of population has garage or parking place (i.e. around 12.7 million people).
Town with 20 to 100 thousand inhabitants — 88% of population has garage or parking place (i.e. around 9.7 million people).
Town with 100 to 500 thousand inhabitants — 81% of population has garage or parking place (i.e. around 4.9 million people).
Town with more than 500 thousand inhabitants — 71% of population has garage or parking place (i.e. around 2.8 million people).

Summarizing, around 37.6 million car owners in Germany potentially have an ability to provide an access to electric charging to other owners of electric vehicles.

Argument 4: The price

Installation price of DC charging station is an order (or two) of magnitude higher, than that of AC stations.

Let’s have a look at the prices.

DC

A Level 3 or DC fast charging station are typically installed through one of the EV charging station networks and can cost more than $50,000 to install.

AC

AC Level 1 and 2 charging stations cost between $500 and $5,000 per charging port depending on type and features.

As you can see the installation of one DC charging station can be 10–100 times more expensive, meaning that for each DC station you can have dozens of AC stations which can serve way more people.

Argument 5: Smaller power consumption

Fast charging stations have high energy consumption and can cause overload of the power grid during the peak time. Modernization of the existing power grid and increase in energy production is a very expensive process if the changes must be made in a short period of time. That is why by starting with charging networks consisting of AC stations we can start to gradually upgrade existing power grid to facilitate a future high power fast charging networks.

Conclusion

It is important to note that DC stations are an important part of the infrastructure, but they should be installed in specific places, like motorways. To increase the adoption of electric vehicles and accelerate growth of the electric charging infrastructure we first need to build a reliable network of AC charging stations.

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