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Highlights Summary

Smart Charging is our cornerstone. Our intelligent algorithms make sure that you squeeze every last kilowatt-hour out of your connection to the grid and that those kilowatt-hours are generated by the sun and the wind. Smart Charging is essential for CPO businesses. And the right algorithm is essential for Smart Charging.

DC Smart Charging

More fast charging stations,
same grid connection

With the European Parliament mandating the presence of fast chargers every 60 km across Europe, DC chargers are increasingly in focus. Plus, charge point operators (CPOs) want to have a network of DC chargers to maximise revenue and offer a fast charging experience to EV drivers. DC chargers are appearing at more and more locations, within cities, on the road, on highways, and around business locations.

AC and DC charging stations are very different from one another. For this reason, using a single Smart Charging algorithm for both AC and DC charging stations will not be efficient.

Understanding AC and DC

When it comes to electric power, there are two forms, called alternating current (AC) and direct current (DC).

Alternating Current (AC)

AC stands for alternating current. In an AC circuit, the direction in which the current flows changes multiple times per second, usually 50 times per second. Think of it like a swing that moves back and forth, but 50 times per second.

Direct current (DC)

DC stands for direct current. In a DC circuit, current is always flowing in the same direction. Think of it as a river that always goes in the same direction.

Note: It is important to mention that the power grid always delivers AC, while batteries store energy as DC. This means that every time a battery is charged, AC power needs to be converted to DC. This AC-to-DC power conversion happens everywhere—when you change your mobile phone but also when you charge your EV!

How is power converted from AC to DC in charging stations?

The AC power from the grid needs to be converted to DC for it to be stored in the battery of the EV. And this is done by a converter.

AC charging stations

Every EV has a converter on board. Whenever you are charging at an AC charging station, the onboard converter converts the AC power from the grid to DC power, which can be stored in the battery. This usually works up to 22 kW.

DC charging stations

If you want to charge faster than that, the converters become so big, heavy, and expensive that it makes more sense to put them inside the charging station. In that case, we can use a much larger converter to charge the EV directly on DC. DC chargers can deliver up to 400 kW or even higher.

Unique features of DC charging

Charging Power

DC chargers provide more power than AC chargers for an EV battery. A single DC charger can take up more power than an entire office parking lot. In the future, even higher charging powers will likely be possible.

Charging duration

AC chargers are found at home, at the office, or on the street. EVs are usually connected to a charging station for, on average, 8–12 hours. DC chargers are common near the highway, where drivers want to charge only as long as necessary and continue their trip as soon as possible. These fast charging sessions are usually quite short. Also, DC charging sessions are normally stopped when the battery reaches 80 percent (state-of-charge). On average, charging sessions on DC charging stations take 37 minutes.

Charging curves

A charging curve shows how much power an EV is taking throughout the charging session. AC charging sessions for different EV types follow a similar charging curve. The charge rate is mostly constant, and when the battery is almost full, it slowly drops to 0. For DC, the charging rate can vary a lot throughout the charging session. Depending on the EV model, it may decrease stepwise as the battery gets fuller, or it may go towards 0 asymptotically. Almost no charging curve is the same.

Given that the typical EV charging behavior is different for AC and DC chargers, GreenFlux designed an algorithm specifically for DC charging to maximise energy efficiency and user experience.

Smart(er) Charging

A charging hub with
10 DC Chargers

Fast chargers are unique. They need a different Smart Charging algorithm than the one designed for AC charging stations. Let us understand how DC Smart Charging solutions ensure high value for CPO businesses through an example.

A business case based in the Netherlands

There is a charging hub location next to a highway where a CPO wants to install 10 DC charging stations, with each having a power capacity of 300 kW. Let us look at the operating costs for such a location:

Firstly, the operating cost does not depend on only the energy you buy and sell. It also depends on how large the grid connection is. In this case, for 10 charging stations, each delivering 300 kW of power, a grid connection of 3000 kW is needed.

10 charge stations x 300 kW per charger = 3000 kW grid connection

The cost of operating such a grid connection depends on the Distribution System Operator (DSO). While the cost is different from DSO to DSO (or, say, country to country), the idea of calculating this cost is the same. The DSOs set this cost, which, in general, includes the following components:

  • Yearly grid fee (can also be monthly).
  • A fee for the maximum power consumption in a year.
  • A fee based on the contracted transport power

The top part of the example on the right displays the annual fees to a DSO in the Netherlands for operating a 3000 kW grid connection. These costs can potentially reach up to 157,000 euros per year.

It is important to note that the cost mentioned does not cover the one-time installation fees for the grid connection. The bottom part of the chart illustrates these installation costs, which can exceed 300,000 euros, depending on the size of the grid connection.

How much power is consumed?

The graph on the right displays total power consumption over time for a single day at this same location.

We can see that the power consumption changes over time. For instance, there is no activity at midnight, but a session starts around 00:30. The total power consumption increases again during the day and decreases again at night.

While we observe some peaks, the graph does not indicate how often these peaks occur.

A few observations from the Use Case

Now, let us arrange the data slightly differently to understand how high the peaks are and which fraction of time the power consumption is above a certain value.

For that, we arrange the power consumption of this location for the period of one month in descending order.

We can read the graph as follows:

  • 50 percent of the time, the load is above 105 kW.
  • Only 0.2 percent of the time, the load is above 1000 kW.

A few other observations from this graph are:

  • Clearly, we do not need a 3000-kW grid connection for this location.
  • 1000 kW would be accommodating, but we have to make sure not to exceed it.
  • This is exactly what DC Smart Charging can do: it ensures the power consumption stays below 1000 kW at all times, allowing us to use a much smaller grid connection.

The graph also highlights that the DC Smart Charging solution has a minimal impact on the users, as:

  • In this example, Smart Charging only needs to interfere 0.2% of the time. This means that only 2 charging sessions were affected, which accounts for less than 0.1% of the total charging session that month.
  • For the two impacted sessions, users received 243 kW instead of 260 kW, extending their charging time by just 30 seconds. They likely did not notice the difference, and most people would accept this trade-off since the energy at this location was provided at a much lower cost.

DC Smart Charging solution saves costs!

Now, let us recalculate the operating costs by reducing the grid connection size from 3000 kW to 1000 kW.

  • The yearly fees go down.
  • The kW-max yearly fee, which is based on peak power consumption, goes down.
  • The biggest difference: the contracted transport power fee drops significantly by reducing from 3,000 kW to 1,000 kW.

Using a 1000 kW grid connection instead of 3000 kW at the same location significantly reduces operating costs, lowering them from 157.000 euros to 52.000 euros.

This example is for just one location. You can imagine the savings across multiple sites.

Plus, DC Smart Charging is a win-win. On one hand, CPOs save significantly on operational and infrastructure costs, while on the other, the impact for users is almost unnoticeable.

Summary

Why DC Smart Charging is Essential!

The charging sessions on DC charging stations are very different from sessions on AC charging stations. Using the same algorithm would make these sessions inefficient and may lead to some concerns, like slow response times and high data consumption.

Taking into account the unique charging behaviors of the DC chargers, GreenFlux developed a dedicated Smart Charging algorithm for DC charging stations that maximises energy efficiency and enhances the user experience.

GreenFlux’s new DC Smart Charging solution is particularly beneficial for locations with multiple fast charging stations. By reducing the required grid connection size, it helps lower the grid connection costs, making it a cost-effective solution.

At GreenFlux, we are committed to accelerating the transition to sustainable mobility through innovative technology like this.

If you are wondering whether it's possible to economically deploy a DC charging network, the answer is yes. GreenFlux’s DC Smart Charging solution is designed to achieve just that. Contact us to learn more.

Pioneering eMobility solutions

Recognised for our expertise in eMobility and pioneering Smart Charging technology, we've been accelerating the energy transition for over 13 years.

In this time, we have empowered some of the world's most ambitious companies, including TotalEnergies, Volvo, EDP, Engie and Equans, to launch and scale their eMobility business.

GreenFlux is proud to be a member of the DKV Mobility Group.

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