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18.03.2020 | 4 minutes

What is smart charging and how can drivers of electric vehicles benefit from it?

The more electric cars drive through Germany, the less CO2 is released into the atmosphere. Smart charging is one of the reasons why the power grid can handle the higher demand even at peak times.

The uptake of electric driving brings many benefits including reduced CO2 emissions, but it also triggers some worries about the existing power-grid infrastructure and how the grid will cope with the increasing power demand, especially during peak hours.

The cost of upgrading or replacing existing electrical grid connections can be quite expensive, and in some cases (of very old infrastructures), may not be possible at all.  So, what’s the solution to manage this peak power demand? We believe that the solution is “smart charging”.

What is smart charging?

Smart charging facilitates intelligent charging of EVs where charging speeds are optimised based on the available grid capacity and in accordance with the vehicle owner’s needs. With smart charging, the owner of the EV infrastructure is not only avoiding expensive grid upgrade & peak charges but also gets the most out of the existing grid connection.

Different levels of smart charging are possible, from simple timed start/stop to Vehicle-to-Grid (V2G*) bi-directional charging. The chosen option will depend on the customer environment and their willingness to try V2G. *V2G charging allows EV drivers to resell electricity to the grid via their vehicle if they wish to).

Through continuous product research and development, Vattenfall InCharge along with partners and suppliers provide the following solutions:

1. Delayed/timed start-stop charge (peak hour handling)

Now with real-time insight into location-wise “available” power for distribution, the distribution system operators (DSO)/utility can send a signal to regulate or turn off ev charging during peak loads. Based on these signals, or according to reduced hourly tariffs, we can start/stop the charging.

This feature allows the user to plug their electric car in as soon as they get home, yet the ev home charger starts only at the defined time or when the rates are cheapest. This also minimises the load curve (typically, there is a high demand in the evening time) and thereby ease-off grid burden - without compromising customer’s comfort or cost.

An experiment conducted by Mckinsey1 in 150 homes shows that the reshaping of the load curve can reduce peak grid demand close to 50%. (from +30% peak demand to +16%)

An illustration which shows that the reshaping of the load curve can reduce peak grid demand close to 50%.

2. Active load balancing

Dynamically adjusting the charging speed/power (kWh) based on the immediate availability of the grid capacity, is the next level of “smartness” we offer. It’s often referred to active or dynamic load balancing.

Most of the smart EV chargers in the market provide ‘standard’ load balancing – which is the process of equally dividing the total available grid capacity. Whereas Vattenfall InCharge, offers ‘dynamic’ load balancing - which actively monitors the real-time load and enables the user to charge at high power while still ensuring that the electrical connection is not overloaded.

The illustration below explains the difference between standard and dynamic load balancing. These scenarios are based on the assumption of a private garage with a grid capacity of 32A (out of which 25A is allocated to EV charging and 7A for other loads such as lighting, heating. etc).

This illustration explains the difference between standard and dynamic load balancing in a private garage.

  • Scenario 1: When the 7A dedicated to other loads (such as lighting in the garage) are in use and just one car is plugged-in, there is no difference between standard and dynamic charging, both EV chargers will charge at 25A.
  • Scenario 2: When the 7A are not being used (0A), standard load balancing EV chargers can only charge at 25A maximum, whereas InCharge dynamic load balancing EV chargers can utilise the maximum 32A to charge at full speed.
  • Scenario 3: When the 2nd car is plugged-in, the standard smart EV charger can only equally divide the available 25A into 12.5A each; whereas InCharge dynamic load balancing EV charger is able to charge both cars at 16A each.
  • Scenario 4: When the 2nd car is a Renault Zoe or similar, it requires minimum 13A to start charging therefore the standard load balancing will not work; whereas the InCharge EV charger will intelligently allocate 14A to the Zoe and remaining 11A to the other electric car.

In case of large car parks, a number of EV charging stations can work together in “clusters” and dynamically balance the available power between them. This ensures that they never exceed the grid capacity, limiting damage to fuse and avoiding peak charges while enabling all the electric cars to get the best out of the available grid power.

"Vattenfall is firmly committed to a fossil-free future, thus constantly investing in development and delivering smart charging solutions. The aim is to encourage an uptake of EVs and save costs for the industry and therefore customers, while reinforcing a sustainable power grid balance”.

Pon Paulraj, Hardware Specialist - Strategies & Product development


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