A quick guide to bidirectional charging

4 min read
Jun 12, 2018 9:00:00 AM

Bidirectional EV charging and Vehicle-to-Grid (V2G) are among the most exciting electric vehicle charging industry advancements.

  • But what do they mean?
  • How are they revolutionising EV charging (and the electricity grid, in general)?
  • What are the differences between bi-directional charging and vehicle-to-grid?
  • What do they have to do with smart EV charging?
  • And who can benefit from it?

You should find the answer to the above questions in this blog post.

What is bidirectional charging? And what does it have to do with V2G?

Bidirectional charging makes it possible:

  1. For EV owners to charge the batteries of their electric vehicles
  2. To take the energy stored in car batteries to push it back to the power grid during peak hours to help balance momentary spikes in electricity demand and prevent power outages.

Bidirectional charging is powered by vehicle-to-grid (or V2G) technology. V2G allows us to communicate with the energy system to help stabilise the power grid through demand response services.

Are bidirectional charging and V2G the same?

Not exactly.

Even though bidirectional charging and vehicle-to-grid are often used as synonyms, there is a slight technical difference. .

  • Bidirectional charging refers to two-way charging (meaning charge and discharge).
  • V2G is a charging technology that allows the one-way flow of energy from the car battery back to the grid (from the vehicle to the grid).

Now, the V2G technology makes bidirectional EV chargers a reality, and no one will point fingers if you use both interchangeably.

New call-to-action

How does a bidirectional charger work?

To understand how bidirectional charging works, you must first understand how electricity circulates from A to Z in the grid.

Simply put, electricity always takes the shortest path to where it’s needed. Thanks to vehicle-to-grid technology, an EV charging device can absorb the electricity stored in a car battery and push it back into the grid, where it will go to the nearest location where it’s needed.

In application, the first beneficiary of bidirectional charging would be the building (or electrical installation) it’s connected to.

What's the difference between bidirectional charging and smart charging?

Bidirectional charging is 100 % dependent on smart charging.

Smart EV charging relies on a real-time cloud connection between an electric vehicle, an EV charging device, and a charging operator.

This cloud connection is a prerequisite for bidirectional charging. Without a real-time cloud connection, no information would flow between the power grid and the vehicle. Consequently, it would be impossible to know when the power grid requires balancing.

To make a long story short, bidirectional charging and smart EV charging are different by nature. Bidirectional charging is a Smart EV Charging feature that will be instrumental in decarbonising our transport industry.

The benefits of bidirectional charging

As the world is moving full force toward full electrification, energy shortage is a significant concern. Bidirectional charging is a sustainable solution to manage momentary spikes in electricity consumption locally.

A necessary step to introduce more renewable-produced energy into the grid

While unlimited and carbon emission-free, renewable energies have a significant caveat: they are unstable and unpredictable. For instance, how can a windmill produce electricity without wind? How can a solar panel produce electricity during the night?

Fortunately, we can solve this problem with better energy storage and management systems. Bidirectional charging (and V2G) is one of them.

Electricity is continuously circulating. If we produce it but neither use nor store it, we waste it. Thanks to V2G and EV batteries, we can store the excess renewable energy in car batteries and pull it back into use exactly when we need it, for instance, to face a momentary spike during a windless night.

No more power grid overload

Counting on electricity stored in EVs rather than stressing the grid during demand spikes will prevent it from overloading.

Let’s take an example. 

Grid overload is something we often observe when temperatures suddenly drop during winter. In such cases, the momentary energy demand spike significantly destabilises the grid, thus causing local overload and energy shortages.

With bidirectional EV charging, the energy stored in EVs circulates to where it’s needed first, supplying power during peak times, thus meeting local needs and preserving the grid.

A significant energy management system upgrade that doesn't require heavy investment

The benefit is two-fold.

First, bidirectional charging and V2G make it possible to upgrade and make a building’s energy management system smart without building it from scratch - thus avoiding heavy investment

Then, bidirectional charging makes it possible to save money on operational electricity costs. Because electricity circulates to the nearest location where it is needed most, plugged EVs can be used as temporary energy reserves instead of consuming extra energy from the grid.

What's the current status of bidirectional charging?

You may be wondering how long it will take for V2G to become mainstream.

We can’t read the future, but all seems to indicate that the V2G revolution is just around the corner. In fact, the technology required for bidirectional charging already exists, and you can see it in action in this video explaining how we’re using V2G daily at Virta’s HQ in Helsinki, Finland.

The second thing required for bidirectional charging to become mainstream is compatible vehicles.

Bidirectional charging is only compatible with V2G-enabled electric cars. Currently, Nissan and their Nissan Leaf are leading the industry. Still, others like the Volkswagen Group, Tesla or Mitsubishi are also building cars that will power our cities and protect the electric grid in the near future.

Finally, bidirectional charging can only thrive and exist with the energy sector's and utilities' buy-in. However, given the current environmental challenges and how it can safeguard the grid and other electrical installations, it’s only a matter of time before most utilities invest in managing renewable energy through V2G technology.

To learn more about vehicle-to-grid, read out our ultimate guide to V2G