How EVs can store energy for homes and power grids

Electric car batteries do not only supply power to electric vehicles, but can also supply energy to buildings and aid in stabilizing power grids via two-way charging capabilities.

Electric vehicles now feature more potent batteries that can be recharged from the energy grid or personal solar panels located on the rooftop.

These systems can serve as storage for homes and the energy grid through a bidirectional charging process, which can help reduce power costs.

What's the mechanism behind it, and are there any downsides?

What is bidirectional charging?

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A fully charged battery can power not only the electric motor, electronics, lights, and heating, but also external devices such as a fridge when camping, a drill on a building site, or even another EV. These additional functions are referred to as V2D (vehicle-to-device) and V2L (vehicle-to-load).

They can provide power for entire buildings using vehicle-to-home (V2H) technology, feed electricity back into the general power grid via vehicle-to-grid (V2G) technology, or simply charge vehicle batteries.

Currently, bidirectional devices are available at a limited number of charging station locations.

What is the storage capacity of a car battery in terms of electricity?

Electric vehicle batteries are becoming more affordable and powerful. The Tesla Model Y's battery, to take an example, has a capacity of at least 62 kilowatt hours (kWh), the VW ID.4's is 77 kWh, and the Renault R5's is at least 40 kWh.

Compared to a two-person household in Germany, a mid-range electric car's battery can charge to its full capacity, covering the household's average electricity consumption of about 54 kWh per week.

Furthermore, the new ID.4 and R5 models are already designed to generate power for buildings and supply electricity back to the grid.

With a two-way charging station, electricity from the house roof can be transferred into the car battery during the day, and vice versa from the car to the house in the evening. As a result, residents can utilize affordable solar power at any time.

Homeowners can save on the cost of installing additional battery storage units for the solar system by linking electric cars and home systems. Typically, single-family solar battery systems have a capacity of 5 to 10 kWh, and can cost up to $10,440.

"Simply put, informed charging and discharging can lengthen battery life by 5 to 10 percent, Robert Kohrs, an expert in smart grids at the Fraunhofer Institute, explained.

How do electric vehicles contribute to stabilizing the power grid?

In Germany, cars are typically driven for less than an hour daily. During the time e-cars are stationary, grid operators can utilize the batteries to temporarily store electricity, thereby offsetting power grid fluctuations.

This will assist in utilizing the rising amount of solar and wind power being directed into national power grids. Recently, this has accounted for 70% of power production in Denmark and nearly 50% in Germany — though it is often available when it is not needed.

Discharged electricity from these renewable sources can be temporarily stored. When energy demand is high, this stored electricity can be fed back into the utility network. Additionally, this helps alleviate strain on gas or coal-based power plants during times of heavy consumption, with a corresponding reduction in the amount of backup energy storage needed to stabilize the utility grid.

A recent study conducted by the European environmental organization, Transport & Environment, estimates that annual savings of 22 billion euros could be achieved through the shared use of car batteries in the EU.

According to the report, electric vehicles have the potential to meet around 9% of the EU's electricity needs, while temporarily reaching up to 20%, making them a crucial component of the electricity system.

The magazine notes that this will demand battery storage systems with a capacity of 74 billion kWh globally by 2050.

By 2050, there will potentially be 1.5 billion electric vehicles worldwide, according to researchers. Given an estimated 60 kilowatt-hours of battery capacity per vehicle, the global fleet could accumulate a maximum total of 90 billion kilowatt-hours of electrical energy.

What are the advantages of car batteries for automotive, residential, and power supply systems?

According to the Fraunhofer study on electric vehicle power integration, e-car owners may save between €31 and €780 annually by sharing the battery power with their home or the power grid.

In the country of France, private owners of the new electric Renault R5 received a complimentary 10,000 kilometers (approximately 6,200 miles) of driving electricity in exchange for plugging their vehicle into a two-way charging station for approximately 15 hours every day.

Raffeiner reported to that more solicitations of this nature are in the process of being developed.

According to a survey conducted by energy supplier Eon, 77% of respondents would use bi-directional charging technology to supply their own structures, while 65% would support electricity networks.

Experts suggest that the new generation of private and public charge stations should operate in both directions wherever feasible.

According to the Fraunhofer study, the estimated increase in initial costs would be approximately 100 euros for small charging stations (up to 22 kilowatts), and around 250 euros for rapid charging stations.

These extra expenditures would be compensated by the savings achieved within a few months of use.

Sources:

https://www.transportenvironment.org/uploads/files/2024_10_Study_V2G_EU-Potential_Final.pdf

This article was originally written in German.

Author: Gero Rueter