boast increasingly powerful batteries that are charged from the energy grid or rooftop solar systems.
But when the car isn’t in use, its can serve as storage for homes and the energy grid via a bidirectional charging process that can reduce power costs.
How does it work, and are there drawbacks?
What is bidirectional charging?
Until recently, power flowed in one direction to (EV) batteries from the charging station.
A charged battery could not only power the electric motor, electronics, lights and heating but external devices such as a fridge when camping, a drill on a building site or even another EV. These additional functions are called V2D (vehicle-to-device), and V2L (vehicle-to-load).
But using the latest bidirectional chargers, can also supply entire buildings with electricity using vehicle-to-home (V2H), or feed electricity into the public grid via vehicle-to-grid (V2G) technology. They can also simply charge car batteries.
However, bidirectional devices are currently only available in select charging station locations.
How much electricity can a car battery store?
The batteries in EVs are becoming cheaper and more powerful. The battery in the Tesla Model Y, for example, has at least 62 kilowatt hours (kWh), the VW ID.4 has 77 kWh and the Renault small car (R5) has at least 40 kWh.
By comparison, the electricity consumption of a two-person household in Germany is around 54 kWh per week. A mid-range electric car could therefore completely cover this electricity requirement with a full battery charge.
In addition, the new ID.4 and R5 models are already designed to power buildings and feed electricity into the grid.
With a bidirectional charging station, can flow from the roof of a house into the car battery during the day, and back into the building from the car in the evening. This means residents can use cheap solar power both day and night.
By linking to the electric car, homeowners can save on installing additional battery storage units for the solar system. In single-family homes, solar battery systems usually have a capacity of 5 to 10 kWh, and cost up to €10,000 ($10,440).
Meanwhile, bidirectional charging is “not harmful to the per se,” said Robert Kohrs, an expert in smart energy grids at German research body, the Fraunhofer Institute. “If you do it right, controlled charging and discharging can increase battery life by 5 to 10%.”
How can electric cars stabilize the power grid?
Cars are driven on average less than an hour a day in Germany. During the time that e-cars are parked, grid operators could use the batteries to temporarily store electricity and thus compensate for fluctuations in the power grid.
This will help use the growing amount of flowing into national grids. In recent years, that has amounted to 70% of power generated in Denmark and just under 50% in Germany — though it’s often available when it’s not needed.
can temporarily store the surplus electricity from these renewable energy sources. When demand increases, the electricity can be fed back into the grid. This also relieves the pressure on gas or coal-fired power plants during periods of high consumption, while less battery storage is required to stabilize the electricity grids.
The savings potential for the shared use of car batteries in the EU could reach €22 billion annually, according to a recent study commissioned by the European environmental organization, Transport & Environment.
The report said EVs could cover up to 9% of the EU’s electricity requirements, and temporarily up to 20%, making them an important pillar of the electricity system.
While the affordable and climate-neutral energy supply of the future will be based primarily on solar and wind power, according to a study published in Science magazine, this will require battery storage systems with a capacity of 74 billion kWh worldwide by 2050.
By 2050, there could be 1.5 billion EVs worldwide, said the researchers. With batteries averaging 60 kWh per vehicle, this global fleet could store a total of up to 90 billion kWh of electricity.
What are the benefits of car batteries for car, home and grid?
According to the Fraunhofer study on EV power integration, e-car owners could save between €31 and €780 per year by sharing the battery power with their own home or the power grid.
In France, private owners of the new electric Renault R5 were offered 10,000 kilometers (around 6,200 miles) of free driving electricity in return for connecting their car to a bidirectional charging station for an average of 15 hours a day.
The offer has been “well received in France, we are getting a lot of interest,” said Thomas Raffeiner from Mobility House, a German-Swiss company that markets bidirectional charging — and the low cost of energy for consumers who utilize the flexibility of . Raffeiner told DW that more such offers are in the works.
According to a survey commissioned by energy supplier Eon, 77% of respondents would use bidirectional charging technology to supply their own buildings, while 65% would support electricity grids.
Experts recommend that the new generation of private and public charging stations should function bidirectionally wherever possible.
The Fraunhofer study estimated that this would increase the initial costs by roughly €100 for small charging stations (up to 22 KW), and by around €250 for a fast charging station.
However, these additional costs would be offset by the savings made 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
The post How EVs can store energy for homes and power grids appeared first on Deutsche Welle.
