By Vera Eckert

Drivers will want to charge their EVs at will to ensure they always have enough power, but letting suppliers do it for them overnight will prevent blackouts, says Vera Eckert

Carmakers around the world are pushing hard for new electricity networks to charge cars more quickly. But in Europe, some power companies and grid operators are testing a slower approach.

A 15-month study of electric vehicle charging in Germany has concluded that consumers can be persuaded to accept slow overnight recharging to avoid brownouts from surges in electricity demand or costly upgrades to power grids.

If millions of EVs hit the roads as governments gradually ban diesel and petrol cars, it will be a major challenge for power companies, especially in Germany, which is switching from nuclear and coal to wind and solar, less predictable sources of energy.

Earlier this year, in its climate action plan, the Irish Government committed to having 936,000 EVs on the roads by 2030. The German study, in the wealthy Stuttgart suburb of Ostfildern-Ruit, has alleviated the concerns of some grid operators that too many electric vehicles (EVs) charging at peak times could cause network crashes.

The engineers at Netze BW, the local grid operator that held the trial, found that all the households left their electric cars plugged in overnight and only half ever charged simultaneously.

“Since the experience with the project, we have become a lot more relaxed. We can imagine that, in future, half of the inhabitants of such a street own electric vehicles,” said Netze BW engineer Selma Lossau, project manager for the study.

Still, with limited EV battery ranges for now, slow, overnight charging doesn’t solve how to persuade drivers to ditch petrol cars. Without a network of fast-charging stations for electricity replenishment, drivers may be wary of using EVs for long trips. Carmakers want fast-charging stations to encourage widespread adoption.

Slower, or delayed, charging has gained traction in Norway, Europe’s leading EV market, where 50% of new cars are zero-emission.

A study by energy regulator NVE showed that Norway, which has a population of 5.3m, faces a bill of 11bn crowns (€1.2bn) over the next 20 years (for low and high-voltage grids, substations and high-voltage transformers), unless it can persuade car owners to charge outside peak afternoon hours.

The investment cost could drop to 4bn crowns if cars are charged in the evening, and close to zero if batteries are only plugged in at night, NVE said.

NVE is proposing a tariff to penalise peak-hours charging. Tibber, a Norwegian power company, offers cheaper electricity for EV charging if you let Tibber decide when your car is charged, while firms such as ZAPTEC adjust charging to the available grid capacity.

Some of the 10 households that participated in the Stuttgart trial said they initially wanted to keep topping up their cars, for fear of running low, but soon adapted to letting the power company do it overnight.

“At the start, I did not want to take any risks and charged frequently, in order to feel secure. Over time, I changed my outlook,” said Norbert Simianer, a retired head teacher, who drove a Renault Zoe during the trial.

“I grew used to the car and became more at ease in handling the loading process.”

Simianer and his neighbours were given electric cars and 22 kilowatt (kW) wall-boxes for their garages, alongside two charging points in the street, all free of charge.

In return, they gave up their normal cars and allowed Netze BW, which is a subsidiary of German utility, EnBW (EBKG.DE), to monitor and carry out a deferred and scaled-down charging process, during a seven-and-a-half-hour period overnight.

Netze BW tried various options, either slotting cars in one after another, at the maximum, 22 kW charging flow, or lengthening the charging time for individual cars by adjusting the power flow, or combining both methods, Lossau said.

The participants, who used apps to check the status of their car batteries, grew accustomed to the lack of instant charging capability, because their vehicles could always handle their everyday commutes of up to 50km (31 miles). EnBW said nine of the 10 households in the trial on Ostfildern-Ruit’s Belchenstrasse kept the wall-boxes and most were considering leasing electric cars.

Lossau said monitoring 10 households did not in itself provide the “empirical mass to draw conclusions for the load profile of all of Germany.”

She also said there would need to be better communication between EVs, the grid, and consumers for the system to function efficiently on a large scale.

“There will have to be more exchange of information between e-cars and the grid to update the loading status in real-time, because, otherwise, there can be the wrong impression about the speed of loading,” she said.

Utility companies developing so-called vehicle-to-grid (V2G) services, however, are struggling to persuade some automakers to use technology that allows two-way flows of information, and power, between batteries and grids.

Carmakers such as Volkswagen, Daimler, and Ford, for example, are prioritising one-directional fast-charging to overcome consumer resistance to EVs.

Japan’s Nissan has pioneered V2G, though Germany’s BMW (BMWG.DE) has now decided to develop it too, saying cooperation between cars and grids will be key to making e-mobility ready for mass markets.

“It is about making sure there is enough supply for the electric cars and that the lights do not go out elsewhere,” a BMW spokesman said.

The cars don’t just load when it’s best for the market, but they can also supply power back to the grid to help even out demand spikes. There has to be more progress on the data exchanges, however. It is not yet the standard.

Nevertheless, the Ostfildern-Ruit trial has raised hopes that power grids might be able to cope with an influx of electric cars, especially if the consumers play ball.

Even if drivers resist overnight charging, suppliers of software and equipment to power grids, such as Germany’s Siemens (SIEGn.DE), are also looking at safer and more efficient ways to manage how and when power is used to charge cars.

The German city of Hamburg, for example, started a three-year pilot project this month, with Siemens, to pre-emptively identify overloads on transformers and along cables, and manage EV charging points accordingly.

“Loading processes offer so much flexibility that the overload on the networks can be reduced by deferring loading times or reducing the load that is supplied,” said Thomas Werner, expert at Siemens Digital Grid.

“This happens through the digitisation of hardware and software and with communication technology,” he said.

Using software to protect aging power networks from predictable surges could also avoid costly hardware upgrades to parts of the 1.7m km of distribution grids in Germany.

With fewer than 100,000 electric-only cars in Germany, there is little threat of blackouts from over-demand. But the transport ministry, in Berlin, envisages up to 10m electric cars on the roads by 2030.

Germany has 21,000 charging points. That’s an increase of 50% over the last year, but still barely a fraction of future needs.

In Ireland, an additional 1,000 extra charge points will be installed over the next five years as part of a new on-street infrastructure scheme. Richard Bruton, the minister for communications, climate action, and environment, has announced funding that will help local authorities provide a widespread rollout of electric cars.

They will receive €5,000 to develop 200 charge points every year until 2025.