Bidirectional charging: E-cars can store renewable electricity – Knowledge

On January 15, 2023, it became clear that the expansion of renewable energies brings new challenges. On that day, renewable energies could have covered 96 percent of Germany’s electricity requirements, with wind power alone accounting for 80 percent. But because there were no power lines, the electricity could not always flow to where it was needed. It would have been practical to be able to temporarily store the electricity and later feed it into the grid. Since fluctuations in power generation are increasing with the further expansion of wind power and photovoltaics, the need for storage options is also increasing, not only in Germany but worldwide.

According to researchers from Leiden University and the US National Renewable Energy Lab, the solution to this problem is already in sight. According to this, electric cars could contribute to stabilizing the power supply by temporarily storing energy in their batteries. The researchers working with Chengjian Xu report that by 2030 they could practically meet the global demand for energy storage on their own if enough vehicle owners take part in Nature Communications.

In it, they calculate that the short-term global storage requirement in 2050 should be somewhere between 3.4 and 19.2 terawatt hours (TWh). The batteries from electric cars could then already provide between 32 and 62 terawatt hours of capacity for the grid, thus covering the demand generously. The scientists have already deducted the amount of energy required for driving the electric cars, so drivers would not have to accept any restrictions.

Used batteries could also contribute to the power supply

In principle, batteries from electric vehicles can help the power grid in two ways. Firstly, by charging e-cars primarily when sufficient electricity is being generated and returning it to the grid when it is needed. This technology is called “bidirectional charging” or “vehicle to grid”. Another option is to reuse discarded batteries. Batteries whose capacity has fallen below 70 to 80 percent are usually no longer suitable for driving a vehicle – but they can be used as energy storage for the power grid. The batteries would only have to be checked and rewired. Given the economic value of discarded batteries, the researchers estimate that about three-quarters of old batteries are eligible, while about a quarter are likely to be recycled.

How much energy can actually be temporarily stored in these two ways depends on how quickly the fleet of electric cars grows. In the International Energy Agency’s (IEA) optimistic scenario, around 138 million battery electric cars would be on the roads in 2030, compared to 17 million today. Of these, only one in five e-car owners would then have to take part in order to cover the assumed average demand. In a conservative scenario, the expansion would be about half as fast. Then 38 percent of the drivers would have to take part. In addition, there are the batteries that have been discarded. Therefore, a moderate participation rate would probably be sufficient in practice. As early as 2030, e-cars could significantly support the energy transition, the researchers write.

Nevertheless, governments must quickly lay the foundations for bidirectional charging, according to the study. For example, vehicle owners who provide electricity should be rewarded for doing so. Companies could possibly even be required to participate. In addition, it needs the necessary hardware and software for charging and discharging to work.

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