The automobile was invented for locomotion, as the “mobile” in the name says. This also applies to electric vehicles. However, these models can not only be used for driving, as a storage medium they can also make a contribution to the future of energy use. With bidirectional charging, the electricity can be directed in two directions and not only flows in the direction of the electric drive, but also supplies the home network with the electricity it needs.
This storage solution is optimal if the electricity is generated by a photovoltaic system. BMW and E.On are currently conducting a practical test to find out how sensible it is to use the combination of solar power and the e-car as storage. The use in private households is part of the large-scale project “Bidirectional Charging Management” by BMW and its partners, which is funded by the Federal Ministry for Economic Affairs and Climate Protection.
Two families in the Munich area are currently testing how bidirectional charging can be integrated into their everyday lives. The appropriate technical equipment was installed by E.On in the two households, and BMW supplied the BMW i3 that had been converted for the new technology. A team of experts from the two companies is accompanying the project, evaluating the data and looking for possible improvements.
In order for an electric vehicle to mutate into an electricity storage device, it must be equipped with a bidirectionally chargeable battery so that the electricity can flow in both directions. However, the direct current used by electric cars must be converted into alternating current for the household infrastructure using an inverter.
In the pilot project of the two companies, the interaction of the battery with the photovoltaic system is examined. The battery of the e-car is charged with excess solar power, which can later flow back into the domestic power grid if required. With this solution, customers can use a larger proportion of the generated solar power themselves.
This creates a win-win situation, because using the vehicle battery improves the energy independence of households, while at the same time energy costs are reduced and the photovoltaic system pays for itself more quickly. In view of the ramp-up of electromobility, there will be more and more potentially usable storage capacity in the form of e-car batteries over the next few years. Therefore, in the future, many automobiles with the appropriate technology can be used as a kind of swarm battery, thus relieving the power grid.
“It is an important step for the energy transition to also use the battery capacity in the e-car as part of a holistic energy management system,” explains Filip Thon, CEO of E.On Energie Germany. And: “We are convinced that bidirectional charging will play an important role for our customers in the future – and we look forward to intensively testing the technology together with our partner BMW. We expect valuable insights for future products in terms of our integrated energy solutions for the home of the future.”
According to the E.ON experts, the bidirectional charging system might not only supplement home storage for photovoltaic systems in the future, but might also be used in older systems, which can often only be retrofitted with battery storage at great cost. The model applications also make an important contribution to the energy transition and at the same time relieve the power grids.
In Japan, this technology has been mandatory for several years to keep households supplied with electricity following natural disasters. That is why most of the models that are equipped for this technology currently come from Japan.
User-friendliness is important for the acceptance of the application. In order to ensure this, certain targets for bidirectional landing, such as the state of charge, can be defined. For example, users can specify a minimum amount of energy that should remain in the battery of the e-car and thus always have enough range for everyday journeys – despite the fact that electricity is fed into the grid. After all, the car should remain mobile at the end of the day. (Walther Wuttke, cen)
