The “i-rEzEPT” project for the integration of electric vehicles into public and private electricity grids is delivering impressive interim results. For about a year, the project participants have been using a Nissan LEAF not only to meet their mobility needs, but also to use the electric car as a temporary storage unit for the electricity they generate themselves via a photovoltaic system.

In a short film, the project partners draw a first preliminary conclusion.



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Within the scope of the field trial, e-car pioneer Nissan provided 13 homeowners from all over Germany who have a photovoltaic system with a Nissan LEAF and a corresponding charging station. The aim is to make the most of the household’s supply of self-generated solar power, relieve the strain on the public electricity grid and at the same time reduce the operating costs of the e-vehicle.

The participants take advantage of the Nissan LEAF’s special ability to perform bidirectional charging, often referred to as vehicle-to-grid technology (V2G for short): The vehicles can store surplus solar energy generated on the roofs of houses in their batteries and later release it to the household or feed it into the public grid as needed.

“i-rEzEPT” was launched by Nissan together with Bosch.IO and the Fraunhofer IAO and IFAM institutes. The project is being funded by the Federal Ministry of Transport and Digital Infrastructure as part of the Electric Mobility Funding Guideline with a total of 2.39 million euros.

“Electric cars should be charged when electricity from wind or solar power is available,” says Stefan Sonntag, Electric Mobility Programme Manager at NOW GmbH, a company of the Federal Ministry of Transport. “i-rEzEPT is testing exactly this out, making it possible to use this energy not only as green driving power, but also to supply your own home with electricity.”

The interaction between the LEAF and the home power grid is coordinated by a local energy manager from project partner Bosch.IO. This was developed, based on the Bosch IoT Gateway software. This ensures, for example, that the vehicle’s range is only slightly affected, as a maximum of ten to 30 percent of the battery capacity is used to supply power to the household. If necessary, a full charge of the vehicle can also be prioritised – for example before starting a longer journey. The Fraunhofer IAO and IFAM institutes in Bremen and Stuttgart analyse the data on electricity use anonymously. For this purpose, Fraunhofer IAO uses a specially developed data platform and determines forecasts for the availability of the individual vehicles.

“The data is necessary to obtain a scientifically supported statement about the business model of bidirectional charging and to identify potential user groups,” says Stefan Lösch from Fraunhofer IFAM.

“Especially against the backdrop of an increasing number of people working from home, there is huge potential here to use renewable energy efficiently and reduce emissions in transport,” adds Vincent Ricoux from Nissan Center Europe. “We therefore are anticipating that interest in this technology will continue to grow in the future.”

The project name “i-rEzEPT” stands for “Intelligent power recovery-capable electric vehicles for self-power maximisation and primary balancing power market participation” (German: “Intelligente Rückspeisefähige Elektrofahrzeuge zur Eigenstrommaximierung und Primärregelleistungsmarkt-Teilnahme”). With the project, the initiators are striving to further promote the proliferation and acceptance of electric vehicles and also to highlight the role that electric cars can play in stabilising both public and private power grids.

However, until an affordable V2G system for end consumers can be put into practice, the legal basis, among other things, has yet to be established. This can then serve as the springboard for the development of innovative products that offer a competitive alternative to stationary battery storage.