LINE-FEED - Plug-in Photovoltaic Storage for the Wall Socket

The project LINE-FEED develops technologies that are required for a photovoltaic storage system which can be installed by anybody by simply plugging it into a wall socket. The aim is to create a storage system for households in urban areas that do not have the possibility to install a photovoltaic system themselves.

Short Description

Starting point / Motivation

Photovoltaics and the associated decentralized storage systems are key technologies on the way to a sustainable energy system and climate-neutral cities. Due to the technical design of state-of-the-art PV systems, these are mainly used in single-family houses and industrial buildings. Due to the new legal framework, shared photovoltaic installations are being used more and more on residential buildings in urban areas.

Contents and goals

The aim of this project is the technological development of an electricity storage system (and the necessary components), which can be installed in all households, including small city apartments, by plugging it into an ordinary wall socket. The system will have all the technical advantages of large storage systems. If solar power is available, the storage is charged from the socket and after sunset the energy is fed back into the same socket and supplies the household with decentralized renewable energy.


In order to implement such a system, three technological problems have to be overcome:

  • Feedback control - How much power must be charged in the battery and fed back, and when?
  • Measurement technology - How much power is currently used in the household?
  • Line-Battery-Interface "LiBIF": a bidirectional charging circuit that charges the battery from the grid with a specified power and can also feed a specified power back into the grid.

The basis of the measurement technology is the patented process, which was developed by the founding team of the start-up EET at Graz University of Technology. It is able to detect the current electricity demand of a household by means of high-frequency measurement approach without additional hardware. The "LiBIF" Line Battery Interface is the component that is able to efficiently charge the energy into the battery or to release it from the battery back into the household's grid.

Expected results

The aim of the two-year project is a functional test system that solves these technical questions. The results of the project are, on the one hand, the technological development of the previous mentioned components and the realization of a functional prototype. The functions are tested with this prototype and, if the project is successful, the system will be industrialized to enable energy storage in all apartments.

Project Partners

Project management

Dipl.-Ing. Dr. Christoph Grimmer, EET GmbH

Project or cooperation partners

  • Graz University of Technology, Electric Drives and Machines Institute
  • Energie Graz GmbH & Co KG

Contact Address

EET - Efficient Energy Technology GmbH
Herrgottwiesgasse 207
A-8055 Graz
Tel.: +43 (316) 232-203