International Research Atelier: Battery Energy Storage Systems in Distribution Grids

German version

The international research atelier, a workshop organized by the working group Grids and Energy Systems (AGNES) from the Institute of Technical Energy Systems (ITES), has been taking place for three years now as part of the International Week at Hochschule Bielefeld - University of Applied Sciences and Arts (HSBI). Each year the event is a magnet for interested researchers and industrial companies, both nationally and internationally. This year's international exchange on 15 May focused on battery storage systems in distribution networks and was organized in cooperation with VDE.

Challenges for future distribution grids
Prof. Jens Haubrock, Head of AGNES, highlighted the relevance of research cooperation between universities and industry, in particular grid operators. The climate targets set by Germany and the EU, such as covering 80% of electricity consumption from renewable energy sources by 2030, are making grid operation increasingly complex. Electricity generation from renewable energies fluctuates depending on the weather, while at the same time all sectors are being electrified, resulting in rising electricity consumption. The majority of renewable energy generation plants along with new loads such as electric vehicle charging stations and heat pumps are both connected in the distribution grid. This reconstruction creates the threat of grid congestion and makes it necessary to take a closer look at the ever-changing load flows. Prof. Haubrock presents the solutions to this problem: Grid expansion and exploitation of flexibility through, for example, battery storage in the distribution grid. Grid expansion is capital-intensive and time-consuming. The use of flexibility, on the other hand, is quicker and technically easier to implement and could be a short-term solution for ensuring grid security and stability in parallel with grid expansion. Prof. Haubrock's clear conclusion: cooperation between universities and industry is essential in managing the energy transition because it is the "engineers and technicians who are implementing the energy transition" - and they are qualified at universities.

International research: AI4DG

The international research project AI4DG: AI on the edge for a secure and autonomous distribution grid control with a high share of renewable energies is investigating specific solutions for the use of flexibility in the distribution grid. Researchers from HSBI and the Universities of Grenoble and Bielefeld, together with the grid operator Westfalen Weser and the company Atos Worldgrid, are researching the grid-friendly use of battery storage in the distribution grid. Katrin Schulte, a doctoral student at AGNES at HSBI, explains the problem: in a grid area with many photovoltaic (PV) systems, backfeeds between the low and medium voltages occur on sunny days, which can acutely overload operating resources. To counteract these overloads, private household battery storage systems were developed to charge and discharge based on a prediction of the grid load. This is done in such a way that back-feed peaks are minimized. This control system is currently being validated in a field test with real homeowners. 

Julius Dresselhaus, a student trainee at Westfalen Weser, explains the potential of grid-serving battery storage systems in the energy transition. For a future scenario with several battery storage systems in the grid area, the grid-serving use of battery storage systems can reduce overloads on the transformer and even avoid limit current violations on the supply lines. Hélène Schricke from the French company Atos adds further potential. Battery storage systems allow for the maximization of local production, as it enables the unregulated operation of renewable energy systems during periods of local overload, with their energy being stored in battery systems instead. Both conclude that the use of storage systems can make an imminent grid expansion less cost-intensive and even postpone it.

Future research
Legislation has also identified solution strategies in the Energy Industry Act (EnWG). In response to the increasing curtailment of renewable energy plants due to grid congestion, §13k describes the use of electricity volumes in additional switchable loads. These must be flexible in their operation and contribute to the transformation to a greenhouse gas-neutral, reliable, secure and affordable energy supply system. In response to local overloads, §14a stipulates the grid-oriented control of controllable consumption devices and controllable grid connections.

Controllable consumption devices include, in particular, heat pumps, charging points for electric vehicles that are not accessible to the public, systems for generating cooling or storing electrical energy and night storage heaters. Both pieces of legislation are based on the grid status assessment and forecast. The concrete implementation of these measures still requires further cooperation between universities and industry. For this very reason, the presentations were followed by a relaxed get-together with all participants, during which the topics were discussed further.