European Institute for Energy Research

Only a few low-temperature aquifer thermal energy storage sites (LT-ATES) exist in Germany. Our project aims to demonstrate the implementation of a LT-ATES system in an urban area motivated by the increasing demand for cooling in summer. The backyard of an office building complex in Berlin-Mitte was chosen as our test site. Due to the densely built-up conditions, it was not possible to implement a classic doublet system. A coaxial well with a drilling depth of 27 m and a filter distance of 6 m was therefore implemented, which can only be operated using a flow-through principle. In a coaxial well the groundwater is drawn from the lower end of the well system and fed to the heat pump via the inner pipe. After the thermal energy is extracted, the groundwater is re-injected via an outer pipe within the same borehole into a shallower layer. The injection of cooled or heated groundwater in winter and summer, respectively, results in vertical circulation of the groundwater within the aquifer.  The permissible temperature spread is limited to 3 K in Berlin. With reference to the local ambient groundwater temperature of around 13 °C, the thermal loading of the aquifer therefore can only vary between 10 °C and 16 °C. The well system was planned as an integrated heating and cooling source as part of the energy-efficient building refurbishment and is used to cover the base load with a maximum flow rate of 6 m³/h. The well went into operation at the end of June 2024.We monitor the thermal-hydraulic, geochemical and ecological influences on the aquifer using three monitoring wells which are also located in the backyard. Fiber optic cables were installed for depth-differentiated temperature measurements. In addition, continuous measurements of groundwater level, conductivity and flow rates are carried out. To record the thermal influences on the groundwater ecology, groundwater samples are regularly taken at the site and compared with other samples in Berlin.The potential for seasonal heat storage in the aquifer has been modelled indicating a potential thermal short circuit in the well configuration and raising the question of whether the well system is a seasonal regeneration of the aquifer rather than an active thermal storage. Increasing the distance between the filter sections might solve the problem. Preliminary monitoring results show a significant and increasing influence of the air temperature over the course of the summer and over the entire well length causing a interaction with well operation.

Currently, higher shares of renewable electricity are promoted to reduce global Greenhouse Gas (GHG) emissions and decarbonize the energy sector. Electrolysis can help their integration into the grid but also for energy vector production.In this context, Protonic Ceramic Electrolysis Cells (PCEC) are considered a promising clean energy technology. The ARCADE project focused on developing a cost-effective metal supported Protonic Ceramic Cell (PCC) reactor. Its environmental performance is compared to an existing Solid Oxide Electrolysis Cell (SOEC) using Life Cycle Assessment (LCA).Results show that the faradaic efficiency heavily influences a PCC's environmental performance while manufacturing has minimal impact except for potential human health concerns from metal use. To get more detailed results, further studies on PCC performance, degradation and effect of scaling up from single cells to larger systems are needed but, already at the current state, PCCs show potential for clean energy.

Microgrids are one of the solutions to tackle rural electrification issues in developing countries. EDF R&D and EIFER developed PREMO Grid, a tool that plans the Low voltage network of a microgrid using a set of geographic data. The proposed network layout is first done by an algorithm that minimizes the total length respecting local constraints like rivers and roads. It is then sized according to electrotechnical constraints.

Over the last years, the German energy transition has led to diversification and decentralization of the electricity market. Today, digitalization forms a key driver for innovation. Several established electricity suppliers and emerging start-ups have responded by offering novel business models (BMs) in “Digital Energy Communities” creating an intertwining network of actors. This analysis discusses the emergence of novel BMs and the end-users’ role in this market segment with regard to participation opportunities and provides a definition of digital energy community BMs. Out of the 106 relevant BMs in the German context, the authors selected 26 BMs with regard to actuality and representativeness. They were mapped against criteria that influence citizen engagement. Our findings suggest that 14 BMs represent emerging companies, while 12 BMs are products of established market players. Many of the novel BMs focus on providing online marketplaces. Surprisingly, only one of them allows citizens to participate in the BM financially. The findings suggest that while the digital energy community BMs provide opportunities for citizen participation in the energy transition, roles and responsibilities must be more clearly defined. Digital energy community BMs can only minorly contribute to citizen participation as citizen engagement is not fundamentally inherent in their value proposition.

We studied the impact of infrastructure networks on relict floodplain forest along three stretches of the Upper Rhine (Kembs-Efringen-Kirchen, Strasbourg-Kehl and Beinheim-Iffezheim) and the Inn-Danube (Mulheim-Obernberg, Passau-Ingling and Engelhartszell-Jochenstein), each on the border between two countries. We analysed land use patterns within a 500 m wide buffer area along the main channel using photo-interpretation and compared the situations between the 1950s, 1980’s and 2010’s. Temporal changes were assessed with transition matrices and selected spatial metrics, including fragmentation indices. Over this period, forest area remained similar at three sites, increased slightly at two sites and decreased at one site. However, on average, 12.5% of floodplain forest had changed location (range: 7.3% (Engelhartszell-Jochenstein)– 26.5% (Kembs-Efringen-Kirchen)). The natural development of unmanaged areas and agricultural abandonment after World War II has led to the emergence of young riparian forests along rivers. In the Upper Rhine region, the results showed asymmetry in these two factors, with unmanaged natural areas most important on the French side and agricultural abandonment on the German side. Along the Inn-Danube, agricultural abandonment has led to an increase or stagnation of floodplain forest areas. In most cases, development of transport infrastructure between the 1950s and 2010s has caused fragmentation of the forest area, reducing the relict forest to a patchy green corridor with reduced functionality and interfacing. To go further and improve the management of these relict forests, we have to investigate the interdependency between practices related to infrastructure operation and the role that biodiversity plays for stakeholders.