Energy flows have to be considered across multiple sectors if the energy transition is to be implemented successfully. This increases the flexibility of the overall system to efficiently balance out energy supply fluctuations between the power grid, the mobility sector and district heating demand, while at the same time ensuring the stability of the power grid. Against this background, the Institute of Networked Energy Systems at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is currently developing a digital simulation of a real hybrid regulating power plant as part of the HyReK 2.0 (Hybridregelkraftwerk) research project, which is funded by the German Federal Ministry for Economic Affairs and Energy. The power plant provides frequency containment reserve in the Hastedt district of Bremen and makes efficient use of an interface between the power grid and a district heating system.
Combining power storage, heat storage and an electric boiler
This innovative power plant concept combines a large stationary battery system with a heat storage system and an electric boiler. When the battery is fully charged, any excess energy, for example caused by a strong wind from the North Sea, is directly converted into heat. This excess energy can be stored, if required, or immediately supplied to the district heating network. The Oldenburg energy researchers aim to optimise the flexibility of this hybrid regulating power plant so it can provide multiple services. A second research objective is to assess the environmental, economic and social aspects, and identify the potential for implementing this new hybrid solution. “The increasing use of renewable energy sources results in more and more severe fluctuations in the supply of electricity. Until now, these have been balanced out using positive or negative frequency containment reserve that mostly originates from conventional power plants. Our aim is to demonstrate potential ways in which this service can also be provided in a decarbonised energy system with these hybrid regulating power plants,” explains Theys Diekmann, HyReK Project Manager at the DLR Institute of Networked Energy Systems.
Simulation model based on real load profiles
The new power plant technology became operational in July 2019 and the Institute of Networked Energy Systems is developing a simulation model based on the real data from the facility. It is planned to use a high-performance computer analysing the service for the grid on an experimental basis to observe the positive influence of the power plant on the grid in detail. The total energy consumption of the Hastedt area is taken into account based on real load profiles. Technical devices at a pilot-scale level such as an inverter, which is the interface between the battery and the power grid, are also represented in the simulation with the support of the manufacturer and project partner AEG Power Solutions.
Providing greater efficiency and increased durability for the overall system
“We want to use this as a basis for developing the technology in such a way that the activities of individual power plant components are not viewed separately, and are instead aligned towards the overall system behaviour,” explains Diekmann. “This will enable us to optimise the efficiency and durability of the system and the individual components, thereby allowing an economically viable operator concept to be derived.” How valid the simulation is will become clear as the project progresses through the transition into simulated practice. The simulation data can then be implemented in the power plant technology in the real laboratory together with the power plant operator, Bremen-based swb AG. “This will enable us to validate various operating modes, such as how precisely the electrical energy is stored in and withdrawn from the battery,” says Diekmann, looking ahead.
Power-to-heat technology minimises the need to expand the network
In addition to focusing on the Bremen hybrid power plant, the DLR researchers are also looking at the ‘big picture’, Diekmann asserts: “Using the simulation model, we are already in a position today to simulate the energy scenarios that we expect for the future. This allows us to identify potential further options for flexibility around the hybrid concept. Aside from frequency containment reserve, for example, we also want to use power-to-heat technology as an additional system service so that we can develop strategies to design the future energy system without having to expand the grid.” At the same time, in order to identify the conditions under which the hybrid approach for power plants could develop into a successful model, the Institute of Networked Energy Systems is preparing an economic assessment of the implementation potential in Germany and is analysing the contribution the hybrid approach would make towards ensuring greater flexibility (resilience) in the entire national energy system. Environmental, economic and socio-technical analyses are also being carried out for the HyReK model in order to obtain a more whole-system view of the power plant and to identify the potential for sustainability at an early stage.
Promising transformation in implementing the energy transition
The investigations have already shown that hybrid technology appears to be a promising transformation path for the energy transition. “Frequency containment reserve is currently still predominantly being provided by fossil-fuelled power plants, but in the long term we need to provide this through decarbonised systems. That is the challenge,” Diekmann emphasises. “This is why we are already using the HyReK project today to explore possible options for replacing conventional power plants with new technologies in a cost-effective manner for tomorrow’s energy system.” In addition to the technical aspects, the DLR researchers are also focusing on future business models for shaping the market: “We are preparing recommended actions which show how innovative technologies can be operated cost-effectively and sustainably over the long term.”