DLR is developing a simulation model containing strategies for managing and operating a unique hybrid system consisting of a large stationary battery system and a power-to-heat unit
Energy flows have to be considered across multiple sectors if the energy transition is to be designed successfully. This increases 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 in the power grid. Against this background, the Institute of Networked Energy Systems at the German Aerospace Center (DLR) currently develops a digital replica of a real hybrid regulating power station as part of the HyReK 2.0 research project (“hybrid regulating power station”, funded by the Federal Ministry for Economic Affairs and Energy). The power station provides frequency containment reserve in Bremen's Hastedt district and particularly makes efficient use of the interface between the power grid and district heating.
At the Institute of Networked Energy Systems the team around HyReK project manager Theys Diekmann (right) produces a simulation model which optimises operation of the hybrid regulating power plant of the Stadtwerke Bremen on a laboratory scale.
Photo: DLR (CC-BY 3.0)
Combining power storage, heat storage and an electric boiler
This innovative power station concept combines a large stationary battery system with a heat storage and an electric boiler. When the battery is fully charged, any excess energy, for example caused by a fresh breeze from the North Sea, is directly converted into heat. This excess energy can be stored, if required, or supplied directly into the district heating network. The Oldenburg energy researchers aim to optimise the flexibility of this hybrid regulating power station so it can provide multiple services. A second research objective is to assess ecological, economic and social aspects and to determine the potential for implementation of this new hybrid solution. “The increasing use of renewable energies results in more and more severe fluctuations in the supply of electricity. Up to 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 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 develops 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, i.e. 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 longer 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 deduced.” 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.
A 15-megawatt battery storage system ensures that the hybrid regulating power plant can stabilise the power grid with positive or negative frequency containment reserve.
Photo: swb AG
Power-to-Heat technology minimises the need to expand the network
In addition to focussing on the Bremen hybrid power station, the DLR scientists 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 instance, 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. Ecological, economic and socio-technical analyses are also being carried out for the HyReK model in order to obtain a more holistic view of the power station 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 towards 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 stations with new technologies in a cost-effective manner in tomorrow’s energy system.” In addition to the technical aspects, the DLR scientists are also focusing on future business models for shaping the market: “We are preparing recommended actions which show how innovative technologies can be operated economically and sustainably over the long term.”