Holistic heat supply solution with H2
Project title:
energy4CHP - CO2-neutral energy supply in energy-intensive commercial enterprises - hydrogen-based sector integration in the provision of heat and electricity
Funding body:
Federal Ministry of Research, Technology and Space (BMFTR)
Project duration:
01.06.2023 – 31.12.2025
Principal investigator of the project:
Prof. Dr. Mark Jentsch
Project partners:
The WIR! alliance partner Wissenschaftlich-Technisches Zentrum für Motoren- und Maschinenforschung Roßlau gGmbH is involved in the project alongside the Chair of Energy Systems at Bauhaus-Universität Weimar. Hyrican Informationssysteme AG is an associated partner.
Team members involved in the project:
Artjom Kolwa M.Sc., Dipl.-Ing. Christian Gebhardt-Scholz, Benjamin Breuer M.Sc., Kaspar Schmädicke B. Sc., Nicole Meyer M. Sc.
Project outline
Within the framework of the joint project, an integrated overall system for the CO2-neutral energy supply of the test halls of the research company WTZ Roßlau gGmbH with electricity and heat is to be developed, implemented and tested. The focus here is on the technical integration of an electrolysis plant and a bifuel-argonPowerCycle (APC) CHP, which can be operated conventionally with natural gas and ambient air or with hydrogen and pure oxygen in the circulation system, with a photovoltaic system as well as a hydrogen storage infrastructure and a ground heat storage system with heat pump. In addition, the project includes the development of a suitable oxygen storage system as well as the control integration of the entire plant with the hydrogen storage system and the existing photovoltaic system. Furthermore, the storage of process heat is to be made possible via a geothermal borehole in the ground. This decentralised solution for energy supply is intended to demonstrate a feasible alternative to the supply of electricity and heat based on a natural gas CHP plant in order to relieve the supply systems for natural gas in the future.
The sub-project of the Bauhaus University Weimar is taking on tasks in the basic data collection, preparation of operating scenarios, planning, modelling and simulation of the entire system as well as the development of a common specification for the trial operation of the system components in the network. The central development goal is the conception, technical implementation and testing of a "thermodynamic switch" for different heat sources for heat supply in buildings. In addition, a basic EI&C concept including AI-based forecasts for plant operation will be developed, a thermal ground model for foundation heat storage will be developed and the scientific basis for design and calculation software for multi-energy storage system solutions for the intelligent integration of renewable electricity and heat supply will be created. The sub-project also includes the implementation of process data storage and processing as well as the evaluation of the measurement data from the joint trial operation of all system parts of the collaborative partners with a validation of the achieved target parameters. This serves to optimise the EMSR system and the AI forecasts as well as to evaluate the system and its components in terms of their transferability to different companies in the manufacturing sector. Figure 1 summarises the concept of the energy4CHP project.
Project progress
During the course of the project, changes to the originally planned overall system structure were necessary at the project partner. The initially planned geothermal boreholes could not be implemented due to approval.
Design and technical implementation of the foundation heat exchanger:
In order to maintain a high level of innovation, a new solution for a corresponding heat storage concept was developed - a foundation heat exchanger, illustrated in the sketch below.
The foundation heat exchanger is not thermally separated from the floor below, which is why the (total) heat storage capacity is greater than that of the building component alone. The component was largely thermally decoupled from the sides and top using 100 mm thick XPS thermal insulation panels.
To investigate the heat flows, 20 thermocouples were installed at different depths both inside and outside the concrete element. There is also a measuring point to determine the groundwater level and temperature.
The component measuring 10 x 2.5 x 0.3 meters was erected by the project partner at the end of 2024.
As a result of the system adaptation, there was a significant reduction in the expected storage capacity of the foundation heat storage tank. However, in order to continue to ensure a consistent overall system structure of the demonstrator environment, a new balance limit was defined for the test operation of the heat distribution system - a specially constructed building, the “energy station” with control room, engine and electrolysis test bench as well as heating and heat distribution center.
This was modeled as a 3-zone simulation model and the expected seasonal heating load was determined.
The modeling was carried out for two different scenarios with regard to the energy quality of the building envelope - variant 1, which reflected the actual state without insulation of the exterior walls, and variant 2, in which the analyses were carried out taking into account subsequent insulation of the exterior walls with 50 mm.
As a result of the investigations, it was decided within the project that variant 1 (without insulation of the external walls) could be regarded as more load-dynamic and therefore more suitable for further investigation in the course of the project.
Design and technical implementation of the “thermodynamic switch”
The final concept developed describes a toroidal heat distribution network consisting of nodes, with each node being linked to 4 other nodes. By using a large number of nodes and linking them, a multi-dimensional structure, a so-called torus network, can be constructed, which is generally used in the parallel interconnection of computer processors (see Figure 6 below). During the planning and construction of the heat distribution network, the torus was unfolded to create a 2D plane. On the one hand, this had the advantage of simpler production, and on the other hand, this plane can be used to investigate different heat flow paths with the aid of thermography.
With the help of this multivalent, multidimensional network, different fluid circuits can be set up within it, which in turn can be dynamically interconnected (see figures below).
By mapping several internal circuits within the heat distribution network, heat flows of different temperature levels can be effectively interconnected. The heat management of the test environment is defined by the following sources/sinks:
- ground, which can be used as both a heat source and a heat sink. Heat is coupled in and out of the ground using the foundation heat exchanger described above. A brine-to-water heat pump is used to raise the extracted heat to the level required to heat the building.
- ambient air, which can be used both as a heat source and a heat sink. A recooler is used to extract and recover heat from the ambient air. A brine-to-water heat pump is used to raise the extracted heat to the appropriate level.
- CHP, which can be used as a heat source. The heat is already provided at a high temperature level. If the CHP unit is operated using electricity, it can be cooled directly with the recooler.
- electrolyser (possibly LOHC system), which can be used as a heat source. The heat is provided at a medium temperature level, which in turn can be used to improve the COP (coefficient of performance) of the heat pump by raising the temperature of the brine flow (or the heating water circuit return) accordingly before it enters the heat pump.
- Heat accumulator, which can be used both as a heat source and a heat sink. The heat accumulator can absorb and release heat at different temperature levels, depending on the supply and demand. This is a conventional short-term hot water storage tank (buffer tank).
- Building spaces, that can be characterized as both heat sources and heat sinks. For example, a test bench room that is too warm can be used as a source. However, the rooms are primarily regarded as heat sinks due to the heating. Heat is transferred to the rooms with the aid of air-water heating coils or conventional radiators.
Conventional heat exchangers are used to couple various heat flows into and out of the heat distribution network, which makes it possible to handle more than one fluid flow (e.g. coolant, brine, heating water, drinking water, etc.) - as shown in the following diagram.
The inner and outer circuits are used to convey fluid and to feed heat into and extract heat from the heat distribution network. The redistribution of thermal energy (heat) between the individual sources or sinks takes place within the heat distribution network. Control valves switch internal circuits according to the optimum operating strategy - shown in the following diagram.
A set of drawings and corresponding material lists were created for the detailed design implementation of the concept. The overall assembly can be seen in the following illustrations.
EI&C concept
As part of the EMSR technology (measurement, control and regulation), the heat distribution system is monitored and controlled using a Wago PLC (programmable logic controller). Various sensors record temperatures, system pressures, flow rates and the water level in the area of the foundation heat exchanger (via a level probe). The measured values of the thermodynamic switch read and evaluated by the PLC are then bundled and transferred to a higher-level data management and control system (Raspberry Pi with Home Assistant) via TCP/IP, Modbus or MQTT - shown in the diagram below.
In addition to the switch's PLC, the Home Assistant instance communicates with the weather station and the other components of the heat supply network (CHP, electrolyser, LOHC, heat pump, LoRa station).
Based on the measurement data received, the respective operating scenarios are evaluated as a result of intelligent control logic implemented using Node-RED.
The smart energy control and interaction of the individual EI&C components can be summarized as shown in the following diagram.
Outlook
The first partial commissioning of the heat supply system with heat pump, recooler, foundation heat exchanger, buffer storage tank and thermodynamic switch is planned for the second quarter of 2025.