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Spliethoff, Hartmut
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Spliethoff
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Hartmut
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Hartmut Spliethoff
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The potential of CO2-Plume Geothermal (CPG) Systems for CO2 component manufacturers: opportunities and development needsSchifflechner, Christopher; de Reus, Jasper; Spliethoff, Hartmut; O. Saar, Martin; Schuster, Sebastian; Brillert, DieterSubsurface reservoirs play an important role in decarbonizing the energy sector, be it through geothermal energy production or carbon capture and storage (CCS). In recent years, there has been an increasing interest in CO2-Plume Geothermal (CPG) systems, which combine CCS with geothermal, using CO2 instead of water as a subsurface heat and pressure energy carrier. As explained later in the paper, applying CO2 as a subsurface working fluid can be more efficient than water as it has a higher mobility (inverse kinematic viscosity) and as its large thermal expansion coefficient results in a thermosiphon effect that reduces the pumping power required. CO2 can also directly be utilized in a turbine for power generation. Furthermore, since CPG systems are added to full-scale CO2 Capture and Sequestration operations, all of the initially injected CO2 is ultimately stored. CPG therefore constitutes of both CO2 Capture Utilization as well as Storage. This paper assesses the huge technical potential of the CPG technology, identifying a potentially highly relevant market for CO2 equipment manufacturers and discusses the current research demand, based on the current state of the art of CO2 equipment. Both temperature and pressure levels are significantly lower than CO2 turbine designs investigated and proposed so far for other applications, such as waste heat recovery. Together with CPG-specific requirements, due to produced fluid impurities, it becomes evident that significant further development efforts are still necessary regarding future commercial CPG CO2 turbines.- DESIGN AND CONSTRUCTION OF A REVERSIBLE ORC TEST RIG FOR GEOTHERMAL CHP APPLICATIONSKaufmann, Florian; Schifflechner, Christopher; Wieland, Christoph; Spliethoff, Hartmutfor their ability to supply heat or electricity flexibly. While many publications focus on their application in Carnot batteries or domestic systems, geothermal applications got less attention. In geothermal combined heat and power plants, reversible ORCs offer the possibility to generate electricity in times of low heat demand and supply additional heat to a district heating network (DHN) in peak load times. In previous work, the authors showed that this increases plant utilisation and reduces the load of commonly used peak-load gas boilers. This work presents the design and construction of a fully reversible ORC test rig capable of flexible operation as ORC or high-temperature heat pump (HTHP). It extends the state of the art by design and construction of a test rig for experimental validation of a previously untested cycle layout for geothermal applications. The test rig is supplied by a 200 kW hot water heating circuit as a heat source and uses a fully reversible 20 kW twin-screw machine. A closed loop intermediate cooling circuit allows simulating a DHN with varying temperature levels and mass flows during HTHP operation. This paper provides insights into the design methodology and the test rig’s intended operating range and performance. Thus, the paper provides valuable insights for the research community regarding conceptual and experimental activities on reversible ORC systems. Moreover, an in-depth description of the constructed test rig, its components and instrumentation and finally the preliminary control concepts are given. Commissioning and first experimental results are expected in the year 2023.
- EVALUATING THE WASTE HEAT SOURCES IN A VERY LARGE CRUDE CARRIER AND THE POTENTIAL INTEGRATION OF ORGANIC RANKINE CYCLE CONFIGURATIONSStainchaouer, Amalia; Schifflechner, Christopher; Wieland1, Christoph; Spliethoff, Hartmut
- DEVELOPMENT OF A GENERALISED LOW-ORDER MODEL FOR TWIN-SCREW COMPRESSORSKaufmann, Florian; Irrgang, Ludwig; Schifflechner, Christopher; Spliethoff, HartmutTwin-screw compressors (TSC) are commonly used in heat pump processes due to their robustness and flexibility. They exhibit two core properties, i.e. the swept volume and the built-in volume ratio (BVR), which heavily influence their capacity limits and off-design efficiency. Several models of vastly different computational costs have been proposed in literature to calculate the performance of TSCs. For applications that rely on large amounts of simulation runs, the computational cost of the compressor model becomes an essential factor. This work presents a new low-order model, which can accurately predict a TSC’s behaviour. First, a semi-empirical model from literature is slightly adapted and used to generate performance data for a large operational field. Then a polynomial model with a linearisation for high pressure ratios is fitted to this data. The model uses the external pressure ratio and volumetric compressor inlet flow to calculate isentropic efficiency and compressor speed. Both input parameters are normalised with a reference flowrate (calculated from the swept volume) and the BVR, respectively. This results in a generalised model of low numerical cost, which can be used for explorative studies independent of the specific machine size and BVR. A gain in computational speed by a factor of roughly 375 is achieved compared to a semi-empirical reference model. The model displays good predictive accuracy when used to predict the performance of machines with similar BVRs, but different sizes. When there is a difference in size and BVR, the prediction accuracy is still reasonable but significantly declines for small pressure ratios. Nevertheless, the proposed new approach extends the state-of-the-art by introducing a low-order model, which combines the advantages of low computational cost, good accuracy, physically correct predictions over a wide operational range and scalability to different machine capacities and BVRs.
