ESCO – Design and Operation of Energy plants with supercritical Carbon Dioxide (sCO₂) as working fluid

The overarching objective of the project is the fundamental technical design of systems and components of sCO₂ cycles for waste heat recovery and thermal energy storage. The project is based on the findings of the techno-economic analyses for complete systems gained in the CARBOSOLA project and on the use of the test facility set up in CARBOSOLA.

Topic 1: Development of innovative components, materials and coatings for energy systems operated with sCO₂

The main cost drivers of sCO₂ plants are the relevant main components such as the heat exchangers, heat sources and turbomachinery. The project is therefore investigating cost-efficient component designs and testing alternative materials. This also concerns the integration of a thermal energy storage unit into the sCO₂ process.

Objectives are:

• Improving the performance of cost-driving components through modern manufacturing processes (additive manufacturing, diffusion bonding) and innovative design methods.
  Partners involved: Kelvion, HZDR
• Integration of thermal energy storage systems in sCO₂ cycles, for the storage and reconversion of excess capacity from renewable energy sources.
  Partners involved: Keramik-Institut, HZDR
• Evaluation and validation of novel or suitable materials and fluid seals for sCO₂ applications.
  Partners involved: Siemens Energy, Kelvion, HZDR
• Investigation of compressors and fluid accelerators in sCO₂ circuits.
  Partners involved: TU Dresden, Siemens Energy, HZDR

Topic 2: Operation, process control and measurement technology

In an energy system characterised by fluctuating energy sources, frequent start-up and shut-down processes and partial load operation are particularly relevant. For this reason, investigations into the dynamic operation of sCO₂ systems are being carried out both theoretically and experimentally. The development of the measurement technology required for this is also part of the project. Ultrasound-based flow measurement is being developed and experimentally qualified specifically for the application at prevailing high temperatures and pressures. As there are both gas and liquid components in the process during transcritical operation, the development and experimental verification of a two-phase CO₂ measurement technology is necessary.

Objectives are:

• Analysing effective control methods for sCO₂ cycles and testing them in practice.
  Partners involved: HZDR, Siemens Energy
• Design, manufacture and experimental investigation of ultrasound flow measurement technology for sCO₂ systems.
  Partners involved: Endress+Hauser SICK, HZDR
• Development of modern two-phase CO₂ measurement technology for transcritical CO₂ circuits, including electronics development and validation.
  Partners involved: Teletronic, HZDR

Topic 3: System characterisation and techno-economic analyses for cycles with heat removal, thermal energy storage and fluid mixtures

A novel system architecture for sCO₂ heat engines using temperature-stabilised heat dissipation offers the potential to increase cycle efficiency and ensure a stable operating point all year round. Based on absorption refrigeration technology, a new type of heat dissipation system is modelled and practically integrated into a cycle. Furthermore, different system concepts for electro-thermal energy storage from renewable energies are analysed, which consider an electric heater or a sCO₂-based heat pump for charging the storage system. Finally, the influence of sCO₂-based fluid mixtures or impurities will be analysed and a possible increase in efficiency will be identified. Techno-economic assessments will be carried out for these cycle architectures in order to promote the commercialisation of this technology.

Objectives are:

• Investigation of novel sCO₂ cycles with integrated absorption cooling process.
  Partners involved: TU Dresden
• Technical and economic optimisation of the system architectures of sCO₂ power cycles with integrated thermal energy storage.
  Partners involved: DLR, HZDR
• Characterisation of the system behaviour of sCO₂-based fluid mixtures and impurities.
  Partners involved: TU Dresden

Project partners

Siemens Energy (Koordinator)
Kelvion
KI Keramik-Institut GmbH
Endress+Hauser SICK
Teletronic Rossendorf GmbH
Deutsches Zentrum für Luft- und Raumfahrt e. V.
Helmholtz-Zentrum Dresden-Rossendorf e. V.
Technische Universität Dresden

Funding

Design and operation of energy plants with supercritical carbon dioxide (sCO₂) as working fluid - ESCO (BMWK, 03EE5157H). The authors are responsible for the presented content.