Hydrogen is widely expected to be an important energy carrier in future. In fact, it can only be an environmentally friendly and sustainable alternative to existing sources of energy, if it is produced without harmful pollution and particularly without substantial carbon emissions. Some potentially very exciting and appropriate options for ‘clean’ production of Hydrogen on a massive scale are thermochemical cycles, which use concentrated solar energy or nuclear energy to supply the heat necessary to split water using a closed cycle of chemical reactions. Small-scale experimental precursors to eventual integrated laboratory-scale experiments have been operated successfully to date and continue to show promise for larger-scale systems. Nevertheless the technical challenges of bringing hydrogen production to the demonstration state within the next decade are significant.
HycycleS aims at the qualification and enhancement of materials and components for key steps of thermochemical cycles. The focus of the project is the decomposition of sulphuric acid which is the central step of processes from the sulphur based family, especially the Hybrid Sulphur Cycle and the Sulphur-Iodine cycle.
The Hybrid Sulphur Cycle has as a high temperature thermochemical step, the thermal decomposition of sulphuric acid, combined with low temperature electrolytic reaction of water and sulphur-dioxide (Figure 1). It is a “Hybrid” process in that some of the energy necessary to split the water is supplied as electricity.
The SI process is a “pure” thermochemical cycle in which all energy is supplied as heat. It comprises three reactions which are performed in separate process sections.
HycycleS Figure 2
In the HycycleS project, emphasis is put on materials and components for sulphuric acid evaporation, decomposition, and sulphur dioxide separation. The suitability of materials and the reliability of the components will be demonstrated in practice by decomposing sulphuric acid and separating its decomposition products using scalable prototypes. The final aim is to bring thermochemical water splitting closer to realisation by improving the efficiency, stability, practicability, and costs of the key components involved and by elaborating detailed engineering solutions.