Production of hydrogen, carbon monoxide or other chemical commodities at demonstrator scale using tailored concentrated photon fluxes

Abstract

The defossilisation of the chemical industry and the transport sector represents an important but just as much difficult task on the path towards effective greenhouse gas emission reductions. Photoelectrochemical, photocatalytic or plasmonic systems driven by concentrated photon fluxes are ecologically and economically promising options to allow sunlight-powered production of chemical commodities and solar fuels from water and carbon dioxide. These systems enable carbon dioxide utilisation and can thereby provide carbon dioxide sinks. The use of concentrated sunlight allows compact systems, which are potentially more cost-efficient than alternative approaches and facilitate product gas collection. The solar input for these systems needs to be tailored depending on the specific requirements of the system to be investigated. In particular, the average concentration ratio and the homogeneity of the irradiation profile on active surfaces as well as spectral characteristics have a significant influence on the system performance. A detailed experimental assessment of these systems in practical application environments and under varying operation conditions, such as concentration ratio, is necessary to realistically determine system characteristics, explore performance limits, identify bottlenecks, derive optimisation options, and finally to promote complete exploitation of the potential of systems and their components. For that purpose, DLR operates unique solar test facilities which deliver concentrated natural or artificial sunlight at different scales. They cover the complete range from laboratory scale up to the MW industrial scale as well as a wide range of concentration ratios. Moreover, DLR designs comprehensive experimental set-ups including suitable secondary optics and means of photon management as well as powerful data acquisition and control systems. We use the experimental data as an input for techno-economic analyses (TEA) and life cycle assessments (LCA) and consequently, we can investigate a technology comprehensively. A holistic experimental assessment of complete systems including inherent additional devices and required peripheral equipment is crucial for the compilation of reliable input for the TEA/LCA of technologies. Additionally, the system size should be sufficiently large to allow capturing characteristics relevant for large-scale applications to deliver meaningful TEA/LCA input. We have worked on the development, modelling, optimisation, experimental assessment/demonstration and/or TEA/LCA of photoelectrochemical, photocatalytic, and plasmonic systems in the framework of numerous national and international projects and thereby considered the production and utilisation of by-products. An exemplarily compilation of our contributions to different past and current projects will be presented, amongst them regarding the projects FlowPhotoChem, SPOTLIGHT, and PECDEMO. In FlowPhotoChem a system, that comprises a photo-electrochemical, a photocatalytic, and an electrochemical reactor module, for the production of diverse hydrocarbons, in particular ethylene, from water, carbon dioxide, and sunlight is being developed. DLR takes care of system modelling and experimental assessment in the high flux solar simulator. SPOTLIGHT deals with a photonic device that converts carbon dioxide and hydrogen into methane or carbon monoxide using a plasmonic catalyst. DLR is responsible for testing the device under concentrated sunlight in the solar furnace and ensuring an appropriate interface to the solar input as well as to an LED light source. PECDEMO delivered a hybrid photoelectrochemical-photovoltaic tandem device for light-driven water splitting. DLR supported the reactor development, contributed to techno-economic analyses, and was in charge of the final demonstration of the system on DLR’s solar concentrator facility SoCRatus. The insights gained so far indicate that photoelectrochemical, photocatalytic or plasmonic processes can make a significant contribution to the production of carbon neutral (or even negative) chemical commodities and fuels.