The activities performed in the subtasks are:
Subtask A: Material Design and Selection
The objective of this subtask is to commonly develop and promote design strategies for efficient, selective and stable materials for solar chemistry technologies via the following
specific objectives:
- To develop photoactive materials based on non-critical elements with enhanced conversion efficiency for different reactions (overall water splitting,,using waste/sea water, CO2 valorization/reduction, N2 fixation to ammonia…)
- Design and synthesize multifunctional junctions to improve the light harvesting across the full sun-spectrum (keeping stability in water). This also includes the development of new design strategies for photothermal reactions
- Standardized protocols to characterize and evaluate the synthesized materials
- Automatized methodologies to produce and scale up materials
- Development of selective catalysts for different target reactions
- Use of Life Cycle Analysis (LCA) to determine the environmental, technoeconomic and social impacts on the photoactive materials production
The work of Subtask A is structured into four project areas.
A.1 Material Design and Selection
This activity will leverage the information gathered in the various expert projects on material design to gain a common understanding on most promising materials for catalyst in different structures and other components, such as membranes.
A.2 Material Synthesis and Fabrication
In this activity, the material synthesis and fabrication techniques of structures and components are shared, and available testing/characterization results are discussed in order to gather a common understanding of the characterization and standardization needs of the materials in the subsequent activity A3.
A.3 Characterization, Standardization and Testing
This activity will bring together the expertise of the community to discuss how photoactive materials shall be best tested and compared. Within workshops defined protocols and key performance indicators will be developed. This shall guide material developers to eliminate errors made in the calculation of the performance assessment and enable a fair comparison of various photoactive materials and components.
A.4 Optimization and Scaling
In this activity, experts will focus on industrial exploitation potential and pathways of the photoactive materials and components. This might include how to overcome limitations in material availability and costs or challenges in manufacturing. The definition of standardized testing protocols of activity A3 shall also be enlarged to
include tests in real-world conditions (e.g., material behavior under sunlight exposure). Importantly, this activity aims to bring scientific experts together with the material and manufacturing industry to establish partnerships for industrial applications.
Subtask B: Solar Photoreactor Design
The objective of this subtask is to develop and promote design strategies for efficient solar photoreactors via the following specific objectives:
- Investigate and analyze existing solar photo-reactor designs
- Provide a fundamental understanding of ongoing processes in photoreactors and based on this, a deep analysis of key design considerations
- Deal with optimization potential and open research questions to increase efficiencies in solar photoreactors
- Promote collaborative initiatives for reactor studies under defined conditions (reaction, photon flux/solar receivers)
- Common definition of key performance indicators for reactor assessment
- Develop design strategies for combined solar photoreactor units
- Facilitate closer collaboration among different disciplines – reactor development, solar collector, material development – to increase awareness and visibility
The work of Subtask B is structured into four project areas.
B.1 Review of photo-reactor designs
In this activity, existing photoreactor designs will be collected and discussed via the open exchange of studies and projects on currently available solar photoreactor designs. In this way, the strengths and weaknesses of currently applied designs are analyzed in expert discussions. Also, existing performance metrics applied in these reactor studies, including their system boundaries and framework conditions, are collected.
B.2 Analysis and assessment of photoreactor processes
Studies that deal with a fundamental understanding of ongoing processes in photoreactors will be shared. This can include studies on the kinetics of photocatalytic, photoelectrochemical or photothermocatalytic processes, the influence of thermodynamic properties on the reaction, identification of reaction limiting-steps, or studies on transport phenomena. Such fundamental studies will help to identify key design considerations for photoreactors based on the process requirements and constraints identified in experimental work throughout the projects.
B.3 Collaborative definition of key performance indicators
Based on the above analysis of existing experimental work, the expert group will collaboratively establish common definitions of key performance indicators that are key for assessing reactor performance. In addition, the Subtask group shall commonly define a standardized framework for solar photoreactor assessment. This framework might include specified reaction conditions and defined solar photon flux. It might also allow us to differentiate between fundamental tests on the influence of reactor geometries and flow behavior versus overall performance testing of complete solar photo reactor units.
B.4 Design strategy development and current research questions
Eventually, by aiming to bring all expert knowledge together, common design strategies for solar photo reactors will be developed. Based on this, open research questions will be summarized.
Subtask C: System Integration
The objective of this subtask is to develop new concepts for solar photochemistry installations and to set positive accents for future economic developments by developing efficient systems to generate solar fuels and chemicals from various (secondary raw) materials and the sun. Specific objectives of Subtask C are:
- Preliminary piping and instrumentation design.
- Issues and safety requirements in the design of the photofuel separation,
- purification and storage steps (taking into consideration the specific chemical physical characteristics of the water and catalysts).
- To develop standardized procedures for the testing of integrated systems at least at pilot scale, based on the outcomes of Subtask A (Material testing) and Subtask B (solar photo reactor testing)
- Draft Life Cycle Assessment (LCA) based, for the moment, on pilot plant results.
- Evaluation of solar to photofuel conversion standardization
- Assessment of Analytical Techniques for Fuel and Chemical Compound Standardization
- Overall potential of photofuel production as a function of site location. Simulation tool.
- • Industrial wastewater/sacrificial agents in the catalytic process.
The work of Subtask C is structured into six project areas.
C.1 Piping and Instrumentation Diagrams for pilot plants
In this activity, preliminary piping and instrumentation diagrams for translating the huge available lab results to pilot plants will be designed, and guidelines for the construction of the prototypes will be developed. Besides, issues and safety requirements in the design of the photofuel separation, purification and storage steps. As preliminary background, hydrogen separation applied in electrolyzers could be used as a baseline, but considering the specific chemical-physical characteristics of the wastewaters used as sacrificial agents and photocatalysts. Determining the industrial application of remaining products like oxygen
C.2 Standardized procedures for testing
In this activity, standardized procedures for the testing of integrated systems, including analytical methods, will be proposed. Solar conversion processes into photofuels need a proper evaluation of the incident solar radiation, a proper system operation, adequate analysis of products (including target photo-fuel, intermediates, by-products, etc.), consistent interpretation of reaction mechanism, proper selection of catalyst concentration, etc, for a reliable system evaluation and scale-up. This activity will leverage upon the results of Subtask A (Material testing) and Subtask B (solar photoreactor testing).
C.3 Life Cycle Assessment (LCA)
Not many works are devoted to the study of the impact of laboratory processes on the solar production of photofuels from an environmental, economic, and social point of view. Conclusions could be significant, pointing out process costs that are not negligible at the laboratory level before implementation at the pilot plant and on a future industrial scale. In this way, similar studies at pilot plants are really scarce, and they are undoubtedly an important tool for future industrial scale.
C.4 Standardization of solar conversion for full system evaluation
There are many controversies regarding a proper evaluation of solar energy conversion into chemical energy based on a nonstandardized selection of key parameters such as incident photons wavelength, photoreactor characteristics, and photocatalysts band-gap, as well as analytical methods, among others. This activity will leverage the results of Subtask A (Material testing) and Subtask B (solar photoreactor testing).
C.5 Potential of photofuel production
Based on properly standardized solar energy conversion into chemical energy, a simulation tool for photofuel production as a function of site location is needed. Depending on available projects throughout the Task, existing models and modelling tools for photofuel production processes can be collected, or new models established, merging process models with solar collector models. At least the requirements of such modelling tools can be collected along the course of the task to initiate further studies and specifically to deploy such simulation tools in potential studies later on.
C.6 Sacrificial agents in the photocatalytic process
Sacrificial agents are needed to improve photofuel production by photocatalysis. Most of these would be organic. Complex and high-added-value reagents should be systematically avoided for this, and so far, the appealing choice will be the use of organic pollutants and/or originating from biomass. Therefore, the identification and localization of production sources and synergies with other waste and wastewater treatment are needed. In these fields, the participant activities include presentation of project results, active discussions of results and common development of the Subtask deliverables via workshop participation and review of reports.