The FPC system involved three different types of reactors combined into one system: a photoelectrochemical (PEC) flow reactor, a photocatalytic (PC) flow reactor and an electrocatalytic (EC) flow reactor. Each reactor type was first individually developed and optimised.
Two PEC flow reactors were developed for water splitting or carbon dioxide (CO2) splitting. The water splitting PEC reactor met the objective of hydrogen production above 0.25 kg H2 per day (>0.4 kg H2 per day) in a system utilizing partially rare materials, operating at 900 suns, reaching > 25% solar-to-hydrogen (STH) (surpassing the > 20% STH target). New materials (membrane, catalysts) that operate at high current density were also developed. The water splitting technology was applied to CO2 splitting yielding a lab scale reactor with solar-to-CO efficiency of 17%, far above the 7% project target. Upscaling of the PEC-CO2 reactor to higher input power was further investigated with promising results.
Three different types of PC reactors were developed and tested using different photocatalysts. The most promising PC reactor demonstrated the production of CO for 100 h from CO2, H2 and concentrated sunlight, and was scaled-up for integration in the FPC system, with design modifications to increase thermal stability and operating pressure. Operation at up to 90 suns on irradiated areas of 0.25 cm2 was possible, achieving temperatures of near 700 degrees C in the photocatalyst bed at atmospheric pressure.
Novel work on the EC reactor has included the development of catalysts, membranes, and reactors towards the goal of enhancing the yield, rate, and selectivity of converting CO (and CO2) to valuable products, such as ethylene. Several key features differentiating CO2 and CO electrochemical reduction have been obtained, resulting in improved EC reactors for ethylene production. The final design achieved C2+ product selectivity exceeding 80%.
The PEC, PC and EC reactors were serially assembled into a demonstrator FPC system, guided by reactor and system models to identify the optimal reactor combinations to deliver the highest efficiency. The experimental campaign testing the system successfully demonstrated the production of solar ethylene using CO2, H2O and concentrated artificial light, at production rates that were orders of magnitude larger than the best state-of-the-art demonstrations (albeit below the project targets).
In parallel with the reactor development, Life Cycle Assessment (LCA) methodology was used to consider environmental impact, cost and energy efficiency and to compare with alternative technologies. The social impact of “solar chemicals” and their direct and indirect costs to society were also examined using Social Life Cycle Assessment (S-LCA) and Life Cycle Cost (LCC) methods. LCA and LCC results fed back into the reactor design and development as recommendations to improve the environmental profile of selected materials/components. Overall, FlowPhotoChem technologies are promising in terms of environmental performance when compared to competitive technologies, significantly reducing CO2 emissions when scaled-up and operating at optimal capacity. Using a Real Options Approach (ROA), FPC technologies show strategic value and potential profitability under flexible investment timing and uncertainty.
Market analysis and exploitation planning were also undertaken. A techno-economic analysis for the reactor system was developed and used to carry out a detailed costing analysis of the integrated reactor, as well as a sensitivity analysis and costing predictions for future scale-up and commercialisation scenarios. Three separate market entry scenarios for the next decade were developed to lead to commercial production of solar ethylene, components for electrochemical CO2 and CO electrolysers and solar syngas plants. Two Exploitation Workshops were held in Uganda to support market research and explore how EU-Africa collaborations can contribute to a clean and just energy transition.
