Periodic Reporting for period 1 - SolDAC (Full spectrum SOLar Direct Air Capture & conversion)
Reporting period: 2022-09-01 to 2024-02-29
SolDAC’s main ambition is to reinvent the ethylene industry, which is the chemical industry’s primary building block, by proving an emerging breakthrough technology for producing technically and economically competitive and climate-neutral sustainable ethylene and co-product ethanol from solar energy and air.
The project features a photoelectrochemical conversion (PEC) unit, allowing the direct conversion of CO2 into ethylene. The PEC exploits bandwidth-selected light from a solar collector (FSS) that splits the solar spectrum for electricity and heat generation at efficiency higher than standalone PV modules and standalone solar thermal collectors. Heat is used in an innovative direct air capture (DAC) unit at ultralow temperature (~60°C), fostering the eventual circular integration with heat networks. The DAC unit removes carbon dioxide from the air, concentrates it to 95+% and compresses it to feed the PEC stack and a pipeline for carbon dioxide storage. This allows the carbon footprint of the whole sun-to-chemicals process to be offset and enables gain in carbon credits, opening an opportunity to exceed climate-neutrality and produce carbon-negative C2 products. The process is energetically self-sufficient, economically viable and carbon-negative on the condition that each unit (DAC, PEC, FSS) reaches new targets in efficiency.
The overall objectives are:
- To produce carbon-neutral ethylene and by-product ethanol from the air in an independent off-grid decentralised and market-competitive process powered by solar energy.
- To guarantee the techno-economic feasibility of the SolDAC process.
- To demonstrate the reduction of the "cradle to grave" carbon-footprint of the SolDAC individual process units.
- To popularise Carbon Capture, Utilisation and Storage (CCUS) technologies in society.
SolDAC responds to most of the strategic directions outlined by the EU 2050 long-term strategy for net-zero GHG emissions as follows:
- It contributes to maximise the benefits of energy efficiency: the SolDAC process does not add further pressure on the energy system. The FSS system allows the complete use of the whole solar spectrum, reaching efficiency that rivals with the best combined power generation plants. The utilisation of an independent off-grid energy source restraints the energy available on site and sets the implicit requirement of DAC and PEC units with unprecedented efficiency.
- It contributes to maximise the deployment of renewables and the use of electricity to fully decarbonise Europe’s energy supply: the project relies on solar energy as only source of renewable electricity, heat and light that is combined with the CO2 and water resources available in the air to produce C2 products. SolDAC’s autonomous process is virtually replicable in any setting.
- It contributes to reach a competitive EU industry and the circular economy as a key enabler to reduce GHG emissions: the successful implementation of the integrated SolDAC process, brings along the benefits from the EU Emissions Trading System (ETS) on carbon credits. The production of carbon-neutral C2 products will allow to close the carbon cycle above the ground, fostering circularity and eliminating the emissions associated with the production from petrochemicals.
- It contributes to tackle remaining CO2 emissions with Carbon Catpture & Storage: thanks to the DAC unit, this project shows the promise for a carbon-neutral (and possibility carbon-negative) C2 products production, cancelling the emissions of a sector that is deemed difficult to decarbonise.
The project features a photoelectrochemical conversion (PEC) unit, allowing the direct conversion of CO2 into ethylene. The PEC exploits bandwidth-selected light from a solar collector (FSS) that splits the solar spectrum for electricity and heat generation at efficiency higher than standalone PV modules and standalone solar thermal collectors. Heat is used in an innovative direct air capture (DAC) unit at ultralow temperature (~60°C), fostering the eventual circular integration with heat networks. The DAC unit removes carbon dioxide from the air, concentrates it to 95+% and compresses it to feed the PEC stack and a pipeline for carbon dioxide storage. This allows the carbon footprint of the whole sun-to-chemicals process to be offset and enables gain in carbon credits, opening an opportunity to exceed climate-neutrality and produce carbon-negative C2 products. The process is energetically self-sufficient, economically viable and carbon-negative on the condition that each unit (DAC, PEC, FSS) reaches new targets in efficiency.
The overall objectives are:
- To produce carbon-neutral ethylene and by-product ethanol from the air in an independent off-grid decentralised and market-competitive process powered by solar energy.
- To guarantee the techno-economic feasibility of the SolDAC process.
- To demonstrate the reduction of the "cradle to grave" carbon-footprint of the SolDAC individual process units.
- To popularise Carbon Capture, Utilisation and Storage (CCUS) technologies in society.
SolDAC responds to most of the strategic directions outlined by the EU 2050 long-term strategy for net-zero GHG emissions as follows:
- It contributes to maximise the benefits of energy efficiency: the SolDAC process does not add further pressure on the energy system. The FSS system allows the complete use of the whole solar spectrum, reaching efficiency that rivals with the best combined power generation plants. The utilisation of an independent off-grid energy source restraints the energy available on site and sets the implicit requirement of DAC and PEC units with unprecedented efficiency.
- It contributes to maximise the deployment of renewables and the use of electricity to fully decarbonise Europe’s energy supply: the project relies on solar energy as only source of renewable electricity, heat and light that is combined with the CO2 and water resources available in the air to produce C2 products. SolDAC’s autonomous process is virtually replicable in any setting.
- It contributes to reach a competitive EU industry and the circular economy as a key enabler to reduce GHG emissions: the successful implementation of the integrated SolDAC process, brings along the benefits from the EU Emissions Trading System (ETS) on carbon credits. The production of carbon-neutral C2 products will allow to close the carbon cycle above the ground, fostering circularity and eliminating the emissions associated with the production from petrochemicals.
- It contributes to tackle remaining CO2 emissions with Carbon Catpture & Storage: thanks to the DAC unit, this project shows the promise for a carbon-neutral (and possibility carbon-negative) C2 products production, cancelling the emissions of a sector that is deemed difficult to decarbonise.
During the first 18 months, main activities have been focused on the design of the three units that make up the SolDAC system applying a life-cycle thinking approach to sustain all project developments and final outputs.
Regarding the FSS, main work performed, and achievements are:
- Development of a spectral splitting Fresnel-based collector including numerical modelling and prototyping
- Implementation of an absorption filter system in order to adapt the collector output to the conversion process
- Design and numerical model of an optical guide network able to transfer selected bandwidths to the conversion processes
Main work and achievements related to the PEC stack unit are:
- Development of a model to predict and correlate parameters and performance with the other technologies developed within the project
- Definition of a benchmark device for a flexible electrochemical CO2RR
- Synthesis and fabrication of catalysts/electrodes of up to 10 cm2 reaching a combined FEC2 > 85% at > 200 mA / cm2, and with 25 cm2 electrodes, FEC2 > 85% at < 200 mA / cm2
- Fabrication of the PEC stack but not tested yet under bias-free conditions (as FSS is required)
Regarding the DAC unit development, work carried out and achievements are:
- Development of the thermodynamic model of the whole SolDAC process
- Characterisation of 2 materials in H2O, CO2, N2 isotherms and kinetics
- Identification of a range of suitable commercial material for the contactor
- Production of the CO2 contactor, collector and compression beds
- Identification of a range of suitable drying material
- Production of the water harvester (integrated nanoporous material/heat exchanger unit)
- P&ID of the CO2 capture process and water harvester
- Automation of the multi-bed process
- Testing the heating and cooling management strategy
Also, an economic model for the SolDAC integrated system and a financial evaluation tool have been developed to guide and monitor the evolution of the competitiveness of the solution during the project lifetime and beyond.
Regarding the FSS, main work performed, and achievements are:
- Development of a spectral splitting Fresnel-based collector including numerical modelling and prototyping
- Implementation of an absorption filter system in order to adapt the collector output to the conversion process
- Design and numerical model of an optical guide network able to transfer selected bandwidths to the conversion processes
Main work and achievements related to the PEC stack unit are:
- Development of a model to predict and correlate parameters and performance with the other technologies developed within the project
- Definition of a benchmark device for a flexible electrochemical CO2RR
- Synthesis and fabrication of catalysts/electrodes of up to 10 cm2 reaching a combined FEC2 > 85% at > 200 mA / cm2, and with 25 cm2 electrodes, FEC2 > 85% at < 200 mA / cm2
- Fabrication of the PEC stack but not tested yet under bias-free conditions (as FSS is required)
Regarding the DAC unit development, work carried out and achievements are:
- Development of the thermodynamic model of the whole SolDAC process
- Characterisation of 2 materials in H2O, CO2, N2 isotherms and kinetics
- Identification of a range of suitable commercial material for the contactor
- Production of the CO2 contactor, collector and compression beds
- Identification of a range of suitable drying material
- Production of the water harvester (integrated nanoporous material/heat exchanger unit)
- P&ID of the CO2 capture process and water harvester
- Automation of the multi-bed process
- Testing the heating and cooling management strategy
Also, an economic model for the SolDAC integrated system and a financial evaluation tool have been developed to guide and monitor the evolution of the competitiveness of the solution during the project lifetime and beyond.
Results so far are:
FSS: Based on the simulated results obtained, the thermal efficiency of the receiver is found to be a bit lower (10%) than the expected, but the goal is to reach a 38% efficiency. It should be noted that thermal efficiencies > 31% would be beyond the state-of-the-art. Regarding the electricity production process, the PV-cell design is based on a 2-junction metamorphic architecture with a theoretical efficiency near 30%. By taking into consideration the theoretical optical efficiency of the solar concentrating unit, the goal 22% light-to-electricity efficiency KPI will be met.
PEC stack: Developed materials for the 2 half-cell reactions, including novel cathode configurations and photoelectrodes for the anodic side, have been evaluated in a benchmark cell, reaching values beyond the proposed KPIs: Faradaic efficiency of ethylene of 70% at 250 mA cm-2, in a system of 10 cm2. The electrode and cell upscaling have also been carried out, and the final PEC system has been fabricated and assessed, reaching values relatively lower than the initial KPIs. Despite this, the 25 cm2 system achieves impressive Faradaic efficiency values of combined C2 products (i.e. ethylene and ethanol) of around 80%.
DAC: Semi-commercial nanoporous materials have been identified and prepared that can be regenerated with low grade heat down to 60 °C still producing a viable CO2 working capacity.
Environmental sustainability has been considered in the units’ development from the very early. Material selection has been guided to avoid the use of critical raw materials (CRM) and minimise those having more environmental concerns based on an Eco-design approach. Twelve recommendations were formulated, aiming to go beyond the environmental benefits of the stated KPIs.
FSS: Based on the simulated results obtained, the thermal efficiency of the receiver is found to be a bit lower (10%) than the expected, but the goal is to reach a 38% efficiency. It should be noted that thermal efficiencies > 31% would be beyond the state-of-the-art. Regarding the electricity production process, the PV-cell design is based on a 2-junction metamorphic architecture with a theoretical efficiency near 30%. By taking into consideration the theoretical optical efficiency of the solar concentrating unit, the goal 22% light-to-electricity efficiency KPI will be met.
PEC stack: Developed materials for the 2 half-cell reactions, including novel cathode configurations and photoelectrodes for the anodic side, have been evaluated in a benchmark cell, reaching values beyond the proposed KPIs: Faradaic efficiency of ethylene of 70% at 250 mA cm-2, in a system of 10 cm2. The electrode and cell upscaling have also been carried out, and the final PEC system has been fabricated and assessed, reaching values relatively lower than the initial KPIs. Despite this, the 25 cm2 system achieves impressive Faradaic efficiency values of combined C2 products (i.e. ethylene and ethanol) of around 80%.
DAC: Semi-commercial nanoporous materials have been identified and prepared that can be regenerated with low grade heat down to 60 °C still producing a viable CO2 working capacity.
Environmental sustainability has been considered in the units’ development from the very early. Material selection has been guided to avoid the use of critical raw materials (CRM) and minimise those having more environmental concerns based on an Eco-design approach. Twelve recommendations were formulated, aiming to go beyond the environmental benefits of the stated KPIs.