Optimizing Carbon Dioxide Removal in Built Environments

Jia Jie Gan

Climate change has been a global crisis that the world has been experiencing for the past few decades. Various efforts and agreements have been made, such as the Paris Agreement adopted in 2015, with the goal of keeping global temperatures below 1.5°C above pre-industrial levels. As of the year 2023, global temperatures are nearing 1.4°C above pre-industrial levels. In response to this, countries and industries around the world are putting greater efforts in reducing their carbon emissions. However, to attain net-zero emissions, carbon removal is also necessary. Out of the various carbon removal methods, direct air capture shows to be one of the more promising avenues. Direct air capture (DAC) is measurable and quantifiable, making carbon accounting easier. DAC is also land efficient, compared to other methods such as reforestation and biomasses. However, current DAC solutions offered are in the form of large plants and facilities. Pairing these DAC plants with renewable sources of energy enable them to be carbon negative, thus these plants are currently implemented mainly in locations where geothermal energy is present. This makes it difficult for such solutions to be implemented at a widespread level. Other DAC companies have begun to innovate in indoor environment, bringing DAC technologies and capabilities to urban cities. Unfortunately, these current indoor solutions have complications, in that they require retrofitting of current building facilities, causing stakeholders to incur large costs and inconveniences. A research team at Singapore University of Technology and Design have developed a novel Carbon Capture Composite (C3) film that removes CO2 from the environment passively and can be deployed in indoor environments as well. This technology is still being developed, and application methods have yet to be explored fully. Thus, this thesis looks to cover this research gap, to design a novel concept of applying the C3 film as a viable DAC indoor product. In this thesis, a folded form factor for the C3 film is explored, taking inspiration from heat radiators with high surface area to volume ratios. Different fabrication processes were attempted to modify the C3 films into the folded form factor, the most effective being the moulding of the folds via heating. The folded form factor was further studied to understand how folding affected the C3 film’s adsorption capabilities. Based on the experiments done, it was observed that the smaller air channels due to folding resulted in a 30% decrease in the film’s adsorption performance. On the other hand, having tighter folds with a smaller bending diameter allows more film to be fitted into the same volume of space, which effectively increases the exposed surface area of C3 film to adsorb carbon. Having the bending diameter of 6mm would have a 90% increase of surface area compared to the bending diameter of 15mm. It is found that at bending diameters below 12mm, the increase of surface area outweighs the decreased adsorption performance, resulting a net increase of CO2 removed. As a result, the potential CO2 removed with a bending diameter of 6mm is 35% higher than that at 15mm. Furthermore, the film was discovered to have a bending limit at 6mm, resulting in breaking and tearing at bends any lower diameters. Thus, the bending radius of 6mm was chosen for the development of the prototype. After the new form factor was validated, the prototype was designed and developed around it. The prototype was to have the functions of containing the C3 films and to expose the C3 films to the ambient environment in a controlled manner. To achieve this, the prototype was broken down into the following subsystems: film housings, the exposure mechanism which consisted of a seal and a moving lid, and the exterior frame. The film housing that held the folded C3 film first started as a rigid acrylic housing, but later evolved into a cardboard housing that could be easily assembled and was more lightweight compared to acrylic while being sufficiently rigid. For the exposure mechanism, a continuous lid that can roll open and expose the films was chosen as it would be easier to operate compared to having multiple lids that had to be actuated. The initial prototype lid was made up of linkages that could be rolled from solid linkages to meshed linkages that would expose stored C3 film. However, this concept had a tedious fabrication process and was not scalable due to the large number of linkages that had to be made and assembled. The lid evolved from linkages to a film, which had meshed areas which would act as the openings to expose the film. The film lid was observed to be a more effective option, as it had a smaller footprint, allowing the prototype to shrink in size. Its simple assembly allowed it to be implemented on both the top and bottom of the prototype, creating two openings which further increased the exposure of the C3 films to the environment, thus improving CO2 removal. The film lid can be easily scaled as well to create larger prototypes with more films. The material of the film lid had to be iterated as well. The initial lid used a PET film. However, when put to the test with C3 film loaded in the prototype, the CO2 levels were decreasing at a rate similar to if the lid was opened. This suggested that there was a leak of sorts in the lid. Further experiments later indicated that the PET film was permeable to CO2, resulting in the C3 film being able to adsorb CO2 through the PET film. The lid material was thus changed to an aluminium-coated mylar film. The new mylar film proved to be a suitable lid material, sealing the C3 film to prevent active CO2 adsorption and keeping CO2 levels stable when the lid is closed. Additionally, when the exposure mechanism was tested, the CO2 levels experienced an exponential decrease when the lid was opened as programmed, validating the prototype’s ability to expose the C3 film in a controlled manner. This thesis serves as groundwork of a product concept that can be further developed, scaled and refined into a DAC product to serve users in the urban environment.

Optimizing Carbon Dioxide Removal in Built Environments

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