The Green Lean Amine Machine: Harvesting Electric Power While Capturing Carbon Dioxide from Breath

Abstract

As wearable technologies redefine the way people exchange information, receive entertainment, and monitor health, the development of sustainable power sources that capture energy from the user's everyday activities garners increasing interest. Electric fishes, such as the electric eel and the torpedo ray, provide inspiration for such a power source with their ability to generate massive discharges of electricity solely from the metabolic processes within their bodies. Inspired by their example, the device presented in this work harnesses electric power from ion gradients established by capturing the carbon dioxide (CO2) from human breath. Upon localized exposure to CO2, this novel adaptation of reverse electrodialysis chemically generates ion gradients from a single initial solution uniformly distributed throughout the device instead of requiring the active circulation of two different external solutions. A thorough analysis of the relationship between electrical output and the concentration of carbon capture agent (monoethanolamine, MEA), the amount of CO2 captured, and the device geometry informs device design. The prototype device presented here harvests enough energy from a breath‐generated ion gradient to power small electronic devices, such as a light‐emitting diode (LED).

Harvesting Electrical Power during Carbon Capture using Various Amine Solvents

“…We also expected relatively low power output when using MEA and DEA, the solvents that form stable carbamate species, based on the analysis done in previous work that demonstrated that the carbamate formed by MEA had a much lower permeability than bicarbonate across the anion-exchange membrane. 38 We observed that DEA exhibited the highest viscosity and ammonia exhibited the lowest viscosity of the solvents tested, which aligns with DEA producing the lowest short circuit current and ammonia producing the highest short circuit current.…”

“…For example, in previous work, we captured approximately 0.6 mol of CO 2 per mol of MEA. 38 Nonetheless, we expected that these reactions reflected the general relationship of these CC solvents, and, because of the logarithmic relationship between salinity gradient and electric potential ( Supporting Information , Equations S1–S4 ), we considered this approximation to be sufficient for the comparison of the different CC solvents. We generated the rich solution for each CC solution by dispersing CO 2 into the solution until the pH stabilized ( Table 1 ).…”

“…The conductivity of the lean and rich solutions influenced the power output by affecting the internal resistance of the device. 38 Table 1 displays the measured conductivities of the different CC solvents at the concentrations used in the experiments presented in Figure 3 .…”

“… 23 Recently, we demonstrated that lean CC solutions can be used as the low-salinity solution instead of distilled water. 38 In principle, this design allows the amine solutions to remain in a closed system with flue gas and heat as inputs and pure CO 2 , treated emissions, and electrical energy as outputs. Additionally, because the conductivity of the lean solution is higher than that of distilled water, the use of the lean solution reduces the internal resistance of the device and increases power density.…”

“… 27 , 32 , 39 , 40 For this reason, we used MEA in previous work when we demonstrated a novel CCRED design that could produce electrical power from the ion gradient generated when capturing CO 2 in breath. 38 In the CCRED device presented by Kim et al, the authors used N -methyldiethanolamine (MDEA) because the energy required to regenerate MDEA is lower than that required for MEA. 23 A number of other CC solvents, including diethanolamine (DEA), 2-amino-2-methyl-2-propanol (AMP), and ammonia, as well as mixes of CC solvents have been proposed to strike the balance between fast reaction kinetics and lowering the regeneration energy cost.…”