Development and Evaluation of Low-Cost CO2 Sensors for Buildings

There is a significant opportunity to improve building energy efficiency and indoor environmental quality by accurately monitoring CO2 levels. However, current CO2 sensors tend to be expensive or require regular recalibration. This work presents research related to the initial development and evaluation of two novel CO2 sensors based on chemiresistive and resonant mass sensing techniques. Prototype sensors were assessed in a bench-top test chamber at temperatures, humidity levels, and CO2 concentrations, typical of indoor environments. Under these conditions, prototype sensors required only 60 mW of power, or less. Further, each sensor was developed to have a footprint of less than 25 mm2 and a cost of less than $50. Given the relative low cost, small size, and potential for low power consumption, these sensors may serve as an attractive alternative to the commercial CO2 sensors that are currently available

Development and Evaluation of Carbon Dioxide Sensors for Building Applications

Current global efforts in building information research include the development of low-cost, high reliability sensing systems capable of quantifying metrics such as human occupancy, indoor environmental quality, and building system dynamics. Such information is of high value for model development, building energy management, and improving occupant comfort. Further, indoor air quality (IAQ) has been a growing concern in recent years, only to be exacerbated by the COVID-19 pandemic. A common provisional measure for IAQ is carbon dioxide (CO2), which is regularly used to inform the ventilation control of buildings. However, few commercially available sensors exist that can reliably measure CO2while being low cost, exhibiting low power consumption, and being easily deployable for use in applications such as occupancy monitoring. This work presents research related to the initial development and evaluation of low-cost, stable, and easily deployable sensors for monitoring indoor CO2 levels in buildings. Two different types of sensors are presented that have the potential to perform as well as current commercially available CO2 sensing technologies, at significantly lower costs. The first is a chemiresistive sensor that is fabricated using a carbon nanotube thin film in conjunction with a blend of branched poly(ethylenimine) (PEI) and poly(ethylene glycol) (PEG), which serve as a CO2 absorbing layer. The second is a resonant mass sensor, functionalized with similar polymer-based materials including a blend of PEI and poly(ethylene oxide) (PEO). Prototype sensors were assessed in a bench-top environmental test chamber which varied temperatures, relative humidity levels, CO2 concentrations, as well as other gas constituents to simulate typical and extreme indoor conditions. The results indicate that the proposed system could ultimately serve as an attractive alternative to commercial CO2sensors that are currently available