We are focusing on sensing VOC concentrations (Volatile Organic Compounds) by building high accuracy systems that are capable of measuring gas pollutants at the ppb level while being fast-responsive, easy to deploy on both drone systems and ground stations and capable of providing real-time data. Existing standard VOC sensing solutions are however expensive, time consuming and fail to operate in real-time. This means that a new sensing solution needs to be developed in order to overcome the limitations of universal solutions so that sensing devices are built in a compact and low-cost form, which would make performing accurate on-drone VOC sensing a possible operation. In this regard, we are considering one of the main spectroscopic detection techniques, Quartz Enhanced Photoacoustic Spectroscopy (QEPAS), which has proven to be a perfect candidate for in-situ and real-time trace gas detection, because of an unmatchable level of compactness, extremely high sensitivity (down to parts per trillion), immunity to environmental noise and its proven reliability, ruggedness and in-situ operation. We therefore design and experimentally test a compact QEPAS sensor prototype for trace gas detection of 3 main gas pollutants (methane, ethane and propane).
In addition to the engineering design of the QEPAS sensor, our objective is to demonstrate that our QEPAS is capable of measurements whose quality would normally associate with laboratory-based detection techniques such as mass spectroscopy or chromatography, but from a device well over two orders of magnitude smaller in volume. To that end, we deployed our QEPAS sensor in order to detect, in real time, with high precision the concentration of the targeted gases in the air with exceptional selectivity without the need for continuous calibration, or re-programming.
Our extensive out-of-laboratory experiments showed the following significant results:
- The QEPAS peak signal is constant over 1-hour measurement. Therefore, the sensor calibration shows the possibility of measuring the CH4 atmospheric concentration.
- The methane QEPAS signal is independent from the water concentration above the threshold. Therefore, the QEPAS sensor is able to detect methane and water in natural abundance.
- During the daytime hours, the methane concentration increases and reaches peak values up to 2.4 ppm during two rush periods, one starting around at 10:00 am and the other one starting at 2:00 pm. Thus, the results obtained so far could be highly correlated to car emissions.
Publications
- Boubrima and E. Knightly, “Robust Environmental Sensing using UAVs”, ACM Transactions on Internet of Things (in press).
- Petrolo, Z. Shaikhanov, Y. Lin, and E. Knightly, “ASTRO: a System for Off-Grid Networked Drone Sensing Missions”, ACM Transactions on Internet of Things (in press).
- Shaikhanov, A. Boubrima, and E. Knightly, “Autonomous Drone Networks for Sensing, Localizing and Approaching RF Targets,” in Proceedings of IEEE Vehicular Networking Conference (VNC), December 2020.