PFI:AIR - TT: Prototype mid-infrared, methane sensor for natural gas leak detection on small unmanned aerial systems

Princeton University, Princeton NJ

Investigators

Abstract

This PFI: AIR Technology Translation project focuses on translating new advances in laser-based, trace gas detection to identify methane leaks in the natural gas supply chain by using small unmanned aerial systems. The laser-based methane sensor for small unmanned aerial systems is important because it will result in increased safety by preventing explosions, improve the environment through reduced emissions of greenhouse gases to the atmosphere, and increase profits in the gas/oil sector through more product reaching their customers. The project will result in a prototype methane sensor for small unmanned aerial vehicles, which are rapidly increasing in their use and applications. No existing commercial methane sensors are sufficiently small, lightweight, and sensitive to be deployed on small unmanned aerial systems (those with wing spans of about a meter) for natural gas leak detection. The laser-based methane sensor has the following unique features: low mass (1 kg), small volume (1 L volume), fast response (10 measurements per second) and high-precision (2 parts per billion methane). These features will allow for efficient natural gas leak detection through decreased operating costs, increased safety of operation in populated areas, and more accurate leak identification when compared to the current method of visual, manned-aircraft patrols. This project addresses the following technology gaps as it translates from research discovery toward commercial application. The project synthesizes two rapidly developing technologies, mid-infrared laser spectroscopy and small unmanned aerial systems, and capitalizes upon their desirable attributes of high sensitivity detection and high-dexterity sampling, respectively. A newly-developed, interband cascade laser (ICL) operating at a wavelength of 3.3 microns will be used to probe the strongest (fundamental) absorption band of methane to achieve the necessary sensitivity. The ICL will be coupled into an optical cavity and integrated onto a small unmanned aerial system. The sensor will be exposed directly to the free airstream and not require any sample cells, inlets, or manifolds, thereby reducing size and mass. Sensor accuracy, particularly critical during the wide range of atmospheric conditions and vibrations experienced in-flight, will be maintained through the use of an in-line reference cell with multiharmonic wavelength modulation spectroscopy. Sensor flight performance will be verified with controlled releases of methane, and flight demonstrations over pipelines will be conducted. In addition, key personnel involved in this project, a graduate student, will receive entrepreneurial experiences and see how laboratory discoveries are translated into commercial products through working with operators in the drone and gas/oil industries. The project engages a leading small unmanned aerial systems service provider to test and demonstrate the new sensors to its clients in the gas/oil industry at FAA-approved locations and operations. The technology will improve pipeline monitoring in specific and other trace gas detection in general in this technology translation effort from research discovery toward commercial reality.