Geologic Sequestration Training and Research (GSTR) -
Recovery Act: Development of a 1 x N Fiber Optic Sensor Array for Carbon Sequestration Site Monitoring
Performer: Montana State University
Project No: FE0001858
NETL has partnered with Montana State University (MSU) to develop a low-cost, reconfigurable 1 x N fiber optic sensor array for subsurface, large area monitoring of carbon geologic storage sites. This type of technology can be used to assess soil gas CO2 fluxes over a large area. MSU is first focusing on developing a single channel fiber optic sensor and a fiber probe. The fiber sensor probe is the portion of the detector system that will be placed underground allowing the photonic bandgap (PBG) fiber to be used for subsurface CO2 measurements. PBG fibers are dielectric fibers that prevent propagation of electromagnetic waves in certain frequency ranges. The transmitter detector components include a laser, a reference photo-detector, and a fiber circulator. MSU is developing software to operate the single channel fiber sensor that will control the operating wavelength of the laser and record the laser temperature, reference detector voltage, and transmission detector voltage. The CO2 concentration will be measured based on the amount of light absorption between the transmitter and receiver array. MSU is performing laboratory testing to demonstrate that the single channel fiber optic sensor can monitor elevated CO2 concentration successfully in a controlled setting.
The initial single channel fiber optic sensor (Figure 1) and fiber probe (Figure 2) will be refined and a 1 x 4 fiber sensor array developed. MSU is applying the experience gained from designing the initial fiber sensor array to develop a second generation fiber sensor probe design. The 1 x 4 fiber sensor array is incorporating all the necessary optical components, including a 1 x 4 fiber optic switch, and custom software to operate the array. Once the sensor detector array and four sensor detectors were operational, MSU developed a response curve that shows the transmission as a function of concentration for known CO2 concentrations. The measured response curve was compared to a published theoretical response curve to confirm the operation of the fiber sensor array. The 1 x 4 fiber optic sensor array underwent initial field tested at the MSU Zero Emissions Research Technology (ZERT) field site which was developed for providing controlled underground CO2 releases (Figure 2). Final testing is to be completed later in the project.