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.
Fundamental and applied research on carbon capture, utilization and storage (CCUS) technologies is necessary in preparation for future commercial deployment. These technologies offer great potential for mitigating carbon dioxide (CO2) emissions into the atmosphere without adversely influencing energy use or hindering economic growth.
Deploying these technologies in commercial-scale applications requires a significantly expanded workforce trained in various CCUS technical and non-technical disciplines that are currently under-represented in the United States. Education and training activities are needed to develop a future generation of geologists, scientists, and engineers who possess the skills required for implementing and deploying CCUS technologies.
The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL), through funding provided by the American Recovery and Reinvestment Act (ARRA) of 2009, manages 43 projects that received more than $12.7 million in funding. The focus of these projects has been to conduct geologic storage training and support fundamental research projects for graduate and undergraduate students throughout the United States. These projects include such critical topics as simulation and risk assessment; monitoring, verification, and accounting (MVA); geological related analytical tools; methods to interpret geophysical models; well completion and integrity for long-term CO2 storage; and CO2 capture.
Overall, the project will make a vital contribution to the scientific, technical, and institutional knowledge base needed to establish frameworks for the development of commercial-scale CCUS technologies focused on ensuring that CO2 injected into the storage formation remains in the injection zone(s). The project is leading to the development of a low cost sensor that can be used to monitor geologic storage sites for high CO2 fluxes (often a signal that CO2 may be leaking from the injection reservoir) in real-time over a large area. A CO2 sensor capable of this application can contribute to ensuring the integrity of the storage site and preserving public safety by detecting and determining the location of high concentrations of CO2. Additionally, this project offers student research opportunities that will help cultivate a workforce trained in the skills and competencies required to implement CCUS technologies.
The primary objective of the DOE's Carbon Storage Program is to develop technologies to safely and permanently store CO2 and reduce Greenhouse Gas (GHG) emissions without adversely affecting energy use or hindering economic growth. The Programmatic goals of Carbon Storage research are: (1) estimating CO2 storage capacity in geologic formations; (2) demonstrating that 99 percent of injected CO2 remains in the injection zone(s); (3) improving efficiency of storage operations; and (4) developing Best Practices Manuals (BPMs). The objective of the project is to develop a low cost 1 x 4 fiber optic sensor array for sub-surface CO2 detection. The sensor array is being developed to be economical, scalable (up to N fiber probes using one laser and two detectors), easily deployable, and reconfigurable for use in CO2 soil gas detection over large surface areas in a real time application. The results of this project will contribute to ensuring long term storage of CO2 by verifying that no detectable releases have occurred. Additionally, university students will have hands on training in the development and deployment of a fiber sensor array for carbon storage monitoring.
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