The University of Southampton

Photonics-based sensors to detect rising ocean greenhouse gas levels and toxic pipeline leaks

Published: 14 August 2020

Ocean methane and hydrocarbon levels will be measured using a new generation of low cost optical fibre isotope detectors in a prestigious fellowship at the University of Southampton.

Rand Ismaeel from the Optoelectronics Research Centre (ORC) will develop the sensors for use in miniaturised Autonomous Underwater Vehicles (AUVs) in the five-year Research Fellowship from the Royal Academy of Engineering.

Methane is a potent greenhouse gas that exists in enormous quantities in the form of hydrates, which are ice-like storehouses on the sea floor. The increase in ocean temperatures can cause these hydrates to decompose and release ancient methane to the atmosphere, intensifying the greenhouse effect and global warming.

The joint project between the ORC, National Oceanography Centre (NOC), Planet Ocean and the Université de Lyon will provide a unique, efficient and affordable technology that sheds light on methane transformation at different depths and temperatures as well as its emission patterns to the atmosphere.

In addition to methane mapping, the fellowship will design the sensors to provide an effective early warning system for oil pipeline failures, mitigating their catastrophic and costly environmental impact.

Dr Ismaeel says: "This fellowship will transform the methodology of ocean hydrocarbon detection from bulky, unreliable and expensive technology to the next generation of ocean photonics sensors, suitable for surveying the ocean at low cost.

"By introducing these smart tools, it will be possible to revolutionise the way oil and gas companies perform their pipeline inspections. It will also allow the creation of new policies and regulations that oblige these companies to perform these inspections and make them more frequent.

"The vital raw data generated from these new sensors about the life cycle of ocean methane will deliver new insight into the entangled effects between methane, methane hydrates and global warming. It is crucial that we channel the latest scientific advances to help address such global challenges."

Commercially available methane and hydrocarbon sensors are all based on gas extraction from water, which worsens the technology's response time and selectivity. They are also incompatible for integration into AUVs and need to be deployed stationary on large vessels or gliders.

The new detectors will be capable of measuring and differentiating dissolved ocean hydrocarbons in the near infrared region for the first time without being converted to gas.

The devices will be designed to be compact, efficient and low power to fit in the nose of ecoSUB Robotics AUVs, part of Planet Ocean Ltd. Dr Ismaeel will work closely with project partners from Planet Ocean to mechanically integrate the fibre optic sensor into the subsea vehicle.

The efficient design adapts light circulation technology investigated during Dr Ismaeel's PhD and postdoctoral experience at the ORC. The light in this geometry will circulate back and forth in the optical fibre and resonate at a very specific wavelength that matches the absorption wavelength of the targeted molecules.

To further enhance the selectivity to methane, a selective layer will be developed in collaboration with Université de Lyon and The Arctic University of Norway. The project will integrate the multi-parameter V-lux fluorometer into the ecoSUB, developed and provided in-kind by project partners Chelsea Technologies Group.

Sensor performance will be tested under a pressure experienced at 6,000m underwater and temperature of 2°C at the NOC's world class pressure and environmental test facilities. Field tests for pipeline inspection will be performed in collaboration with Blue Ocean Monitoring and oil and gas firms.

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