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Laser pinpoints methane leaks at biogas plants

20 Nov 2014

Portable system spots leaks from up to 15m; set for commercialisation within 3-5 years.

Germany is a keen advocate of biogas; the country is now home to almost 8,000 biogas plants. Biomass-derived methane gas generates both electricity and heat. In 2013, German operators produced more than 26.4 TWh of electricity or about 17 percent of the gross electricity generation from renewables, supplying 7.5 million households.

However, servicing biogas plants is challenging. Methane escapes are particularly problematic – from safety, economic and environmental perspectives. Now researchers are working on a new technique that helps to better detect leaks. In their approach, a laser can discover leaks contactlessly and from several meters away.

The R&D project is funded by the German Federal Ministry of Food and Agriculture, researchers and a measuring equipment manufacturer are now develop a technology to allow plant operators to find leaks in all system parts quickly, inexpensively and safely. After 18 months' of R&D work, the scientists have developed a laser-based demonstrator that can remotely detect biogas or natural gas escaping from leaks. They say it is faster and more accurate than was previously possible.

The project involves the Fraunhofer Institute for Physical Measurement Techniques, Freiburg, the Fraunhofer Institute for Environmental, Safety and Energy Technology, Oberhausen, and the measuring instrument manufacturer Schütz Messtechnik, Lahr.

Identifying methane

The technology developed at the Fraunhofer IPM is based on optical emission and backscattering spectroscopy. In the process, the light of a strong laser beam detects escaping methane. Simultaneously, the gas irradiates part of the light back. The scientists analyze this proportion and can then determine the gas concentration from the absorption spectrum of the escaping substance. Since the gas spectrum is precise, only methane is selectively measured.

This technology has been developed into the pictured demonstrator. It stands on a tripod and is directed at the part of the plant equipment to be inspected. The optical portion of the measurement system comprises the laser, detector, camera and rangefinder. A connected tablet PC collects the data and evaluates it. The screen displays the graphically edited information concerning the escaping methane and the exact position of the leak. Measurements from up to 15m away are possible.

Researchers can make highly precise measurements: They have adapted the output wavelength of the laser optimally. For example, a common flange joint in a plant measures about 15cm across, which can be assessed in three to four measurement procedures. The technology detects excessive gas concentrations in rooms and determines whether these are dangerous to humans.

Dr. Johannes Herbst, measurement technology expert at the Fraunhofer IPM, expects the technology to be ready for the market in the next three to five years. In the laboratory, the researchers are currently refining various other functions. They have succeeded, for example, in detecting methane without the backscattered light. For this purpose, the gas itself is illuminated by a strong laser. “In the future, the measurement team will be able to easily check the entire system from the ground. It used to be necessary to climb ladders and identify the leaks on the spot,“ said Herbst.

About the Author

Matthew Peach is contributing editor to optics.org.

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