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Optical sensors to measure hydrogen gas concentration in humid environments – hydrogen energy production

 

Supervised by Dr Patricia Scully with Dr John Vaughan (School of Chemical Engineering and Analytical Science)

The aim of the project is to identify conditions for an optimised coating to be used in an optical sensor to measure hydrogen gas concentration at low concentrations in real conditions. This includes humid environments, in order to facilitate a remote sensor that can work in field conditions independent of temperature and humidity.

This project develops hydrogen sensitive optical coatings to assess their response to low concentrations of hydrogen in humid environments. To date, all Hydrogen sensors are affected by humidity whether they are optical or electronic/catalytic, which poses difficulties for operation in field conditions. Our preliminary results indicate that the sensors we have developed are not affected by humid environments. Since the sensors are interrogated optically, they are intrinsically safe and ideal for use in explosive/flammable atmospheres.

Commercially available hydrogen sensors use electrical measurements at the sensing point, but this could ignite an explosive atmosphere resulting from the hydrogen leak that the sensor is designed to detect. Optical fibre based sensors for hydrogen detection are advantageous due to the intrinsic safety factor of using a detector based on optical rather than electrical changes. Using an electrical current/voltage sources in a potentially flammable environment could ignite an explosion. Optical fibres enable a light signal to be propagated over 100s of metres or even kilometres, so that the light source and detection electronics can be kept remote from the hydrogen source, preventing accidental electronic ignition of leaked hydrogen.

Aims include:

  • to optimize optical coatings that can selectively and rapidly detect hydrogen at low concentration (less than 1%) without relative humidity affecting the sensor
  • to evaluate coating response under variable conditions of temperature and relative humidity occurring in a fuel cell or water cooling system (-15ºC to 40ºC; 0 to 70% humidity)
  • to assess the potential of a low cost sensor that is highly selective, durable and responds rapidly to low concentration of hydrogen under variable conditions of humidity and can be interrogated remotely and sense in point and distributed configurations via an optical fibre link
  • to build a demonstrator based on a LABVIEW interface and remote optical fibre link.

Applications include hydrogen fuel cell safety monitoring and monitoring hydrogen used with seawater to generate oxygen via electrolysers in nuclear submarines. Reduction of greenhouse gas emissions by securing a cheap and environmentally friendly supply of energy is a major socio-economic driver facilitated by hydrogen and fuel cell technologies. Hydrogen sensors are affected by moist air or humidity arising from the vented enclosures being open to the weather, whether they are based on optical or electronic/catalytic.

R R J Maier, B J S Jones, J S Barton, S McCulloch, T Allsop, J D C Jones and I Bennion. (2007). Fibre optics in palladium-based hydrogen sensing. J. Opt. A: Pure Appl. Opt. 9, S45–S59.

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