Metal Oxide sensors for effective monitoring of methane emissions
Metal Oxide (MOx) sensors have become a key tool in the battle to detect, quantify and reduce GHG (greenhouse gas) emissions, due to their low cost, small size, and high sensitivity to gases like methane. However, out of the box metal oxide sensors have insufficient sensitivity to meet detection limit demands from operators, regulators, and certifiers of natural gas.
Calibrating and testing metal oxide sensors
Qube Technologies invests significant R&D resources to improve the capabilities of every metal oxide sensor we deploy. When new metal oxide sensors arrive at a Qube testing facility, they arrive uncalibrated, with a detection resolution of about 100 ppm (at 100 meters). This resolution is nearly ten times greater than the 1-2 ppm limit we need to produce accurate inferences of emissions quantities. Calibrating these sensors requires a great deal of precision, expertise, and testing, something that sets Qube Technologies apart from other continuous monitoring technology providers.
Each Qube sensor goes through a rigorous two step calibration process, first in a controlled lab environment, and then in the field. During initial calibration, sensors are subjected to various gas concentration, temperature, and humidity cycles. Then, outputs from each sensor are calibrated so that they match known test chamber input quantities. Once in the field, sensors are calibrated once more to account for background emissions.
Accounting for drift when using metal oxide sensors
Over time, there is another factor that users of metal oxide detectors need to consider. Drift.
Metal oxide sensors are susceptible to a gradual, and variable change in sensor response. All metal oxide sensors suffer from drift, and over time they will experience a shift in their measured baseline. Qube regularly monitors each individual sensor for drift, and if an adjustment is necessary, Qube can update the calibration coefficients remotely, over the air, saving operators money and labor that would otherwise be needed to send out a crew. Remote calibration is especially helpful for hard-to-reach locations, or across large operations where hundreds or thousands of sites may be monitored.
The case for metal oxide sensors
Metal oxide sensors can be a powerful tool for energy companies to manage and reduce methane emissions, but only if they are tested and calibrated to support the high-fidelity detection requirements of continuous monitoring programs. Contact us to learn more.