Growing the CO2 refrigerant market with low power sensors

The reduction of harmful greenhouse gases is also a key consideration, as these traditional gases contribute up to four thousand times more than CO₂ to global warming.

Dr David Moodie, Technical Manager at GSS, said: "CO₂-based water chillers, chest freezers, beverage coolers and heat pumps are increasingly being developed and commercialised, making this a very exciting new market for us as providers of innovative CO₂ sensors. For example, CO₂-based refrigeration systems are in use in a large number of Swedish supermarkets, with other countries following this trend towards a highly green refrigeration solution."

It is important to have CO₂ sensors in this application to monitor for potential CO₂ leaks. CO₂ exists in the atmosphere, and background (normal) outdoor air levels are around 250-350 ppm. CO₂ is harmless to humans, except when concentrations are four to five times greater than normal.

For example, at 2,000-5,000ppm, health problems such as headaches, loss of attention and slight nausea may be experienced. As CO₂ gas is odourless and colourless, leaks could easily go unnoticed. A speedy warning of increased CO₂ levels is therefore vital in ensuring people's safety in CO₂ refrigeration applications.

GSS has a range of standard CO₂ sensors for refrigeration applications. The ExplorIR-W is a particularly robust design, built with mid-infrared LED technology at its core. It's this solid-state technology that enables the earliest warning of any possible CO₂ leaks. This also provides the required long lifetime and high precision needed in leak detection applications.

Available with an extended temperature range, the ExplorIR-W can operate right down to -25ºC as required in many supermarket freezers. It is available in measurement ranges of 0-5%, 0-20% and 0-100% CO₂ concentrations according to the specific application. The sensor can be adapted for special requirements, or developed into a custom CO₂ sensor solution for leak detection applications.

GSS technology
CO₂ sensors work by measuring how much light is absorbed by CO₂ molecules in the 4.2 and 4.4 microns range as it passes through the sample gases, which is called Non-Dispersive Infra Red (NDIR) absorption. The amount of absorption indicates how much CO₂ is present.

GSS developed proprietary LEDs that are specifically tuned to emit at these wavelengths. The LEDs use very little power and turn on almost instantly, enabling sensor readings to be made in less than a second.

As a result, GSS has pioneered the development of CO₂ sensors that can be powered by batteries for long periods of up to ten years. Competitor sensors use IR sources that require significantly more power per measurement and also take much longer to reach a stable condition for a measurement, resulting in the need for mains power.