How incoming CO2 legislation will increase energy usage

In the spirit of what the IoT makes possible, Neil Ricketts, Chair of Gas Sensing Solutions (GSS) shares how IoT sensors are assisting with CO2 detection

COVID-19 has raised awareness of the importance of in-building air quality, with legislators around the world seeking to reduce the risk from viruses and exposure and other airborne pollutants.

While not toxic in and of itself, CO₂ levels are a key correlative indicator of multiple airborne pollutants and, as such, many regional and national governing bodies have enacted, or are planning to enact laws stipulating maximum exposure levels.

Here in the UK, we’re at the proposal stage. In the US, multiple states (from California to Massachusetts) have already implemented acts of legislation, many of which focus on their public schools.

Elsewhere, laws have been enacted by countries such as the EU, Japan, Canada, Australia, and China, with proposals underway in multiple others from the UK to India.

Effect of legislation on CO₂ and pollutants

Such legislation is vital but creates a subsequent problem. HVAC systems (heating, ventilation, and air conditioning) are responsible for approximately 40% of the total energy used by a building, and by increasing ventilation we therefore increase the need to heat/cool this air.

In short, the legislation will add significantly to the energy consumption of these buildings, both increasing energy costs and (somewhat ironically) increasing CO₂ emissions elsewhere in the process.

IoT solutions

Of course, not all the air in the building needs to be refreshed at once, and localised monitoring enables smaller, more targeted air changes to be made. In doing so, this significantly reduces the required heating/cooling.

IoT sensors are already used to monitor gases, and CO₂ sensors exist. However, there is a challenge in undertaking accurate measurement across buildings through CO₂-monitoring IoT systems. Traditional NDIR sensors typically use a broadband IR source (incandescent bulb) which makes this type of sensor `require more power.

And while modern buildings may have the power-supply networks to roll out such systems in every room, in older buildings such as hospitals and schools, this can only be achieved via battery-powered IoT systems, transmitting over a standard such as LoRaWAN or Bluetooth Low Energy. And using these traditional methods would require very regular battery changes, with the time/cost of regular checking and replacing batteries making this prohibitively expensive.

Traditional sensor topologies

Sensors are moving away from incandescent IR emitters, with solid-state LEDs and MEMS emitters now being used.

LEDs are the most used light source and, like elsewhere, offer the lowest power consumption and longest mean time to failure. But even using LEDs, the power consumption is typically in the region of 50 to 150 mW average, with a peak of 300-400 mW.

An alternative sensor topology

Significant energy savings can be made. CO₂ sensors for IoT applications do not need to run continuously and by adjusting the duty cycle to run only when required it is possible to bring this down significantly.

Additional efficiency gains can be made through the use of better-optimised signal processing algorithms and hardware that reduce computational load. Similarly, the introduction of sleep modes and through the use more energy-efficient components elsewhere on the board it is possible to create an efficient IoT system capable of being rolled out in spaces where monitoring is possible.

By applying these techniques, it’s possible for IR sensors to run at sub 1.5 mW with a peak of 33 mW. This enables sensors that are not just in the range of coin cell operation, but also in the range of energy harvesting supplies.

Conclusion

Without localised testing across a building, health legislation intended to improve in-building air quality and reduce our exposure to CO₂ will directly lead to an increase in energy consumption from HVAC systems and therefore greater levels of pollutants emitted into the atmosphere.

If we are to minimise these effect, upcoming legislation needs to consider the use of IoT sensors throughout buildings to minimise the volume of air that requires refreshing and reheating/cooling.

Such sensors exist, however their high-power consumption levels make them badly suited to many facilities, especially schools / hospitals and other older buildings where power networks are not accessible in every room.

However, our work has shown that by adapting LED sensor topologies specifically for IoT systems via changes to the duty cycle, the implementation of more efficient algorithms and by considering the power consumption of every on-board component it is possible to reach the low power levels required for such systems to operate on a coin-cell or from energy harvesting.

Author: Neil Ricketts, Chair of Gas Sensing Solutions (GSS)

There’s plenty of other editorial on our sister site, Electronic Specifier! Or you can always join in the conversation by commenting below or visiting our LinkedIn page.