HEATING, VENTILATION & AIR CONDITIONING


Why IoT will play a key role in reducing energy consumption


HVAC systems are already responsible for approximately 40% of the energy used in the average building. But, energy usage is set to rise even further


thanks to incoming CO2monitoring legislation. Neill Ricketts, chair of the ultra-low-power CO2 sensor developer, GSS, examines how IoT systems can help


C


arbon dioxide is not directly toxic, but it is a key correlative indicator of multiple airborne


pollutants, including COVID-19 and other viruses. With the pandemic acting as a catalyst to


raise awareness of the importance of in-building air quality, many regional and national governing bodies have begun the process of enacting legislation to limit concentrations as a way to limit exposure to other more dangerous airborne particles. In the US, multiple states (from California to


Massachusetts) have already implemented acts of legislation, many of which focus on their schools and other public buildings. Elsewhere, laws have been enacted by governments including the EU, Japan, Canada, Australia, and China, with proposals underway in multiple others from the UK to India.


THE ROLE OF IOT Such legislation requires air to be refreshed regularly, and therefore heated or cooled. According to research by the Australian government, HVAC systems (heating, ventilation, and air conditioning) are already responsible for approximately 40% of the energy used in the average building. While this figure will vary from country to country, increasing ventilation will increase the need to heat or cool this air, and therefore the cost of and pollution from running such HVAC systems. IoT systems have a huge role to play in


minimising this, monitoring localised CO2 levels and enabling only specific areas at risk of breaching to


be changed. Like for many other gases, IoT CO2 sensors do exist, however, there is a challenge in


implementing them – especially when it comes to deploying them in a traditional IoT set up with standalone battery powered devices left alone to report. And that challenge is power. NDIR sensors typically use an incandescent bulb


to generate a broadband IR source, which would take this sensor beyond the range of battery powered devices. Of course, modern buildings may have the power-supply networks to roll out


Some of the key countries implementing or considering legislation to limit CO2


such systems in every room, but this is simply not the case in many older buildings, and given much of the legislation is focused on hospitals and schools, which tend to be in older buildings, battery-powered IoT systems are needed.


ALTERNATIVE SENSOR TOPOLOGIES It should be highlighted that incandescent IR emitters are being replaced by solid-state LEDs and MEMS emitters, with LEDs now the most used light source. These do lower the power consumption (and also improve mean time to failure), but even with LED-based sensors, power consumption would be in the region of 5 to 150 mW.


WHERE ENERGY SAVINGS CAN BE MADE The duty cycle is a key starting point, with adjustments enabling the sensor to only run


when essential. For such applications, CO2 sensors could run safely every 10-15 minutes. Similarly, the introduction of sleep modes can help reduce power demands further. Elsewhere, the use of more energy-efficient components and the deployment of better-


optimised signal processing algorithms and hardware can


The GSS COZIR ULP NDIR CO2 sensor has adapted the duty cycle and signal processing algorithms to reduce the power consumed by orders of magnitude


32 ENERGY & SUSTAINABILITY SOLUTIONS - Autumn 2024


reduce computational load. Through these techniques, an IR sensor would be able to run at sub 30mJ per measurement, giving 100µW average power for 5-minute interval measurements. This enables sensors that are not just in the range of AA or coin cell operation, but also in the range of energy harvesting supplies, which would allow it to be positioned and forgotten about.


CONCLUSION It is ironic that health legislation intended to improve in-building air quality and reduce


our exposure to CO2 will directly lead to an increase in energy consumption and therefore (depending on use of renewables) likely more


CO2 in the atmosphere. IoT sensors positioned throughout buildings


have the potential to minimise these effects by reducing the volume of air being refreshed and reheated/cooled. However, the power


consumption of most existing CO2 sensors make them ill-suited to such applications, especially in older buildings with limited access to power networks where required. Lower-power designs, such as that employed by


the COZIR Blink sensor, are therefore required. Our work has shown that by adapting LED sensor topologies it is possible to meet these demands and operate on AA or coin cell batteries – or even with energy harvesting systems.


GSS www.gassensing.co.uk www.essmag.co.uk


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