Using People Counting to Optimize Carbon Footprints and Energy Expenditure in Buildings


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A large amount of money and energy is wasted globally on heating, ventilation, and lighting of vacant spaces in buildings.1 The development of “smart” HVAC and lighting systems depends on the progression of versatile and accurate people-counting solutions.

New sensor development, with the capability to accurately measure the occupancy of a room without infringing on privacy, is offering all kinds of businesses and organizations a method to significantly decrease energy consumption in their buildings.

It is costly to provide heat, light, and air-conditioning for buildings. These structures account for around 40% of global energy and use approximately 60% of the world’s electricity.1 Yet, each day, around the globe, businesses are spending money on heating, cooling and illuminating vacant rooms and buildings. Recently, strict building regulations have resulted in a significant enhancement in the thermal properties of buildings. However, this attention has not been given to room occupancy.

People counting provides a method of radically reducing the amount of energy used by HVAC and lighting systems in buildings. HVAC and lighting can be optimized through continually monitoring the number of people in a room. For example, lights can be switched on when a room is being used and switched off when it is vacant.

Additionally, heating can be controlled to increase when people arrive at work and decrease when people begin to leave work at the end of the day. Ventilation can be given in direct response to the number of people in a room.

The large amount of energy that is consumed by buildings globally means that even a tiny percentage reduction in building energy consumption signifies a huge amount of saved energy.

Research demonstrates that having control over HVAC systems in response to room occupancy leads to huge proportional savings. Studies at the Norwegian Building Research Institute state that primary schools could anticipate a reduction in the energy consumption of their ventilation systems by more than 50% when using IR sensors to modulate ventilation systems in response to demand. This is in comparison to using fixed-volume ventilation.2

A sustainability consulting firm, Cundall, reported that hotels could anticipate total energy savings of 25-28% through the adjustment of heating and power systems in response to room occupancy.3

By using these same principles in office buildings, universities, and any other buildings with constantly changing occupancies, there is potential to heavily reduce the amount of energy used by buildings.

Businesses and organizations could have the ability to make large savings in their energy costs, in addition to significantly reducing their CO2 emissions, if they adopted such methods.

Selecting the Correct Sensor for the Job

As a result of the above research outcomes, there is a need for the introduction of a versatile sensor with which the occupants of a room can be counted. However, while several different types of the sensor have been suggested and utilized with limited success, problems with accuracy, price, and privacy are delaying widespread implementation.

For instance, high-resolution cameras need costly image-processing hardware. In addition, cameras record identifiable pictures of individuals, which presents security fears and in numerous cases, local legislation may not allow it.

These privacy issues are avoided by using ultrasonic detectors, however, they often present false-positives because of machinery or air turbulence. Radio-frequency detectors require individuals to wear tags, on top of several accuracy issues.

Infrared Time-of-Flight Sensors

Due to the requirement of a versatile, low-cost sensor for people counting, a range of 3D infrared sensors has been developed by Terabee. They provide highly accurate people counting without recording identifying information about individuals.

The Time of Flight (ToF) principle is used to operate Terabee’s sensors. Invisible and safe infrared (IR) light is emitted by the sensor, and precise measurements are made of the time it takes for it to reflect back from a surface. Then, this “time of flight” is used for the calculation of the distance of an object from the camera.

This technology leads to IR ToF sensors being uniquely well-suited to people counting applications. For example, Terabee’s TeraRanger Evo 64px records accurate depth information from 64 points over a 15  field of view.5

Terabee sensors are intrinsically anonymous, and the moderately low spatial resolution means that identification of personal elements, like clothing or facial features, are not captured by the camera in detail. However, the 3D spatial information is sufficient enough to accurately determine when people are moving into and out of a room and count them.

In fact, after years of testing and refining the algorithm for people-counting, Terabee’s sensors have the ability to measure room occupancy with 98% accuracy. By putting a device in a doorway, the number of people entering and leaving a room can be counted, leading to continuous monitoring of room occupancy.

This information can be used to make HVAC and lighting systems increasingly efficient. For larger doorways, the Terabee 3Dcam 80x60 measures the distance of 4,800 individual points over a 74° x 57° field of view.6

Terabee’s sensors have been refined so they are robust, dependable and cost-effective. With either USB, I2C or UART connectivity, the devices are designed to plug-and-play as part of basically any network, leading to them being perfectly suited to integration as part of smart HVAC and lighting systems.

Additionally, because the IR sensed by the sensor is emitted by the device itself, these sensors operate in dark conditions; and the discrete form factor of the devices means that they can be utilized in virtually any building.

References and Further Reading

  1. Ahmad, J., Larijani, H., Emmanuel, R., Mannion, M. & Javed, A. Occupancy detection in non-residential buildings – A survey and novel privacy preserved occupancy monitoring solution. Appl. Comput. Informatics (2018). doi:10.1016/j.aci.2018.12.001
  2. Mysen, M., Berntsen, S., Nafstad, P. & Schild, P. G. Occupancy density and benefits of demand-controlled ventilation in Norwegian primary schools. Energy Build. 37, 1234–1240 (2005).
  3. Guest Room Control Systems How much energy can your hotel save with Interact Hospitality?
  4. Yang, J., Santamouris, M. & Lee, S. E. Review of occupancy sensing systems and occupancy modeling methodologies for the application in institutional buildings. Energy Build. 121, 344–349 (2016).
  5. Small and lightweight ToF depth camera | TeraRanger Evo 64px. Available at: (Accessed: 10th March 2020)
  6. 3D TOF Camera | Compact Sensor | 3D TOF Technology. Available at: (Accessed: 10th March 2020)

This information has been sourced, reviewed and adapted from materials provided by Terabee.

For more information on this source, please visit Terabee.


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