Know Your Sensors: Making Buildings Smarter

Commercial buildings consume a lot of energy to provide the services required by their occupants. According to statistics, electricity accounts for at least 60% of building energy consumption, but not all energy is used efficiently. For example, corridors and public spaces may be brightly lit for extended periods of time even when no one is present. Heating, ventilation and air conditioning (HVAC) systems in office buildings typically account for around 40% of total energy consumption, and to ensure that energy is not wasted, smart technology is required on a large scale.

Over the past two decades, greater sustainability and energy efficiency have been driven by stringent government and industry regulations that require existing buildings to reduce energy consumption and reduce carbon emissions, while requiring the use of sustainable materials for new construction buildings and integrate intelligent automation systems that can efficiently manage energy consumption.

At the heart of all of this is serving the people in the actual building, whether they use it as a home or a work environment. Providing building automation systems (BAS) can make occupants more comfortable, so the key to improving energy efficiency is the ability of a building to adjust and adapt to the needs of the people (or not) that live in it.

Research conducted by Memoori shows that worldwide building systems revenues are growing significantly, aided by the development of smart buildingsInternet of Things(IoT) technology, which is increasingly known in the construction industry as the Building Internet of Things (BIoT). Building energy and control systems accounted for the majority of sales, followed by physical security/fire detection ($23.2 billion). Based on these figures, Memoori forecasts that the global BIoT market will grow from just $34.8 billion in 2017 to $84 billion in 2022 (19.4% CAGR). Research and Markets, on the other hand, is slightly more conservative, predicting it will reach nearly $52 billion by 2023.

Buildings that can sense people

Smart buildings need to be equipped with technologies that “see” or “perceive” the presence or absence of people. In addition to detecting occupants, the ability to track their location or movement within a building can also maximize the efficiency of various systems. Furthermore, thanks to artificial intelligence (AI), buildings can finally adjust and prepare rooms according to the preferences of the occupants.

However, we don’t want to get off topic here. This article will focus on how smart buildings perceive and count occupants from an energy saving perspective.For example, occupancy can be usedsensorTo automatically turn on or off the lighting in corridors and rooms according to the presence or absence of people, which can reduce the power consumption of lighting. Complementing the ambient light sensor, the brightness of the lights can be adjusted according to the intensity of sunlight in the room, further saving energy.

One obvious way to enable smart buildings to “see” their occupants is to use cameras equipped with high-resolution CMOS image sensors. ON semiconductor‘s Python series of image sensors offer flexible configuration, accurate image rendering and low read noise at high-speed operation. They support frame rates from 80 to 815fps, so they can capture fast-moving scenes without distortion. These 4.5 to 4.8 μm pixel image sensors have resolutions from VGA to 25MP, and several product variants are optimized for tasks such as motion monitoring, security and surveillance. The 2.3MP Python2000 features an on-chip programmable gain amplifier and 10-bit analog-to-digital converter. It supports pipelined and triggered global shutter readout modes to reduce noise and provides greater dynamic range through the use of correlated double sampling (CDS) techniques.

Know Your Sensors: Making Buildings Smarter

Figure 1: Python image sensor example from ON Semiconductor.

Considering that these cameras are only effective in line of sight, multiple cameras need to be installed in some specific spaces, but there is a risk of invasion of privacy. This can be solved by using a face-blurring machine vision system. Mounting the camera on the wall will still keep occupants constantly on the alert that Big Brother is watching them all the time.

While sensing the presence of people is enough to control lighting, smart buildings also need to be able to count people in a given space for services such as on-demand control of ventilation. This requires the use of an occupancy-based detection model algorithm that can estimate the number of people present without the use of cameras. Together with sensing information such as temperature, humidity and CO2 sensors, the HVAC system will be able to automatically provide optimal environmental conditions .

Other sensors used to detect the presence of occupants include passive infrared (PIR) motion sensors that have less impact on the system and are cost-effective. PIR devices offered by Panasonic include the wide-field EKMB and EKMC series, which are available in both flat and rectangular forms and can inspect up to 150° on a single axis. Available in 1µA, 2µA, and 6µA models, these sensors can accommodate a variety of battery-powered applications, and their overlapping detection areas determine motion in direct proximity to the sensor.

Omron Electronics’ D6T series are ultra-sensitive infrared thermal sensors that take advantage of Omron Electronics’ proprietary MEMS sensing technology. Unlike PIR sensors that rely on motion detection, the D6T series uses body heat sensing to determine whether someone is present. In addition to automatically turning off lights or air conditioners when no one is present, they are also suitable for monitoring room temperature and sensing abnormal changes such as overheating that occur, thereby helping to prevent fire.

Know Your Sensors: Making Buildings Smarter

Figure 2: Omron’s D6T infrared sensor.

Texas Instruments (TI)’s IWR1642 series includes sophisticated single-chip mmWave sensors with integrated FMCW radar technology, operating in the 76-81GHz frequency band with continuous chirps (chirps) up to 4GHz. Manufactured on a proprietary low-power 45nm RFCMOS process, these sensors are ideal for use in building automation applications such as people counting. The sensors integrate a DSP subsystem with a high-performance C674x processor core for RF signal processing, and an ARM R4F-based processor subsystem for front-end configuration and control, as well as support for calibration functions.

In addition to access control, RFID systems can also be used to count people in commercial buildings to some extent. In most cases, this method is able to determine the total number of people in a multi-tenant building. However, making nuanced and accurate statistics is only feasible in buildings or facilities used by a single company (or overseen by a single property management unit).

sensor array or system

Different types of occupancy detection and people tracking/counting sensors each have their own relative advantages and disadvantages, depending on cost factors and the layout of rooms within a building. Therefore, it is necessary to consider systems that employ sensor combinations or arrays to improve detection accuracy in a given environment. The sensors themselves also require less maintenance, helping to reduce overall energy consumption.

Texas Instruments’ (TI) occupancy detection reference design featuring the IWR6843 mmWave sensor for indoor and outdoor people counting applications features the MMWAVEICBOOST and IWR6843ISK evaluation modules and the LAUNCHXL-CC1352R1 wireless microcontroller unit (MCU) LaunchPad.

Figure 3: Texas Instruments’ LAUNCHXL-CC1352R1 LaunchPad development kit.

Silicon Labs’ PIR Occupancy Sensor Evaluation Kit is an add-on board for the EFM32 and EFR32 starter kits that demonstrates occupancy sensing and ambient light sensing systems using both connected and unconnected MCUs. Compatible with the SLSTK3402A EFM32 PG12 starter kit, this evaluation kit also provides a real-time GUI Display of PIR motion signals, performance summaries, and test methods.

If sensors could operate without consuming current, they could dramatically improve the energy efficiency of buildings. Molex’s Transcend series of wireless occupancy sensors are self-powered, providing a cost-effective way to control energy consumption in unoccupied rooms. The sensor harvests photovoltaic energy from indoor lighting and uses RF technology to wirelessly communicate with other nearby Transcend devices. With these sensors, if a space is not occupied for a certain period of time, the building automation system can reset temperature levels, turn off services such as lighting.

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