Wireless Sensors: The Eyes and Fingertips of Intelligent Building Systems

Smart buildings deliver savings and more

Moves to implement smart building management systems are substantially motivated by concerns regarding the environment, sustainability and energy prices. According to figures from the US Green Building Council, quoted by the Environmental Protection Agency (EPA), buildings account for 36% of total energy use and 65% of electricity consumption.

With the emergence of energy-saving technologies, some in the building industry suggest that energy is the largest controllable operating expense in a building. As an example of the level of savings that can be made over time, the California Energy Commission claims to have trimmed more than $74 billion from end-users’ energy bills since 1977 in California alone, through building-related efficiency initiatives such as its Title 24 regulations.

Some 70% of the electricity supplied to buildings is believed to be consumed by lighting and Heating/Ventilation/Air-Conditioning (HVAC) systems. Smart management of these services can help reduce electricity consumption by saving energy normally wasted due to excessive heating or ventilation, or lighting unused areas. Alongside the opportunity to make savings, smart building systems can also help property owners increase the value of their assets by offering greater comfort for occupants. Corporate customers looking to rent office space can understand the link between a comfortable working environment and better productivity, and may also find it easier to recruit skilled employees who expect pleasant working conditions.

Intelligent building systems can improve comfort for occupants by ensuring that rooms and spaces are not over-heated or over-ventilated, and by optimizing light levels in specific areas as needed to support the tasks or activities being carried out. Smart, adaptive controls such as these can be used in conjunction with an intelligent approach to building design that maximizes use of natural resources such as daylight and atmospheric pressure to assist the building’s lighting, ventilation and cooling systems. The orientation of the building and its windows can significantly influence the amount of natural light available during normal working hours. In addition, engineered building products such as adjustable fanlights or solar light pipes can be used to manage daylight and top up light levels in targeted areas.

All about the sensing

By monitoring temperatures, air quality and light levels throughout the building, and comparing the data with occupancy information, the smart building management system can help optimize energy consumption and assist with planning new services in the future to maintain comfort levels as usage patterns change. The data collected can also help building managers identify cost-saving opportunities. For example, if lighting in one area is found to be operating at its maximum level without dimming for extended periods, facilities managers may choose to install additional lights and increase dimming to boost reliability. Other services such as motion-tracked illumination can enable extra cost savings by enabling lights-out operation in some types of buildings such as warehouses or data centers.

As smart building management systems become more widely used, creative system designers and software engineers will be able to conceive new and more imaginative capabilities. On the other hand, software features and performance will be governed by the data available to the system. Smart building management depends on networks of sensors to collect information from throughout the building. By combining occupancy sensing with monitoring of temperature, air quality and other aspects of the environment, the sensor network represents the eyes, nose and fingertips of the system. With knowledge of occupancy and environmental conditions throughout the building, the smart management system can also help improve safety and security, by controlling safety equipment such as fire dampers and providing accurate information about occupants’ whereabouts in the event of an emergency.

As far as occupancy sensing is concerned, a number of techniques have been proposed. These include video-based techniques as well as Passive Infrared (PIR) or ultrasonic detection. Researchers at Stanford University have shown how an array of smart video cameras can be used to detect both the presence and location of room occupants, enabling the dimming of individual lights to be adjusted to optimize energy consumption while providing adequate lighting for each occupant. To safeguard privacy, the video information from the cameras is deleted as soon as the analysis has been completed.

PIR sensors rely on motion to detect occupancy. As such, the sensors are vulnerable to false triggering by non-human objects moving within the sensor’s field of view. On the other hand, the sensor may falsely indicate that a room is unoccupied if occupants have been sitting or standing extremely still.

Panasonic has overcome these challenges with its NaPiOn series of sensors, which are available in a number of different types offering various detection characteristics. The EKMC1601111 is a general-purpose sensor, while other options include the AMN32112 optimized for detection of much smaller movements.  The EKMC16031111 provides another option offering extended detection range of up to 12 meters. These detectors deliver further advantages for designers, such as a high-density embedded circuit design featuring an integrated amplifier that simplifies external circuitry (Figure 1), as well as ultra-low current consumption of 1 µA allowing use in ultra-low-power or battery-less sensors.

Figure 1: A high level of integration minimizes external circuitry and simplifies design.

Wireless and battery free

Wireless networking is likely to be the preferred solution in the smart-building market. Compared to wired alternatives, wireless allows easier installation with minimal disruption. Wireless sensors can be installed without interfering with existing structures, which can be especially helpful in older buildings where modifications may be undesirable or in some cases not permitted. The market analyst ON World has predicted that wireless sensor networks will be responsible for the majority of growth in intelligent building systems to 2023. The report, which was published late 2013, also suggests that 70% of wireless sensor network shipments will be associated with HVAC and lighting controls.

Self-powered wireless sensors deliver even greater freedom by eliminating any need to replace batteries throughout the life of the unit. The wireless standard ISO/IEC 14543-3-10 caters for this type of application, and is optimized for wireless devices with ultra-low power consumption such as battery-less sensors that are powered purely using energy harvested from the ambient environment. EnOcean has developed a set of Equipment Profiles that work with the ISO/IEC 14543-3-10 lower layers (Figure 2) and ensure interoperability between compliant products from different manufacturers. Sensor makers can quickly begin developing self-powered wireless sensors incorporating EnOcean technologies, using a development kit such as the EDK350U. The kit contains software tools, an API, a programming board, and a selection of modules that enable building and connecting various sensors and actuators.

Figure 2: ISO/IEC-compliant radio and standardized Equipment Profiles ensure interoperability.

Developers of smart building systems, who do not want to devote precious resources to building their own self-powered devices, can choose ready-to-use sensor families based on EnOcean technologies, such as ZenNet Lighting Controls by Thomas Research Products. The TWO-WL-W occupancy sensor is powered by solar energy from natural indoor light, and incorporates a PIR motion sensor. The sensor sends messages to connected devices when movement is detected. A number of lenses are available to help optimize the PIR’s response. Wall- or ceiling-mount configurations are available, and the ZenNet range also includes battery-less rocker switches and intelligent relays. DigiKey can also supply EnOcean-based sensors, relays and switches by Illumra.

Conclusion

In today’s energy-sensitive world, smart building management systems offer a clear value proposition to commercial premises owners and their tenants. Although lower utility bills are a key attraction, additional benefits such as improved comfort and safety further enhance the value these systems can deliver. With clever software, tomorrow’s building-management systems could deliver even greater efficiency, convenience and comfort, but only if they can depend on their eyes, ears and fingers: the sensors that can identify where people are and the environmental conditions they are experiencing at any time of day or night.