Energy-harvesting sensors can bring smart-building benefits without the wires
The demands on our office buildings have changed. Fewer people are occupying these spaces, and more building owners, planners, and facility executives are valuing flexibility, digitalization, and energy efficiency. Employees, who are gradually returning to the office, want assurances of a virus-free space, not to mention a comfortable, healthy, and safe environment. Meanwhile, buildings still account for nearly 40% of global CO2 emissions through their embodied energy as well as their operation.
Because intelligent networked spaces can balance these multidimensional objectives, they are increasingly capturing the attention of executives and managers. IoT sensors measuring occupancy, carbon dioxide, noise, and light have been in use for years, but their costs have come down. At the same time, they are becoming easier to install and maintain. By obtaining their energy from sources in their immediate surroundings, such as occupant movement, light, and temperature differences, sensors can operate without wires and batteries. Consequently, an owner can gain the benefits of sensors without worrying about energy supply and consumption.
IoT sensor benefits in smart spaces
Because few offices will be fully occupied for the full work week for the foreseeable future, many workstations will sit unused. Through desk-sharing and hybrid working models alone, employers can save up to 30% of costs for furniture, energy, and rent. IoT sensors can record how many people are in a room and monitor which workstations and areas are in use, allowing owners, operators, and planners to digitally map and optimize space.
Information on desk availability can direct energy management decisions and notify employees in real-time which workstations are available. Employees can then situate themselves in areas with their preferred temperature, with specific colleagues for team activities, or with the technical equipment needed for their task.
Unused desks can also be significant energy and capital consumers. In areas rarely or sporadically in use, temperature and solar sensors can inform heating, cooling, ventilation, and lighting controls to adjust automatically if these systems communicate on the same network. Data on space utilization can help identify areas rarely in use, which in turn can help companies decide whether to continue leasing them.
Carbon dioxide sensors can maintain or even increase worker productivity; more importantly, they can maintain employee health by monitoring room air quality and CO2 levels. If 10 employees spend about an hour in a meeting room without sufficient ventilation, their bodies will feel as if they each had consumed two glasses of wine—at that point, productive work is hardly possible. Sensors can alert occupants when CO2 concentration is approaching a critical level and increase airflow into the space, whether through mechanical systems or by notifying occupants to open windows.
Renewable energy sources for wireless sensors
New construction projects will often consider and integrate smart infrastructure into their planning. For retrofits, the headaches associated with opening existing, perhaps historic, building walls become a nonissue with wireless sensors, which can attach directly to walls, windows, and ceilings. Wireless sensors offer flexibility in installation placement and network expansion potential without the need for cables.
Furthermore, energy-harvesting radio sensors can forego the need for batteries and copper wiring, both energy-intensive products. Instead, they source their energy from movement, light, and temperature differentials.
In kinetic energy harvesting, electricity is generated from movement. For example, vibration sensors attached to desks can reliably monitor which workstations are in use—and without consuming power. Pressing a switch can activate an electromechanical energy converter that generates enough energy from the press of a button to switch appliances or lights on and off, to call up light scenes, or control roller shutters. This is also suitable for window contact sensors, which report when a window is open.
Similarly, a water sensor might use a swellable material that activates an electromechanical energy converter when it contacts water and expands, sending a radio signal to a valve that interrupts the water supply.
Small photovoltaic cells mounted on sensor modules can convert sunlight into electrical energy. They don’t need much light—200 lux or less are enough—to monitor humidity, temperature, window contacts, or occupancy. The energy is stored internally, ensuring the sensor’s operation on days without adequate sunlight.
With a Peltier element and a DC-to-DC converter, a wireless sensor can generate energy from a temperature differential of just 2 degrees Celsius. This method is ideal for self-powered heating valves that use the temperature difference between the heater and the environment to change settings and communicate via radio with a solar-powered room controller.
IoT Benefits
Leveraging existing IT infrastructure can expedite the implementation of a smart IoT solution while offering savings in project costs. Combining self-powered radio sensors—the most common of which harvest energy from light—with Wi-Fi access points allows collected sensor data to be sent to the cloud for analysis with the help of IoT software. Along with their ease in installation and maintenance, battery-free and wireless radio sensors can help owners gain the benefits of turning their new or existing offices into smart, flexible, and safe workspaces.
Raoul Wijgergangs is CEO of EnOcean, a provider of wireless, energy-harvesting technologies, switches, and sensors for buildings worldwide.
