Energy harvesting and NFC - the duo for IoT systems

With the help of this resource-saving technology, the sensors provide important data that can be used, for example, to save energy in buildings and thus reduce their CO2 emissions. These sensor systems must be easy to implement and adapt to specific requirements, particularly in existing buildings.

This is where NFC (Near Field Communication) comes into play as an ideal supplement for commissioning self-powered sensor and switch modules. An integrated NFC interface enables the sensor to be configured via an NFC reader or an NFC-capable smartphone or tablet.

The functions range from reading out product information and storing product properties on the tag to updating the firmware or sending and receiving a radio telegram in the NFC tool via the radio chip of a sensor. This opens up completely new possibilities for product developers to adapt self-powered sensors for a wide range of applications and customer requirements, and allows installers to work more efficiently.

A resource saving technology

The climate debate has been a regular topic on the news for months, if not years, and the consequences of climate change are happening right before our eyes. Melting ice on the polar caps is causing sea levels to rise, some regions are struggling with too much precipitation due to the more frequent occurrence of extreme weather events, while other places are suffering from extreme heat waves and droughts. Energy consumption plays a key role in this and therefore heating and electricity in buildings should only be switched on when needed. Innovative smart home solutions can, among other things, control electricity consumption and regulate, for instance, the heating temperature when windows are open. Embedded in the Internet of Things (IoT), sensors report the exact usage requirements of a building to the consumer or can predict them.

Special innovative technologies are to be used to combat climate change. Many of these technologies already exist, including energy harvesting wireless sensors from EnOcean. Energy harvesting is an established technology in both building automation and the smart home for wireless switches, sensors and also actuators that receive their energy from the immediate surroundings. Solutions include battery-free switches, window handles, sensors to measure light, temperature and humidity, occupancy detectors and radiator control valves.

With this technology, the smallest amounts of energy from the environment are collected, stored in battery-free wireless sensors and converted for the communication and function of them. Energy is obtained from movement, light and temperature differences. Pressing a switch, for example, activates an electromechanical energy converter that provides energy for a telegram based on this movement. This technology is particularly suitable to use in buildings, as the signal can switch lights and household appliances on and off or control light scenes.

Using the same principle, a kinetic window contact can report whether a window is open or closed. Another way of using this technology in buildings is to implement a battery-free water sensor. Here, the energy converter is activated as soon as water comes into contact with the swelling material at the bottom of the sensor. This type of sensor can be conveniently positioned under the washing machine or bathtub and prevents water damage by sending a radio signal.

When generating energy from light, the light intensity of interior light is sufficient to enable small solar cells to supply wireless modules with power. These include temperature, CO2 and presence sensors, solar-based window contacts or humidity sensors. A solar-powered temperature sensor module, for example, can reliably measure the temperature in a room, even with low power consumption. Once the energy storage device is fully charged, the module remains completely functional for about a week, even in total darkness.

Energy can also be obtained from temperature, because electronic devices are already supplied with sufficient energy when the temperature drops by two degrees Celsius. A DC/DC converter and a Peltier element are combined for this process. This form of energy harvesting can be used, for example, to operate self-powered radiator control valves that use the temperature difference between radiator and environment.

With help from the resource-saving technology of energy harvesting, the sensors and modules provide data to save energy and thus CO2 in buildings. For example, the heating can be regulated when windows are open, unused devices can be turned off completely or the light in empty rooms can be switched off.

Energy harvesting technology is particularly well suited for the conversion to self-powered wireless sensors in buildings, as the sensors can be freely positioned in the room and are maintenance-free. In addition, it is not necessary to lay wires through the walls. This is an important aspect, especially in listed buildings, where no conversions whatsoever are permitted.

Radio sensor solutions based on energy harvesting technology also increase safety and comfort in smart buildings. Moreover, savings in energy and operating costs of up to 40% can be achieved, for example with occupancy detectors that switch off the light when the room is empty, meaning this resource-saving battery-free technology not only hugely benefits the environment but the building owner too.

NFC for easy commissioning of sensors

Many buildings are part of a portfolio of properties and therefore, such a sensor system has to be implemented as easily as possible and adapt to specific requirements. This is especially important when there are thousands of sensors in a building that provide the data for individual and needs-based optimisation processes. The commissioning of self-powered sensor and switch modules via NFC offers a simple solution for this. With this type of wireless communication, data is transmitted from an NFC device to an NFC reader over a short range of a maximum of two centimetres. These can be NFC-enabled smartphones or tablets. EnOcean has developed its own app for this purpose called ‘EnOcean Tool’.

This makes it easy to configure and commission EnOcean NFC devices like the new STM 550 multisensor, which combines temperature, humidity, lighting, acceleration and magnetic contact sensors in the original PTM form factor, and the PTM switch module with NFC interface. Due to the short distance between the two devices, data transmission via NFC offers high data protection. Two communication modes are important for energy harvesting: the reader/writer mode, which reads data from NFC-capable objects, and the peer-to-peer mode for data exchange between two devices.

Installers and OEMs are the main beneficiaries of this type of data transmission, because NFC makes the configuration and commissioning of switches and sensors much less complex and therefore faster. This reduced time consumption means that installers work much more efficiently.

The following features make NFC particularly interesting for installers and OEMs:

• The modules do not need to be removed from their switch frames for commissioning and configuration.
• Storage costs are reduced because the devices can be configured directly on-site.
• With NFC, the complete commissioning of the device can be documented. Installers can therefore trace exactly which settings have been made in advance, thus saving time-consuming and expensive tests on the device.
• In IoT projects, OEMs can set all specific device links required for an individually planned system in advance by using NFC.

So with NFC, devices are not only configured and commissioned more quickly and more easily, but installers and OEMs also save valuable project time and, as a result, can cut costs at the same time.