Energy harvesting wireless — the secret to M2M’s success
The deeper the interconnection of these devices, the more flexibility is demanded of the technologies. That’s a major reason why energy harvesting wireless technology is increasingly being adopted within M2M devices, products and building automation systems.
Today, M2M is considered a future-oriented growth market with high expectations. The predictions range from over 300 million by 20171 to 50 billion devices connected to the Internet by 20202. Deploying the millions of distributed devices lead to a challenge: How should they be powered and how will they communicate? One solution is energy harvesting wireless technology. Wireless sensors and relay receivers enable simple deployment of intelligent nodes, however, wireless devices require power – historically this meant pulling a lot of wires or installing and replacing batteries. Devices powered by energy harvesters are maintenance-free and independent of batteries or other external energy sources, paving the way to a simpler installation of millions of devices connected to each other and the Internet.
Energy from the surroundings
Due to the energy harvesting principle the wireless modules gain their power from the surrounding environment and therefore work without batteries. In the process, an electrodynamic energy converter uses mechanical motion or a miniaturised solar module generating energy from light. Combining a thermoelectric converter with a DC/DC converter taps heat as an energy source. Even these small amounts of harvested energy are sufficient to transmit a wireless signal. The addition of a capacitor can ensure adequate power storage to bridge intervals when little or no energy can be harvested.
For optimal radio frequency (RF) effectiveness, the radio protocol, standardised as ISO/IEC 14543-3-10, uses sub 1 GHz frequency bands. This provides a safeguard against other wireless transmitters, whilst offering fast system response and elimination of data collisions. In addition, sub-GHZ radio waves have twice the range of 2.4 GHz signals for the same energy budget, and better penetration within buildings. As a reference point, duplicating the energy harvesting wireless system at 2.4 GHz system requires about four times more receiver nodes to cover the same area. That increases its cost compared to a sub-GHz solution, for example. RF reliability is assured because wireless signals are just 0.7 milliseconds in duration and are transmitted multiple times for redundancy. The range of energy harvesting wireless sensors is about 300 meters in an open field and up to 30 meters inside buildings.
Building automation as a model for M2M
Energy harvesting devices are particularly attractive as replacements for batteries in low-power electronic systems such as wireless sensor networks, because of the logistics involved in the time-consuming tasks of acquiring, installing, and changing the batteries. Today, energy harvesting wireless technology is very well established providing M2M solutions in the building automation sector, bridging the control of light, HVAC and other fields of building technology to smart home, smart metering and energy management systems.
Wireless and batteryless technology significantly eases energy monitoring and control in buildings with only little intervention into the existing systems. The wireless devices are highly flexible to install so that individual components, wall switches, sensors and relay receivers can be easily networked to form an intelligent system without complex cabling. In addition, dispensing with batteries eliminates the burdensome need to maintain the devices’ energy supply in a regular time period, which can be up to each year.
An example for such a flexible automation system is HVAC control. Here, a thermostat, VAV (Variable Air Volume) or fan coil controller receives information related to occupancy, temperature, humidity, window position or CO2 from the respective batteryless sensors and controls the opening and closing of valve actuators for radiators, or dampers for VAV systems. At the same time, the controller sends status information to a central building automation system, and receives control messages from the BAS system. This enables the building to be monitored from a central location, that can be remote from the building itself, and to implement building wide settings, such as holiday shutdown, for example.
Self-powered intelligence for heating
Enormous progress is also being made on the product side, leveraging advancements in energy harvesting: revolutionary self-powered radiator valves, from Kieback&Peter for instance, generate energy from the difference in temperature between the hot water and the surrounding air. This energy powers both the communication with a controller or BAS system, and to turn the valve itself. Without cables or batteries, these wireless devices are especially easy to install, and they require no maintenance.
In further optimised systems, central equipment such as boilers or air handling units are integrated into the wireless communication system enabling scalable HVAC generation on demand, visible and controllable over the Internet on a PC, tablet or smart phone.
Secure monitoring instead of battery failure
Alarm systems, such as water detectors for example, are a second field, which batteryless wireless technology is opening up, due to its specific features. Here, the reliability requirements are a lot more stringent than those required for lighting controls. A system failure not only means a malfunction but can cause much more serious consequences for other systems that depend upon the equipment being monitored. It’s a fact that more malfunctions are caused by battery failures than by the electronics, especially in large systems. Energy harvesting overcomes this issue.
From everywhere into the Cloud
Via gateways, the standard-based energy harvesting technology can also communicate with Ethernet, WiFi, GSM/UMTS/CDMA and other networks for integration in cloud services. Here, all data collected by batteryless wireless sensors is encrypted and transmitted to a cloud service over the Internet. The data packages are encrypted with an AES-Algorithm with 128 bit-keys. Furthermore, every telegram comes with its own rolling code. A forever changing authentication code is generated, based on the rolling code and the AES encrypted data package, and then validated by the receiving system. The same proven mechanism also takes place by locking or unlocking a car with a wireless key. For even higher requirement of data security, application-specific encryption mechanisms can be integrated, too.
The gateways connected to a control and visualisation software by TCP/IP can be used to control all relay receivers and sensors bidirectional offering energy management as-a-service. Therefore facility managers, building owners and businesses can monitor important inventory, equipment, assets and energy related information from anywhere at any time, via the cloud. Critical building related data is automatically pushed to the cloud, freeing owners and managers from the often-challenging coordination and expense of hosting onsite servers.
One of the major advantages of such a cloud-based solution is that the management system arrives completely pre-commissioned from the manufacturer and ongoing device commissioning is expertly done on behalf of the client and pushed out from the cloud. The users are granted unlimited access to their remote, dedicated virtual server with their own IP address, accessible from a desktop or smart phone.
Future power of energy harvesting
Today the need for wireless applications with ultra-low power consumption and the advancements in establishing communication standards offer M2M providers new opportunities to innovate and evolve their products and devices. Already the acceptance of international standards is accelerating the development and implementation of energy-optimised wireless sensors and wireless sensor networks associated with M2M environments. In addition to the already established markets for home and building technology, there seems to be a natural progression in its use in smart homes, smart metering and the smart grid as well as solutions for industry, logistics and transportation.
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