Energy Harvesting Wireless – the Clever Way to Smart Grid

ENERGY HARVESTING

Energy harvesting wireless – the clever way to smart grid

By Armin Anders, EnOcean

When measured data from many different points must be available to an intelligent controller, power cables or batteries can prove to be a drawback. Energy harvesting wireless technology can overcome the problem, connecting a large number of battery-less and maintenance-free sensors into existing WiFi or mobile networks. Figure 1. Structure of the smart home

A main task of smart grids is to integrate – are confronted with the challenge of increas- networks. Different wireless standards can be thousands of decentralized consumers and ingly complex electricity grids. The realization used for this purpose, for example GSM, Blue- suppliers into an intelligent, automated con- of such a sophisticated system requires au- tooth or WiFi. These standards support appli- trolled system. For this, the required intelligent tomation solutions which enable the grid to cations in which large volumes of data must load control does not take place in the utilities control itself and react quickly to changes in be transmitted quickly, for example in smart headquarters but rather in the individual supply and demand. Therefore, it is intended metering systems. However, the high data rate homes. This brings the need for smart home to network centralized and decentralized energy comes at the price of high energy demand at systems into play which contributes an addi- suppliers, including buildings producing elec- the remote node, which requires a continuous tional benefit: besides energy management, tricity by photovoltaic installations, to an in- supply of power either over cables or using smart homes offer the user added value through telligent system that provides energy only high-power batteries with large capacity. higher security and comfort. As a consequence, when needed, updating in real time. This re- the intelligent connected house is not only a quires continuous data flow and processing For smaller devices, such as sensors for detect- must for smart energy control. It also paves from all involved parties, which means from ing data, these technologies are only suitable the way for a better user acceptance of the millions of information points. up to a limit. This is particularly true when smart grid by offering additional benefits than measured data from many different points just more transparent energy costs. There are established technologies already, pri- must be available to an intelligent controller. marily in the field of automation, which can Here, power cables or batteries can prove to However, in reality most existing buildings be a driver for the smart grid. In a building au- be a drawback in complex applications. Bat- are not a smart home yet, and require retro- tomation system thousands of sensors measure teries last for only a limited time, depending fitting measures. To keep these measures to a data from many different points, recording upon the application, and must therefore be minimum, it calls for technologies, such as en- data on temperature, CO2, light or room occu- replaced regularly and disposed of properly. ergy harvesting wireless, which are as simple pancy to enable a central control to manage all In such a highly connected system, which a as possible to install, to operate and to extend technical building areas in an optimized way, smart grid requires, this can be costly and lead at any time. meeting individual requirements. It is not much to down times. of a stretch to go from building automation to The future aim of smart grid requires utilities an energy management system. Thus, the build- Energy harvesting wireless technology can to adapt their prices to the actual demand ing automation principle can be the basis for overcome these challenges, connecting a large through electricity rates varying with the time smart grid automation processes. A major chal- number of battery-less and maintenance-free of the demand. In this context, all those in- lenge is how to network an increasingly large sensors into existing WiFi or mobile networks. volved – utilities, metering device manufac- number of individual wireless nodes or sensors Energy harvesting wireless technology stems turers, billing services, installers and consumers that can communicate with long-range wireless from a simple observation – where sensor

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data resides, sufficient ambient energy exists on the international wireless standard ISO/IEC tems based on this open protocol are already to power sensors and radio communications. 14543-3-10 which is optimized for ultra-low available from a number of manufacturers, Harvestable energy sources include: motion, power and energy harvesting applications. The for example meters from Eltako and the control indoor light and temperature differentials. profiles allow for products from different man- system from BSC. The Eltako components These ever-present sources provide sufficient ufacturers to be able to communicate and work read and transmit the current electricity, water energy to transmit and receive radio signals amongst themselves. Via gateways, EnOcean and gas consumption, including accumulated between wireless switches, sensors, actuators wireless devices can be connected to different meter figures, by means of energy harvesting and controllers, sustaining vital communica- communication standards such as Ethernet/IP, wireless technology located at a variety of tions within an energy management system. KNX, BACnet or LON. points inside a building. In addition, the soft- Instead of batteries, miniaturized energy con- ware monitors and displays the current meter verters generate power for the wirelessly com- Especially for smart meter applications, the readings and compares them against default municating devices, keeping the maintenance members of the EnOcean Alliance have defined values. This makes all relevant data available effort to a minimum. a specific device communication protocol, the for systems processing it for intelligent energy Automated Meter Reading (AMR) profile for management on demand. Data security and For optimal indoor RF effectiveness, the radio battery-less wireless devices. Smart meter sys- data reliability play an important role for the protocol uses sub-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 material 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. This 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.

A major requirement of reliable and cost-effi- cient systems is interoperability between the products of different manufacturers – which is why a smart grid calls for standardized technologies. Interoperability of different end-products based on energy harvesting technology has been an important success factor for the technology establishment on the market. For this reason, the EnOcean Alliance, a consortium of companies working to further develop and promote self-powered wireless monitoring and control systems for sustainable buildings, have formalized standardized application profiles (EnOcean Equipment Profiles, EEP 2.5), based

Figure 2. The EnOcean Equipment Profiles (EEP) are integrated in the application layer.

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basis for a smart grid. For the automation of a residential building, individual components, gadgets, wall switches, sensors and relay re- ceivers are networked to form an intelligent energy harvesting wireless system which com- municates with a wide-range network such as WiFi or GSM. As a result, the building systems (lighting, heating and shading), security technology and other home devices can be con- trolled automatically as well as visualized and changed from a multimedia device. The net- working of individual components and a central control makes the home more comfortable and also more secure, while saving energy at the same time.

Wireless and battery-less technology signifi- cantly eases energy monitoring and control in Figure 3. Example of connecting battery-less devices to a room controller buildings with only little intervention into the existing systems. The wireless devices are highly smart grid. EnOcean radio already offers the an even higher requirement of data security, flexible to install so that individual components basics for a reliable two-way communication application-specific encryption mechanisms can be easily networked to form a deeply con- and uses secure frequency bands. For a higher can be integrated, too. nected system without complex cabling. In ad- level of data security, an encryption mechanism dition, dispensing with batteries eliminates can be used. The data packages are encrypted The roots of energy harvesting wireless tech- the burdensome need to maintain the device with an AES-Algorithm with 128-bit keys. Fur- nology in building automation bring another energy supply in a regular time period, which thermore, every telegram comes with its own benefit, especially for the user: it can be the in- can be up to each year. Because of these specific rolling code. A forever changing authentication terface between smart metering and a smart characteristics, energy harvesting wireless is code is generated, based on the rolling code home system, which offers security and com- ideally suited for the last communication level and the AES encrypted data package, and then fort. This provides the requested added value in smart grid applications, providing the user validated by the receiving system. The same for a better consumer acceptance of the smart additional benefits and value by combining proven mechanism also takes place whilst lock- grid. At the core of a smart home are the same the comfort and security of a smart home ing or unlocking a car with a wireless key. For communication technologies which build the system under intelligent energy control.

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