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Self powered technology cuts energy costs

Self powered technology cuts energy costs
Tougher environmental standards and soaring energy costs demand optimised concepts for the way we use our energy. Andreas Schneider of EnOcean looks at how self-powered wireless technology can play a key role in reducing operational and maintenance costs.

Over ten years ago Energy Harvesting was known only to a small group of research engineers. But if you google it today you will find nearly two million hits. The idea behind solutions from the likes of EnOcean is to harvest the necessary power from its surroundings - from linear motion, light or differences in temperature, for example. The amount of energy obtained in this way is enough to send a wireless signal, and turn on a light for instance. EnOcean technology has been adapted for use in building automation and industrial installations. 

The technology is characterised by efficient energy converters, ultra-low-power electronic circuitry and a reliable wireless protocol. The wireless signal is transmitted in the 868MHz or 315MHz frequency band, meaning it fits into a broad range of products worldwide. The telegrams are just one millisecond long, which is approximately one hundred times shorter than the signal of a conventional wireless switch.

Installation and parallel operation of hundreds of wireless switches and sensors in restricted spaces is straightforward. To exclude transmission errors, a telegram is randomly repeated twice in the space of about 30 milliseconds to significantly reduce the probability of collision. The range is 300 meters in the open and up to 30 meters inside buildings. Each EnOcean module comes with a unique 32-bit identification number to exclude any possibility of overlap with other wireless switches. 

Based on the broad experience, EnOcean developed its new Dolphin wireless sensor platform for bidirectional communication. Major components of Dolphin system architecture are the STM 300, TCM 300 and TCM 320 wireless modules.

STM 300 features an energy harvesting interface for the implementation of self-powered products. The average total power consumption of the bidirectional sensor module is so small that, depending on the configured operating cycle, it can be powered fully autonomously round the clock by a tiny indoor solar cell and a buffer capacitor. 

Extreme temperatures
The combined sensor/actuator module is also attractive for the possibility of working in temperature extremes ranging from -25 through +85degC. System integration is again on 34 SMD pads, in this case with 16 I/O ports. The ready installed firmware enables cyclic reading of external sensors and unidirectional transmission of measured figures. Three analogue and four digital inputs are sampled. The user can also configure the wake-up and send cycles individually. 

The TCM 320 module can be used as a networked actuator and/or repeater. On its 16-pin connector it will allow very fast and simple integration into other devices and solutions. The module features 11 I/O ports that are individually programmable using application software from EnOcean. The firmware that comes ready installed enables bidirectional serial communication, single-channel or four-channel relay operation, single-channel dimmer operation and a single- or dual-stage repeater functionality for wirelessly spanning larger distances. The TCM 300 module comes with the same firmware functionality, plus it can be used as a gateway for complex automation systems. Measuring just 19x22x3mm, this Dolphin module is substantially more compact. For system integration the four edges of the module feature a total of 34 SMD pads, 14 of them serving as I/O ports. The TCM 300 can be 'pick and place' soldered like a large SMD chip. 

The nucleus of the new modules is the large-scale-integrated Dolphin chip. This features an energy harvesting interface and a complete RF transceiver for the wireless communication developed by EnOcean with its extremely short data telegrams. The ASIC, designed for ultra-low power consumption, also integrates a microcontroller plus various user-configurable I/O ports to detect analogue or digital measured values or status information and as switching or control outputs. 

The spectrum of solutions that can be realised with Dolphin modules includes bidirectional wireless system components incorporating a LAN gateway, a USB interface or another interface to various types of proprietary building automation bus system. 

For example, the STM 300 Dolphin module can be used to create a small and ultra-slim room control unit that is simply stuck to the wall. An operating unit with integrated environment sensors transmits momentary temperature, humidity, brightness and air quality readings wirelessly. In addition, it can receive status information from a central building automation system, such as operating mode, current ventilation level, air-conditioning operating mode and new target values for the environment sensors. 

The room operating unit also has a liquid-crystal display that shows readings as well as various status information. Low-power EnOcean technology enables a room operating unit of this kind to work without any batteries - just a miniature solar cell. With the energy harvesting principle, extremely user-friendly devices can continue to operate without any need for maintenance.

The self-powered wireless technology has been deployed in over 100.000 buildings worldwide. One example is the NH Hotel Group, third largest hotel group in Europe. The Madrid-based Hotel Group cuts its energy consumption and CO2 emissions by implementing EnOcean-based solutions in more than 5,000 rooms. A keycard switch forms the basis of the self-powered system, acting as door key and master key for automatic activation/deactivation of lights, heating and climate control. 

The act of inserting the keycard into the wireless reader device - which can be placed anywhere in the room - generates sufficient energy for sending a wireless command, for example to turn on the lights. The guest rooms were retrofitted during the normal hotel operation, at zero inconvenience to guests or hotel staff. On average 30 rooms per day were retrofitted with the system. The Hotel Group foresees a return on investment in well under two years.
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