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Renewing energy efficiency of existing facilities

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Automation systems can help to significantly improve the carbon footprint of buildings. Retrofit projects in particular call for innovative, wireless technologies that can be easily installed and operated at relatively low cost. Graham Martin, chairman of the EnOcean Alliance, explains

Buildings account for about 40% of primary energy consumed. Whereas newly constructed facilities typically incorporate energy-efficient buildings and equipment, existing buildings, however, are often less efficient and face greater retrofit challenges. 

Sensor-based data collection
The intelligent control of energy requires sensors to collect the relevant data from several points of measurement with receivers to process the information. A larger system can comprise hundreds to thousands of these sensing devices requiring power and communication.

This is an obvious example where wireless sensors and switches are the most cost effective solution: particularly in retrofits, in situations where project timing is critical, where there is an abundance of glass fenestration (making wiring difficult) and where it is desirable to have device maintenance kept to a minimum.

There are already established technologies, primarily in the field of building automation, which can be a driver for intelligent energy management. In a building automation system, for example, thousands of sensors measure data from many different points, recording data on temperature, CO2, light or room occupancy to enable a central controller to optimise the building environment and meet individual requirements. It is not too difficult to go from building automation to an energy management system. Therefore, building automation principles can be the basis for energy automation processes.

A major challenge is how to network an increasingly large number of individual wireless nodes or sensors that can communicate with long-range wireless networks. Different wireless standards can be used for this purpose, for example GSM, Bluetooth or IP. These standards support applications where large volumes of data must be transmitted quickly, for example in smart metering systems. However, high data rate comes at the price of high energy demand at the remote node, requiring a continuous supply of power either over cables or via large capacity batteries.

Drawback of cables and batteries
For smaller devices, such as sensors for data collection, these technologies are suitable up to a point. This is particularly true when measured data from many different points must be available to an intelligent controller, whereas power cables or batteries can prove to be a drawback in complex applications. Batteries last for only a limited period of time, depending upon the application and must be replaced regularly and disposed of properly. In connected energy control systems this can be costly and lead to system failures.

Energy harvesting wireless technology can overcome these problems, connecting a large number of batteryless and maintenance-free sensors into existing Wi-Fi or mobile networks that process data for intelligent energy control.

Flexibility with energy harvesting
Energy harvesting wireless technology stems from a simple observation – where sensor data resides, sufficient ambient energy exists to power sensors and radio communications. Harvestable energy sources include motion, indoor light and temperature differentials. These ever-present sources provide sufficient energy to transmit and receive radio signals between wireless switches, sensors, actuators and controllers, sustaining vital communications within an energy management system. Instead of batteries, miniaturised energy converters generate power for the wireless communication of devices, keeping the maintenance effort to a minimum enabling a highly flexible installation.

For optimal indoor RF effectiveness, the EnOcean radio protocol uses the 868 MHz frequency band in Europe which offers fast system response and elimination of data collisions. RF reliability is assured because wireless signals are less than one millisecond in duration and are transmitted multiple times for redundancy. The range of energy harvesting wireless sensors can be about 300 metres in open air and up to 30 metres inside buildings. The EnOcean Alliance, a non-profit technical organisation with more than 350 members worldwide, defines standardised application profiles for batteryless wireless devices. This ensures that solutions from different vendors can be wirelessly connected in a system, enabling system planners, integrators or facility owners to find the right pieces of equipment for their individual requirements.   

Energy saving effects
Energy management, by definition, is the process of monitoring, controlling and conserving energy in a facility. Energy management systems that utilise energy harvesting wireless building automation and control technology are ideal for retrofitting existing spaces and with no batteries, there is virtually no maintenance. Such a solution controlling HVAC and lighting can be expected to save between 20 to 40 percent on energy.
For example, if a sensor detects that a room or area is no longer occupied, lights can be automatically switched off and the HVAC systems automatically controlled, saving an average of 30 percent energy compared to a non-automated system. Alternatively, if enough natural sunlight is entering a room then lights can be automatically programmed to dim or switch off completely.

Integrated system approach
Based on batteryless technology, an intelligent system can be realised by interconnecting automated thermostats, window contacts, humidity sensors, occupancy sensors or CO2 sensors. These are just a few examples of the products in place, to regulate climate control automatically. In an intelligent automation system, for example, a room controller receives information related to temperature, humidity, window position or CO2 from the respective sensors and controls the heating or cooling accordingly. At the same time, the room controller sends information to an energy controller. This automation calculates the demand as a function of outdoor temperature and flow temperature to control energy generation.

The more complex a cooling or heating installation is, the more information it takes to control it. This is where the self-powered technology demonstrates its advantages. Single room controllers with energy harvesting wireless technology and the integration of self-powered wireless sensors to capture values can significantly reduce and optimise the energy needs of a modern HVAC system. Additionally, information can be transmitted wirelessly to a HVAC regulator or programmer, without batteries and with no need for maintenance or servicing. 

Information from everywhere
Wireless and batteryless technology facilitates energy monitoring and control with little impact into the existing infrastructure. The wireless devices are highly flexible to install so that individual components can be easily networked to form a deeply connected system without complex cabling, especially in retrofit projects. Due to these characteristics, standardised batteryless technology is ideally suited for the last communication level in energy management applications, providing the needed data from each measurement point optimising control and enabling a comfortable user experience together with a fast ROI between two and seven years at the same time.

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