Automating buildings provides comfort with energy and money savings - Voltimum

Climate change and growing shortages of resources are the major challenges of today. In addition, many countries around the world are dependent on imported energy.  Efficient and sustainable energy usage is therefore an urgent necessity. Much energy can be saved in buildings, as the following figures from a study1 illustrate. The average of all sources results in a saving potential in the order of:

• Room heating control: approx. 14 - 25 %
• Heating automation: approx. 7 - 17 %
• Shutter control: approx. 9 - 32 %
• Lighting control: approx. 25 - 58 %
• Ventilation control: approx. 20 - 45 %

This results in an average potential energy saving of around 11 to 31%.

Lighting is a very significant contributor to overall energy consumption (and CO2 emission). By combining presence detection and light control in accordance with external light levels, as much as 40% energy savings are possible compared with manual switching. Looking at heating and cooling, by controlling set points in individual rooms using presence detection, up to 25% energy savings can be made.

Clearly, if building automation helps achieve such savings, it must be considered, despite the initial outlay. The good news, of course, is that saving energy also saves money - often a great deal of it.

What is building automation?

A building automation system (BAS) is a computerised distributed control system that is an intelligent network of electronic devices. It is also a building management system (BMS) with added automation. It can control people's entry through doors with access readers (card readers, codes, CCTV, iris recognition systems etc), the fire and security systems (motion detectors, CO, smoke/ionisation detectors, alarms, call points, emergency lighting, CCTV cameras, recording facilities, control panels etc), the lighting (room occupancy sensors, shutter blind motors, control systems), HVAC (temperature/humidity sensors, central heating controls, drives, chillers etc), and mechanical systems (pump/air-conditioning motors, lifts, hoists etc), interfaces to service and building control systems, remote control and audio/video control.

All these functions can be controlled, monitored and signalled via a uniform system without the need for extra control centres, and all the hardware elements need to be connected by a secure and reliable Building Automation Network (BAN).

A home and building automation systems enables centralised adaption of the building automation system to users' needs (time schedule, set points etc), and centralised optimisation of the home and building automation system (tuning controllers, set points etc), in addition to standard control functions.

Until quite recently, most automated buildings tended to use fieldbus-based control systems, typically having a single twisted pair cable backbone. Once installed, more control functions can usually be added without any re-cabling. Control scenarios are easily changed or extended without disruptive refurbishment work. Almost any control combination is possible, the only real constraint being the cost of commissioning and programming.

Things are changing, though, and Ethernet is now being increasingly used, as are wireless protocols for exchanging data over short distances from fixed and mobile devices, connecting several devices and overcoming synchronisation problems.

A building controlled by a BAS is often referred to as an 'intelligent building'. Increasingly, the techniques can be applied to the domestic arena - the so-called 'smart home', though here the BAS can also control scene setting and mood lighting. Such systems can also be readily linked to home entertainment systems, either using one of the established audio/visual protocols (e.g. DMX512) or by using a multi-function infrared 'commander'.

In smart homes, the possibilities of your washing machine talking to your mobile are now very real - perhaps becoming part of an 'Internet of Things'. Such wireless technologies aim to revolutionise the personal connectivity market by providing freedom from wired connections and enabling links between portable computers, mobiles, portable hand-held devices, and Internet connectivity. Systems such as Bluetooth work because they have been developed as cross-industry solutions.

The technologies:

A range of techniques are used to carry out energy management and building control tasks. Some simple analogue systems, such as timer-controlled water heaters and thermostatic radiator valves, have been around for decades; others are far more complex. Typically, a central control unit runs the entire system, based on information supplied by sensors (such as pre-set instructions for some of the devices), and by controls from building operators. Commands can be sent through a two-wire fieldbus system, power lines, telephone lines or fibre-optic cables - or, increasingly, wirelessly. The fieldbus system acts as a backbone for the system automatic controller and devices.

Sensors send signals over a transmission medium to the devices (such as actuators), which might be used to turn on heating, or control an entire air-conditioning system. Sensors and actuators are programmed and linked as requirements dictate, so that building facilities managers can alter equipment settings according to their wishes via a keypad, telephone or PC.

Some developments have been based on distributed-intelligence microprocessors. Here, 'intelligent' peripheral units manage a variety of local tasks and functions, while the central unit acts as a supervisor.

Today, building automation networks typically comprise a primary bus and secondary bus. The primary bus connects higher level controllers to the network. Ethernet, WiFi and USB can be used as the primary bus. The secondary bus should be simple and easy to access, and it connects to low-level elements (sensors and actuators). Technologies include RS-232, RS-485, CAN, X10 and Zigbee (and the latter's IPv6 implementation, 6LoWPAN).

A decade or more ago, the European Installation Bus (EIB) and LonWorks were the leading open technologies, but others included, CEbus and SmartHouse from the USA. More recently, LonWorks is still a leading technology, while European Home Systems and BatiBUS merged with EIB to form the KNX protocol. Then there is BACnet.

LonWorks - The dominant 'backbone' for such systems is increasingly Ethernet-based. For example, Echelon's 'LonWorks' building automation system uses the Ethernet as its backbone. In such a system, the backbone remains a constant, while the application layers (such as a fan) vary. System transmission media are typically 24V bus cable, via infrared, the Ethernet and wireless technologies.

Included in each of the standards created around LonWorks are two physical-layer signalling technologies, twisted pair free topology and power line carrier. The two-wire layer operates at 78kbit/s using differential Manchester encoding, while the power line operates at 3.6 or 5.4kbit/s (frequency dependent). The LonWorks platform also uses the affiliated IP tunnelling standard ISO/IEC 14908-4 (ANSI/CEA-852). This is used by a number of manufacturers to connect devices to IP applications or remote network-management tools. Indeed, many platform-based LonWorks control applications have been implemented using IP integration - either in the controls infrastructure or at the UI/application level, using IP-routing products or web services.

Of the over 90 million Echelon enabled devices installed worldwide, over 40% percent are used in industrial control, but very large numbers of devices are found in BAS. Used in an industrial environment, a LonWorks system works differently from open device networks such as Profibus, Modbus and DeviceNet, as it is a fully peer-peer network. Instead of passing data through a master, devices can exchange data with any other LonWorks device on the network.

The core technology is LonTalk, which provides an implemented, maintained, debugged and proven protocol that implements full functionality of the seven-layer OSI protocol standard. The protocol for accessing a LonWorks Network is a version of CSMA better suited for control applications - Persistent CSMA with Collision Avoidance and optional Collision Detection. Network data exchanged on LonWorks is configured using a network configuration tool. This aligns an input of one device to an output of another in a way that is independent of operation or application software in either device.

LonWorks is a standard technology for many of the global standards organisations including ASHRAE, IEEE, ANSI, SEMI and many others. It is becoming a major commercial buildings network standard, with a number of building automation systems suppliers standardising on it. These include Siemens Building Systems. For example, Siemen's DESIGO RXC offers flexible control of individual room comfort in public buildings, office complexes, school and hotels. It can be used for existing as well as new plants to provide optimum energy efficiency. DESIGO RXC is easily integrated into building automation and control systems because it uses LonWorks, which allows numerous electrical and mechanical systems to be combined.

BACnet - Developed under the auspices of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the client-server based BACnet (building automation and control networks) is now an American national standard, a European standard, a national standard in more than 30 countries, and an ISO global standard.

BACnet can work upon several physical/datalink layers, including Ethernet, LonTalk and point-to-point RS-232 link. It can also work on top of IP, either via IP tunnel or BACnet/IP protocol. A BACnet network comprises one or more IP subnets, while local, remote and global broadcast management is specified within and between BACnet/IP and traditional BACnet networks, and is carried out by defining the capabilities of a BACnet Broadcast Management Device (BBMD). IP Multicast can also be used. BACnet/IP communication is implemented by defining a protocol layer (BACnet Virtual Link Layer or BVLL). This approach is easily extendible to other transport mechanisms, such as IPv6, ATM etc.

Defining an extensible mechanism for peer-to-peer management of BACnet messages means that encryption/decryption and compression/decompression can be performed without altering the existing standard. Routing between BACnet/IP and non-BACnet/IP networks is specified, including where IP and non-IP BACnet devices reside on the same LAN. Routing between multiple BACnet/IP networks is also possible.

Five network technology options are available, including Ethernet and ARCNET (which can use a variety of physical media, such as coaxial cable, twisted pair and fibreoptic). For devices having lower speed requirements, BACnet defines the MS/TP (master-slave/token-passing) network designed to run at speeds of 1Mbps or less over twisted pair wiring. BACnet also defines a dial-up PTP protocol for use over phone lines or hardwired EIA-232 connections. In addition, Echelon's LonTalk can also be used on various media. However, LonTalk cannot automatically communicate with BACnet systems as Echelon has its own generic control language that is also transported by LonTalk.

The BACnet library provides an application layer, network layer and MAC layer communications services for Win32, Linux, RTOS, or microcontroller. A number of companies provide hardware and/or software that can be used to implement a BACnet communication capability.

KNX - This has become a new global standard in building technology. One major member company, ABB, has branded its KNX-enabled products i-bus.

To see clearly the elements of the BMS, download using the link near the bottom of the page this ABB schematic, which shows the management, structure and topology of an intelligent building control system – in this case using KNX technology (.jpg image - 537 kB file size)

KNX, which is three previous standards combined - the European Home Systems Protocol (EHS), BatiBUS, and the European Installation Bus (EIB) - is a standardised (EN 50090, ISO/IEC 14543) OSI-based network communications protocol designed for intelligent buildings. KNX is based on the communication stack of EIB, but has been enlarged with the physical layers, configuration modes and application experiences of EHS and BatiBUS.

Take ABB's i-bus KNX, for example. On a room level, this intelligent building control supports users in optimising the energy consumption, and it also provides information to installation or building control engineering for setting parameter optimisation.

In a recent building case study, all room states are visualised at a central point via KNX. The lighting is now controlled using presence detection, external brightness and timer programs. The heating saves energy through individual room temperature control using a central timer and visualisation system. The blind control has been praised by occupants because it prevents unnecessary heating of rooms by using automatic shading. The use of i-bus KNX, combined with building shell modernisation, has improved the energy efficiency to just over 25kWh/m2 annually - a huge 84% lower than before. There is more on KNX elsewhere in this issue.

BMS can also incorporate special lighting control networks - an example is the important lighting-specific control protocol, Digital Addressable Lighting Interface (DALI), which is now a standard. DALI uses differential pair with fixed baud of 1200bps. Each DALI bus can address up to 64 devices, and when configured as a subsystem of the whole BMS, more devices can be added. DALI is based on Digital Signal Interface (DSI), which is also a lighting control interface. Other lighting interfaces include DMX and Philips' Dynalite.

Wireless advance:

A report by IMS Research2, entitled 'The EMEA and Americas Markets for Building Automation Controllers, Software and Sensors - 2011 Edition', found that buildings are increasingly being automated using wireless networks. The study showed that in 2011, wireless sensors accounted for just over 15% of the 21m building automation sensors shipped in the EMEA and the Americas markets combined. The study also forecast that the number of wireless sensors is likely to increase to over 25% of total building automation sensors in EMEA and the Americas by 2015.

Wireless solutions offer significant benefits over hard-wired systems, just as they do in manufacturing and process automation, but a different advantage is in retrofit installations, which, using conventional hard wiring techniques, can be highly invasive, damaging and expensive. This is especially so with older or historic buildings. Instead of drilling holes and running cables, contractors can install wireless sensors, which saves time and money and causes far less damage and disruption. With new builds having high ceilings, wireless building automation sensors can be installed more quickly than cables. However, wireless devices are generally more expensive than wired equivalents. Indeed, IMS Research predicts that the extra cost of wireless devices may reduce take-up, and the organisation predicts that wired sensors will take largest share of the market over the next five years.

For the future:

The building automation marketplace is not forecast to regain its pre-2008 crisis level until sometime this year3. The fastest growth is expected to be in healthcare and educational buildings, then commercial buildings, with office buildings last. However, new building construction has experienced relatively slow uptake, though this is now changing. Existing building retrofits, which represent around 70% to 75% of the market, are not growing as fast as they ought, mainly because smaller building owners are still often unaware of the potential benefits. Even so, legislation in countries around the world, as well as fast developing network and control technologies, will ensure that there will be major business opportunities in building automation.

1 Biberach University of Applied Sciences, Institute for Building and Energy Systems - 'Energy saving potential using modern electrical installations' 2008.
2 The IMS Research report looks at building automation controllers, software and sensors, and predicts growth.
3 Report - BCS/2010 by BCS Partners (www.bcspartners.net).

This article first appeared in the Industrial Ethernet Book 2012.