Jody Muelaner explores how a building management system works and the range of equipment and systems with which it can work
Building operations and construction uses more energy than any other sector. Energy use within buildings accounts for about 28% of global CO2 emissions, mostly for heating, cooling, ventilation and lighting. It has been estimated that better control of energy use in buildings could save 6% of all energy use (www.is.gd/miceva). This energy use often represents a significant cost for businesses, as well as an opportunity to demonstrate environmental credentials.
Better management of building systems can dramatically reduce energy consumption. Computer controlled systems are the best way to do this, with the ability to control and monitor heating, cooling, ventilation and lighting, as well as less energy intensive functions, such as fire protection and security. These control systems are referred to as a building management system (BMS) or a building automation system (BAS).
Building management systems are already well-established for large new commercial buildings. However, even in these applications sub-optimal configuration can increase energy use by 20%. Use of BMS in smaller buildings and even homes is now increasing as the use of Internet of Things (IoT) devices is enabling much greater use of lower cost connected devices, a trend sometimes described as the forth industrial revolution (Industry 4.0). Within this trend, buildings fitted with a BMS are now being referred to as ‘smart buildings’.
As well as saving energy, a BMS can make a building safer, improve plant reliability and life, reduce maintenance costs and increase staff productivity. If poorly implemented, a BMS can have negative impacts by removing occupants’ ability to control their environment.
HVAC & LIGHTING
Heating, ventilation and air-conditioning (HVAC) is generally the most power-consuming aspect of building operations. A BMS allows individual rooms to be controlled depending on occupancy, but this may require more responsive heating and cooling. It also allows better use of passive heating and cooling through the opening and closing of windows and control of blinds and other shades.
It is relatively straightforward to control lighting for occupancy, since lights can be turned on and off instantly. Heating and cooling, however, often have considerable lag, which requires more careful consideration. This can be dealt with in two fundamental ways: firstly, by using more responsive heating and cooling systems; and secondly, through adaptive occupancy scheduling.
Radiant heating is able to respond far more quickly to changes in occupancy. This is because instead of heating the air within a building, it directly heats the occupants, in the same way as sunshine. Radiant heating means that room temperatures can be maintained at significantly lower temperatures while remaining comfortable. The same is true on a sunny day, when it often feels far warmer than the actual air temperature, as soon as the sun goes in the real temperature is felt. With radiant heating, the same system that controls lighting can also control heating, simply switching it on as people enter a space.
Infrared heating has long been popular in agriculture. Heating the air within agricultural buildings would be extremely expensive due to a lack of insulation and very high levels of natural ventilation. However, heat lamps can be easily fitted over pens holding livestock, such as chickens or lambs, providing a cost effective way to heat the animals.
Gas-fired infrared radiant heating systems provide the improved controllability and heating efficiency of radiant heating with the lower energy cost of natural gas. This makes them better suited to larger-scale heating applications.
Steve Sherman, MD of supplier Schwank UK, says: “Gas-fired infrared radiant heating systems, being decentralised, offer businesses a high degree of flexibility in how their heating installations can be configured. Intelligent temperature control technology can make a positive contribution to energy management in industrial and commercial buildings.”
After HVAC, lighting is typically the next largest user of energy. With modern designs for passive heating and cooling, lighting can even become the main energy requirement. Lighting controls can reduce unnecessary artificial lighting by using motion sensors and schedule in combination with daylight harvesting louvers.
While unconnected smart lighting is able to turn on and off as occupants move through a building, only a BMS is able to integrate this function with the use of daylight harvesting, heating and cooling.
To do this most effectively, the BMS must evaluate the current heating or cooling demand and availability of passive light and heat from the sun. Louvers or blinds will then be opened or closed to minimise the energy required for lighting and heating or cooling. Electrical lighting will then only be turned on if it remains necessary.
The easy access to information related to all of a building’s systems, which a BMS can provide, can help provide detection of faults and assist with the planning of maintenance activities. Maintenance staff can then be more effective, spending less time diagnosing faults and more time on preventative maintenance.
An example of the way that a BMS can reduce maintenance and make building systems more reliable is the monitoring of a sprinkler system. The BMS can provide information on the status of the main pump, jockey pumps, panel health and any fault signals.
The sensors and actuators within a BMS must communicate with its controller. Standard network protocols such as C-Bus or Profibus may be used although Internet protocols are becoming increasingly popular. BACnet is a communication protocol designed specifically for Building Automation and Control (BAC) networks, based on ASHRAE, ANSI, and ISO 16484-5 standards. The Building Controls Industry Association recommends the use of BACnet.
The risk that cyber-attacks can shut down systems does not only affect buildings fitted with control systems. The increasing trend for all areas of modern life to be dependent on internet connected devices makes us vulnerable to cyber-attacks.
QinetiQ has warned that the BMS is often the most vulnerable part of an organisation’s IT network, with installers often lacking in security knowledge. A BMS is effectively a type of industrial control system (ICS) and such systems have a long history of significant cyber-attacks, starting with the 1982 CIA attack on a Siberian gas pipeline which caused a large explosion.
An example of a direct attack on a BMS is the Tridium Niagara vulnerability which gave control of locks, lifts and CCTV cameras within many organisations using that BMS system. Indirect attacks are also possible, for example, in 2013 US retailer Target had its accounts hacked through vulnerabilities in the network-attached HVAC system, resulting in 40 million customers having their payment card details exposed.
There are also wider national security concerns beyond these isolated criminal attacks. In a conflict situation, coordinated state attacks could shut down large parts of critical infrastructure, for example, hospitals without lighting and offices with doors and lifts locked.
These significant threats are not a reason to abandon BMS, but rather should motivate planning for security during installation and maintenance of these systems.
BMS TO OTHER NON-ENERGY SYSTEMS
As well as the heating, cooling, ventilation and lighting functions discussed above, BMS may also control electric power controls; security, observation and access controls; fire protection systems; lifts and elevators; plumbing; and intercom systems.
Connecting these additional systems carries benefits beyond energy conservation. For example, fire systems are already connected with interlinked smoke alarms, door closers and sprinklers. If a BMS has control over ventilation, then linking this to the fire system can enable a building to slow the spread of fire, direct smoke away from escape routes and prevent people from being trapped. Specific measures might include closing windows and dampers in ventilation ducts, turning on fans to evacuate smoke and parking elevators on the ground floor to prevent their use during the fire.
Connecting building control systems can also enable sensors to be shared, reducing overall cost and complexity; for example, using motion detectors for security systems, as well as to control heating and lighting.
A properly implemented building management system can greatly reduce a building’s energy use and maintenance while also making it safer and more reliable. However, if poorly implemented, a BMS can make it difficult for occupants to control their environment and greatly increase the dangers of cyber-attack. Both new builds and retrofits should seek to utilise the benefits of BMS while fully considering occupiers needs and security best practices.
BOX OUT: Hallé St Peter’s adopts new systems
Siemens is helping the Hallé orchestra cut its costs by 35% through energy reduction. It has created an integrated digital solution to make Hallé St Peter’s, the historic recording and rehearsal venue in Manchester, energy efficient. The new £4.3m three-storey extension, known as The Oglesby Centre, includes sensors that monitor and automatically adjust temperature, air quality and lighting to achieve optimal room conditions. You can find out more in OE’s February 2020 issue, p8, also available at www.is.gd/mogehi.
By Jody Muelaner