Automated buildings bring great benefits to occupants and owners alike, such as improved energy efficiency and comfort. However, the control systems must maintain high levels of reliability to maximise the quality and effectiveness of those benefits, such as saving energy and other running costs.
Where control problems do occur, the occupants, used to the high levels of service offered by such buildings, can become quickly frustrated at any reduction of services. But now maximum reliability can be achieved using affordable redundant systems technology pioneered in the world’s most demanding industries and reconfigured for facilities management.
Intelligent buildings enable facilities managers to manage resources more effectively, improve building security, reduce energy consumption and control costs. At their heart is a control network that integrates virtually every system in the building to a central control panel, from which they are managed either manually or automatically. They can, of course, be overridden in the event of an emergency such as a fire, security breach or energy overload. Many systems also track these conditions and include automated response mechanisms to intervene where necessary.
There are many case studies available that show how an automated building is cheaper to run than a manually controlled one; how they are safer, more energy efficient, adaptable and flexible. However they all assume that the automation system does not break down throwing the building into expensive disarray!
To be fair, it is virtually impossible to work out the costs of a breakdown, as they would depend on what parts of the system failed, what the consequences were, if there were contingency plans in place, and the time taken to fix the problem. So perhaps it is sufficient to note that a building automation system going down is at least very inconvenient and at the other end of the scale, could compromise security and safety systems leading to significant unexpected costs.
Mitsubishi Electric is one of the largest automation and control companies in the world, with a history of innovation in the development of today’s highly reliable technical integrated solutions. Its experience ranges from the smallest and simplest installations to the most demanding where systems interruption cannot even be tolerated.
In the latter category, which would include nuclear reactors, oil rigs and fuel depots, a technique known as redundancy has been used to reduce the possibility of failure to infinitesimal levels. In simple terms this means installing two (or more) control systems in parallel configuration: one is used to run the plant, the other is kept in reserve, fully tracking the activity of the primary system in a ‘hot standby’ mode of operation. If the primary system fails in any part, the standby instantly switches in to maintain the services without any loss of performance. The chances of both systems failing at the same point and at the same time are virtually nil.
Historically one of the main problems with dual redundancy has been cost. In traditional redundant technologies, there can be twice as much control equipment to buy, twice as much to install, commission and maintain, requiring twice as much space and twice as many man-hours. Plus there has been a significant cost to interfacing the two systems. All this means redundant systems have had to be justified on a cost/risk basis and have only been suitable where huge costs, damage or other significant dangers could occur as a result of a control systems failure.
But control systems are based on electronics, and like their consumer counterparts, production costs tend to fall as the switching capacity of the silicon chips increases. (One rule of thumb says that capacity doubles every 18 months.) This also leads to a steady reduction in equipment size and greater integration of functions onto a single chip, which reduces commissioning complexity considerably.
So over a period of time more and more industries have found that redundant control systems become much more commercially viable, and they can afford to install such systems giving a huge boost to system reliability. Thus in recent years dual redundancy has spread from critical care suites to entire hospitals, from air traffic control centres to their road traffic monitoring equivalents, from international banking systems to high street branches and from tidal flood control facilities to sewage outfalls.
A new controller
The newly launched QnPRH controller from Mitsubishi has reached a price point which opens up redundant options to virtually all building automation projects. The basic controller is based on a programmable logic controller, the workhorse of the manufacturing industry, but it has the sort of programming capacity that previously was only available from specialised and expensive BMS systems. Also, due to the scalability and adaptable technology of the product, key areas of the control process can now be targeted for redundant operation offering real cost reductions whilst significantly enhancing reliability.
With QnPRH, instead of one big central computer a building automation system can now be based around a network of smaller controllers spread around the facility, each controlling either a local area, a specific function or possibly a separate but related building. A typical system could have each area set up in redundant configuration with a hot standby unit fully communicating other controllers in the building. Often there is also a small supervisory controller overseeing the whole system to provide a long stop security and to give the human operators a main control point.
Complementing QnPRH, Mitsubishi has a suite of software programmes designed to provide specific functions. For instance MX4 Energy is an energy monitoring and optimising program that can provide complete analysis and management of energy use in even the most complex of buildings.
In conclusion, with Mitsubishi Qn, the development of control technology has just crossed a Rubicon that will change building automation for ever. Suddenly hardware, installation and maintenance costs are being slashed at the same time that technical capabilities and reliability are soaring to new levels. We certainly have a lot to look forward to.