Time to rationalise your Building Energy Management System

06Jan

Kevin Sheldrake reveals why a unified approach to control services such as HVAC and lighting will consequentially improve a buildings performance.

In the term ‘building energy management system’ the last word is frequently disregarded but a dictionary definition of the word ‘system’ is “a set of connected things that work together for a particular purpose.” This points to the importance of thinking about BEMS as a single network.

Thinking of the building and building services as an integration of building systems in a singular network can have significant impact on your long term energy management strategy. This more integrated approach to designing, installing and operating building services is something that the sector has been striving for over the past two decades.

It’s not uncommon to experience building services working inharmoniously with each other, for example; heating and cooling running concurrently and lights on at night when the building is unoccupied. The truth of the matter is that our buildings are frequently not run in a methodical manner. A poorly designed system can increase carbon emissions unnecessarily and be uneconomic to run.

Yet the market continues to develop innovative and energy saving control solutions which will provide greater visibility and performance tracking. This has made it easier for an occupant of any building to choose and implement an appropriate tried and tested BEMS strategy, helping reduce its carbon footprint, provide an improved working environment as well as one that will work into the future, easily reflecting changes and variations in the building usage.

Utilising this type of system can ensure that services such as HVAC and lighting are only used when required. Setting parameters ensures a steady temperature can be programmed into the BEMS to ensure the building stays within certain performance parameters. Ultimately, the building operates for and in response to the requirements of occupants.

As buildings and building services equipment become more advanced, the functions of today’s buildings are also becoming more complex. The demand for detailed information on building performance means that collecting and delivering that data is very important – and relies on the communications networks of the BEMS, which in turn rely on good quality wiring.

Communications networks are used extensively in building management systems at the automation and management levels. These are often known as the primary levels of a BEMS network. Devices further down the network, at the device level, such as sensors, and I/O modules including indicators and actuators, would traditionally require separate wiring runs to link them to primary level.

This means that if a project plan includes a high number of these devices spread over a wide area, then the wiring costs using the traditional approach could be high. This may result in a compromise to the design of the system, with field devices omitted because it is considered too costly to include them and so the BEMS cannot offer the functionality that the designer has in mind.

Hence why it is vital that building managers should consider smart wiring systems, more emphasis on this could make all the difference in terms of capital cost and long-term efficiency.

The very latest wiring technologies and techniques simply overcome this problem. For example, a 2-wire bus system (such as Dupline from Carlo Gavazzi) can link field devices together, without the requirement to connect each separate sensor or actuator back to the primary level of the building management system.

Essentially, this creates decentralised sensors and I/O modules, giving much greater flexibility on the distribution of devices without the costs of extra wiring. There are also sensors for CO2, temperature and humidity that can now be powered from the bus. This further reduces the need for wiring to power the devices. Also, a 2-wire bus cable can be run from sensor to sensor, collecting all the measured values. Each sensor does not have to be individually wired back to the main controller.

Forward-thinking manufacturers are leading the way on creating more potential for a single-system approach. For example, Carlo Gavazzi now offers a DALI Gateway from its Dupline wiring system, making it possible to integrate HVAC with lighting applications.

The current industry approach to contracting means that lighting is specified as ‘electrical’ and HVAC as ‘mechanical’. This creates a false message that the two have to be controlled separately – an expensive and unnecessary approach. By putting the ‘system’ firmly at the heart of building management, designers and installers will deliver all-round better buildings.