Building blocks

The twin imperatives of saving costs and meeting environmental targets are forcing companies to run the rule over every aspect of their operations in the quest for energy efficiency. Increasingly, this includes their most fundamental corporate asset of all — the roof over their heads.

Automation technologies more commonly associated with industrial sectors are finding favour with the building services industry as it looks to offer customers control and management systems able to deliver the levels of sophistication demanded.

One of the biggest names in industrial automation, Mitsubishi Electric, confirmed that building automation has risen up its agenda. Adhering to the time-honoured principle that it is best to get your own house in order before advising others on how to sort out theirs, Mitsubishi turned its attention to its headquarters in Hatfield, Hertfordshire, in a bid to show what could be achieved by installing the latest control and management technologies.

The Hatfield building is, according to Mitsubishi, a classic example of the type of commercial premises that companies are now looking to overhaul. Built in the 1980s, when energy efficiency was a relatively low priority and carbon impact was off the radar altogether, it still looked the part but was ripe for refurbishment below the surface.

As well as applying fundamental energy-efficiency measures — better thermal insulation and the installation of low-energy lighting and solar panels — the project team took a hard look at the building's control system.

This was replaced with an up-to-date system based around Mitsubishi's own MX4 energy software solution, MX4 Scada and PLCs.

The existing air conditioning was not made by Mitsubishi, although some of the company's own switchgear was present in the main switchboard and would be replaced by air-conditioning units made by another division of the company.

Chris Evans, a senior member of the automation team working on the project, said that the limitations of the previous arrangement were clear. 'The general controls were designed for open-plan spaces and became difficult to balance once we installed offices into some of the larger open-plan spaces,' he explained. 'There was local control for the air-con and lighting in individual rooms, but, at times, this could be considerably sub-optimal.'

Evans and his colleagues divided the Hatfield building into zones, each with its own control network and integrated via Mitsubishi's corporate local-area network (LAN). Their first step was to monitor electricity consumption in each sub-circuit, to which end the team installed 25 energy meters from ND Metering Solutions and networked them via CC-Link to the control PLC.

The use of CC-Link open control network technology was central to Mitsubishi's plans for its improved Hatfield premises, according to the company. CC-Link's virtues, when applied to building control, include the ability to add or replace items of equipment without shutting down the entire system.

Evans explained that building control systems, as with their industrial counterparts, can require a huge amount of cabling. 'CC-Link allows each control device to be daisy-chained on a single network or multiple networks for more complex architectures,' he said. 'It doesn't require the more complex setup or slave device files of other open networks, making it extremely easy to install and to add further devices if the system expands.'

About six weeks into the monitoring process, the team had enough useful data to begin making some decisions, often involving reasonably simple steps that delivered quick returns. For example, it emerged that bank holidays were not programmed into the existing control system's calendar.

Armed with the results of the 'soak test' (as the initial monitoring phase is known), the team will implement control strategies that take full advantage of the technology now in place. The PLC will take over control of the Mitsubishi air-con units, allowing building managers to use the system to decide when and for how long the system is running.

Evans explained that the Hatfield project demonstrates the potential of a flexible control infrastructure applied to a building. Once in place, it can be added to easily and deliver significant benefits without the need for substantial extra investment, he said.

The bottom line is how significant those benefits will be. 'Our expectation is that we will reduce energy consumption and running costs by 25 to 30 per cent — and that is starting with a system that wasn't particularly inefficient in the first place,' said Evans.