Industrial automation improves building control efficiency

07 July 2009

An automation company is completely overhauling the building control systems in its own offices, and expects to make significant cost reductions through energy saving.
Building automation engineers are turning more and more often to industrial automation technologies instead of the traditional dedicated controllers.

Industrial automation improves building control efficiency

They are finding that improved data collection and interpretation means systems can be both optimised against set criteria such as energy saving and more easily adapted to changing needs and circumstances.
Equally is it possible to achieve both a monitoring and control strategy using the same infrastructure.

Automation giant Mitsubishi Electric has found itself involved in such projects increasingly often, and recently has been applying its expertise to its own offices in Hatfield, Hertfordshire.

"Our building is typical of many commercial premises in this country," explained Chris Evans, a senior manager in the Automation Division. "It was built in the 1980s, long before anyone worried too much about energy consumption or environmental impact. It is still looking smart, functional and modern, but we decided that at 25 years old a comprehensive review of the building management system was in order."

The project team developed a schedule for refurbishment, starting with upgrading the thermal insulation and swapping to low energy lighting. Solar and PV panels were deployed to supplement the demand from the mains supply, while ground source thermal balancing replaced many of the air conditioning cooler units. Additionally the existing building control system was replaced with an up-to-date system centred around Mitsubishi's own MX4 Energy software solution, MX4 SCADA and PLCs (programmable logic controllers).

The building was designed and built for Mitsubishi in the mid 1980s. The air conditioning was not Mitsubishi's manufacture but the main switchboard included Mitsubishi switchgear.

Evans again: "The general A/c controls were designed for open plan spaces and became difficult to balance once we installed offices into some of the larger open plan spaces. There was local control for the aircon (and lighting) in individual rooms, but at times this could be considerably sub-optimal."
"We knew that between the MX4 suite and our powerful Q-series PLCs, we could create a much more flexible and controllable system that would self-regulate itself to save energy and minimise running costs.
And because we would be using Mitsubishi Air Conditioning technology from our sister division integrated into our own controllers and switchgear, we knew everything would be as efficient, green and intelligent as possible."

The building was split into a series of zones each with its own control network. These were integrated over the company LAN (local Area Network) to give an efficient yet simple overall architecture.

"The first phase was to monitor the electricity usage in each of the building's sub circuits. To do this we fitted our energy meters, from our CLPA partner company ND Metering Solutions in Bradford, to the existing distribution panel in the switch room. A total of 25 meters were fitted and all networked via CC-Link back the control PLC."

A CC-Link 'open' control network was chosen because Mitsubishi has identified CC-Link as having great potential in building control systems. It offers many advantages, including the ability to add, remove or replace individual items of equipment without shutting down the whole system – very useful in facilities management applications. The ND meters have a CC-Link interface fitted as a standard option.
The idea behind phase one was to do an extended soak test of the building, identifying patterns of energy use and highlighting trends and hot spots.

"Building control systems, just like their industrial automation counterparts, can require an incredible amount of cabling," explained Evans. "CC-Link allows each control device to be daisy-chained on a single network or multiple networks for more complex architectures. CC link does not require the more complex set up or slave device files of other open networks, making it extremely easy to install and to add further devices if the system expands. The cost saving in installation time can be staggering, particularly on larger systems."

Six weeks into the soak test, trends were emerging- some of which were being addressed with a simple application of common sense. For instance it was realised that equipment in the kitchen was being left on over the weekend, and that bank holidays were not programmed into the existing controller's calendar.

"Such issues were 'low hanging fruit', we could easily address them and see an often-significant payback," said Evans. "Once we have analysed the results of the initial monitoring phase, we will be able to implement sensible control strategies to maximise efficiency and cost savings. The PLC system will take over control of the Mitsubishi air conditioning units utilising our proven integrated solution with the A/c controllers allowing us to control when and for how long the air conditioning system is operating. Allowing some local manual settings but implementing an overall "policing" system to automatically turn off the units when not required."

"A further addition would be to incorporate occupancy monitoring and lighting control in meeting rooms to further maximise efficiencies again allowing local control within set parameters, and automatically powering down after everybody leaves."

Evans explained that with a flexible control infrastructure in place, it is relatively easy to add further controls either in individual zones or across the whole building.

"Its a process of evolution really. We won't be implementing everything at the beginning, but we will add control elements over time. This very much mirrors what can happen in a typical building evolution, the difference with our solution, is that once the infrastructure has been put in place to monitor the energy usage, the flexibility of our solution means that a control strategy can be achieved without the need for major extra investment. Overall our expectation is that we will reduce energy consumption and running costs by 25-30%, and this is starting with a system that wasn't particularly inefficient in the first place."