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The art of control

Having the latest technology will not bring energy efficiency  gains unless it’s operated intelligently. Alan Aldridge reports

While HVAC equipment is becoming ever more sophisticated, operating costs can only be minimised by the use of effective controls. However, people want a well-regulated internal environment, and they also want to avoid paying more than necessary to achieve that goal.

With the advent of new materials and more advanced technologies, equipment is becoming more adaptable and sophisticated without the increases in size and price that might have been expected only a few years ago.

But achieving the right comfort conditions is about more than just the building services themselves, it is also about the controls applied to the equipment. This allows the right environmental conditions to be maintained while at the same time minimising energy waste. A good analogy is the low-energy light bulb.

No matter how much more efficient it is, there is still wastage if it is left on unnecessarily – controls are there to ensure the right amount of energy is consumed at the right times.

Using energy as efficiently as possible will also reduce carbon emissions, an important consideration today when organisations have to comply with the CRC Energy Efficiency Scheme and stakeholders want to see evidence that groups in both public and private sectors are attempting to ‘green’ their operations.

Fine control of comfort conditions requires effective control strategies. This will also offer the opportunity for reducing energy consumption. Given that building regulations require far greater savings to be achieved in the case of air-conditioned buildings than those with natural ventilation, delivering these savings through better control is a priority for manufacturers and installers.

With advances in the miniaturisation of electronics, much greater power can be packaged into a standard control box.

Electronics have also seen significant falls in component prices as more and more of them are manufactured in developing markets with lower costs, therefore it is possible to get much more power for the equivalent investment.

This has encouraged more intelligent controls with more processing power embedded locally, rather than at a central processing unit in the energy/building manager’s office.

Other evolving technologies include wireless signalling, with micro-servers being included in the individual control units, allowing outputs to be accessed remotely via a PC.

With hardwiring becoming a thing of the past  in some instances, installation costs for control systems are also falling along with the drop in equipment costs.

One example of the impact of newer approaches to controls has been the introduction of Variable Speed Drives (VSDs) on motors of all types, including air conditioning fans. By ensuring that motors run efficiently at a variety of part loads, the old problem of increasing loss of performance with decreasing load has been largely overcome.

When intelligent controls are integrated into more general Building Energy Management Systems (BEMS), optimisation of all the energy services can be better achieved.

Here, technologies such as automatic Monitoring & Targeting (aM&T) can make a big difference. This automatically collects and analyses metered data, freeing the energy manager from tedious repetitive manual procedures such as regular meter reading  and data input.

Building regulations require sub-metering in different building zones and with the advent of cheaper metering and powerful aM&T systems, these can work together to keep different areas of a building at the required comfort levels.

As part of an overall energy management strategy, energy consumption can be driven down across the working day (see figure). AM&T also offers other benefits – building regulations give an allowance against the Target Energy Rating (TER) for a building if aM&T is installed.

A perennial problem with energy-using equipment is the occasional failure of timeclocks to adjust to the change from GMT to BST and back. An extra hour’s heating/cooling during the day (with additional manual overrides at others) can cause significant energy waste.

Alan Aldridge is executive director of the Energy Services and Technology Association

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