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Get on the energy bus

Jul 2011 Smart Homes | Comments Off on Get on the energy bus
Get on the energy bus

When installing a home automation system, contractors should consider using a basic bus system. End users can use the bus system to take simple targeted action to reduce their energy consumption in the future, argues Paul Collins:

Rising utility prices and legislation are all driving the energy efficiency agenda. With metering and sub metering now becoming commonplace in commercial buildings, thanks to Part L2, the next step is to take targeted action to reduce consumption. It’s simply not enough to measure consumption unless an organisation is going to take the next step.

Intelligent building systems can help users take that next step by introducing control where it is needed. Simply putting the backbone of such a system in place is not expensive and from here it is easy to add control both now and in the future.

KNX-compliant systems

Using a KNX bus system enables all aspects of a building to be controlled, monitored and signalled from a single uniform system without the need of extra control centres. These might include lighting, shutter control, security systems, heating, ventilation, air conditioning and alarms.

The system uses a single twisted pair cable called a bus line that links input devices such as sensors with outputs such as lighting or heating; these can communicate with each other using RF technology or through cabling. For a cabled system the devices simply tap off the bus line. It avoids the multi-core cabling of a conventional hardwired solution. Once the infrastructure is in place there is almost infinite flexibility for building control.

A KNX system is about more than just control, it is about using the technology to intervene and reduce energy consumption when it is not needed. For instance, heating and lighting should only be switched on when they are needed. Lighting can be controlled automatically in relation to both occupancy and the intensity of the daylight using intelligent sensors. Research has shown that this alone can cut lighting consumption by up to 70%.

Part L describes as reasonable provision for 90% of energy consumption of each fuel should be metered and assigned to end-use categories – but the guidelines stop there. However, the point of measuring the use of energy is so that areas using large amounts of energy can be recognised and targeted. A plan to cut the consumption can then be put into place.

This is where a KNX system can be effective because once the target areas have been acknowledged, it can be used as a solution to problem high-energy areas. A bus system is flexible so more or different control is easily added as and when metering indicates the need to do so, with minimum disruption to end-users.

A KNX system is also a truly open protocol system so there is no restriction on which KNX manufacturers’ products you use for a given solution.

An example – Staples

One example where a bus system has been used to reduce energy consumption is stationery retailer Staples in its 140 stores nationwide. For the retail area, a combination of a master switch and timers control the lighting. In the backroom and staff areas, PIR movement detectors control lighting and heating.

On entering the store the lighting is turned on by a secure key switch. This turns on half the lighting in the retail area for cleaning. Ten minutes before the store is due to open a timer switches on all the lights in the public areas.

At the end of the day, half the lights in the public areas are turned off ten minutes after closing and the last person leaving the building turns off all the lighting using the master key switch.

The system installed in the Staples stores can be extended in the future and more circuits and control devices are easily added, or existing control can be changed by re-programming the system. The results from metering could potentially motivate these changes. This is why it is worth investing in the backbone of an intelligent system.

Staples, for instance, could achieve further energy savings using the same system. Lighting could be dimmed or switched in response to daylight levels and occupancy; heating and air conditioning can also be controlled in response to different inputs, whether by timer, PIR sensors or a combination of both.

Changing or adapting the system involves limited hard wire change – a simple to install twisted pair bus cable runs around each store. This enables minimal disruption to the public and staff.

All the inputs, such as timers, PIR detectors and switches, plus the outputs such as contractors to switch the lighting circuits and heaters, simply tap onto the bus cable using connectors. Each input and output is then assigned an address using a programmer. Finally each input is programmed to switch certain output addresses.

Staples is an example of how a simple control system is easily retrofitted to an existing building to provide energy efficient solutions compared with manual switches and controls. The system in Staples can also be easily upgraded should the company want to adapt it in response to metering findings in the future to reduce energy consumption further.

Measure, and then act

There is no point in metering if action does not take place in response to the results that it finds. A KNX bus system offers a solution that means this can take place with little disruption. It enables a company to be green, and continually be aware that it’s saving energy optimally and reducing energy costs. It is therefore worth investing in the backbone of an intelligent building system now so that changes can be made in response to metering results in the future.