Lighting - Control systems come out of the shadows01 August 2005

In the early days of lighting, the first person into the office, building or workshop generally just switched the light on at a wall location, interrupting the power supply and causing a surge of demand for power throughout the plant. At the end of the working day, the opposite activity took place and made no allowance for the need for different levels of illumination at different workplaces, from start to finish.

Advances in lighting technology - including controls, switches and dimmers - now provide benefits to the business in making better use of energy, and saving money in the operation of plant and equipment. Lighting controls can be operated manually or automatically, using light and occupancy sensors, but they need to be easy to use, or transparent and unobtrusive in the workplace.

Systems must also be capable of relatively easy installation and configuration, with remote and local programming capability, to enable 'office moves', or scene setting, change of use within open-plan workspaces. The majority of applications of electronic and digital lighting control are energy saving and enable the user to claim savings under the government's Enhanced Capital Allowances (ECA) scheme.

Illuminating data

In the UK, according to the Carbon Trust, lighting consumes around 20% of all generated electrical energy. Lighting installations - in design and operation - will affect the way people work and go about their tasks and, of course, lighting is an essential element in providing a safe working environment. The design of 21st century lighting systems must maximise the use of available daylight, provide the required lighting levels, in combination with controllable internal lighting, and deliver efficient use of electrical energy.

Digitally-controlled dimming systems provide the most energy-efficient lighting for offices, buildings, workshops and factories, and can deliver savings on energy bills of as much as 70%. Today, the need for control of energy costs is greater than ever before, and digital and software systems are rapidly replacing the older analogue systems.
One of the external drivers for this has been the introduction of the Climate Change Levy back in 2001, and business in the UK can further reduce the costs of implementing energy-efficient lighting under the ECA scheme. Under this arrangement, two of the principal criteria are:

- Lighting is only switched on when needed - minimising energy consumption
- Taking advantage of daylight availability, lighting levels (output) is regulated to minimise energy consumption.

Capital allowances can be offset against the business's taxable profits and take the place of depreciation charged on commercial accounts. In 2001, the government introduced 100% first-year capital allowances for energy-saving investments to promote the take-up of energy-efficient technologies.

Energy-efficient lighting includes luminaires, lamps, high-frequency control gear for linear and compact fluorescent lamps, and lighting controls, as detailed in the ECA's Energy Technology List.

To qualify under the ECA scheme, control equipment also needs to comply with EN50081, EN50082, and the relevant sections of EN60669 or EN60730.
Lighting control systems have become ever more sophisticated in recent years and available from a range of manufacturers, although many, including Ex-Or, Thorn, Osram, Tridonic, Phillips and others, have gone much further and developed 'smart systems'. The latest ideas are centred on two-wire digital, rather than analogue control, with distributed intelligence in the luminaires and ballasts, and the settings controlled by software, rather than being hard-wired.

Development of the ballasts that provide soft, flicker-free starting uses the same sensitive electronic components as stereo systems, video or DVD players. Also, daylight-compensating devices, presence detectors suitable for fluorescent lighting with digitally addressable lighting interface systems (DALI), offer individual, group and remote control.

1-10VDC analogue systems are the traditional way of controlling fluorescent lighting, described by the EN60929 standard. They include a dimming circuit, but mains power to the ballast and luminaire is controlled by a separate switch, external to the ballast. However, analogue controls are hard-wired and the additional components needed add to the complexity, with voltage drops in the control circuits that can lead to unwanted differences in lighting levels at each luminaire.

DSI was introduced by Tridonic, a division of Thorn Lighting, DSI ballasts are a digital electronic control that move the power switch from the wall to the luminaire itself. The system utilises a 2-wire control in a BUS network to transmit signals from a control module to the luminaires, instructing them to turn on or off, brighten or dim, as necessary. In order to determine when and by how much to dim, input signals from presence - which may be PIR - and lighting level (photo cells) sensors provide the essential data. When to activate may also be linked to timing devices or access control systems, with information carried on the control networks, with protocols conforming to RS standards.

ACN is a control protocol, primarily developed for use in the USA, and usefully makes use of Ethernet bus architecture. With building and factory automation systems making wider use of industrial Ethernet, this, too, may well expand into the lighting control world, using know communication protocols.

DALI is probably the most far-reaching of all of the current lighting control systems available and is based on open standards. It offers similar functions as for DSI, but provides for communication with each luminaire, where every ballast/luminaire has a unique address. As an open architecture, the DALI system can be integrated into existing control bus systems using gateways, thus providing the opportunity to phase in improvements to existing infrastructure and protect the current investment, but allowing for future development in energy efficiency and cost savings.

Integration of bus and protocol systems, such as CAN (Controller Area Network), LonWorks and EIB (European Installation Bus), builds on the distributed intelligence of modern luminaires, with reduced complexity in system design.

How they work

The major key to unlocking efficiency benefits and direct cost savings has been the introduction of the controllable, programmable systems, outlined above.
Most available systems today, whether from Ex-Or, Osram, Phillips, Thorn and others, provide the modular elements necessary to manage 'intelligent luminaires', equipped with high-frequency ballasts. The systems all use digital technology, with light and presence detectors that are effectively plug and play. And while some require programming and addressing, all use the intelligence built into the luminaire and ballast circuits.

The detectors - whether occupancy or daylight compensating - are connected to the BUS control network that enables the system to transmit signals to the ballasts, covering both DSI and DALI, to enable dimming, and switching on or off of the light.
DALI was the world's first non-proprietary or open standard that allows any manufacturer's devices to interface and inter-operate with any dimming, control, or sensor. The control system itself uses twisted pair cabling - commonplace within the telecommunications and factory automation sectors - to communicate with its maximum of 64 ballasts. Each of these intelligent ballasts - and hence the luminaire - can be moved from one zone to another by sending simple commands to the control unit, using handheld or other programming devices.

This flexibility means different lighting can be delivered at the touch of a button for varying work patterns, office moves; even change of use of premises can be dealt with by simply reassigning luminaire groups. Importantly, lighting groups are not assigned at the design or installation stages, but set later using a hand-held or other controller. With DALI, the power and control networks are separate, although the standard does provide for the inclusion of the two-wire control pair in a five-core cable. And the control wires are mains voltage rated, eliminating the need for special cables.

Complexity is reduced in the design and installation, since all switching and dimming is provided through the control circuits, with no need for relays to switch on or off the luminaires. Another key benefit of the system is that changes to lighting arrangements or scenes can be synchronised. Even if luminaires are operating at different dimmer settings, since each is uniquely addressable, the control signals sent to change settings in any group will all be received at the same time. Equally, where lamps fail, the status of the lamp is reported back to the DALI controller, providing greater flexibility and capability in lighting maintenance regimes.

Each of the available systems allows multiple scenarios to be programmed in, and covers multiple lighting groups or zones.

Deployment

Under current building regulations, energy-efficient lighting must be used in all new and refurbished premises with a floor area above 100m2. Approved Document L provides design information covering:

- Effective use of daylight
- Choice of lamp type
- Association of control gear and power factor correction
- Luminaire efficiency
- Use of lighting controls.

Electronic controls are now found in almost every non-domestic application, from all types of office environments, including conference rooms, multi-function and recreational spaces, for scene setting to creating ambiance lighting. Among some of the more obvious installations are those within call centres, such as that provided by Ex-Or for Prudential Assurance at its 500-seat Abbey Gate centre in Reading, or at Heathrow's Terminal 5, from Osram. Fittingly, too, the Carbon Trust offices in London are equipped with an energy-efficient lighting control system (see box item, below).

Factories, workshops and warehouses all benefit from electronic controls and, coupled with the correct luminaire, will offer cost and energy savings. Managed facilities such as business parks, as a result of deploying these control systems, may only need to specify one basic luminaire, without specifying a particular lamp. From a maintenance perspective this offers clear benefits. Systems that deliver ballast or luminaire status information over the controlling bus network improve the responsiveness and efficacy of lighting management.

Climate change and global warming may be with us, but we have the technology to at least make better use of what we have, maximising the investment in energy-saving technologies and reducing operational costs in workplaces and public spaces across the UK.

SOE

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