CPD Programme
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control is restricted to being simply ‘on’ and ‘off’ at the whim of the occupant. The use of a controlled lighting environment
has been shown to improve employee comfort and health by providing a safe and secure work environment[3]. Where occupants are allowed to affect control on their own personal working environment (through, for example, task-oriented lighting) their satisfaction with their working environment and productivity rises and it has been shown that the improved visual environment can reduce absenteeism[4]. Increases in productivity of just a few per cent could alone pay back the installation cost of intelligent light control systems.
Total energy savings By controlling the whole lighting installation, the annual energy use, as well as the maximum demand drawn from the electricity supply grid, is moderated – particularly where a lighting installation includes predominant daytime use and daylighting opportunities are exploited. Reduced lighting energy consumption can significantly diminish the carbon footprint of the building – each kWh of grid supplied electricity is likely to create about 0.5kg CO2. The local night-time environment can also directly benefit by reducing light pollution from unnecessary lighting. Figure 2[5], which is based on data gathered
by a system’s manufacturer, indicates that, with the adoption of ‘state of the art’ control for a ‘typical’ office building, lighting energy use may be reduced by 60% at the same time as reducing the building cooling costs by 20%. Maintenance costs can also reduce as lighting operation times are controlled.
Lighting control In 1959 a physicist named Joel Spira invented the world’s first solid-state light dimmer. In the succeeding half century this technology has evolved into integrated total light management control systems, where, for example, room occupation sensors, linked with daylight
Lighting energy savings Fine tuning lights Vacancy sensing Personal control
Daylight harvesting Total lighting savings
Heating and cooling energy savings Dimming
Controllable window shades Total heating and cooling savings
sensors and solar shading devices, are employed to automatically adjust the lighting levels according to the type of building use without any human intervention. By incorporating lighting level sensors together with algorithms that can determine the position of the active shading devices (blinds, louvres and bris soleil), these devices can be adjusted to reduce glare, heat gain and, as a result, trim cooling loads. The systems can provide enhanced user input (for example, using simplified control panels in rooms to enable single point lighting ‘mood’ control) and accessible monitoring so that, at a glance, occupiers can track changes in energy consumption. The marketplace for such systems is currently buoyant, with many systems being interoperable (able to communicate and operate with devices and systems from other suppliers), thereby creating a complicated array of intertwining solutions. The DALI (Digital Addressable Lighting
Interface) has been the technology that initially moved widespread adoption of automated lighting control forward. DALI is a digital communications system that was initially designed to provide lamp dimming and switching control. Each controlled lamp has a DALI dimmable ballast (transformer) with its own individual digital address allowing the lamp to be switched and controlled continuously from full output to a few percent of maximum. One of the reasons for the wide adoption
of DALI is its simplicity of connection; DALI ballasts are connected with two parallel wires (a ‘bus’) in a star or daisy-chain formation that provide the control signal and power to operate the ballast control. Operating at low voltage and within strictly specified limitations[6], the system is particularly robust and resistant to interference. Controller devices can now include a wide variety of inputs such as control panels, switches, light sensors, occupancy sensors and from virtual ‘control panels’ on
20% reduction 15% reduction 10% reduction 15% reduction
60% energy savings 60%
The headquarters of the New York Times in Manhattan, where the priority was to give natural light to occupants
personal computers, PDAs and smartphones. Each controller can send messages directly to a ballast device or to another controller, and ballasts can be addressed individually or as part of a group.
Integrating lighting control DALI was originally conceived as a standalone system to control lamp ballasts. However, with the improvement of building fabric and the rise in occupant expectations, lighting has become an increasingly significant part of building energy consumption. This has driven the need to incorporate lighting control into the overall building management system and has, in turn, generated a profusion of standards and protocols. Probably the most significant underlying standard is IEEE 1451 – Standard on Sensors and Actuators (implemented in 1997); this is a suite of guidelines each aimed at standardising a different aspect of communications for smart transducers (sensors and actuators) [7]. Both wired and wireless protocols build
Lighting energy savings 20%
10% reduction 10% reduction
20% energy savings Figure 2: Example of possible energy savings in an existing office building 64 CIBSE Journal November 2010 HVAC energy savings
upon and integrate wth IEEE 1451. Some protocols provide gateways or bridges with DALI systems (such as that shown in Figure 3); and some, such as IBECS (integrated building environmental communications system) use their own microcontroller on each sensor and device. IBECS has recently been expanded to allow control of standard DALI ballasts – further blurring the differentiation between systems. The advent of low-cost wireless systems is challenging the original ‘simplicity’ of the two wire DALI. Wireless technology is particularly pertinent in refurbishment projects where additional data cabling may
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Nic Lehoux/Gensler
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