|
*
In the drive for sustainability in non-domestic buildings, simple lighting control can offer the biggest carbon savings argues Steve York product manager for Hager’s Klik brand. Here he puts the case for occupancy sensors that also manage lighting in response to natural daylight.
In his recent budget statement the chancellor announced that all new public sector buildings will have to be zero carbon by 2018. Lighting can account for 50% of a building’s total electricity consumption and represents a massive slice of its carbon footprint. With the public sector leading the way in the low/zero carbon drive, it is an area that cannot be ignored.
Under-controlled lighting is wasteful. Consider an office or school. Typically there will be a sharp rise in electricity use in the mornings, generally before many people arrive. Then there will be no decrease in the middle of the day although staff and/or pupils may be at lunch and natural daylight is at its highest level. Finally usage will continue to be high late into the evening even though there is only minimal staffing.
Simply controlling the lighting in response to occupancy or absence detection plus natural daylight levels can cut such consumption by half. Depending on the building this could cut electricity use by a quarter.
So it is time to take lighting control beyond a simple light switch or dimmer on the wall. In the past some building management systems have been over complicated. While the functionality was present it was often not used because the end user did not understand how it worked. In addition its very complexity could lead to glitches or system problems.
Yet lighting control does not need to be complicated. Modern sensors can combine occupancy or absence detection with daylight linking. All the intelligence is in the device and an electrician is more than capable of installing and commissioning them. Best of all there is no need for end users to understand how it works in order to make substantial savings.
Present or absent?
Lets begin with occupancy levels. Lighting unused space is one of the biggest areas of waste in our drive for energy conservation.
Mention occupancy sensing to many people and you will hear a groan, many associate it with the lights turning off unexpectedly and then having to wave frantically at the sensor to turn them back on. Well the technology has improved. With our Klik OS sensors for example, there is a detection diameter of 6 metres and its sensitivity by passive infrared will pick up even the smallest movements.
For simple switchstart or analogue lighting, presence detection means that the sensor will detect and switch the lights on when someone enters the area. Then after a time delay it will switch them off when they leave.
Even greater savings can be realised by opting for a system that has absence detection only. Again this will detect movement when someone enters the area but will not switch the lights on. If the person wants the lights on then they need to use a separate manual wall switch. Again the system will detect when there is no movement and, after a delay, will switch the lights off.
Absence detection is often preferred since a conscious decision has to be made to turn the lights on, but it will effectively remember to turn them off for you.
Occupancy sensors for digital lighting control systems operate in the same way but instead of turning the lights on and off they dim them up or down after a time delay before switching them off after a further time out period. This has the advantage of prolonging lamp life.
Daylight harvesting
We can also make savings by making more use of natural light.
Modern construction realise's that there is a huge source of light that occurs naturally -the sun. Making the maximum use of daylight in the building is often part of the brief. Yet even in these situations lights are often turned on by habit, even though natural light levels are more than sufficient. By managing overall light levels in response to natural light, you keep both your staff and your accountant happy.
Importantly you will also be managing your carbon footprint effectively.
Often occupancy sensors also have a photocell and can also manage light levels.
Taking our own Klik occupancy sensor for illustration, this can operate in one of three modes; as just an occupancy sensor or it can manage the light levels in either passive or active mode.
In the passive light management mode, the sensor will stop the lights switching on if the lux levels are above a set point, but then will not switch them off during occupancy. Active management has the same functionality but will also switch off the lights if the photocell detects that there is enough natural light to achieve the desired light levels.
Again digital lighting solutions offer even greater control, functionality and cost savings. Here the combined occupancy sensor and light cell will dim the lighting up and down to maintain constant light levels. It combines daylight and artificial lighting to provide an optimal solution.
Employing such a strategy is called daylight harvesting. It makes a lot of sense since
daylight is generally available when most non-domestic buildings are occupied. If the lights are operating at full output, when there is plenty of natural light available, then no energy is being saved.
Sensible solutions
Generally sensors control groups of lights, from two to twelve, depending on the application.
There are several types, from basic occupancy sensors to those that also combine light sensing for fully dimmable control systems that maximise energy savings.
Although the drive for sustainability may tempt you to opt for a digital lighting control system, which use sensors that will dim the lights up and down in response to both movement and daylight levels, stop and think first.
Consider your building. Lighting closest to windows will benefit most from daylight harvesting. Move further away from the windows and you may just require occupancy sensing. And then there are areas with no natural light such as corridors, stairwells and toilets.
So in conclusion when you are considering energy conservation it is only common sense to target the areas where you can get maximum return. Lighting can account for half of total electricity use in a building, so instead of relying on light switches or dimmers consider the use of sensors. You can always combine them with wall switches for some manual control, but they will at least turn unneeded lights off.
For further information contact:
Hager Sales Office
Hortonwood 50, Telford TF1 7FT
T: 0870 240 2400 F: 0870 240 0400 E: sales@hager.co.uk W: www.hager.co.uk
|
