Keeping control in the classroom
Given that the government’s has stated its commitment to achieving carbon neutrality for schools by 2016, it’s clear that the education sector is to play a pivotal role in meeting the UK’s overall emissions targets.
Many of these improvements in energy performance will be delivered through initiatives such as Building Schools for the Future (BSF) and the Primary Capital programme. Both of these will include significantly higher insulation levels and better air tightness in school buildings, so that space heating demands fall and heating is no longer the main consumer of energy.
As a result, lighting is set to become a far more significant contributor to overall energy consumption; so taking proper control of lighting will also become more important in delivering the overall objectives.
At the same time, it’s important to recognise that these are long-term initiatives that will take many years to complete, and the BSF programme has already suffered some delays. In the meantime, there are many schools that are wasting energy through poor lighting control so suitable measures for these also need to be considered.
It’s also worth noting that schools and other educational buildings are amongst the most challenging of applications to control effectively because of the variety of uses to which teaching and other spaces are put. Not only does occupancy vary during the day but schools are also being used more widely by the local community outside school hours.
In addition, the people responsible for managing the lighting within the school will vary considerably from one site to another. Larger schools may have a full-time facilities manager or general manager while, at the other end of the spectrum, smaller facilities may have to share this resource with several other sites.
Clearly, then, it’s important not just to specify controls that will provide the best energy savings without compromising on visual comfort; the level of complexity of the controls must be aligned with the technical knowledge of the people who will be using them.
At the same time, each space within the school needs to be considered separately if the lighting is to yield the maximum benefits within the budgets available.
For example, some classrooms will be in use constantly through most of the day so there may be a temptation to leave the control to the teacher, who can turn the lights off when the room is vacated – if he or she remembers. In reality, though, there will be times when the teacher is distracted by other priorities and the lights are left on unnecessarily.
Here it makes sense to use occupancy detection to ensure the lighting is switched off as soon as the room is vacated. And the same applies to specialist rooms such as science laboratories and music rooms, where use may vary throughout the day.
Similarly, there will be many others areas of variable occupancy throughout the school, ranging from toilets and corridors through to sports halls and assembly halls. Again, presence or absence detection will help to reduce electricity consumption.
There will also be some spaces that receive more natural daylight than others so dimming or switching off the lighting when there is sufficient daylight is another obvious measure. Typically, this facility will be restricted to the luminaires closest to windows.
In such circumstances, the control strategy is vital in achieving not just the right level of control but also the buy-in of the users. If the automated elements of the lighting control fail to address what is happening in the space, school staff will become disillusioned and may well resort to any manual override facilities that are available. Inevitably this would lead to the building not performing as it was designed to do and, thus, not achieving targeted energy performance.
An example of effective, tailored lighting control can be found at Arthur Mellows Village College, a comprehensive community school in Peterborough. The school has recently benefited from an £8.4 million grant to build new buildings and carry out extensive refurbishment – energy efficient lighting was a key criterion.
This criterion was met with the help of CP Vitesse Plus marshalling boxes in the classrooms, providing multi-channel switching for the control of up to three rooms, PIR and switch control, dimming options and daylight linking. Presence management has also been included in the scheme to allow the occupancy-based switching of the luminaires. The system also provides daylight linking on the lighting closest to windows.
Occupancy detection was also provided for corridors and toilets. MWS-1 microwave sensors proved ideal for corridors, as they have a detection range of up to 30m, so that effective control could be achieved with the minimum number of sensors. In toilets, MWS-3 microwave sensors were used for presence/absence detection, using an adaptable sensor head to change the detection angle to suit the different sizes and shapes of the spaces.
A similar strategy was applied at Wood View Learning Community, where self-contained microwave sensors provide absence detection in classrooms. Again, these are linked to Vitesse Plus marshalling boxes to combine the occupancy control with daylight linking.
Adapting to needs
In other school spaces there may be a demand for more sophisticated levels of control. This is particularly true for multi-purpose spaces such as halls, which are frequently used for a number of purposes ranging from badminton to school plays, assemblies and parents’ evenings.
In these spaces, the lighting plays a major role in facilitating the activity itself, as well as creating an appropriate environment, so it’s important that the school can easily adjust the lighting to suit. Here, scene setting controls that will quickly configure the lighting in different, pre-set combinations make adjustments very simple.
Retrofit to full effect
As I mentioned earlier, there are many schools that will not benefit from the government’s initiatives for some years to come – but they can benefit from retrofitting relatively simple and inexpensive controls in the meantime.
Typically, the first place to start will be areas of variable occupancy such as corridors, toilets and stairwells, where it is very straightforward to retrofit simple controls to existing lighting. The level of control achievable will be determined to some extent by the nature of the existing lighting and many schools will not have luminaires with dimmable ballasts but on/off switching can still provide significant energy savings.
Just as importantly, this approach requires minimal input from school staff as it is virtually a ‘fit and forget’ solution. Such simple measures are also very affordable and will deliver lower cost of ownership through extended lamp life to provide a fast payback.
At the end of the day, it all comes back to the very sensible strategy of considering each space and treating it accordingly. There are very few instances where a ‘one size fits all’ strategy is going to achieve the best results and schools are no exception. In fact, although all new and refurbished schools will have to meet standard specification criteria – in terms of kgCO2/m2/yr – they will achieve this in very different ways so the lighting control needs to offer the same flexibility.