Don't forget the basics

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It is important those involved in lighting design don’t overlook the ‘basics’ in favour of opting for the latest technologies. Stephen Woodnutt of Delmatic explains why technology should be used to enhance good lighting design

 

It’s probably true to say energy management is now a component of everyday life for those involved in managing buildings. So, too, is the search for ways to improve energy efficiency in both new and existing buildings, and electrical engineers have an important role to play in guiding the end client to the most appropriate solution.

To that end, lighting often comes under scrutiny because of its significant contribution to the energy consumption of many buildings. In particular, new energy-efficient light sources and the controls to optimise their operation have a particularly high profile.

However, there is a very real danger this focus on technology to save energy becomes an alternative to sound design rather than an enhancement, especially when the potential benefits of control are grossly exaggerated as this just leads to over-inflated expectations.

The fundamental principles of lighting design should remain the same irrespective of whether LED light sources or a sophisticated lighting management system are to be used. Namely that the design should ensure the visual comfort of occupants, enable them to perform their tasks – and use the minimum amount of energy in doing so.

I am prompted to this view by a recent case study in this magazine which claimed 70% energy savings following the introduction of a lighting control system. As someone who designs and manufactures lighting control systems I’m all in favour of extolling their virtues but this level of saving can only be achieved if the lighting was poorly designed in the first place.

Yes, significant energy savings can be achieved through effective control but the role of the controls is to fine-tune the performance of an already-efficient system and align its operation to building usage. Consequently, if a lighting system is properly designed the additional savings that can be achieved over and above the inherent efficiency of the system will certainly be significant but are very unlikely to reach 70%. It should not be possible to achieve more than around 30% additional energy savings over and above the inherent efficiency of the system – unless the lighting control is integrated with other services or people in the space are to be plunged into darkness!

In fact, over-reliance on controls to achieve efficiency threatens to dilute the skills and experience of the electrical engineer, by leading people to give less thought to the key criteria of the lighting design.

It is the engineer’s expertise that is required to understand the lighting requirements of the project and design the best solution. Such a solution encompasses the layout of the space and the distribution of light that needs to be achieved, as well as the illuminance levels.

This leads to the selection of appropriate luminaires, positioned so as to minimise contrast between the working plane, vertical surfaces and ceiling and to ensure there is no glare on display screens. In parallel, light sources are selected to achieve the required lumen outputs at the right colour temperature and with maximum energy efficiency.

Beyond this, having designed the system as efficiently as possible, the specification of luminaires, lamps and control gear also needs to take account of the desired level and breadth of control that is anticipated within the project budgets. Then the controls can be used to align the operation of the lighting to the usage and occupancy patterns of the spaces and ingress of natural daylight.

As noted above, there may also be opportunities to integrate the lighting control with other services – such as blinds, security, lifts, life safety and HVAC – to achieve even greater savings. For example, each degree of temperature saved through control achieves around 4% savings, so linking HVAC operation to occupancy, managed through the lighting management sensors, can deliver significant savings.

In this case, where services are to be integrated it is important to select an interoperable system using an open protocol. Another benefit of open protocols is they are fully scalable so it is easy to extend or reconfigure the systems in relation to changes in building usage – or to add extra functionality as new technologies become available. This element of ‘future-proofing’ is invaluable as it enables buildings to maintain the levels of efficiency they were originally designed to achieve throughout their life.

As an industry we have a duty to provide building operators with services that are aligned to the ways they want to use their buildings while helping them to reduce energy and life cycle costs. As mentioned earlier, I am all in favour of using the latest technologies to help achieve this, but not at the expense of sound design principles.

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