Electrical Contracting News (ECN) ECN-Nov2017 - Page 60

SPECIAL FEATURE ENERGY MANAGEMENT Choosing the protocol Smart lighting controls can be utilised in a number of ways to increase energy efficiency monitoring uses an active photocell within a light sensor and measures real time natural light. It can then switch fixed luminaires on or off, or vary the light output of regulated luminaires. Who’s there? Another commonly used parameter for lighting control, of course, is occupancy – on the grounds that there’s little point in lighting a space if there’s nobody in it. Here, the choice of occupancy sensors is important and usually comes down to a choice between passive infra-red (PIR) and microwave. PIR sensors are the most commonly used motion sensing technology and have been tried and tested in a wide range of scenarios. However, most have a limited range (typically 7m diameter from a mounting height of 2.8m) and limited movement sensitivity. This means that in areas such as corridors, several sensors may be required to give full coverage. However, some manufacturers are now offering PIR sensors that can be mounted at 20m. An alternative is to use microwave sensors, which can be configured to give 360° coverage or directional coverage over a longer distance. These have greater range and sensitivity than PIRs (from 7m diameter to >25m in directional mode). When using microwave sensors, it’s important to be aware that they can ‘see’ through glass or partition walls and they can be adversely affected by a significant presence of steel in the environment. On and off or up and down? A key decision to make early on in the project is how the lighting is to be regulated, besides providing a ‘smarter’ solution that is responsive to change. It may also be that the smart solution for one space is different to that for another. 60 | November2017 For example, in an office building there will usually be a few cellular offices and small meeting rooms, where the space is either occupied or unoccupied. Here, a simple on/off response to occupancy or lack of it may be all that’s needed. In the same building, there will typically be larger areas of open plan office space where at any one time some workstations will be in use while others aren’t. Such areas will also receive variable amounts of daylight depending on time of day and proximity to windows. In these situations, a smarter regulated solution will be to configure the system to respond to daylight levels across the space and include some zoning to detect occupancy of individual or small groups of workstations. In such cases, absence detection is usually the most efficient form of occupancy control. Moreover, it is important to light different areas of an office building in- line with their function, with an emphasis on lighting the task – as recommended in EN 12464-1. For example, a typical UK office building has around 60% of its space as corridor, yet these areas are lit to the same levels as workstations. Similarly, in a warehouse where certain racking aisles are only visited very occasionally, on/off switching may be acceptable. However, there may also be aisles in the same warehouse that are accessed frequently during the day. Here, it makes more sense to dim the lighting when the aisle is unoccupied and then ramp up the light levels when someone approaches (on foot or in a forklift). Of course, these are only a couple of examples of how the lighting control requirements for a smart building may vary. Tailoring each system to the precise needs of the building, and re-commissioning the lighting as those needs change through the life of the building is essential for achieving maximum benefits. “A key decision to make early on in the project is how the lighting is to be regulated.” Providing a regulated lighting control system necessitates the use of regulated control gear, of which there are three main types. These are 1-10V analogue, DSI (Digital Serial Interface) and DALI (Digital Addressable Lighting Interface). Each has advantages and disadvantages. 1-10V analogue dimming systems are very familiar as they’ve been around for years and the ballasts are cheaper than digital equivalents. They are also very simple to install and commission and dim suitable lamps to between 3% ձи)=ѡݹͥՔ)́ѡչѥ䁽х)́Ё́᥉ȁձѤɍե)%Ёͼՙ́ɽͥ)͔͕́ȁչ́ͼ)ѡЁ͍ɕ́ɕեɕȁչ)ȁѡմͼѡɽȁ)ɥ䁍̸͍)M$́ɔɕѥٕ䁅ɑ)ݡɕѼѡȁɽѽ̰ݥ)ɽ٥Ѽ̔Ĕ)ٔѡЁٔɽѽ)Սɔɔեхȁ)ɽ́ձѥɍե̸ хM$)ͼɽ٥aݥэdɔ)ѥ͕ɝ䁕䁅ɽ)Qɽ́Ёɥ)͍́́ЁѼ͍ɕ)!ݕٕȰM$́ɔ䁅م)ɽȰѡЁхѱ)Ʌ́ɕЀɅͥѥЁѽ)ɔɕեɕѼѕЁѡͥ)1$ѕ́ɕ́䁽ѡ)ͅمх͍́ɥٔQ䁅ɔ)́ɽѼ͔ѡĴXѕ)ɔѕ䁵ձѥѥ)ՙɕ́ͼӊéͥѼa͡)ɽչdQݥݸѼ̔Ĕ)ѡɕѥ䰀ĔݥѠѡѥ)ՅaѽՍdɔͼ1$)́ѡ䁝ѥхɐ)1$́ͼٔͽݹ̸ͥ)Q䁍Ёɔѡѡȁɽѽ́)ѡɕՍѥɝ䁍յѥ́)ȁɕѥ͡ݥѠ1M$)̰ѡ䁅ͼɅ܁ɕЁхѱ)ЁхȁѼͥ1$)ѕѡѡȁɽѽ̸)1$ɕͅ͵Ёѥ)́յɕ́Ѽ٥Յ)ɕ͕ɽɅͼѡЁ)ɕЁѡ̸Q́ɕͅ)́ͥݥѠѡ1$ɽѽ)́ѡɕͽ́ݡ͵)ե́Ց͵Ёѥѡ)́1$ɥٕٕ́ѕ̸)MЁѕ́ͼͥ)ɕɕQ́́ȁمх)ȁեɅѽ̰ݡ䁹Ѽ)ѡѥɽѕݡ)ե̸ͅ)MЁ)=ѡѡ́ѡЁ́ե)͵Ё́́Ѽم䁕٥ɽх)Ʌѕ́ѼեЁѡ́)ݡͼٕɥѡɝ䁕䁅)٥ɽхəɵѡЁѡե)ݹȽɅѽȁ̸Qх)Ёѕɵ́٥Յа危)٥ɽхЁ́ѡ́́)ɕѡЁeЁɕեݥѡ)͵Ёѥ́Ё͵Ёե) A81ѥ ɽ)ܹѥɽ