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Low Energy Lighting Guide

Root3 Guide to Energy Saving for commercial & industrial Lighting Applications

1. Choice of lamp & Fitting

Energy and costs can be saved in many ways in terms of the type of lamp or light fitting selected in any particular property. In an office application the fluorescent tube is the most common lamp in use.

Normally twin or quad tube fittings are used in many sizes including the 600mm (2ft) up to 1200mm (4ft) being most common but other lengths can be fitted. A 4 tube 600mm X 600mm lighting fitting will typically consume approximately 82watts of energy as the tubes are 18watts each and the control equipment inside the light fitting used to regulate the fluorescent gas consumes approx 8watts depending on the make, giving a total of 80w.

Example 1: 100 standard fluorescent fittings (quite conservative for a small office) the energy consumed would be 80w X100 equating to 8000w or 8kw. Taking an average unit cost per Kw of 10p that would equate to £7.20 per day based on a 9 hour day. This would equate to £1,800 over a full 50 week year.

So what are the options?

There are two options to decide upon, low energy fluorescent (called T5 lamps) or LED lamps. Low energy fluorescent is cheaper to purchase than LED and on a limited budget this could be a great solution. The main 2 negative points for opting for T5 fluorescent would be firstly the life of the tubes is limited, similar to standard fluorescent and depending on manufacturer could be anything from 2000 to 9,000 hours of use. The control gear contained within a fluorescent fitting also has a limited life time operation therefore maintenance costs will increase with this option as breakdowns and replacements would be necessary. The costs saving between standard fluorescent lighting and T5 low energy lighting is approx 34%

Example 2: 100 T5 low energy fluorescent fittings (quite conservative for a small office) the energy consumed would be 64 X100 equating to 6400w or 6.4kw. Taking an average unit cost per Kw of 10p that would equate to £5.76 per day based on a 9 hour day. This would equate to £1,440 over a full 50 week year.

LED Tubes on the other hand do not require any control gear as they simply require a mains power supply so maintenance costs will be saved. The LED tube (depending on manufacturer) will also have an extensive life time operation lasting considerably longer than its fluorescent competitor, some brands offering up to 50,000-60,000 hours of operation guaranteed again making maintenance costs nonexistent. The negative considerations with LED lamps is the initial upfront cost, generally higher than the fluorescent option and secondly the light output need to be carefully selected as many claim LED can be replaced on a like for like basis with fluorescent in terms of light output but careful consideration should be made to ensure this is the case. The costs saving between standard fluorescent lighting and LED lighting is approx 50%

Other lighting technologies such as Halogen lamps including the common GU10 50w lamp are very inefficient and therefore LED is a fantastic alternative as the 50w equivalent would be a 7w LED lamp, offering a 87% saving.

Example 3: 100 LED fittings (quite conservative for a small office) the energy consumed would be 40 X100 equating to 4000w or 4.0kw. Taking an average unit cost per Kw of 10p that would equate to £3.60 per day based on a 9 hour day. This would equate to £900 over a full 50 week year.

We have found they every property is different and depending on size and usage each of the LED and fluorescent tubes have their pro’s and con’s and choice should be considered based on what’s suits the application, preference of either technology should never be pre-defined

2. Consider Dimming your Lighting

Dimming of lighting is a great way to save money. Dimmable fittings and a dimmable switch are all that’s required and the results can be fantastic. Setting lighting to be dimmed for room can knock substantial cash from an electricity bill, to get the very best from dimming we would recommend dimming in combination with other control techniques such as daylight sensors or PIR sensors.

3. Daylight Sensors

Daylight sensors are an absolute must for energy saving in buildings with large solar intakes such a windows and atria’s. The daylight sensor will monitor the natural daylight comng into a space and adjust the lighting accordingly against a pre-determined set point. As an example the current required ambient lighting levels for general office working conditions is between 300lux & 500lux. This is the minimum for office light levels and anything higher recorded in the office would mean the lighting would not be needed. Connecting a daylight sensor to the installed lighting system the occupier can regulate the light level of the office depending on the external weather conditions. When daylight sensors are used in conjunction with dimmable light fittings the lights can slowly raise and fall depending on the brightness of the natural lighting coming into the office from outside. Anything below 300lux and the lights are always on, and above 500lux and they are always off and anything in between are controlled to work with the variable external light levels – perfect.

4. PIR occupancy Sensors (motion sensors)

PIR is the most common motion sensor to control lighting as they can be used in many different and wide applications. Controlling office or factory lighting is the norm for this technology where infer red sensors can switch lights off and on as have someone is in the area. This type of control managed to get a poor reputation in the early days as building occupants where often left in the dark jump up and down trying to get the lighting back on. These days the detection angles are much better and with a good design planned out correctly the areas should be well covered to “see” anyone working within the office or factory space. Security lighting is another area where you will find PIR technology commonplace.

5. Time Controlled lighting

Time controlled lighting has historically been used to control external lighting. This is due to the fact that external lighting is fairly constant in terms of the operation as it can be set to come on an hour after the office closes for 12 hours for example whereas internal lighting usage is very unpredictable sue office working hours, etc, etc. The downside to this operation is that the lighting has no idea if it’s the summer time or winter time and the timer could be turning lighting on when it does not need to be on. All external light generally speaking should be operated on a photocell, which is a daylight sensor and therefore will only operate when required. Timed lighting is used best in applications such as tuning lighting on when combined with a PIR sensor so that a guaranteed requirement of the lighting can be established before the lights are turned on, security lighting is a good example of this application.

6. Use of Natural Lighting

Daylight is free, so use it where ever you can! Sometimes the obvious gets missed but if office blinds are closed, open them and turn off the lights. Sometimes depending on the position of the building the sun will only be on in the office during the morning and as it raises the subsequent glare can be too much for the occupants but why not open the blinds in the afternoon and let the daylight in. Solar film placed on windows can be used to block the sun out but still let enough light into the property to negate the need to turn the lights on.

Installing roof lights is another inexpensive method of receiving free lighting. These are generally very strong clear Perspex sheets that can be installed on the roof by removing existing roof tiles so that natural lighting can be seen.

7. Correct switching of lighting

This is most common in compartmentised offices where partitioned walls are erected to suit the need of the occupiers at the particular time. The office lighting layout is usually 1 or 2 switches for the entire larger room so when a new set of smaller offices are introduced into a larger office the light fittings will be moved to suit the new layout but the switching can be neglected. This results in several small offices that are not occupied all the time having their lights left on during the day as they operate within the general work pattern of the larger offices.

8. Staff & Management buy in

Management buy-in to energy saving techniques and processes is of absolute importance to successfully achieving good energy and cost saving benefits within a property. Simple poster awareness and short educational videos can get staff thinking about energy saving within the workplace or perhaps running energy saving competitions, all helps getting staff onside. Staff are the key to really driving down energy costs and are a company’s number 1 weapon as they are ready and available to turn lights off when they are not needed without any technology being purchased.

The main consensus is that if management don’t buy into energy saving how can staff be expect to buy into also. From the very top good energy management ethos should be passed all the way down the chain.

9. Design Check

Large scale Lighting is generally installed after a lighting design has been produced. This is a process normally carried out by a piece of software with room dimensions and lighting characteristics being fed into the software and results in a lighting layout and number of fittings being calculated to give the required amount of light into a given space/room. Sometimes a design for whatever reason does not get carried out and lighting is installed at “best guess” by the electrical contractor. In order to ensure they do not “under spec” the lighting levels sometimes over specifying can occur and too many lights are installed within a property. Getting the lighting design checked is a good way of reducing light fittings and therefore reducing energy and costs should the occupier feel that some of their areas are “too bright”

10. Finance for Upgrades

Modern low energy lighting is something that help’s everyone. The users normally find the lighting is of better quality and does not give off as much heat, the property owner has reduced his electricity and maintenance overheads and the government is slowly working its way to its carbon usage reduction goals. In a bid to improve on the take up of low energy products and government/carbon Trust for example via Siemens financial services have introduced the energy efficiency finance scheme whereby loans are available to companies wishing to improve the efficiency of their buildings. The loans are a great idea as the key rule to taking a loan out is that the monthly energy savings achieved by installing energy saving products must be more than the monthly cost of the loan therefore the building owner should not see any additional expense in the loan repayments. For example, having a lighting scheme installed costing £3000.00 may cost £55 per month on a finance loan but if the energy saving by installing the lighting equate to £75 per month it has not cost the building owner any additional capital.