Over the last few years building operators have been assailed by a raft of challenges relating to energy and carbon. These include Part L for new build and major refurbishments, and the importance of BREEAM points for new build as well. In addition, building energy performance is being measured, and publicised, through initiatives such as Energy Performance Certificates and Display Energy Certificates.
For larger energy users there is also the Carbon Reduction Commitment Energy Efficiency Scheme (CRCEES) to contend with, requiring them to buy carbon allowances in relation to their energy consumption. And while the CRCEES was initially designed to reward good performance, since the Comprehensive Spending Review it has become more of a carbon tax.
Going back a decade or two the first port of call to look for savings would have been the heating systems as these were far and away the biggest consumers of energy in most buildings. However, as buildings have become better insulated the heat losses to the outside have been greatly reduced. Plus, the increase in internal heat gains from office equipment has increased, reducing the need for additional space heating.
Consequently the contribution of lighting to overall energy consumption has increased significantly. Indeed, it has been estimated that lighting accounts for around 30% of carbon emissions in a typical modern office building. So it’s unsurprising that building operators and the specialists they employ are taking a closer look at lighting and what they can do to make it more efficient.
Making the right choice
The key issues when it comes to reducing lighting energy consumption are the efficiency of the light source, photometric efficiency of the luminaires and the way the lighting is controlled. In addition, there are other factors, such as total cost of ownership and return on investment that are influenced by factors such as lamp life and associated maintenance costs.
In relation to these factors, it’s the light sources that tend to get the most publicity – unsurprisingly as they are at the heart of much lighting innovation. However, it’s important to keep the claims for new or improved light sources in perspective and dilute the hype with a healthy dose or realism.
Light emitting diode (LED) light sources illustrate this point very effectively. LEDs have been hailed as the panacea for energy efficient lighting for many years now, but early LEDs were certainly the source of considerable disappointment for many building operators. Essentially, they simply didn’t deliver the light output, lamp life and colour temperature consistency that was required for effective ambient or feature lighting and tended to be confined to signage and other applications where light output wasn’t so critical.
More recently, there have certainly been considerable improvements in LED performance and the realistic potential for their use has broadened. However there are still limitations that specifiers and their clients need to be aware of.
Unfortunately, the claimed benefits of LEDs have been heavily publicised so that many energy, sustainability and facilities managers have been given the impression that they must switch to LEDs if they are to achieve their sustainability goals. The reality, though, is that in many cases high efficiency T5 fluorescent light sources (in luminaires that have been optimised for T5) combined with effective controls, still offer the best solution in terms of all of the criteria outlined above.
One of the reasons for this is that the return on investment is particularly important in these straitened times where organisations are reluctant to invest in building improvements unless they can see a reasonably quick payback period. With LEDs the criterion that mitigates against a fast payback is the cost of the lamps – typically ten times that of a linear or compact fluorescent lamp. LED luminaires also tend to be expensive compared to fluorescent luminaires, simply because of the economies of scale in relation to the volumes sold.
Given this huge difference in price there needs to be a significant reduction in installed electrical load to deliver an acceptable return on investment. This, in turn, depends on what type of lamp LEDs are displacing. If a 50W halogen lamp is being replaced with a 7W LED then there is clearly a massive reduction in installed electrical load and the investment is relatively easy to justify.
However, the situation is not as clear when it comes to LEDs as an alternative to already efficient fluorescent light sources. Indeed, there are some 600mm x 600mm LED fittings on the market that will consume as much power as a 600mm x 600mm fluorescent fitting.
So then it comes down to other factors that contribute to total cost of ownership and the main argument for LEDs in this respect is their long life and the resulting reduction in maintenance costs. Certainly high quality LEDs offer a longer life than a standard T5 fluorescent lamp – some LED manufacturers claim up to 45,000 hours.
However, T5 technologies have also improved in recent years and there are now lamps on the market with a life of nearly 20,000 hours, and some special premium T5 lamps claim a 45,000 hour life. In these circumstances it’s necessary to calculate whether the maintenance savings sufficiently offset the extra cost of the LED lamps.
The other thing to consider in this respect is the likely life of the lighting installation. Office lighting is typically replaced every six to seven years, so it’s worth questioning the value of a high capital cost installation in relation to its projected life. Indeed, in retail applications, the life of the lighting is likely to be more like two to three years before the store gets a make-over.
In refurbishment projects the previous lighting will also impact on the calculations. Upgrading from older T8 fluorescent lamps is a very different situation to upgrading from T5 lamps, for instance. In this case, changing from T8 to T5 will nearly always be a more cost-effective option than installing LED lighting.
Or there may be a requirement to replace high or low bay SON lighting with a more efficient alternative. A 400W SON lamp in a high bay fitting can be replaced with a 4 x 55W T5 fitting to give a comparable light output with an immediate reduction in energy consumption. Introducing T5 lighting also opens the door to more sophisticated control for even greater energy savings. In these situations LEDs aren’t even worth considering because they do not have sufficient light output for these mounting heights.
At this stage I need to make it clear that I am not against LED lighting and I believe it has great potential as light outputs increase and LED lamp prices fall. However, I do feel there is a need to redress the balance and highlight the limitations of LEDs in the face of all the hype. There are already a number of applications that lend themselves perfectly to LEDs, but there are many more where alterna
tive solutions will be the best solution.