Lighting Industry

Why we need to urgently rethink luminaire design

A group of men and woman examine a light fitting
Helen Loomes, right, believes a rethink of luminaire design will deliver more environmental benefits than a return to ‘lamps and luminaires’

Helen Loomes on why a return to replaceable light modules could be a misstep for the industry.

SCIENCE-BASED investigations should be the basis of our plans for a sustainable future, and Trilux has contributed to an important piece of research that gives us facts and data on which to base our developments for the future. 

This is a European community project called Repro-light and has been conducted over the last three years by a consortium of lighting industry partners.

The research and development element contributed by Trilux looked at sustainability and the circular economy of luminaires. 

The results of this research have surprised me and changed my way of thinking for the future.

I also feel I must inform others as I know legislation is being considered which might prove to be a false move.

The crux of the matter is developing luminaires with elements that can be removed for repair or maintenance – specifically LED modules, very much going back to the days when we would replace a lamp once it had failed. 

It all seems to make sense until you look at the fine details of embodied carbon and use of rare earth metals within these LED modules.

We conducted an environmental lifecycle assessment of a typical luminaire which quantifies the environmental impact of the product over its entire lifecycle. 

The lifecycle starts with the production, where you put materials and energy in, and record the waste and emissions resulting from that process. 

The product is then used over a long period consuming energy and often generating emissions, then at the end of life, again you use materials and energy to dispose of it and wasted resources are the result. 

The impact is quantified in different matrix – we focused on the midpoint markers, that is, the primary energy demand which is measured in mega Joule, and also we had a deep look at what are termed the abiotic depletion potential (ADP) of elements. 

This represents the increased extraction of resources which are very rare on earth leading to depletion of mineral reserves.

We generate certain environmental burdens for the luminaire – using energy to produce the luminaire and materials used. 

We also accounted for the material mining process and transportation to the Trilux facilities.

When just looking at the quantity of materials, we have a lot of metal and plastic (not only for optical systems but also for insulation), then there are wires and electronic components in the control gear and the LED module.

Looking deeper at the materials used, the most precious elements – the ADP elements that are limited on earth – are in the electronics in the LED modules and the control gear. 

The next materials of importance are in the housing and the wiring, steel and copper and then in the optics which are plastic, mainly PMMA. These are negligible in respect of ADP element consumption.

The obvious opportunities to improve in this step are to use as little material as possible and to use recycled instead of virgin materials – the steel and copper in the luminaire already contain some recycled elements. 

We also want to design long-lasting luminaires so that the production process is not repeated too often.

Our solution was to design an improved product that saves materials and especially the most precious materials.

As the LED modules have the major ADP contribution, we addressed this in two ways. 

First, the LEDs were replaced by ones which do not have a gold bond wire because the gold contained in standard LEDs is a large proportion of the ADP total and second, the LED module got slimmer so we need less copper and less materials for the board itself. 

In all, we achieved a reduction of 61 per cent of the ADP element content.

The new design also saved on energy consumption. We reduced this by 11 per cent just by replacing the LEDs to the newest version thus increasing the efficacy from 157 lumen per watt to 179 lumen per watt. 

Another big improvement incorporated light management systems. Using daylight and presence control, you can get approximately another 30 per cent energy savings. 

This has a big impact on the ‘use’ phase of the luminaire.

The electricity used to operate the luminaire is by far the largest energy contributor at 99 per cent compared to 1 per cent for energy used in production. 

The generation of this electricity also has additional material consumption as we need to generate the electricity, and this accounts for 26 per cent on top of the production materials. 

It is essential that we decrease the energy in the use phase because this is so large, not only by upgrading the LEDs but also by taking light management systems into account. 

But this brings us to the interesting questions raised earlier; what happens if the luminaire fails? 

Should we exchange the failing component, maybe the control gear or the LED module, or do we have to dispose of the complete luminaire and replace it with a new one? 

Do we want to have luminaires that are maintenance-free or have some components which can be exchanged regularly like lamps in earlier times?

The actual after-sales data of Trilux showed that only 1 per cent of the luminaires are expected to fail within their nominal lifetime and the largest percentage due to the control gear. 

The LED modules account for less than a quarter of all failures – that is one quarter of one percent. 

Looking at an example in an industrial hall with 369 luminaires – because of the 1 per cent failure rate we can assume that four will fail, three because of the LED control gear and just one because of the module. 

To enable the replacement of an LED module, we have to change the design of the luminaire a little bit.

For example, we have to account for some additional connectors in the luminaire which have extra ADP elements. 

Now the problem escalates, because these extra connectors are needed for all the 400 luminaires just to have the ability to exchange the LED module in one instance!

This example shows that using a non-exchangeable LED module, you end up with a lower contribution to the ADP elements. 

Because this tiny extra energy usage of just 0.4 per cent for the additional connectors for the design change, does not compare to the savings that you have in the production of a non-exchangeable luminaire. 

So, in total you end up with a very small negative extra. 

This leads us to a conclusion, on the material side, that you are better off saving on the majority of luminaires and replacing a complete luminaire in the very small percentage of cases where there is a failure. 

The components in the old luminaire can still be recycled.

However, there is another reason why you might want to exchange an LED module – as a scheduled replacement of degraded LED modules in order to restore the luminaires energy efficiency. 

The light output decreases over time and because of this, you have to use a maintenance factor in light planning to ensure that at the end of the lifetime you have got sufficient illumination for the application, which means over lighting at the start. 

The apparent solution to both points is to say we will regularly exchange the LED modules so that we always have the most efficient one but the great drawback is that you generate even more LED module waste which contains the most precious materials. 

In an application with 100,000 hours of lifetime, it does pay off to regularly exchange the LED modules. 

With one, two or three exchanges over these 100,000 hours, you are decreasing the energy consumption. 

However, there is a further aspect; because for three changes you have to produce three LED modules and the old ones are typically just disposed of as waste… from the material side this isn’t a good solution. 

I want to highlight an alternative. It’s not new and is called constant light output, where you are programming the luminaire to compensate the LED degradation by increasing the forward current through the LEDs. 

This means that you can avoid the maintenance factor in your light planning, again saving energy on over lighting. 

You also have no additional material for the LED modules, and it has the lowest material input needed. 

From the energy aspect it is nearly as good as having one exchange of the LED module. 

The only way that exchanging the LED modules to keep the efficiency high might become a valid case is if you can reduce the ADP element in the LED module spare parts. 

We have seen in the Repro-light project that we can make some progress here. 

The next-generation luminaire with a shrunken LED module will reduce its contribution to the ADP elements. 

You could afford one exchange and then it’s a draw from the material point of view.

The dimming of the LEDs also leads to the fact that the lifetime is elongated. 

As LEDs degrade over their lifetime, their luminous flux decreases. 

This depends on the temperature of the LEDs, which in turn depends on the current flowing through them. 

So, if you dim it, in effect the degradation rate also decreases. 

A Repro-light model calculation showed that the resulting lifetime might be up to 87,000 hours, which is quite a considerable elongation of the lifetime just because of the daylight and presence control.

To summarise the total savings which we made in the Repro-light project, we compared the environmental impact of the benchmark luminaire, and the next-generation luminaire including the use of a light management system. 

We achieved energy savings of 38 per cent and material savings – expressed in ADP elements – of 55 per cent which is considerable progress. 

So, the successful steps towards more sustainability were the improved product design; reduction in precious materials mainly in the electronics components, an efficiency upgrade for the LED module, and use of a light management system or even simple constant light output technology. 

We tried some other steps, like the discussions of longer use time and exchangeable LED modules, but they did not prove useful in this case. 

It might be different in other applications or luminaires, so continued research is essential and Trilux will investigate further into other scenarios.

Now we come to the end of life and disposal.

The real question is why are luminaires disposed? Maybe the technical lifetime of the luminaire is not always the problem and we confirmed this.

We conducted a survey among lighting professionals and we asked them whether it is determined by the framework of the application or by the product lifetime, and they say in most cases it’s the application. 

People want to replace the luminaires even though they are still working. 

So how can we make our customers want to use our products for longer?

 This is the crucial question not just elongating the lifetimes more and more.

To be even more controversial, what about standardising the dimensions or the design of luminaires, or maybe even mechanically, electrically, thermally, and photometrically?

Will that lead to commodity products? If we also standardise the light distribution or the light emitting surfaces and appearance, isn’t that also a benefit for the customer? 

Can he exchange one luminaire for another, without even having to drill new holes in the ceiling?

If we really want to proceed with the standardisation of light and luminaires, one has to raise the question: what will happen to our creative freedom?

Will there be any space for individual lighting and customised solutions? 

This is certainly an important question which cannot be answered easily and conclusively.

  • Helen Loomes is business development director, international sales at Trilux Lighting.