How to design a high performing luminaire
Get 6 simple steps to keep in mind the next time you design a new luminaire.
We have all seen terrifying photos of melting icebergs due to global warming, and on a global scale there is an increased focus on getting more out of less resources, minimizing our negative environmental footprint. In Europe, lighting accounts for approximately 12 percent of the total consumption of electricity[i]. This makes lighting one of the heaviest consumers of electricity, substantiating that even smaller energy-efficiency gains have a major impact on the total environmental footprint.
According to Danish Environmental Protection Agency, the largest negative environmental impact within lighting comes from the energy consumed during the use phase of the lamp; thus, it’s good sustainable thinking to consider energy-efficiency in the design phase of a new luminaire or when retrofitting an existing luminaire.
DESIGN ENERGY-EFFICIENTLY IN 6 STEPS
Designing a luminaire is not only about the appearance, but also about getting out as much light as possible, delivering the light where you want it to go and handling the glare. Based on our more than 25 years of experience within glare control, we have gathered a few tips that can help you design even more efficient luminaires.
Step 1: Always use a high-reflective Reflector
A high-reflective surface optimizes the internal reflection, ensures that no light is lost inside the luminaire, and exploits the light optimally. The reflector can also proactively be used to shape the beam of the light exiting your luminaire; thus, you need to choose between specular and diffuse reflective properties to obtain the desired light distribution.
Different options of reflectors are available on the market:
- Reflective films
- White reflector paint
- Aluminum reflector
The ideal choice of reflector depends on your mechanical design, but most importantly: Remember to use a reflector film! It’s a cost-efficient way to increase energy-efficiency.
In our world, we work with plastic reflectors from 0,21 up to 1mm thickness. When a reflector has been designed and implemented properly, we have often experienced performance increases of 10, 20 or even up to 40%!
Step 2: Control the light by choosing the right optics
When it comes to controlling the light, many options are available. In general, it’s important to keep in mind that maximum light transmission is a key figure when trying to build as efficiently as possible. A clear plastic typically varies from 89-92% light transmission whereas an opal diffusor varies from around 60% up to around 90%.
Three typical cases:
- Microprism
A microprism is used when it’s required that the luminaire fulfills the requirements of EN12464 concerning glare. For optimal functionality, it needs to be produced in a clear material with the highest possible transmission, often 92%. - Diffusor (Lambertian distribution):
A diffusor foil is used when there are no requirements to light control and UGR19 norms. It’s applicable for lamp hiding and when a matte, opal surface is required. One of the benefits of using a diffusor foil is that the apparent brightness of an opal surface is the same regardless of the observer’s angle of view. The higher diffusion of light, the less transmission. An opal diffusor foil varies from 60-90% transmission. The right choice of diffusor foil depends on the pitch and distance of the LEDs. - Microprism and diffusor in combination
If you use a microprism on its own, the luminaire gets a very technical look. This is due to the physical shape of the prisms which create a visible pattern from the prisms’ shape. To avoid this, an opal diffusor foil can be added on the backside of the prism. Hereby the diffusor foil removes the visible pattern while the prisms cutoff any high angles. Remember to use a diffusor foil with highest possible transmission.
Visible pattern from the prism’s shape.
Diffused pattern by adding a diffuser foil.
Step 3: Distance between LEDs and diffusor foil
Consider the distance between the LEDs. If they are closely placed (low pitch), they will appear less visible and a diffusor with lower haze level could be used. But also, the distance between the LEDs and the diffusor foil plays a role for the appearance of the luminaire. The closer the LEDs are placed to the diffusor, the more visible they will appear, but this can be prevented by adding an effective diffusor.
Step 4: Avoid light traps
Make sure light is not send in traps where it is wasted, decreasing the efficiency of the luminaire. Use reflectors to exploit the light in full and avoid unnecessary gaps inside the luminaire where the rays can escape. Even small reflector parts can make a huge difference.
Step 5: Design for later retrofit
As a rule of thumb, a lamp has a lifespan of 20 years, but this is only a small step within a fast-turning product lifecycle. Thus, from a sustainability point of view, it makes sense to design a luminaire that is either viable for later retrofitting to extend product life or for upcycling the materials. For luminaires, this can be done by using easy-to-change light sources, and optical lighting components and batteries that are replaceable.
Step 6: Choose quality electronics
Electronics are beyond our scope, but from a sustainability point of view, we know from experience that it’s important to choose quality LEDs, drivers and power supplies that enable longer product life cycles. Electronical parts are heavy power consumers, and it’s important to prevent them from superheating as their efficiency and lifespan decrease at higher temperatures.
[1] According to Working Paper about the consequences of requirements to environmental-friendly design of light sources from the EU Commission, October 2019.