A systemic approach to lighting

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Evaluation of lighting efficiency is moving away from just considering the efficacy of the light source towards a more holistic overview that takes account of what actually happens in the space. Stewart Langdown of Ceravision explains the benefits, using high efficiency plasma (HEP) lighting as an example

 

In the recent consultations about the Building Regulations 2013 it has become clear Part L (Conservation of fuel and power) will continue the work of previous versions in increasing the efficiency of lighting. And it is doing so through a more holistic approach that looks at the final result, rather than the elements that make up that final result.
For example, when Part L first started to impact on lighting it was very focused on the efficacy of particular light sources, seeking to reduce the use of incandescent sources and replace them with discharge sources such as fluorescent, metal halide, high pressure sodium etc.

Subsequent versions of Part L then went on to look at the overall efficiency of the luminaire, taking account of the light output ratio, as measured in terms of luminaire lumens per circuit watt – and known as the ‘technology requirement’. This move began to reflect the actual performance of the lighting in the space, recognising that a badly designed luminaire could negate the benefits of an efficient light source.

Although the details for Part L 2013 haven’t yet been finalised it’s almost certain they will include two key elements that take this trend further. One is to the increase the minimum luminaire efficiency, probably from the current 55 luminaire lm/W to 60 luminaire lm/W.

In parallel, it appears the Lighting Energy Numeric Indicator (LENI) will be accepted as an alternative to the technology requirement above, or the two may be used in conjunction with each other. The important thing here is the LENI also takes account of how the lighting is controlled, bringing it even closer to the realistic use of the lighting in the space. Many lighting pundits also believe that the LENI will become the de facto measure of efficiency in Part L 2016.

So what does all that mean for the electrical engineer involved in lighting design? I would suggest it encourages, and facilitates, more of a ‘systems thinking’ approach that delivers better value to the end client. This is because it leads towards a solution that encompasses value for money, reduced cost of ownership, lower environmental impact and good lighting, rather than just focusing on the light source.

Of course, it’s a difficult habit to kick as we still tend to talk in terms of LED lighting, HID lighting, fluorescent lighting, plasma lighting etc. But we really do need to get beyond the light source in terms of specification, even if we continue to use these terms as a ‘shorthand’ for communication.

For example, the driving need for improved energy efficiency and reduced carbon emissions, backed by some very good marketing, is creating the impression that LEDs are the only light source of the future and will be the industry’s universal panacea. This simply isn’t the case and while I think LEDs are very good light sources in the right applications (below 150W) there are attempts to use them in quite inappropriate ways.

This is because there is a tendency to think of the LED light source, rather than the LED lighting system. For instance, a badly designed luminaire with poor thermal management will prevent the LED light sources from performing at maximum efficiency – and shorten their life.

And there are plenty of other examples of the system failing to bring out the best in the light source. Most luminaires are an assemblage of components from different manufacturers – lamps, control gear, reflectors, diffusers etc. They may be compatible with each other and capable of functioning together but they lack the synergies to enhance each other’s performance. And getting one of the components wrong can have disastrous effects on the whole system.

Other considerations include the quality of the lighting, such as avoiding excessive glare and achieving good colour rendering, as well as the way the lighting is controlled in relation to the way the lit spaces are used.

When all of these influences are considered it’s clear that a more effective and productive approach will be to consider the whole package in the context of where it will be used. This can be illustrated by considering new plasma lighting systems that are now entering the market and how the characteristics of plasma lighting exemplify a ‘whole system’ approach in the hands of the right manufacturer.

High efficiency plasma
High efficiency plasma (HEP) lighting will be less familiar to Electrical Review readers than many other light sources but the technology has been around for many years. It is only recently, however, this technology has been packaged into a practical solution for a wide range of lighting applications.

The HEP system is an electrodeless lighting platform that consists of four integrated elements: a quartz radio frequency (RF) resonator and integral plasma burner (lamp); a transition unit (the system which couples the RF energy from the source into the resonator); an RF source in the form of a magnetron and an AC power supply.

The integrated burner and resonator contain an inert gas and metal halide salts. RF energy resonating within the lamp ionises the gas to form a plasma that combines with the metal halide to vaporise the metal halide salts, emitting an intense, bright light that does not need to be corrected with phosphors.

This bright white light has a colour rendering index (CRI) of up to 95 and the colour temperature can be adjusted by changing the chemical dosing to provide a range from 2,000K to 12,000K.

Furthermore, HEP lighting produces a compact, spherical light source that enables precise focusing of optics at the optimal point. This is in contrast to other light sources where the nature of the light source imposes limitations on the efficiency of the optical system.

As a result of this precision, HEP luminaires deliver an exceptionally high light output with no shadows from the lamp and can be supplied with a range of light distributions for different applications. The intensity of the light makes HEP ideal for applications requiring high light output that are traditionally served by HID light sources, such as high and low bay applications.

This design also means there are no wiring connections to the light source and no electrodes, thus minimising the risk of premature lamp failure.
The HEP combination of light source and optics brings real benefits for the end user. For example, it enables 300W light sources to deliver the same illuminance as 400W HID lamps – or to maintain the same illuminance with fewer luminaires. Either way, the installed electrical load is greatly reduced. HEP luminaires can also be dimmed to 30% of light output.

Crucially, the dimming relationship is linear so that, for example, a 50% reduction in light output results in a 50% reduction in energy consumption (dimming of HID lamps is not linear and does not deliver the same energy savings).

Keeping overall performance very much in mind, HEP lighting is also highly controllable, using RF technology to provide wireless communication between sensors and the control network. The control network uses Internet Protocol (IP) which can be accessed using a range of mobile devices such as smart ‘phones and tablet computers. Each luminaire and sensor has its own IP address for highly flexible control, as well as monitoring of key parameters such as burning hours, light output over time and energy consumption. The system can also be used in conjunction with other IP-based technologies, such as RFID (Radio Frequency Identification) tagging.

So with HEP what we have is a lighting system that exploits the strengths of light source, luminaire and controls in the context of the application. As such it demonstrates the benefits of a ‘system thinking’ approach that reflects the actual performance of the lighting in situ, rather than the theoretical performance of a light source that may be impacted by other factors.

Clearly, like other lighting technologies, HEP is particularly suitable for certain lighting applications and won’t be the best solution for others. The key point I am making is that if we start to think of all lighting like this, irrespective of the light source, we will be taking a positive step towards making the best use of the technologies available to us.