The revolution in light sources

LEDs (light emitting diodes) are the light source of the present and the future. They are characterised by their very small size, high efficiency, long life and ease of control in terms of intensity, shade and colour.

They also offer power, low consumption, flexibility of use; unlike discharge lamps, they can be switched on and off hot and are able to emit full brightness immediately after switching on; all characteristics that make them suitable for a very wide range of lighting applications.

Innovative technology

Although they radiate light in the same way as conventional light sources, LEDs have little in common with familiar lamps such as incandescent or gas discharge lamps.

They are electronic chips made up of adjacent layers of special semiconductor components. When an electric current flows through them, LEDs emit light radiation in a process known as 'electroluminescence'.

The luminous efficiency benefits from the fact that the emission takes place in the 180-degree range; moreover, in LED modules, light radiation is emitted in one direction, while thermal radiation is scattered in the opposite direction.

Global establishment

Globally, the use of LEDs has increased considerably in recent years, from a market share of 5% in 2013 to almost half of sales in 2019, with an increasing share of integrated LED luminaires.

Very quickly, LEDs have become the leading light source, a dynamic accelerated in EU countries by the gradual banning of other low efficiency sources such as incandescent and halogen lamps.

The establishment of LEDs has also been facilitated by the continuous fall in prices, thanks to economies of scale generated by very high sales volumes: it is estimated that 38 billion LED-based products have been sold in just five years. In 2019, international LED sales reached a historic milestone of more than 10 billion units of light sources (lamps, tubes, modules) and luminaires.

OLEDs appear on the horizon

While LEDs are point-shaped light sources, OLED (organic light-emitting diode) technology offers a further innovation through its flat light sources. This makes it possible - as with a building material - to incorporate extremely thin OLED layers into other components, opening up completely new ways of developing displays and luminaires.

Already used in designer lighting fixtures, it is estimated that OLEDs will also be increasingly used for large-area lighting in the coming years, thanks to their distinctive characteristics: they provide uniform light with high colour rendering and virtually glare-free; full light output is immediate; dimming is easy by varying the operating current; and there is maximum flexibility in colour control. Last but not least, OLEDs are environmentally friendly as they contain no mercury or other harmful substances and are fully recyclable.

Efficiency as the decisive factor

From an already better track record than other technologies, the efficiency of LEDs has improved further in recent years.

Depending on the model, LEDs available on the residential market have an efficacy of more than 100 lumens per watt, and since 2010 the average efficiency of LEDs has improved by 6-8 lm/W per year.

There are countries where the efficacy of LEDs available for residential use already ranges from 110 lm/W to 130 lm/W; to meet the ambitious Sustainable Development Scenario (SDS) targets, manufacturers are already committed to achieving values of 160 lm/W by 2030.

To understand the improvements being made, the effectiveness of compact fluorescent lamps is around 60 lm/W and that of halogen lamps is below 20 lm/W; incandescent lamps dissipate most of their energy in heat, which explains why they were the first to be banned from the EU market (source: IEA).

Colour variation and light colour

A revolutionary feature is that LEDs can produce any colour of light, unlike conventional light sources.

LEDs come in various colours depending on the type of semiconductor used, which determines the dominant wavelength and therefore the colour of the light emitted.

Moreover, depending on the composition and wavelength of the dominant colour, the white light emitted by an LED can take on different tones.

If there is a high proportion of blue tones in the spectrum, the light is perceived as cold white; the higher the proportion of long-wave colours, the 'warmer' the light appears.

IEC EN 12464-1 gives a numerical reference to the different shades of light which are classified according to their 'colour temperature', expressed in degrees Kelvin (K). As a general rule: the higher the colour temperature, the colder the light. A distinction is made between:

• warm white: temperature below 3,300 Kelvin;
• neutral white: temperature between 3,300 and 5,300 Kelvin;
• daylight white / cool white: temperature above 5,300 Kelvin.

Control advantages

LED luminaires also offer features that alter traditional control and monitoring processes.

In the case of automatic presence-dependent control in office environments, for example, the switch-off delay of fluorescent tube luminaires cannot be too short: a value of at least 15-20 minutes avoids too frequent switching that would damage the tubes.

The advent of LED luminaires makes it possible to shorten the switch-off delay considerably, without any negative effects on the life of the light sources.

Apparecchi a LED dimmerabili

Affinché la regolazione della luminosità sia possibile, gli apparecchi a LED devono essere opportunamente predisposti: a questo scopo, driver e sorgenti LED dimmerabili sono identificabili mediante gli appositi simboli.

Colour rendering ratio

The colour rendering value (generally referred to as Ra) depends mainly on the spectral composition of the artificial light and assesses how well the lighting reproduces natural colours compared to a reference light source.

Values of Ra = 100 denote very good colour rendering: modern LED sources are characterised by very good values.

Single Lighting Regulation

In December 2019, the EU Regulation 2019/2020 came into force, integrating into a single text - the Single Lighting Regulation - all the elements of the Ecodesign legislation concerning lighting products that until then had been covered by different Regulations (EC 244/2009, EC 245/2009 and EU 1194/2012).

The new criteria will come into force on 1 September 2021 and the previous Regulations will be repealed. The main objective of the Regulation is simplification to make the legislation easier to apply and to verify by national authorities.

Taking into account the ongoing transition to LED technology, the aim is to have durable and innovative products in Europe that can be repaired and replaced by light sources.

Art. 4 looks at the issue of removal of light sources and lighting units separate power supply by defining characteristics such as:

• replaceable without permanent damage to the container;
• accessibility for verification purposes;
• removability at the end of its useful life.

It is precisely the evolution towards LED technology that has made it necessary to clarify certain definitions:

• Light source is the electrical component that emits light or, for non-incandescent light sources, is adjusted to emit light (or both). Not to be considered as light sources are LED chips, LED dies or LED packages; products containing one or more light sources which can be removed for testing purposes; parts which emitting light contained in a light source from which it cannot be removed for verification as a light source;

• Containing product' includes one or more separate light source(s) or ballast(s), or both. This is the case, for example, with luminaires which can be dismantled for the purpose of separate light source verification or with household appliances containing one light source. However, if a container product cannot be disassembled to check the light source and the separate ballast unit, it is considered to be a light source;
• Control gear is a device, physically integrated in the light source or not, which converts the mains power supply into the electrical format required by the light source. This may include transforming the supply and trigger voltage, limiting the operating and preheating current, preventing cold start, correcting the power factor and/or reducing radio interference.

With the entry into force of the Single Light Regulation, other light sources are being phased out, in particular:

• from 1 September 2021, halogen lamps with an R7s cap with an output of more than 2,700 lm;
• from 1 September 2023, 18, 36 and 58W fluorescent tubes with G13 lamp caps and halogen lamps with G9, G4 and GY6.35 caps.

The measure also includes higher efficiency thresholds for LED sources and the introduction of requirements to limit the flickering of light sources.

Lifespan and durability

For LED (and OLED) light sources, the EU Regulation 2019/2020 defines 'lifetime' as L70B50, i.e. the number of hours between the start of use and the time when for 50 % of the light source population the output has gradually decreased to less than 70 % of the initial luminous flux. From 1 September 2021 the service life must be indicated on the source itself.

Situation and perspectives

The last few years have seen a great evolution in the field of light sources.

The European Directive 2005/32/EC and the subsequent Commission Regulation EC. After more than 100 years on the market, this meant the retirement of incandescent technology and to a large extent also of halogen technology, a necessary step for sources that dissipated most of the energy used in heat and converted only a small part of it into light radiation.

Sales by source type in the 2010-2030 sustainable development scenario (source: IEA)

This decision has resulted in an estimated 32 million tonnes of CO2 emission reduction for EU countries and energy bill savings of around €11 billion; it has also been calculated that, by 2020, the reduction in electricity consumption would be 80 billion KWh, equivalent to the total needs of 23 million European households, and the annual production of twenty 500 MW power plants.  In the field of technical lighting for large buildings, the transition is also underway; in its sustainable development scenario, the IEA estimates that by 2030 LED technology will account for around 80% of the market, with fluorescent sources accounting for around 20% of the total.

References

Commission Regulation (EU) 2019/2020 of 1 October 2019 establishing ecodesign requirements for light sources and separate ballasts pursuant to Directive 2009/125/EC of the European Parliament and of the Council and repealing Commission Regulations (EC) No 244/2009, (EC) No 245/2009 and (EU) No 1194/2012.