LED lighting produces warm white at 200 lm/W from tube lamps
This prototype TLED lamp is twice as efficient as predecessor lamps, basically halving the energy used. With lighting accounting for more than 19% of the world’s total electricity consumption, this innovation promises to drive massive energy and cost savings across the globe. The 200 lm/W TLED lamp is expected to come to the market in 2015 for office and industry applications before ultimately being used in the home.
This is the first time that lighting engineers have been able to reach 200lm/W efficiency without compromising on light quality, with all parameters required to meet the stringent requirements for office lighting. Rene van Schooten, CEO Light Sources & Electronics for Philips Lighting, says, “After being recognised for our quality of LED light (mimicking traditional light bulbs) to creating new experience with Philips Hue (the connected light system for the home), we now present the next innovative step in doubling lighting efficiency.” The TLED lamps are intended to replace fluorescent tube lighting used in office and industry, which currently account for more than half of the world’s total lighting. Conversion to the twice-as-efficient 200lm/W TLED lamps will generate significant energy and cost savings.
In the industry’s effort to break the 200 lm/W barrier, the challenge is to achieve higher efficiency levels at lamp/system level (demonstrated in an end product prototype under real, normal conditions and ready to be incorporated into actual products). Until now, similar efficiency levels have been achieved in a cool and controlled lab setting or on component level, however, when placing the solution in a lamp it could lose up to 50% of its efficiency. Furthermore, to be suitable for real-world applications, the light produced by LEDs must fall within certain technical parameters. If it is too cool or too warm in colour, or lacks a sufficient quantity of red, it will interfere with the way the human eye perceives colour, and will give objects an unnatural tint. Yellow/green emitting LEDs obtained by phosphor conversion, for example, are extremely energy efficient (providing more than 380 lm/W), but practically useless for general lighting purposes.
Comfortable, light for a working environment requires a colour temperature of 3000–4000 kelvins, a colour rendering index of at least 80, and an R9 saturated red level of no less than 20. It is within this context that the magnitude of Philips’ achievement must be understood. Philips’ TLED prototype produces 200 lm/W without scarifying colour rendering index and staying on the black body line [that is, producing light similar to an incandescent source].
There are currently two ways to make white light with LEDs. One method mixes multiple wavelengths of different LEDs to make white light (i.e. RGB); allowing the lighting designer to tune the white light to a specific colour temperature. The second method uses a blue Indium-Gallium-Nitride (InGaN) LED with a phosphor coating to create white light. This is the method that results in the more commonly seen “white LED”.
The new Philips approach combines blue, green and red light to create high quality white light, using aspects of both previous techniques. At the heart of this TLED is Philips Lumileds InGaN LED, recognised as the world’s highest performing blue LED. This LED significantly boosts efficiency from the earlier generation which was at the heart of the L Prize (see below) winning replacement 60W bulb. This high-efficiency source directly provides the blue light component,a nd also excites a phosphor to provide the green element. The white light is balanced by the correct amount of red light from a high-efficiency red LED.
The relative energy efficiency of fluorescent lighting (~100 lm/W) has seen it dominate in office and industrial environments. Homes and shops, meanwhile, have tended to stick with the gentler, warmer light produced by conventional bulbs (operating at around 15 lm/W) or halogen lights (~25lm/W). Philips’ new 200 lm/W LED, however, outperforms all three, and can finally unseat fluorescent lighting as the most energy-efficient technology for general lighting applications.
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