Silicon Valley sets illuminating example of energy efficiency

How LEDs make an energy efficient and environmentally friendly alternative to conventional lighting

provided by Lumileds Lighting

he high-tech industry is not renowned for its concern for energy conservation or the environment. Yet Silicon Valley has come up with a high-tech lighting solution that dramatically cuts down on energy consumption and lasts for up to 30 years without replacement. And all this is based on the same technology that is used for the little red or green indicator lights on your phone, PC or printer: the LED (light emitting diode) or solid state lighting (SSL).

    For some years, SSL has been bright enough to be used in car rear lights and traffic signals. But advances in brightness, or “lumen” output, mean that new “super LEDs,” such as the Luxeon emitter from Lumileds, can provide a realistic alternative to incandescent (bulbs) or halogen lights for in-building, external lighting or flat screen backlights for PDAs and laptops.

    Why is this? Simple: the technology enhancements in SSL devices come hand-in-hand with three compelling arguments for their wider use. SSL devices have very low power requirements, meaning low operating costs and ongoing energy savings. They have exceptional longevity, meaning lower maintenance costs and more flexible deployment. They also stay brighter for longer, a feature known as lumen maintenance.

    So how substantial are the power and cost savings? As a general rule, an incandescent source is 10 to 20 percent efficient in converting electricity to light. Compare this with a SSL device's efficiency of 80 to 90 percent, and it becomes clear that the power savings with LEDs are dramatic.

    There's more to the efficiency story than just wattage input and lumen output. For many indoor applications, it's necessary to shade or filter white incandescent light to a specific color. This means losing half or more of the output intensity because of the shade or filter itself. By contrast, SSL devices produce nearly all their lumens at the desired shade or color.

    To take a specific example, a 12" directional colored spotlamp using a conventional, 140W incandescent bulb generates a white flux of nearly 2,000 lumens. However, the red filter transmits just 200 lm. The corresponding SSL solution, using Luxeon devices from Lumileds, uses 18 LED lamps to produce more than 200 lm of red light while consuming only 14W, including losses in the power conversion circuitry – giving the same light intensity at a tenth of the power. Of course, as an SSL device is inherently directional, achieving broad lighting coverage requires an optical diffusing lens – but the device's efficiency ensures that it still delivers the advantage over conventional lighting.

    These savings could also have a very real environmental impact. In the United States, the potential of SSL for nationwide energy saving has been quantified. Producing electricity to meet the US needs costs $60 billion a year, and around 20 percent of electricity is used for lighting, with incandescent and fluorescent lamps. It's possible to halve this usage for lighting by deployment of SSL in typical lighting applications, saving some $5 billion per year. Of course, the cost of electrical energy is not measured in dollars alone – there's also the environmental cost of carbon dioxide pollution. Add to this the savings in replacement batteries for hand held devices, such as torches and PDAs, and the savings outlined here represent nearly 30 million tons of carbon emission annually from the United States alone.

    The downside to the efficiency of SSL devices is their initial purchase cost. However, when service life is factored in, SSL's cost arguments are persuasive. Most LED vendors cite an operating life of 100,000 hours under typical conditions – or more than 25 years of 12 hours per day working. In contrast, an incandescent bulb is usually rated at 1,000 to 10,000 hours. In many cases, the savings in the replacement unit's cost and labor to replace the bulb easily offset the higher initial cost for SSL. SSL devices are also far more resistant to conditions that result in the early death of bulbs, such as electrical spikes, thermal shock and mechanical stress on the filament. Typically, SSL devices pay for themselves through energy savings over 3,000 to 10,000 hours usage.

    Lumileds Lighting is the world's leading manufacturer of high-power LEDs and a pioneer in the use of solid state lighting solutions for everyday purposes including automotive lighting, traffic signalling, signage, LCD backlighting and general lighting. Lumileds also supplies core LED material and LED packaging, manufacturing billions of LEDs annually. A joint venture between Agilent Technologies and Philips Lighting, Lumileds is headquartered in San Jose, California, with operations in the Netherlands and Malaysia.