Like a LED balloon
Although this may sound complicated, the manufacturing process to create LEDs is well understood. And – like all processes involving semiconductors – it is coming down in cost all the time, and at predictable rates. In fact, the rates are so predictable that there is even a law – called Haitz’s law – that describes the fall. This states that every decade, the cost of producing useful light will fall by a factor of 10, whilst the amount of light generated increases by a factor of 20. Haitz’s law, first proposed in 2000 by now-retired scientist Roland Haitz, is considered to be the LED equivalent of Moore’s Law – a computer industry axiom which states that the number of transistors that can be squeezed on to a computer chip at a fixed cost will double every 18 or 24 months.
This is crucial for LEDs, which are currently around ten times more expensive than incandescent bulbs. Yet decreasing costs are only one part of the excitement.
In traditional incandescent bulbs, only about 5% of the electricity used is converted into light, while the rest is wasted as heat – the bulbs are therefore little more than tiny electric heaters which give out light as a fortuitous side-effect. A CFL tends to be around four times as efficient as a 60W bulb, but LEDs can be up to ten times as efficient.
As a result, the potential energy savings in the future from LED lights are enormous. Although the United States currently has no plans to phase out all incandescent bulbs, the US Department of Energy estimates that if the whole country switched to LED lighting over the next 20 years, this could result in energy cost savings of $120bn, reduce electricity consumption for lighting by a quarter, and reduce carbon emissions by 246 million metric tons. In China it is a similar story, where its central planning agency expects to save 48 billion kilowatt hours of electricity every year, once China's phase-out is complete, and hopes to reduce annual carbon emissions by 48 million tons.
And LEDs have another environmental trick up their sleeve: they last far longer than most other light sources. Incandescent bulbs last around 1,000 hours before burning out, while comparable CFLs last 8,000 to 10,000 hours. LEDs do not burn out in the same way but simply get dimmer over time, and when they fall to 70% of their initial brightness their useful life is considered over. A good LED light should have a useful life of between 30,000 and 50,000 hours, and maybe up to 70,000 in the future, meaning less are thrown away and less are made.
But LEDs do not have it all their own way. One of the biggest challenges they face is the quality of the light that they produce. LED bulbs tend to generate a stark, cold light – a world away from the warm, yellowish light we are used to from incandescent bulbs. This can cause illuminated objects to take on unnatural colours, which the human eye can find uncomfortable or just odd.
This is the result of manufacturers building bulbs from efficient blue LEDs. To create a “white” light, a phosphor coating is applied that emits other colours in the visible spectrum. When these mix – like shining light through two prisms – they produce a white light. Crucially, however, there are “gaps” in the spectrum, and it is these missing chunks that cause the harsh effect.
To get around this, scientists and manufacturers are now working on using a combination of blue LEDs and less efficient red ones to create a warmer glow. Others are working on new phosphor recipes that can convert blue LED light to more parts of the visible spectrum, effectively filling in the gaps.