book_cover_big.gifAs I said earlier, technology by itself can not solve our global warming problem. On the contrary, sometimes new technologies make things only worse (bio fuels for instance). But there are also many cases where technology certainly can help. A good example is that of solid state lighting (SSL). The light source in SSL is a light emitting diode (LED). Let me explain that a bit.

A LED is a device made out of semiconductor materials (for example Gallium Nitride, chemically noted as GaN). It is basically a diode with which you would normally rectify AC current. But by proper geometrical shaping and the right applied voltages the diode can also generate light. The principle of light generating in the LED (electron-hole recombination) allows that high efficiencies can be achieved because heat generation is strongly reduced compared to gas discharge or incandescent bulbs.

About 20% of all electrical energy is used for lighting. For a very long time we used the incandescent bulbs. They have a very low efficiency of converting the electrical energy into light: less than 2%, thus most of the electrical power going into the lamp is converted into heat. The introduction of fluorescent lamps (where a gas discharge is invoked) improves the efficiency considerable up to about 25% (see for instance  An LED can improve this light/power efficiency with about a factor of two (so up to 50%), but can also exhibit a dramatic increase in life time (say a multiple of 10,000 hours versus 1000 hours for an incandescent bulb). Massive research is still ongoing to improve performance and color characteristics of the LED further. Generally it is expected that in the next 10 to 20 years there will be a major shift towards LED based lighting.

The US Department of Energy hopes that by 2025 the total electrical energy needed for lighting can thus be reduced up to 50%, which is of course a substantial number. This can eventually lead to a 10% reduction in overall electrical power requirement of the society.