In order to improve the efficiency of the energy’s employment in buildings, the lighting industry tried to reduced the energy consumption using “home automation”, that is the automatic control of devices, and also the LED lighting, which allows the lowering of consumptions and costs. What is a LED?
LEDs (Light Emitting Diode) are semi-conductor devices with optoelectronics properties because they emit light when crossed by direct current: the electrical conversion of the supply’s alternative current into direct current is made by a “driver”, contained into the lamp.
The LED structure is the one of a p-n- junction’s diode: if it works in forward bias, the supply’s voltage let the recombination of electron-hole pairs and that leads to light emission. The effect employed is the reverse process of the photovoltaic cells, which convert sunlight into electricity.
One of the most important LED’s feature is that it has a low resistance to the flow of current, so that the loss for Joule heating are reduced and the efficiency increases. Moreover, the maintenance costs are low and the average life of LEDs is higher than the one of other lighting sources.
Regarding the photometric features, the emitted light is free from infrared and ultraviolet, so LEDs are suitable for the lighting of photosensitive objects, such as ancient works of art or monuments.
Using different semiconductor materials, different wavelengths, equivalent to different colours, can be obtained: the first LEDs produced were red and used as signal light, then they were realized in other colours (yellow, green), whereas the blue LED earned Akasaki, Amano and Nakamura the Nobel prize in 2014. The white light, employed in smartphone’s flash, can be obtained combining blue, red and green light or making blue light filter through a layer of fluorescent substances.
On sale there are a lot of different LEDs’ configurations: single bulbs, on “arrays” or in the format of halogen or incandescent light bulbs. One of the disadvantages of array’s format is the high quantity of heat produced, hard to dissipate because of the small dimension of the device: engineers are trying to employ Peltier cells, devices capable to convert a temperature’s difference into a voltage, using Seebeck effect.
An innovative technology linked to LED are OLED bulbs, realized with organic semiconductor material, which have a superficial development: this feature makes possible a lot of new application, not only in interior design.
The development of LED technology will bring us to an important costs’ lowering and to adopt new solutions in order to recover energy and increase the energy’s saving.