More than a hundred years old, the incandescent light bulb produces a soft, beautiful glow but 90 percent of the energy it produces escapes as heat. Researchers from the Massachusetts Institute of Technology aimed to bring back the traditional, soft glow of the incandescent light but with the energy-saving capabilities of 21st century technology.
Growing concerns about energy efficiency and regulatory standards have given birth to energy-saving alternatives such as the halogen bulbs, hybrid incandescent, light-emitting diode (LED) and compact fluorescent lamp (CFL). These new light sources certainly provide more light with less energy, yet the light they produce feels cold and hard compared to the soft glow of incandescent bulbs.
MIT physicists created a new incandescent light bulb that keeps thermal energy from scattering. The new design has a conventional light-emitting filament, to which the photonic crystal redirects the dissipating heat back. The filament in turn reabsorbs the heat and converts it to produce light.
"It recycles the energy that would otherwise be wasted," said lead researcher and MIT physics professor Marin Soljacic.
The new light bulb prototype's preliminary efficiency is just 6.6 percent, but this rate is already equal to some of the current LEDs and CFLs. The rate is also nearly double or triple that of current incandescent light bulbs.
Based on computer models, the technology can be refined to achieve 40 percent efficiency. Compact LEDs' energy efficiency ranges between 5 to 15 percent. Fluorescent lights range between 7 to 15 percent while the top-notch incandescent bulbs vary between 2 to 3 percent.
"The results are quite impressive, demonstrating luminosity and power efficiencies that rival those of conventional sources including fluorescent and LED bulbs," commented Princeton University's Alejandro Rodriguez, an electrical engineering assistant professor who was not involved in the MIT study.
The research was published in the Nature Nanotechnology journal on Jan. 11. Soljacic stressed that the research's true potential has yet to be realized as it could have bigger applications beyond light production.
It could be useful in thermo-photovoltaics, an energy-conversion scheme where external heat (such as solar or chemical) is used to make a material glow and produce light. The photovoltaic absorber uses the light used to create electricity. The researchers added that controlling thermal emissions is the study's real contribution.
