The goal of designing lights is to produce lots of visible, natural-looking warm light with very little electricity. This magic combination is very hard to achieve technically
Two lights which are long-lasting and efficient are compact fluorescent lights (CFL) and light-emitting diode (LED). CFLs uses excited mercury to produce invisible ultraviolet-light which is then converted to visible light by phosphors which coat the light tube. The problem with CFLs is that they need special safe disposal because of the hazardous mercury they contain.
LED lights use the same high-tech of technology as silicon-based computer chips and photovoltaic solar cells. These use a sandwich of two kinds of chemically treated silicon: electron donating “N” silicon material and an electron accepting “P” silicon. LEDs produce light when “P” silicon accepts an electron originating from “N” silicon.
LED technology is still emerging. The very high price of LEDs is falling and improved designs are constantly being developed.
A light emitting diode (LED) is used as an energy-efficient, long-lasting replacement for traditional incandescent bulbs. It costs 20 cents on the dollar to run as compared to an incandescent bulb.
A LED is a member of the family of electrical devices using silicon semi-conductor technology. These include computer circuits and photovoltaic panels.
An LED consists of a sandwich or two types of treated (doped) silicon. The “N” negative side of the silicon sandwich is an election donor. The “P” positive side is an electron acceptor. The “N” and “P” sides have electric contacts and are connected together to form an electrical circuit.
When a LED lamp is switched on, electrons migrate from the “N” electron-donor side to the “P” electron-accepter side. When an electron is accepted by a “P” side atom (i.e., falls into a positively charged hole) the electron loses energy. This lost energy is shed from the atom as a photon of visible light.
The reverse of the process occurs in a photovoltaic cell: Light dislodges electrons from the “N” side which migrate to the “P” side. This migration creates an electrical current.
Home lighting typically accounts 2,000 kWh of electrical usage annually– 11% of the home energy budget. A switch of some or all of home lighting to LEDs can be cost effective means of moving towards a zero-energy home.
Annualized costs for both LED bulb-replacement and electricity are much lower than for incandescent bulbs. A scenario below, in which a home is switched to LEDs results in a saving of more than $200 per year. This amounts to an annual return of investment of over 20% on the cost of bulb replacement over a 34-year replacement cycle.
The disadvantage is switching a home entirely to LEDs is that the technology is not mature: The prices are still high and lighting designs still not fully refined. LEDs excel at task lighting when high quality, high intensity light is needed such as in a home office or kitchen.
A compact fluorescent light (CFL) is used as an energy-efficient, long-lasting replacement for traditional incandescent bulbs. It costs 25 cents on the dollar to run as compared to an incandescent bulb.
A CFL is a miniaturized version of the familiar long-tube fluorescent. It has a threaded end which can be screwed into a traditional light socket. Both compact and the long-tube fluorescents use a non-flickering, electronic ballast is to regulate the current so that the lamp runs efficiently and does not overheat.
Fluorescent tubes, which contain mercury and phosphors, produce visible light by a multi-stage process. Electricity excites the mercury vapor in the fluorescent tubes. Excited mercury atoms eject loosely held electrons from their outer orbit. When the electrons subsequently return back into orbit, they shed some of their energy in the form of invisible, short-wave ultraviolet (UV) light. The fluorescent tube is efficient because mercury vapor emits lots of UV light.
The UV light, emitted by the mercury atoms, is converted to visible light by a coating of phosphors on the surface of the fluorescent tube. Earlier versions of phosphors produced light too bluish for consumer satisfaction. Modern tubes have phosphors which produce warm light, similar to that of incandescent bulbs.
Mercury-laden CFLs should not be disposed of in the trash, but taken to a recycling center. Check with your local government recycling program for local CFL recycling options.
Home lighting typically accounts 2,000 kWh of electrical usage annually– 11% of the home energy budget. A switch to CFLs is arguably the best bargain in moving towards a zero-energy home.
Costs for both CFL bulb-replacement and electricity are much lower than for incandescent bulbs. A scenario below, in which a home is switched to CLFs, results in a saving of more than $200 per year. This amounts to an annual return of investment of over 200% on the cost of bulb replacement over a 7-year replacement cycle!!!
Like DwellGreen on Facebook
