What does a light bulb look like? That might appear to be a silly question but the subject of light bulb technology is hot one these days. That's because the federal government is requiring light bulbs to become 30% more efficient by 2012 (law was passed in 2007) and that's driving huge changes in the marketplace
LEDs or light emitting diodes are showing up on store shelves, especially for holiday lighting (read Save Energy with LED Christmas Lights). What are LEDs and where did them come from? They've been around for many years but we didn't know it. For example, LEDs form the numbers on our digital clocks and tell us when our appliances are turned on.
How Do LED Lights Work?
LEDs are different from other light bulbs in many ways. The biggest difference is one versus many bulbs. An incandescent light bulb has a single filament inside one glass bulb. An LED light (left in photo top right) has many tiny lights and each one gives off a small amount of light. We should see the shape of these lights evolve over the years to give us the best lighting possible, along with the aesthetics because we still expect light bulbs to come in certain shapes.
LED lights are made up of many tiny light bulbs that fit on an electrical circuit. They give off light based on electrons moving in a semiconductor material similar to the movement of electricity that powers our computers. What's fascinating is we're already using these lights and don't realize it. There are “visible” LEDs (or VLEDs) like the ones that light up your microwave's digital clock.
The electron's release energy as they move (okay, you only need to get the concept) between orbits and they give off light as they fall from a high energy orbit to a lower energy orbit. The size of the gap between these 2 orbits determines the color of the light given off or “emitted”. A smaller gap gives off infrared light which we can't see, and that's what our remote controllers use. Then there's red light and as the gap between the orbits widens, the light will be green and even larger gaps are blue in color.
Each tiny light is a diode. In an ordinary diode, the semiconductor material will absorb a lot of the light released. LEDs are manufactured specifically to release a large number of electrons outward so we get the benefit of the light. The diodes are surrounded by a plastic bulb that directs the light in a particular direction, forcing the light to bounce off the walls of the bulb until it reaches the end of the bulb which is round.
Benefits of LED Lighting
LEDs have many benefits over conventional incandescent light bulbs. They are far more energy efficient because more than 90% of the energy used by an incandescent bulb is lost as heat. This means they never get hot and they last longer because they don't have a filament that will burn out. They're encased in plastic bulbs which are more durable that incandescent glass bulbs.
The best way to demonstrate the energy savings possible with LED lights is to look at traffic lights which are made up of rows of LEDs, each one the size of a pencil eraser. Many cities are replacing traditional incandescent halogen bulbs which used 50 to 150 watts, with LED units for 3 reasons. The new LEDs save lots of energy, last for years versus traditional bulbs which only last months to provide additional savings and they are brighter. The LEDs are arranged to provide equal brightness across the entire surface, because the light designer has flexibility in how they arrange the individual lights.
LED energy savings are huge. If today's traffic light uses 100-watt bulbs, 24 hours a day, that equals 2.4 kilowatt-hours per day. If a kilowatt-hour costs 8 cents, a single traffic signal costs 20 cents a day or $73 per year to operate. Look at your typical intersection and you'll find 8 signals so a single intersection will cost roughly $600 per year. Big cities have thousands of intersections … so you do the math and you'll see why cities are switching to LED lights, with the potential to save millions of dollars each year.