A Watt Saved
Is A Penny Earned

Power consumption 5 watts
Lumens Chromacity test report
Color type sunny white
Color temperature 4000 - 4500 Kelvin
Equivalent Source 40 watt incandescent or 20 watt CFL
CRI 80
Rated service life +38,000 hours
Voltage 120 VAC 60 Hz
Certifications UL ( Canada & USA )
Test Report IES LM-79-08
Warranty 1 year
Toxicity None The Mercury Cycle Graphic
Dimensions CAD drawing of 5 watt LED bulb
Packaging Solar Patriot (tm ) LED box

Light emitting diode light bulbs are solid state devices that convert electricity into light wave. The use of color LEDs for white light bulbs was developed primarily in Japan in the late 1990's. The newest generation is however more than just a bright flashlight with multiple leds. Rather, the LEDs are driven at higher currents and closer to the visible light spectrum.

These new "high-power" LED bulbs are very efficient. Most of the electricity is converted into light, not heat. While these bulbs are quite expensive, the quantum reduction in power to lumens ratio and very long service life can justify the finial purchase price.

Example: a 40 watt incandescent light bulb costs 90 cents. The US Department of Energy use the median of 3 hours per day, every day for lighting median estimate usage which is 1,095 hours per year. That is 40 watts x 1,095 hours = 44 kilo watt hour / year x $0.12 = $5.25 yearly cost at the "typical" usage. The service life of an incandescent is given at 3,000 hours.

An expensive LED bulb, costing from $50 to $80, uses 5 watts of power x 1,095 hours = 5.5 kilo watt hours x $0.12 = 65 cents per year ( 1/8 the electricity of the incandescent ). Solid state bulbs have very long service lifes estimated at up to +50,000 hours. Which is 3 hours per day for 45 years.

So, then, Which bulb is really "cheaper" ?

How LED Bulbs Work

LEDs differ from traditional light sources in the way they produce light. In an incandescent lamp, a tungsten filament is heated by electric current until it glows or emits light. In a fluorescent lamp, an electric arc excites mercury atoms, which emit ultraviolet (UV) radiation. After striking the phosphor coating on the inside of glass tubes, the UV radiation is converted and emitted as visible light.

An LED, in contrast, is a semiconductor diode. It consists of a chip of semiconducting material treated to create a structure called a p-n (positive-negative) junction. When connected to a power source, current flows from the p-side or anode to the n-side, or cathode, but not in the reverse direction. Charge-carriers (electrons and electron holes) flow into the junction from electrodes. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon (light).The specific wavelength or color emitted by the LED depends on the materials used to make the diode.

Red LEDs are based on aluminum gallium arsenide (AlGaAs). Blue LEDs are made from indium gallium nitride (InGaN) and green from aluminum gallium phosphide (AlGaP). "White" light is created by combining the light from red, green, and blue (RGB) LEDs or by coating a blue LED with yellow phosphor.

Basics Terms

Solid-state lighting (SSL) technology uses semi-conducting materials to convert electricity into light. SSL is an umbrella term encompassing both light-emitting diodes (LEDs) and organic light emitting diodes (OLEDs).

Light-emitting diodes (LEDs) are based on inorganic (non-carbon based) materials. An LED is a semi-conducting device that produces light when an electrical current flows through it. LEDs were first developed in the 1960s but were used only in indicator applications until recently.

Organic light-emitting diodes (OLEDs) are based on organic (carbon based) materials. In contrast to LEDs, which are small point sources, OLEDs are made in sheets which provide a diffuse area light source. OLED technology is developing rapidly and is increasingly used in display applications such as cell phones and PDA screens. However, OLEDs are still some years away from becoming a practical general illumination source. Additional advancements are needed in light output, color, efficiency, cost, and lifetime.

General illumination is a term used to distinguish between lighting that illuminates tasks, spaces, or objects from lighting used in indicator or purely decorative applications. In most cases, general illumination is provided by white light sources, including incandescent, fluorescent, high-intensity discharge sources, and white LEDs. Lighting used for indication or decoration is often monochromatic, as in traffic lights, exit signs, vehicle brake lights, signage, and holiday lights.

Luminous efficacy is the most commonly used measure of the energy efficiency of a light source. It is stated in lumens per watt (lm/W), indicating the amount of light a light source produces for each watt of electricity consumed. For white high-brightness LEDs, luminous efficacy published by LED manufacturers typically refers to the LED chip only, and doesn't include driver losses.

Correlated color temperature (CCT) is the measure used to describe the relative color appearance of a white light source. CCT indicates whether a light source appears more yellow/gold/orange or more blue, in terms of the range of available shades of "white." CCT is given in kelvins (unit of absolute temperature).

Color rendering index (CRI) indicates how well a light source renders colors of people and objects, compared to a reference source.

Common LED Types and Packages

LEDs come in two basic categories: Low power LEDs commonly come in 5 mm size, although they are also available in 3 mm and 8 mm sizes. These are fractional wattage devices, typically 0.1 watt, operate at low current (~20 milliamps) and low voltage (3.2 volts DC), and produce a small amount of light, perhaps 2 to 4 lumens.

High power LEDs come in 1-3 watt packages. They are driven at much higher current, typically 350, 700, or 1000 mA, and-with current technology-can produce 40-80 lumens per 1-watt package.

Typical Structure of a 5mm type LED

Typical Structure of a high-brightness LED

The difference of the LED lighting and traditional lighting

Incandescent bulbs create light by passing electricity through a metal filament until it becomes so hot that it glows. Incandescent bulbs release 90% of their energy as heat.

In a CFL, an electric current is driven through a tube containing gases. This reaction produces ultraviolet light that gets transformed into visible light by the fluorescent coating (called phosphor) on the inside of the tube. A CFL releases about 80% of its energy as heat.

LED lighting products use light emitting diodes to produce light very efficiently. The movement of electrons through a semiconductor material illuminates the tiny light sources we call LEDs. A small amount of heat is released backwards, into a heat sink, in a well-designed product; LEDs are cooler compare to Incandescent bulbs and CFL.

For further reading:

Hands on Journal of sustainalbe practices and REnewable energy endeavors. Home Power magazine

US DOE Energy Star web site. Energy Star

Compare the lumens to power efficiency: photo of 3 light bulb technologies

Thomas Edison would agree

Lower your Carbon Footprint and keep the Change in your pockets !

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POB 409, Fennville Michigan 49408 USA

FAX: 1 269 236 6186

Tel: 1 269 236 6179

email: info@btfsolar.com

25 Dec 08 copyright by BTF Ltd, All Rights Reserved