Light

• Electromagnetic radiation that has a wavelength in the range from about 4,000 (violet) to about 7,700 (red) angstroms and may be perceived by the normal unaided human eye.
• A source of light, especially a lamp, a lantern, or an electric lighting fixture: Turn out the lights when you leave.
• The illumination derived from a source of light: by the light of the moon.

International Year of Light and Light-based Technologies (IYL 2015) is a global initiative adopted by the United Nations to raise awareness of how optical technologies promote sustainable development and provide solutions to worldwide challenges in energy, education, agriculture, communications and health.

Providing light after dark is one of the most important problems throughout the developing world. Without light after dark, children can’t read or do school work. Many of the light sources available, such as fire or lanterns, give off toxic chemicals that harm eyes, and lungs. In some places, there isn’t any wood or fuel to burn or it is very expensive.

Incandescent lighting – has been in use since ?? More energy-efficient options are replacing this technology, which will be phased out in 2014.

• CFL – compact fluorescent light
• halogen
• LED – light-emitting diode

But there are many places where even these more energy-efficient solutions are too expensive or require a source of electricity that isn’t available in remote locations. Here are solutions that have been proposed. Some are award winners in design competitions. Some are in production. All share the goal of providing light to those who need it where ever and where ever that need it.

• Google Science Fair Finalist Invents Peltier-Powered Flashlight – uses temperature differentials to power its LEDs. Her long-time interest is alternative energy because, ‘[she’s] really interested in harvesting surplus energy, energy that surrounds but we never really use.’ Using Peltier tiles and custom circuitry, her design currently runs for 20 minutes or so and costs $26. –2013.06

• d.light s1 – affordable and durable, solar-powered study lamp designed to withstand hot, dusty, and humid environments, improving children’s lives through better education. The lantern gives high-quality light. The stand rotates to ensure that better solar charging is achieved – and allows for the student to adjust the light. The d.light S1 is durable enough that it can be dropped from a height of three meters or even run over by a car without any impact to its functionality.

• GravityLight – charged by a bag that is filled with around 9kg of material and hung from a cord below the light. As the bag descends, a series of gears inside the device translates this weight into energy, providing 30 minutes of light. The light strength can be adjusted, from strong task lighting to a longer-lasting low-level glow, and two terminals on the front allow it to be used as a generator so it can recharge other devices including radios and batteries. It takes only 3 seconds to lift the weight, which powers GravityLight, creating 30 minutes of light on its descent. For free. This design is great for people who live in less sunny places. They cannot rely on solar power, and need new, cheap technologies to provide them with lighting.

Blue Light Affects Sleep – We know that night-time exposure to blue light keeps people up late. The experimental research suggests that an average person reading on a tablet for a couple hours before bed may find that their sleep is delayed by about an hour. New technologies are providing ways to change screen color throughout the day to reduce the impact on users.

Light bulb revolution – LEDs for residential lighting

Incandescent (hot wire) bulbs have been the standard since Thomas Edison. The amount of light given off is referred to in watts. About 70% of incandescent bulb energy consumption goes off in heat. So a 100 watt bulb is consuming 100 watts of electricity but only a small percentage makes light.

Back in the 1980s, Phillips came out with the first “compact fluorescent lamp” (CFL). It gave the same light output as a 100 watt incandescent but used only 18 watts of power. This was confusing to the consumer because watts and light were synonymous. Bulb manufactures had to advertise the light output as “watt equivalent”, i.e. this 18 watt CFL is the equivalent to a 100 watt incandescent. One of the early objections was the harsh color of the light (color temperature) and that too has been addressed and CFLs are available in softer and warmer colors. The CFLs went down in price as demand increased. Now almost every home in the country has one or more CFLs.

LEDs (light emitting diodes) are becoming popular for residential lighting. LED bulbs are already in the stores but are still expensive and look like part of something NASA would shoot into space. That’s because LEDs operate on very low DC voltage. The bulb includes an electronic power supply with a fancy external heat sink. Although they have been available for 20 years, LEDs are gaining wider use with recent refinement of the light, the cost reduction because of increasing quantities produced and the education of consumers. Get familiar with new terms like lumens and color temperature because the new LEDs are even more efficient than CFLs producing lots of light with much lower power consumption.

What’s the problem?

• Ask – What are some of the problems with incandescent light bulbs? What are some of the objections to CFL and LED light bulbs for residential lighting?
• Imagine – Where else are LEDs being used? What makes them attractive?
• Design, Build – What is the confusion with the “size” of light bulbs? Why are units of measure important?
• Improve – What improvements were necessary to get consumers to buy CFLs and LED light bulbs?

Engineering ideas

• electricity, generator, energy, gears, gravity, watts, lumens, color temperature, light emitting diode LED, compact florescent lamp CFL, DC voltage, power supply, heat sink

Do it
Here are some challenges for you to work on…

• design and build a lighting source that could be used in an emergency