Sustainability in Lighting

Artificial lighting is a major energy consumer, consuming nearly 25% of all the US’s energy, so reducing the amount of energy needed for lighting will reduce the over all need for energy. By replacing inefficient lighting types with more energy efficient types can save a household up to $200 a year. Light efficiency is defined as the ratio of light emitted by a device and the amount of input it consumes.

The most energy efficient lighting type is the most abundant of all: sun light. Building houses to better utilize the light and energy from the sun can reduce the need for artificial lighting and electricity dramatically. A Passive Solar Home harnesses the energy and heat from the sun without the use of mechanical devices, such as solar panels.

Aperture (Collector)

The large window area through which sunlight enters the building. Typically, the aperture should face within 30 degrees of true south and should not be shaded by other buildings or trees from 9 a.m. to 3 p.m. each day during the heating season.

Absorber

The hard, darkened surface of the storage element. This surface—which could be that of a masonry wall, floor, or that of a water container sits in the direct path of sunlight. Sunlight hits the surface and is absorbed as heat.

Thermal mass

The materials that retain or store the heat produced by sunlight. The difference between the absorber and thermal mass, although they often form the same wall or floor, is that the absorber is an exposed surface whereas thermal mass is the material below or behind that surface.

Distribution

Solar heat circulates from the collection and storage points to different areas of the house. A strictly passive design will use the three natural heat transfer modes—conduction, convection, and radiation. Fans, ducts, and blowers may help with the distribution of heat through the house.

Control

Roof overhangs can be used to shade the aperture area during summer months. Other elements that control under- and/or overheating include electronic sensing devices, such as a differential thermostat that signals a fan to turn on; operable vents and dampers that allow or restrict heat flow; low-emissivity blinds; andawnings.

            Compact Florescent lighting’s main purposes are high electrical efficiency and durability. In a CFL, an electric current is driven through a tube containing argon and a small amount of mercury vapor. This generates invisible ultraviolet light that excites a fluorescent coating (called phosphor) on the inside of the tube, which then emits visible light.

 Compact Fluorescent Light bulb (CFL):

· can save more than $40 in electricity costs over its lifetime

· uses about 75% less energy than standard incandescent bulbs and lasts up to 10 times longer

· produces about 75% less heat, so it's safer to operate and can cut energy costs associated with home cooling

                  A light-emitting-diode lamp is a solid-state lamp that uses light-emitting diodes (LEDs) as the source of light. An LED consists of an anode and cathode composed of different materials. When electrons flow from one to another they change state, releasing energy in the form of light.

LED bulb:

· Uses at least 75 percent less energy and lasts at least 15 times longer than an incandescent bulb.

· Has efficiency as good as or better than fluorescent lighting.

· Turns on instantly – there is no warm-up time.

· Allows for precise placement of light due to the directional nature of LEDs.

· Produces far less heat than an incandescent, which can reduce air-conditioning needs.

Is durable – performs well outdoors and in cold temperatures.

              High Intensity Discharge lamps offer maximum energy efficiency, high light output, and extremely long life.  Delivering far more light per watt than incandescent lamps, they can be use to achieve huge savings on electricity.

              HID lamps work in a similar fashion to fluorescent lamps.  Current flows between electrodes in an arc stream through a gas, causing it to give of light.   Unlike fluorescent lamps, however, HID lamps are "point sources" of light, and can be used in fixtures that provide for "optical control," or focusing, of the light.

            Cambridge, Massachusetts dog park now has a lamp powered on methane. The methane comes from the methane digester that turns dog poop into methane with the use of special bacteria. Dog owners collect their dog waste in a special biodegradable bag and throw it into the digester - an air-tight cylindrical container, where the dog feces are broken down by anaerobic bacteria. A byproduct is methane, which can then be released through a valve and burnt as fuel. In this case it is being used to power an old-fashioned gas-burning lamppost in a park.