EGEE 102 Energy Conservation And Environmental Protection Efficient Lighting Energy for Lighting We spend about one quarter of our electricity budget on lighting or more than 37 billion annually Technologies developed during the past 10 years can help us cut lighting costs 30 to 60 while enhancing lighting quality and reducing environmental impacts Objectives Lighting principles and definitions Types of lighting and how each works Energy efficient lighting options including daylighting for new or retrofit applications Lighting and Energy Savings Lighting principles and definitions Types of lighting and how each works Energy efficient lighting options including daylighting for new or retrofit applications How lighting is measured The most common measure of light output or luminous flux is the lumen All lamps are rated in lumens The distribution of light on a horizontal surface is called its illumination Illumination is measured in footcandles A footcandle of illumination is a lumen of light distributed over a 1 square foot 0 09 square meter area How much light do we need The task s being performed contrast size etc Ambient Task Accent The ages of the occupants The importance of speed and accuracy Factors Affecting the Quantity of Lamps Required Fixture efficiency Lamp lumen output The reflectance of surrounding surfaces The effects of light losses from lamp lumen depreciation and dirt accumulation Room size and shape Availability of natural light daylight How Much Light In the past spaces were designed for as much as 200 footcandles in places where 50 footcandles may not only be adequate but superior Not only does over lighting waste energy but it can also reduce lighting quality 30 fc of ambient lighting for computer room 50 fc for reading and writing Color Rendition Index The ability to see colors properly is another aspect of lighting quality The color rendering index CRI scale is used to compare the effect of a light source on the color appearance of its surroundings A scale of 0 to 100 defines the CRI A higher CRI means better color rendering or less color shift Types of Lighting There are four basic types of lighting 1 2 3 4 Incandescent Fluorescent High intensity discharge and Low pressure sodium Incandescent Light Filament Light is produced by a tiny coil of tungsten wire that glows when it is heated by an electrical current shortest lives Inefficient Types of Incandescent Bulbs Standard incandescent Most common yet the most inefficient Larger wattage bulbs have a higher efficacy than smaller wattage bulbs Tungsten halogen It has a gas filling and an inner coating that reflect heat Better energy efficiency than the standard A type bulb Reflector lamps Reflector lamps Type R are designed to spread light over specific areas floodlighting spotlighting and downlighting Fluorescent Bulbs filled with an argon or argon krypton gas and a small amount of mercury coated on the inside with phosphors equipped with an electrode at both ends 3 to 4 times as efficient as incandescent lighting Fluorescent lamps provide light by the following process An electric discharge current is maintained between the electrodes through the mercury vapor and inert gas This current excites the mercury atoms causing them to emit non visible ultraviolet UV radiation This UV radiation is converted into visible light by the phosphors lining the tube Fluorescent Bulbs Fluorescent lamps last about 10 times longer than incandescent bulbs Fluorescent lights need ballasts i e devices that control the electricity used by the unit for starting and circuit protection Types of Fluorescents Tube fluorescent Compact fluorescent CFLs CFLs can replace incandescents that are roughly 3 to 4 times their wattage They last 10 to 15 times as long Cost from 10 to 20 times more than comparable incandescent bulbs One of the best energy efficiency investments available High Intensity Discharge HID Lamp High intensity discharge HID lamps provide the highest efficacy and longest service life of any lighting type mercury vapor metal halide and high pressure Theysodium also require ballasts and they take a few seconds to produce light when first turned on because the ballast needs time to establish the electric arc Efficacy This is the ratio of light output from a lamp to the electric power it consumes and is measured in lumens per watt LPW Improved Lighting Controls Snap Switches Photocells Timers Occupancy sensors Dimmers Resources http www eren doe gov erec facts heets eelight html http www misty com don dschla mp html LIGHTING FUNDAMENTALS