Factors in Choosing a Quality Lighting Luminary for a Building - Assignment Example

Name Instructor’s Name Utilisation of Electrical Energy 25 March 2018 Assignment 1 – Lighting Task 1 In choosing a quality lighting luminary for a building, several factors which enhance efficiency and aesthetics have to be considered. This selection is based on efficacy, life and lumen maintenance, colour rendering index, colour temperature, availability, switching, cost light loss factor, utilisation factor and dimming capacity. In selecting discharge lighting luminary for the given environments, all these factors were taken into consideration. a) An office building An office building requires a lighting system that has a high colour rendering, efficacy and glare ability. The best lighting system to produce this system is a low pressure mercury lamp otherwise known as fluorescent lamp. Construction of fluorescents A fluorescent lamp refers to a low pressure mercury lamp powered by an electric current. In construction of a fluorescent lamp, a glass tube is filled with a mixture of argon and mercury vapour at low pressure. The inner side of the tube is coated with phosphoric coating. The basic structure is as in the diagram below. Operation When the light is switched on, current flows through the electrodes in the tube and as a result, it passes through the gas which is contained between the electrodes. The current flow results in the emission of Ultraviolet light from the mercury arc which is converted to visible light by the fluorescent coating found on the inner side of the tube. Associated Circuitry The circuit contains a starter switch (which is a bi – metallic strip), an inductor, a small radio suppressor capacitor and a power correction capacitor that is connected across an AC or DC power supply. The power supply provides the necessary current required to operate the lamp b) An indoor 5-a-side pitch Indoor pitches require much lighting that produces less heat. The best and common discharge lighting luminary in this environment is a High – pressure Mercury Lamp Construction This type of lamp contains an outer glass envelop that is filled with nitrogen gas. The nitrogen gas acts as a coolant in that it keeps the arc tube at correct temperatures. It also contains a quartz discharge tube which is filled with argon gas, and some small amount of mercury which is in liquid form. The either ends of the discharge tube contain two electrodes and a secondary electrode which begins the discharge. The secondary electrode is connected in series with a 10 – 30 Ω resistor. Operation associated circuitry At first there is no current flow when the lamp is powered on. Then the power supply voltage appears across the main electrode and between one of the mains electrodes and the secondary electrode through the series resistor[BBt08]. Consequently, there is production of an arc between the secondary and the main electrode resulting in occurrence of ionisation. The pressure and the heat build-up results in the formation of more high pressure and vaporised arc between the electrodes c) Cul-de-sac street lighting For this type of environment, high – pressure sodium lamps are used Construction It is made of a sintered aluminium oxide tube that is being supported by two rods. The inside of the glass is coated with white material that facilitates spreading of the light. There is a combination of sodium and mercury along with xenon or argon gas in the gas tube[BBt08]. Operation and Associated Circuitry of high – pressure sodium lamps Voltage of high value is passed across the lamp to strike the arc. After about 5 minutes, the lamp goes to full brightness. Task 2 Number of lamps is given by Dividing the office into two rectangles Area (1) of working surface is given by =352.5 Area (2) of working surface is given by =33.25 Illuminance = 405 lux Utilisation Factor = 0.73 The common light loss factor is 0.8 Each lamp delivers a luminous flux of 2750lm The number of lamps is: From the calculated values, the arrangement for the 3.5m by 9.5m rectangle is 3X3 and the arrangement for the 15 by 23.5 rectangle is 11 x8. This is indicated in the diagram below. The design is good since the lighting system produces sufficient lighting for the office while at the same time facilitating conservation of energy Works Cited BBt08: , (B & B training Associates Limited), Read More