Utilisation of Electrical Energy - Assignment Example

?Utilisation of Electrical Energy Utilisation of Electrical Energy Introduction Artificial lighting is currently used all over the world and its use is predominantly non-homogenous. The most commonly source of power used in powering artificial lighting is the electric power, though, in some under – developed countries, there is a widespread use of fuel based lighting. The average consumption of electric energy around the world is approximately 19 % of the total electric energy produced. This calls for the specialized improvement in the lighting efficiency to save energy which translates to conservation of the environment. Different environment requires different lighting luminaries. The choice of a specific lighting luminary in a given environment depends on several factors. Some of the factors that influence the choice of lighting luminaires in given environments include the availability of natural light, the intensity of light required, the availability of energy sources – in this case electricity – among others. This paper discusses the common discharge luminary in different environments. The chosen environments include office building, an indoor – 5 –a – side – pitch, and Cul-de-sac street lighting Office Building For efficiency lighting in an office building, there must be sufficient source of light. This implies that the lighting luminaries used must have a high light intensity. Since the light is always switched on, the luminary must have the capacity to save energy. Considering this factors among others, the best luminary suited for an office building is Fluorescent Lamp. This is the best choice due to the following advantages: Fluorescent lights are cheap Fluorescent lamps generally have a very good luminous efficacy Fluorescent lamps have a very long lamp life (Ranges from 10 000 hours to 16000 hours). This implies less maintenance costs They come in large varieties of CCT and CRI Fluorescent Lamp Construction, Operation and Associated Circuitry The associated circuitry of fluorescent lamp is shown in figure 1 below. Figure 1. The associated circuitry of a fluorescent lamp. Construction and Operation In a fluorescent lamp, light is predominantly produced by fluorescent powders which are activated by ultra – violet radiation originating from mercury. This type of light source is characterized by low – pressure gas discharge light source. Physically, the lamp is composed of a long tubular pipe that contains an electrode on both sides. This tubular pipe is filled with low pressure mercury vapour which is enhanced with an inert gas, in this case, argon, for starting. The emission of the light occurs in the ultraviolet region. The wavelength of the energy emitted falls in the range of 254 – 185 nanometres. The ultraviolet radiation produced is, then, converted into light by the phosphor layer which is coated on the inside of the tube. Most of the initial photon energy, 65 %, is lost by the dissipation since one ultraviolet photon produces only one visible photon. Moreover, the final spectral of the light that is distributed can be varied. This is by different combinations of phosphors. The CCT (Correlated Colour Temperature) of fluorescent light varies from 2700 Kelvin to 6500 kelvin. On the other hand, the colour rendering indices varies from 50 to 95. Different fluorescent lamps have different luminous efficacy depending on their construction. The latest fluorescent lamp has a luminous efficacy of 100 lm/W. This excludes the ballast losses. The operation of a fluorescent lamp is shown in figure 2 below. Figure 2. The operation of a fluorescent lamp. Fluorescent lamps have an ever increasing current. This is harmful since it can destroy the lamp (National Industrial Pollution Control Council. Electric and Nuclear Sub-Council, United States. Dept. of Commerce, 1972). Thus, to correct this, it is designed in such a way that it limits the lamp current. This is seen in instances where it displays the negative voltage to counteract the ever increasing current. In staring and operating a fluorescent lamp, an electronic gear, which incorporates all the equipment, is used. In spite of the advantages of fluorescent lamp stated above, it has some limitations. They include Presence of mercury which is considered an environmental hazard Depreciation of light output with age Ambient temperature which affects the light output. The advantages of the lamp supersede the disadvantages, and thus it’s suited to operate efficiently in an office building. An Indoor 5-A-Side Pitch According to the football association (Football Associaton, 2005), the lighting requirements for an indoor 5-a-side pitch are indicated in the table 1 below Table 1. The lighting requirements of an indoor 5-a-side pitch retrieved from (Football Associaton, 2005). Considering the above stated requirements together with cost, light life among other considerations, mercury lamps are best suited to perform efficiently in this environment. This is due to the fact that the above stated lighting environment requires moderate colour rendering which can be produced by mercury lamps efficiently at low costs. Fluorescent Lamp Construction, Operation and Associated Circuitry The associated circuitry and construction of fluorescent lamps is as shown in figure 3 below. Figure 3. The construction of a fluorescent lamp. Construction and operation of mercury lamps The heart of the lamp is composed of an arc tube that is fabricated with quartz. Also it is fitted with tungsten electrode which is deposited at both ends. In the tube, mercury vapour is partially filled with argon. Argon is essential since it acts as a buffer in carrying the discharge in the process when the lamp is warming up. This results in the production of heat in vaporizing the mercury, thus, bringing it into discharge. During operation, the production of light is by an electric current that passes through the mercury vapour. An arc discharge that is contained in mercury vapour which is at a pressure of 2 bars produces very strong spectral lines with its visibility visible in wavelengths of between 404 nanometres and 435.8 nanometres. The resultant lamps have a luminous efficacy of 40 – 60 lm/W, and CRI that ranges from 40 to 60. The CCT is 4000 K and the lamp life of mercury lamps is 12000 hours. Cul-de-sac Street Lighting The lighting luminary in this environment should possess the following characteristics: Should be very efficient that it saves energy Should have a smaller size to allow it fit in several fixture types Should have a better bulb life Considering these factors among others, the best suited type of luminary to work in such an environment is the High Pressure Sodium Lamps (HPS lamps). This type of light luminary fulfils the above stated requirements efficiently. Construction and Operation of High Pressure Sodium Lamps High Pressure Sodium lamps have a CRI ranging from 20 to 30. It has a lifetime of 24000 hours and it also has 80 – 140 lumens per watt. The use of this type of lamp is suited for municipal lighting, high bay lighting, outdoor lighting, and predominantly street lighting. In its construction, High Pressure Sodium lamps consist of a narrow arc which is supported by a frame. This setting is enclosed in a bulb. The bulb is designed in such a way that it has a very high pressure inside to increase its efficiency. Gaseous forms of sodium, xenon, and mercury are used inside the bulb for the purposes of light production. Aluminium oxide is used in making the arc tube. Aluminium oxide is preferred over other compounds since it has the ability to resist corrosion, thus it can withstand the corrosive effect of the sodium presence in the bulb. The lamp is lit by the pulse start mechanism. In this mechanism, a built-in igniter which is built into the ballast initiates and sends a pulse of high voltage via the arc tube. This pulse results into the production of an arc through the xenon gas. As the xenon lights, the lamp turns sky blue. The flow of the current results into the arc heating up and consequently, mercury vapour lights, and this gives the lamp a bluish colour. As the lamp heats, other material vaporizes, and sodium is the last material to vaporize. As the sodium vapour vaporizes, it strikes an arc over 240 C. To create a more white light, the sodium compound is mixed with other impurities. Besides facilitating the lighting of the lamp, the mercury presents help in blue spectrum light into the sodium light which is purely yellow. The challenge of the lamp is to maintain the vacuum inside. Oxygen together with other gases such as nitrogen should be prevented from entering in. To facilitate this, the gutter is used to keep the vacuum stable by introducing mechanisms by which oxygen and other unwanted gases are sucked out. The amalgam reservoirs at the ends of the of the arc tube store the sodium. The Figure 4 below shows the electronic ballast circuit for High Pressure Sodium Lamps. Figure 4. The electronic ballast circuit for a high pressure sodium lamp. Task 2 Figure 5. The lighting scheme and luminary layout. The lighting system is very efficient since the luminaires used have a high efficacy and high luminous intensity. References Football Associaton. (2005, February). Guide to indoor and outdoor areas for small sided football mini-soccer and futsal. Retrieved from http://www.boysbrigadewales.org.uk/wp-content/uploads/2013/04/5AsideRules.pdf National Industrial Pollution Control Council. Electric and Nuclear Sub-Council, United States. Dept. of Commerce. (1972). Fluorescent lamps: the environmental compatiblity of fluorescent and other mercury-containing lamps; sub-council report. NIPCC. Read More