Application of LED Type Lamps in Domestic and Public Utilities and Gain Capability to Run New Small Investments in Rwanda

The Rwandan State-run Energy Water and Sanitation Authority Company (EWSA) is rapidly increasing the number of population having access to electrical power energy. 30% of electrical energy is used in lighting. The incandescent bulbs, compact fluorescent lamp bulbs as well as fluorescent tubes are mostly used to convert electrical energy into light. The said light sources have many disadvantages such as excessive power consumption leading to giant bills of electricity, short life span leading to continuous replacement of lamps, and emission of CO2. Application of light-emitting diode (LED) lamps in lighting in long term suppresses the aforementioned problems resulting into saving of money that will be used for running new small investments.


Introduction
The electrical energy is a pillar of development in all countries all over the world, thus Rwanda government is pressurizing the State-run Energy Water and Sanitation Authority (EWSA) to augment the power generation capacity and the number of population accessing electrical energy.At home and in public utilities, 30% electricity is used for lighting.The luminous intensity varies with areas to be lighted up and the work to be performed in the area.Therefore, the manufacturers have a task to design lamps in different shapes and wattages aiming at meeting the requirements from different users.
Due to different manufacturing technologies, some lamps are source of greenhouse gases emitted in the atmosphere.Incandescent lamps are mostly concerned by this issue as they contain mercury substance [1].This leads to various diseases, problems of respiratory system of human being, etc.
Incandescent bulbs and fluorescent tubes consume too much power, leading to monthly huge bill of electricity.When the electricity customers are not able to pay the consumed electrical energy whereas they still need it for the next month, they pass by the electrical power-meter and steal the energy.If this case is not identified, there is a big loss in terms of money for electrical energy Distribution Company; if the case is identified, the customers using electrical energy in illegal way pay too much money for penalties.
Like Incandescent bulb and fluorescent tube, compact fluorescent lamp (CFL) has short life expectancy; as a consequence all these three types of light source acquire regular replacement due to short life span.
Giant monthly bill of electrical energy in combination with regular cost of regular replacement of lamps puts a curb on the new investments to all users of Incandescent lamps (IL); Compact Fluorescent Lamps (CFL) as well as fluorescent tubes (FT).Light Emitting Diode lamps (LED lamps) possess longer life span estimated at 50,000 hours and are free from greenhouse gas emission [1,2].These new modern lamps are available on market in various shapes and wattages depending on the needs of users.LED lamps are very efficient, with the same electrical energy consumption as the lamps described in previous paragraph; the former lamps output the greater luminous power.
in Rwanda [3].They relatively have low price compared to CFL and fluorescent tubes, but they consume too much electric power and generate heat.The light emitted by the incandescent lamps is not white, thus it can be harmful to human being eyes when they are installed in the reading rooms.For better white light close to daysun-light, fluorescent lamps replace the incandescent lamps.The fluorescent lamps are dominant in public utilities.With evolution of light source technologies, compact fluorescent lamps (CFL) are the 3rd type of light sources used in Rwanda; nowadays is dominating the incandescent bulbs and fluorescent tubes in domestic houses.CFLs are considered as electrical energy saving lamps, their wattage ranges between 8 W and 40 W. As incandescent lamps, CFLs have limited life span leading to regular replacement of these lamps.The Table 1 illustrates the difference between LEDs, CFL, Incandescent bulbs based on life expectance, input power and cost of one lamp of each type.CFL ranging between 11 W and 18 W, Philips brand is considered in this paper.It has a projected life span of 10,000 hours when it is used in domestic activities and costs 2500 Rwandan francs (Rwf) equivalent to 3.965 United states dollar (USD), calculated using data from the website of national bank of Rwanda, 1 USD = 630.602Rwf [4].
The Table 2 illustrates the energy consumed and compares electricity bill payment when incandescent; CFL and LED types are used over a period of 50,000 hours in electrical circuit containing only one lamp.The price of 1 kWh equals 0.25USD in low voltage net work [5].
Table 3 shows that the type of lamps with shorter life span needs regular replacement leading to a huge number of lamps for long term of use.Table 4 shows the total expenses to running a lighting system of only one lamp for three different types over a period of 50,000 hours.Table 5 shows the projected savings if and only if LED bulbs are used for lighting instead of using incandescent or CFL.Copyright © 2013 SciRes.

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From Table 5, it is seen that the savings increase with the number of bulbs installed in domestic or public utility.Another factor that affects the saving is the time, longer period of time of using LED bulbs leads to important augmentation of savings.
The LED bulbs will replace the incandescent and CFL without changing the existent electrical installation and wiring, the brightness measured in lumen must remain unchanged.The Table 6 illustrates the equivalence in lumen output from different bulbs and for different input power.

LED Tube Lights to Replace Conventional Fluorescent Tube
Designed to replace fluorescent tube, LED tubes are available in 8 and 23 watts, which replace conventional 25-watt and 40-watt T8/T10/T12 fluorescent tubes.T-8 LED Tubes are Ideal for Fluorescent replacement and have many advantages over Fluorescent Tubes.LED based light sources, are environmentally friendly and a much longer life than Fluorescent tube.In addition, T-8 LED Tube produces a wonderful pure white light, colors brighter and viewing is easier on the eyes than with conventional fluorescent tubes [6].Table 7 shows the advantages of T-8 LED tube compared to conventional fluorescent tube.Table 8 illustrates the total saving over 25 years in domestic house and public utility containing more than one lamp.

Conclusion
LED lamps replace incandescent, CFL and fluorescent tube without changing the electrical installation [7].If LED bulbs replace incandescent lamp for a period of 50,000 hours, there would be a saving of 743.35 USD.The replacement of CFL by LED lamps during a period of 50,000 hours, there would be a saving of 35.05 USD.When fluorescent tube is replaced by LED tube for a period of 40,000 hours, the saving is estimated at 61 USD.Domestic and public utilities have more than one luminaire; therefore, the saving is multiplied by the

Table 8 . Saving for a whole domestic or public utility.
of luminaires installed in the concerned area.Another factor affecting the saving is time.At long period of using LED type lamps result in considerable saving that would be used for running new small investments. number