Question

Subject : Engineering Economics.

Presentation Topic: Feasibility study on Energy saving bulb (led) with case study and proof with calulations use engineering economics concepts

Slides: 10  

Answer 1

This analysis examines the potentials of saving electric energy in school lighting by replacing the existent systems of lighting with more adequate ones which are based on LED technology. Our primary goal is to present the methodology used in this analysis since it can be used to determine potential savings in lighting systems of any public building. We have performed the detailed analysis of nine high schools located in Kragujevac, Serbia. The first step was to collect the data about the numbers and types of systems utilized, as well as about the habits of their users. This has revealed the share of electricity consumption for lighting in total electricity consumption. The replacements for each existent light source have been proposed taking into consideration the projected value of light flux depending on the purpose of each room. The calculations of potential savings through the replacement of lighting systems have been conducted taking into consideration not only the savings in electric energy but also the savings made through the maintenance cost reduction. Based on the results, the potential savings range from 53-62% while the payback period for the analysed schools is about 4 years in average.

Methodology

The methodology for determination of potential energy savings and cost savings when the existent lighting sources are replaced with adequate LED lighting sources. The first step was to collect the data from monthly electricity bills for the time period of at least one year including the system for charging electric energy consumption (tariff classes), total electric energy consumption and total costs of electricity. Besides, this phase of analysis includes detailed inspection of all buildings under investigation and interviews with users in order to obtain data about the numbers and types of lighting systems as well as the habits of their users. This is important in order to evaluate time engagement of lighting systems in buildings.

The electric energy consumption for lighting on yearly basis must be calculated for each type

of the lighting system taking into consideration the differences in nominal power of light source as

well as the fact that light sources are not equally engaged during one year. Based on the collected data

about the number, power and type of lighting systems, as well as the working hours of each light

source, the annual electric energy consumption for lighting is calculated with following equation:

ECL = Sigma (i=1 to n) Sigma (j=1 to m) NLHj . Pj . Hji

Where:

ECL [Wh/year] – annual electricity consumption for lighting

NLHj [-] – number of light sources of j-type of lighting

Pj [W] – nominal power of light source of j-type of lighting

Hj [h/year] – the estimated annual working hours of light source of j-type of lighting in i-tariff class

n [-] – number of tariff classes

m [-] – number of lighting source types

The share of energy consumption for lighting in total electric energy consumption

[%]POL is:

POL = ECL/ AEC . 100

Where AEC [Wh/year] is annual electric energy consumption.

Based on the values obtained for electric energy consumption for lighting, data about tariff

systems of charge (category, class) and the price of electricity, the cost ofelectric energy used for lighting CEL.

The next step would be to take into consideration the maximum usage of one light source in

rooms by using daylight control sensors. The installation of light sensors and presence sensors can

reduce the working hours of the lighting systems and electricity consumption also prolonging lifetime

of the light source.