Techno-economic and environmental viability of retrofitting in public multi storey buildings

International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 12, December 2019, pp. 527-540, Article ID: IJMET_10_12_050
Available online at />ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication

TECHNO-ECONOMIC AND ENVIRONMENTAL
VIABILITY OF RETROFITTING IN PUBLIC
MULTI-STOREY BUILDINGS
Gbadega Peter A
Department of Electrical Electronic and Computer Engineering,
University of KwaZulu-Natal, King George V Avenue, Durban, 4041, South Africa
Inambao Freddie L
Department of Mechanical Engineering,
University of KwaZulu-Natal, King George V Avenue, Durban, 4041, South Africa
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ABSTRACT
Multi-storey buildings are becoming a common feature in several campuses and
major cities in Nigeria. This study investigated the pattern of energy consumption of
an existing multi-storey building, namely, the Senate building, University of Lagos. In
this case study, the electrical facilities of the Senate building of University of Lagos
were audited with the aim of improving the energy efficiency of these facilities. The
aim of this study was to assess the pattern of energy consumption and at the same time
investigate the cost effectiveness and environmental-benefit analysis of retrofitting, in
a multi-storey building. The cost effectiveness of different lighting technology
alternatives were considered. The present lighting technology and four other energy
efficient lighting technology alternatives were compared based on their electricity use.
CO2 emissions associated with the Senate building of the University’s electricity use
would be reduced by about 10 %, if the technology alternatives that saved the most
electricity were installed. From the economic analysis point of view, T8-E and CFL
were seen to be cost-effective due their low lamp cost price and life cycle cost

compared to other lighting technology alternatives. This project recommends the
adoption of standards, energy efficiency and conservation measures to ensure
building sustainability within Universities.
Keywords: Energy consumption, cost effectiveness, energy efficiency, economic
analysis, conservation measures, lighting technology.
Cite this Article: Gbadega Peter A and Inambao Freddie L, Techno-Economic and
Environmental Viability of Retrofitting in Public Multi-Storey Buildings.
International Journal of Mechanical Engineering and Technology 10(12), 2020, pp.
527-540.
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Gbadega Peter A and Inambao Freddie L

1. INTRODUCTION
The most important aspect of the world is energy. Its functions include powering various
types of vehicles, heating and cooling of homes and lighting of the cities as well as many
other applications. Everything done by people is linked to energy source in one way or
another [1, 2]. Since the industrial revolution in the 18th and19th centuries the main source of
energy has been fossil fuels. The success of many inventions are as a result of the substantial
contribution of the various types of fossil fuels. This is mainly due to relatively high-energy
content and flexibility in how they can be used. Regrettably, fossil fuels are non-renewable
and, more significantly, owing to their emission of harmful gases to the atmosphere, they
cause pollution [3, 4]. To reduce the effect of these gases, researchers are seeking to
determine the effectiveness of alternative energy sources to meet energy demands. Thus,
renewable energy sources are being considered, harnessed and transformed into usable forms

of energy. Another way to reduce these emissions is to efficiently and effectively make use of
the available energy in order to reduce the environmental effect of energy wastage.
Consequently, it is advised that techniques for energy efficiency improvement be devised and
subsequently applied to multi-storey buildings. This can significantly reduce their energy
demands as well as their carbon footprint [5, 6]. Furthermore, improving the energy efficiency
of homes, businesses, schools, governments, and industries is one of the most constructive,
cost-effective ways to address the challenges of high energy prices, energy security and
independence, air pollution, and global climate change [7].
The most damaging environmental consequence of fossil fuel combustion is the
production of CO2, a gas which affects global heat balance, and contributes to global warming
[8, 9]. In addition to environmental consequences, the rise in energy use is expensive because
more plants need to be built to serve the loads [10, 11]. For many years, it has been suggested
that a cost effective means to reduce the amount of energy used by the human population
would be the adoption of energy efficient technologies, particularly within the industrial and
commercial sectors [10, 11]. Studies indicate that improvements in energy efficiency will
reduce local and regional energy related environmental challenges, and that the widespread
adoption of energy efficiency measures will result in significant reductions in CO2 emissions
globally [1, 4, 8]. Energy wastage is rampant in society today, hence, this study investigates
how energy can be used efficiently to reduce wastage and greenhouse gas emissions. Many
studies have been carried out on the economic viability of Energy Efficient Measures (EEM)
in developed countries. In developing countries such as Nigeria, indiscriminate energy-use
still exists even in new buildings. This is due to the ignorance of consumers and energy
providers on the advantages of EEM. Therefore, this study evaluates the cost effectiveness
and environmental benefits of applying EEM in an academic environment [12, 13]. The aim
of this study is to assess the pattern of energy consumption and at the same time investigate
the cost effectiveness and environmental-benefit analysis of retrofitting, in a multi-storey
building.
This paper is organized in the following way: section 2 is an overview of the mitigation
devices for minimizing energy consumption patterns. Section 3 describes the results and
analyses of various energy management schemes and the economic analysis of various

technologies for cost effective energy consumption. Section 4 concludes the study.

2. MITIGATION DEVICES FOR MINIMIZED ENERGY
CONSUMPTION PATTERNS
The goal of energy efficiency, energy management and energy conservation is to reduce the
consumption of energy. This is usually accomplished by means of data analysis of an energy
audit. Evaluation of energy saving measures is done by creating a list of cost-effective energy

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Techno-Economic and Environmental Viability of Retrofitting in Public Multi-Storey Buildings

conservation measures and determined by using both economic analysis and energy savings
analysis [12, 14]. Firstly, a predefined list of energy efficiency and conversation schemes is
prepared, after which the energy savings due to the various energy conservation measures
related to the building are estimated [5]. The installation or initial costs needed to employ the
energy conservation measures are evaluated and the cost effectiveness of individual energy
conservation measure are explicitly assessed. Steps are then taken to minimize energy
consumption such as lighting improvements, which involves retrofitting of lamps and
utilizing of lighting control systems. Following an initial review of similar projects paying
attention to the challenges faced, execution was logically broken down to the following:
energy audit, demand side management, energy efficiency, cost-effectiveness and
environmental impact (benefits) analysis of energy efficiency measures (schemes), energy
conservation [10, 13].

2.1. Methods Adopted to Carry out the Research

For the purpose of fair presentation and clear understanding of this exercise, this subsection is
concerned with the method of collecting, classifying and processing information gathered
from a field survey. To evaluate the energy consumption pattern in a multi-storey building, a
case study of the University of Lagos Senate house is presented. A walkthrough audit was
implemented to [19, 20]:
 Take note of the kind of lighting being used by the consumers.
 Observe the kind of air cooling systems used in the building.
 Acquire the power ratings of each equipment (theoretical values) and measure the
actual amount of power they consume (experimental value).
Evaluation of the amount of power consumed by the electrical motors (lifts) on a daily
basis in the building was carried out. The energy consumption of lifts typically represents 3%
to 8% of the total energy consumption of buildings, depending on the structure and usage of
the building, the type and the number of lifts [9-11].
2.2.1. Categorization of Rooms
Table 1 Room categories and the 20 room types identified in the energy survey
Room categories
Group 1
Group 2

Group 3
Group 4

Room types
Office
Portal’s unit
Senate house maintenance annex
Council affairs unit
Information unit
Maintenance unit
Electronic data processing unit

Legal unit
CITS (annex)
Reconciliation unit
Student’s records annex
Enquiry unit
Ground floor fittings
Building basement
Expenditure control
Staircase and lobby

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Gbadega Peter A and Inambao Freddie L
Group 5

Senate chamber
UNILAG radio
Conference room
Security unit

A survey of every room in the Senate building of University of Lagos was carried out to
know the number of 1.2 m fluorescent fixtures, incandescent lamps, LED lamps, cooling
technology, heating equipment etc. During the course of the survey, information about the
hours of operation of these electrical appliances were gathered. The rooms were divided into
categories, containing 20 types of room, which were identified within the study buildings as
shown on Table 1. Therefore, based on the operating hours per day, room categories 1 to 5

were defined.
2.2.2. Estimation of Electricity Consumption and Cost
Energy consumption of the light fittings is the product of the number of retrofits, power
consumption and operating hours of a lamp. The annual energy consumption or the amount of
energy consumed yearly by existing lighting technology was computed mainly for individual
room categories. The estimates are expressed as follows:
(

)

(1)

Where
= The number of fixtures.
= The power used per fixture in watts.
= The number of operating hours per year [10].
The results for different fixtures were cumulated to estimate a total kWh/yr value for each
room category. The cost of the electricity used by existing fixtures was also calculated for
each of the five room categories within the buildings using Eq. (2). Electricity cost was
calculated by estimating the percentage of operating hours, demand charge and annual fixed
charge. An example of the calculation is shown below for a particular room category:
(

) *(

)+

(2)

Where

= The annual fixed charge.
= The number of operating hours per year.
= The electricity charge.
At the case study location, the peak charge is N13.61 /KWh. The total electricity costs are
multiplied by N1.3210 to account for the demand charge. The electricity consumption and
cost was calculated for four energy efficient lighting technology alternatives. These four
technology alternatives were chosen due to the fact that they are easy to install, and have the
potential to save significant amounts of energy. For each of the four alternatives, Eq. (1) was
adopted to calculate the amount of electricity consumed yearly in each category. Eq. (2) was
utilized to calculate the annual cost of the electricity utilized by individual lighting technology
alternatives in each room category.

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Techno-Economic and Environmental Viability of Retrofitting in Public Multi-Storey Buildings
Table 2 The four lighting technology alternatives assessed in this study [2]
Light technology Lamp Lamp life
Advantages
ratings
span
(Watt) (Hours)
Electronic ballast
18
7500 Rugged due to its
hard structure
CFL

8
10000 Environmentally
friendly
T8 Electronic
32
8000 cheaper
T5
21
8000 It’s more robust

Table 2 shows the four lighting technology alternatives illustrating the lamp ratings, lamp
life span and the advantages of adopting each of the technologies in the study.
2.2.3. Economic Analysis
Based on the walk-through audit (energy survey) that was carried out, an economic analysis
of the energy consumption pattern was estimated. The results obtained were used to estimate
the cost effectiveness of installing various lighting technology alternatives. In order to
actualize this, the installation cost and 20-year cash flows were calculated for individual
technology alternatives in each room category. The disposal costs, material (including
ongoing maintenance costs) and electricity costs were also considered. The 20-year time span
denotes the life cycle of 1.2 m and 2 m fluorescent lighting systems, which are the longest
lived components (ballasts). This study utilized three economic analyses techniques in order
to determine the cost effectiveness of various lighting technology alternatives, namely: cost of
conserved energy (CCE), net present value (NPV), and simple payback time (SPT) [2, 10].
2.2.3.1. Simple Payback Time
The SPT measures the amount of time required to recuperate the additional investment on
efficiency improvement through lower operating costs. SPT is the time it takes for an initial
investment to be recouped and is found by using the following equations:
(3)
(4)

Although the SPT technique is insufficient for ranking investments based on their anticipated
profitability [19], this technique was adopted due to the fact that it is still globally utilized as a
benchmark for accepting or rejecting potential investments [10, 18].
2.2.3.2. Net Present Value
The NPV technique estimates the present value of an investment n years into the future. NPV
is known as a sound technique for jointly assessing a number of investment opportunities with
different initial investment amounts and differing cash flow patterns [21]. Eq. (5) was used to
calculate the NPV:
∑

(

(5)

)

Where
= The annual cash flow in year t.
= The discount rate.

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Gbadega Peter A and Inambao Freddie L

= The investment time in years.
= The initial investment amount.

The discount rate adopted in the NPV evaluations was calculated to be 8 %. This value
was selected due to the fact that it is within the rate of returns usually expected by commercial
and industrial organizations for an investment in energy efficient lighting technology [12, 16].
NPV can be mathematically expressed as:
(
(

)
(

)

(

)

(6)

)
(

(7)

)

Where
= 8 % (discount rate).
= The number of years.
2.2.3.3. Cost of Conserved Energy
The CCE analysis technique estimates the cost of conserving one-kilo-watt-hour (kWh) of

electricity. If the installation of energy efficient technology results in a CCE, which is less
than the price paid for one kWh of electricity, the project may be considered cost effective.
CCE is described in more detail in [19, 20]. Eq. 8 was used to determine the CCE that related
to a particular investment:
(

(8)

Where the change in annual maintenance cost can be either positive or negative and
annual energy saving is expressed in kWh. CRR is the capital recovery rate, and is used to
annualize the investment. CRR is expressed as:
(

(9)

)

Where d is the discount rate and n is the length of the investment in years.
2.2.3.4. Life Cycle Cost
The evaluation of the cost of a system or product over its entire life span is known as life
cycle cost (LCC). Life cycle cost analysis is a method of determining the entire cost of a
structure, product, or component over its expected useful life. The cost of operating,
maintaining, and using the item is added to the purchase price. In this study, LCC was utilized
to estimate the cost of energy efficiency enhancement of the lighting system based on design
options. The LCC is the sum of investment cost (PC) and the annual operating cost (OC)
discounted over the lifetime of the product. The LCC is evaluated using Eq. (10) [17, 20]:
(10)

2.2.3.5. Energy Savings
Energy saving (ES) is the difference between energy consumption of existing (EC existing)

and retrofit lighting (EC retrofitting) a system. The following equation was used to calculate
energy savings [14, 15].
(11)

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Techno-Economic and Environmental Viability of Retrofitting in Public Multi-Storey Buildings

2.2.3.6. Electricity Consumption and CO2 Emissions
Carbon dioxide emissions related to the electricity consumed by existing 1.2 m and 2 m
fluorescent lighting fixtures were estimated for the whole Senate building of University of
Lagos. For these calculations, it is assumed that the generation of 1 kWh of electricity
produces 1.3 kg of carbon dioxide [18, 19]

3. RESULTS AND DISCUSSION
The site for this study was the Senate building of University of Lagos. This building was
chosen as the study site because the building serves as the heart of the institution where
various activities take place, hence the need for constant supply of electricity. More so, most
of the lighting technology installed in the building is high energy consuming (1.2 m
fluorescent lamps, incandescent lamps and a few LED lights). Generally, AC consumes a lot
of energy compared to modern technology. As a result, there is a dire need to make the
building energy efficient by installing new energy efficient technology (alternative technology
for lighting and cooling). The total energy consumption by all the facilities in the Senate
building of University of Lagos are illustrated by the pie chart in Figure 1. From Figure 1 it is
clear that the facilities that consume the bulk of the energy are cooling (36.4%) and lighting
(26.4%). The energy survey assessed that the lighting system had the greatest potential to save

electricity and reduce electricity related CO2 emissions and was assessed by comparing four
energy efficient lighting technology alternatives. The cost effectiveness of each lighting
technology alternative was estimated.

Figure 1 Pie chart illustrating the energy utilized by all the building facilities

The results of the lighting survey for the room categories are presented in Figure 2. In general,
most lighting fixtures are found in room categories 1 and 3, although room categories 2 and 4
contain most of the single lighting fixtures.

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Gbadega Peter A and Inambao Freddie L

Figure 2 Annual Energy consumption by the lighting technologies

From Figure 2 CFL consumed the least energy compared to the other lighting technology
alternatives. E-ballast also consumed less energy compared to the existing lighting
technology. As a result, CFL and E-ballast are energy efficient lighting technologies which
when installed would make the building more energy efficient.

3.1. Electricity Consumption and Cost
Figure 2 shows the electricity consumption by the 1.2 me and 2 m fluorescent lights in each
room category for each lighting technology alternative. In all cases, room categories 1
(offices) and 2 (Annex and units) consume the most electricity, even though rooms in
category 3 contained the second largest number of globes. This is due to shorter operating

hours within room category 3, and indicates that operating hours is an important factor in the
electricity consumption of 1.2 m and 2 m lighting fixtures. Furthermore, it is obvious that the
CFL lighting technology alternative is by far the most energy efficient alternative.
Undiscounted life cycle costs for various lighting technology alternatives are shown in Figure
3. The costs are divided into electrical costs, initial costs and ongoing maintenance costs. It
can be seen that although ongoing maintenance costs change to some degree, initial costs
change noticeably between the lighting technology alternatives. It is worth noting that T8-E
Electronic is the only technology alternative with low initial costs. Therefore, annual cost
saving and annual electricity costs are shown for each lighting technology alternatives.
Electricity savings are calculated in kWh so that results can be easily compared with respect
to other studies.
Table 3 The electricity cost/use per year of various lighting technology alternatives
Lighting
technologies

Electricity
cost/year (N)
Electricity used
(kWh/yr)
Electricity saved
(kWh)

EXISTIN CFL
G
Million
Million (Naira)
(Naira)

T5
E-BALLAST T8 –

ELECTR
Million
Million
ONIC
(Naira)
(Naira)
Million

0.862

0.395

0.826

0.554

0.944

0.197

0.0089

0.188

0.126

0.216

N/A

0.108

0.0082

0.0712

-0.019

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Techno-Economic and Environmental Viability of Retrofitting in Public Multi-Storey Buildings

From Table 3 it is evident that CFL has the least electricity cost/year, followed by Eballast; this shows that CFL serves as the best lighting technology alternative when cost of
energy-use is being considered. Electricity savings of CFL is the highest of all the lighting
technology alternatives. In view of this, it is expedient to install CFL since it is more
economical.

Figure 3 Life cycle cost for a duration of 20 years

Figure 4 Breakdown of LCC components

From Figure 3 it is evident that CFL has the least life cycle cost which makes it cheaper in
terms of operating costs for a duration of 20 years; this makes it the best lighting technology
alternative from an economic point of view.

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Gbadega Peter A and Inambao Freddie L

Figure 5 Energy savings by the lighting technology alternatives

From Figure 5 it can be seen that CFL and E-ballast save the highest amount of energy
compared with other lighting technologies, therefore installing these two lighting technologies
in a typical building will makes the building more energy efficient.

3.2. Economic Analyses
The results of the economic analysis are shown in Table 4 and indicates that all of the lighting
technology alternatives assessed represent good investment choices if all room categories are
considered together, so they are all economically viable.
Table 4 The estimated net present value of the lighting
Net Present Value
Existing

CFL
T5
E-ballast
T8-E

NPV
Million
(Naira)
40.12

55.7
48.16
25.53

Installation /Initial
Cost (Million)
3.67
5.11
4.42
2.32

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Replacement
Cost (Million)
(Naira)
3.67
5.11
4.42
2.32

Maintenance
/operating
Cost (Million)
0.48
0.48
0.48
0.48

Techno-Economic and Environmental Viability of Retrofitting in Public Multi-Storey Buildings

Figure 6 Chart showing the net present value of lighting technologies

From Figure 6 it can be seen that T8-E has the least NPV of an investment 20 years into
the future due to its low lamp price; in view of this T8-E is the most economically viable.

Figure 7 Chart showing the simple payback time

The SPT measures the amount of time needed to recover the additional investment on
efficiency improvement through lower operating costs. From the analysis, T8-E has the least
payback time, followed by T5, and CFL has the longest payback time. If we are to base our
cost-effectiveness analysis on the time the investment would pay back, then T8-E would be
the best choice to make.

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Gbadega Peter A and Inambao Freddie L

Figure 8 Chart representation of CCE (C/kWh)

The above analysis shows that CFL, E-ballast and T8 are most cost effective, since the
cost of conserved energy is less than the price paid for one kWh of electricity, which is

N13.61.

Figure 9 Chart representation of CO2 emitted per year

From the analysis, CFL has the least amount of CO2 emitted per year, which means it is
the most environmentally friendly lighting technology. Figure 9 shows that more than half of
the CO2 emitted by existing technology can be avoided by the use of CFL.

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Techno-Economic and Environmental Viability of Retrofitting in Public Multi-Storey Buildings

Figure 10 Energy savings for cooling system

The cooling technology alternatives proposed are Panasonic (IS 85.3 W) and LG series
(188.2 W). Both technology alternatives are energy efficient based on the fact that they save
more energy which invariably reduces the energy operating cost. From Figure 10 it is evident
that LG series and Panasonic (IS) save more energy compared to the existing cooling system.

4. CONCLUSION
This work is a detailed analysis of the mitigation techniques of minimizing energy
consumption patterns. To start with, various energy management measures were investigated
critically to gain an overview and better understand the scope of energy management
schemes. After this, various economic analyses were carried out to investigate the cost
effectiveness of the various technologies proposed. From the results obtained, CFL and T8-E
are the best lighting technologies in terms of energy efficiency and cost effectiveness

measures. This project recommends the adoption of standards, energy efficiency and
conservation measures to ensure building sustainability within Universities.

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