• Energy Technology and Management Conference;WlZ
Energy Audit of Commercial Buildings (A Case Study of Global Fleet Oil Ltd. and National Mirror
Houses)
J.E. Elusakin, 0.0. Ajide, T.A.O. Salau and O.G. Idowu
Department of Mechanical Engineering, University of Ibadan, Nigeria
ABSTRACT
The dearth and cost of energy supply in Nigeria calls for planning and management through energy audit.
The object of this paper is to carry out a comprehensive energy audit of the two commercial buildings
commonly referred to as Energy House and Mirror House which are the head offices of the Global Fleet
Oil & Gas Ltd. Company and National Mirror Newspaper respectively, using their 2011 energy
consumption data. The power supplies to both offices are from the same generators which provide two-
third of the power supply to the building in 2011 but with different transformers of 1000 kV A each for the
PHCN power supply. The facilities load were assessed by direct inspection and conversion were done
where necessary. The capacities of the available three generators were 400, 640 & 1000 kW respectively
(using 0.8 power factor) and the maximum load of the facility at any time in a day is 398 kW. This study
has revealed the monumental financial waste on the un-utilized energy and facilities that could be replaced
with energy saver equipment. Therefore, it is imperative that a holistic energy planning and regular
assessment of energy requirements are considered as key components of building projects.
Keywords: Power Holding Company of Nigeria (PHCN), Generators, Maximum Load, Energy
Conservation Opportunities (ECO)
1. INTRODUCTION
Buildings account for almost half of the total primary energy use and related greenhouse emissions
worldwide. Although current energy systems are improving, they still fall disappointingly short of meeting
acceptable limits for efficiency (Moncerf, 20 I 0). Alexandri et al (20 II) reported in their work that energy
savings in the building sector has been a priority of the European .Union over the last decade, and many
measures have been set up to decrease a building's energy needs and gas emissions to the environment.
Office buildings have characteristically high consumption for heating and especially for cooling, due to
their high internal gains. Additionally, their intermittent time table makes their energy needs and
consumption profile more special, with more energy needed to heat-up or cool-down space in the morning
hours. The re-use of a building, initially designed as dwelling, as an office building, depicts its own not so
ordinary) characteristics and energy consumption needs. In their paper, the energy demand and
consumption profile of such a building is given a due attention. Through the energy audit procedure, the
actual electrical and oil consumption were measured and through the thermal simulation, energy saving
scenarios were thoroughly examined. Energy is an important foundation resource of human society's
development. According to the International Energy Agency (2004), the world energy consumption will
be increasing from 10.24 billion tons of oil equivalent in 2001 to 16.2 billion tons of oil equivalent in 2005
and the world energy consumption will increase by 54% in 2001-2025. Reducing the use of energy is an
essential task for the future as the world's greatest environmental impact originates from the use of energy
(OECD, 2004). Due to increased globalization, industries as a whole are facing greater competition that is
forcing companies to decrease their expenses in order to increase their profits (Patrik et al., 2009). In the
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Nordic countries, such as Finland, Sweden, Iceland and Norway Heat Ventilation and Air Conditioners
(HV AC) are considered to be necessary in all building due to their weather condition. In Sub-Sahara
country like Nigeria, installation of heating equipment within all building is not popular. This brings a
slight difference factor and facilities consideration in Energy Audit in Nigeria from that of Nordic and
other part of Europe. Therefore Nigeria and other Sub-Sahara countries will need energy auditing for the
sake of dearth in energy supply and the concomitant hike cost. Nigeria is well endowed with energy
resources (UNDP, 1983). Conversely, the price of energy commodities (electricity, petrol, diesel, kerosene
etc) are very expensive compare with abundant existence of energy resources sparsely located around the
country. Currently, the tariff of PHCN in Nigeria varies between N 4 to N 23 for residential consumer
class N15 to N20 for commercial consumer class, N15 to N22 consumer class industrial, N15 to N 22 for
special consumer class like government house and hospital and N 11 to N 17 for street lighting per KWH
depend on the number of phases and location' (NERC, 2012). These costs are too huge especially to
sustain company's profit and user's comfort. The price of petroleum products grossly becoming
unbearable as the government withdraws from subsidizing the products. Petrol (PMS), Diesel (AGO) and
Kerosene (DPK) currently stand as=N97, N160 and NIOO per litre (PPPRA, 2012). The efficient use of
energy is of prime importance in all sector of the economy .The imperative of an energy shortage situation
calls for energy conservation measure, which essentially means using less energy for the same level of
activity. A comprehensive energy audit of Vitamalt Nigeria Pic, Agbara was carried out by Olugbenga et
al (2012) using portable thermal and electrical instruments with the objective of studying the present
pattern of energy consumption and identifying the possibilities of saving energy in the plant. The
normalized performance indicator (NPI) calculated over the span of five years gave an average of 1.2
GJ/m2 indicating a FAIR range in energy performance level classification (1.0 - 1.2) while significant
savings and improvement in energy usage is achievable. Maximizing efficiency of existing system,
optimizing energy input requirement and significant capital investment in procuring new energy
conserving equipment must be made for the energy performance level to fall into a good range
classification (less than 0.8).
The suggested Solar Power source, according to Melodi and Famakin,(20 11) is still at expensive side and
provides not serious comparative cheaper price. Based on Reference Growth Scenario, GDP growth of 7%
p.a, Nigeria energy demand for year 2010 was 15,730MW (Sambo; 2008). Meanwhile the average energy
supply in last one year does not exceed 4,300 MW (Eyo, 2012). This implies that consumer will have to
source for the 11,430MW from independent power generation. In spite of inadequate supply of electricity
to the economy, Nigeria exports about 70MW to Niger Republic and 560MW to Republic of Benin which
are members of the West African Power Pool (WAPP) with Nigeria (Sambo, 2008). Energy auditing and
planning has been found to be the best strategic approach to manage available energy at relatively low
cost. Tahsin and Vedat (2005) expanded further that energy audits provides an accurate account of energy
consumption and reveal the detailed information needed for determining the possible opportunities for
energy conservation. However, approaches to the process of energy auditing of a building depend on the
environment and purpose of the building. A building could be residential, commercial and Industrial
building. Energy Consumers, whose energy bills use up a large part of their income, and especially those
customers whose energy bills represent a substantial fraction of their company's operating costs, have a
strong motivation to initiate and continue an ongoing energy cost-control program (Wayne, 2007).
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In this paper, energy supply, demand and utilization data for year 2011 of a commercial building (Energy
House and Mirror House) were collected (see figure 1a & fig 1b). The information comprises data on
PHCN Electrical Power bill and cost of running on the available three generators when there is power
outage from PHCN. The research discovered the magnitudes energy wasted in terms of kilo-watt and cost;
and suggest the way to correct the further wastage. The result of this finding will then be of immense
valuable to the company in saving money on energy bills of their two complex buildings.
~
Figi (a) Energy House Figi (b) National House
2. THEORETICAL BACKGROUND
2.1 Electrical Unit Conversions
For single phase:
l(iloWcltt = Faits X (I)
For two-phase (For 208-240 Power Sources, 220 volts is used for calculations)
(2)
For three-phase:-
KiloWart = Felts X (Anlpe-es) X PoweYfacton/3/(10'j~1 (3)
For purposes of this paper, power factor of 0 .8 is used which is more peculiar to the Nigeria power
requirement. The kVA value is always higher than the value for kW.
2.2 Energy Cost
This analysis explains the cost detail of how much is the cost of the energy produced, consumed, utilized
and wasted. The bill from the PHCN is the cost of the energy consumed. But for individual power
generation, the cost of energy produced can be calculated by summing the fixed cost (Depreciation, Taxes,
and Insurance) and operational cost (Fuel cost, Operating Labour cost, Maintenance cost, Supervision)
(Raja A.K, et al., 2006), (Albert and Meht, 2008). Source of power supply to the commercial building are:
Power Holding Company of Nigeria and Company's Generators. Cost of Energy supplied by PHCN is
summation of all monthly bills for 2011. In costing energy supplied by the generators, fixed cost and
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operational cost are determine and summed up. To find the fixed cost, depreciation of the generators is
calculated using sinking value method. i.e.
(4)
Or
Straight Line Method = (initial Cost - 5al-n:l.gl? Value)/ Number of Years of Use f u! Life
(5)
Where r is the interest rate and n is the number of the years. According to Gupta, (1983), the- economic lift!
span of electrical equipment such as generators ranges between 20 to 25year and salvage value of 15%
while Thomsen, (1997) opined 20, 000 running hours for overhauling and regular services are carried out
at 200 hours interval. Other charges on the fixed cost can be neglected as the equipments are very new.
The operation costs are calculated by summing the respective figures of the cost spent on the operational
activities.
3. METHODOLOGY
In this paper, information about a facility's operation and its past record of PHCN utility bills were
collected. The collected data were then analyzed to get a picture of how the facility uses or possibly
wastes energy, as well as to help the company learn what ~reas to examine to reduce energy costs. Data
were collected on hourly power demand (taken on the generator for over a period of time), fuel
consumptions per month, facilities load by direct assessment of the power rating of the facilities and
PHCN monthly Bill. The data collected help in calculation of the Hourly-load table (see table 2), Energy
cost from PHCN (see table 3) and Company's generators (see table 4).
The facilities and the equipment in the building which were found in the course of the gathering of the
information for the auditing exercise were majorly those thing that are common to commercial building.
In the Energy House, there are four-feet fluorescent tube, two-feet fluorescent tube, split unit NCs, central
cooling AICs, standing fans, air- extractors, Computers, TV, Portable Radio, water Dispensers etc. In the
Mirror's House, Compass printing Machine, Compressors, Computer, Scanners, Printer, AICs, ceiling fan,
four-feet fluorescent tube, two-feet fluorescent tube, etc. all these facilities are grouped and their
percentages were also determined as tabulated in table I.
Table I: Categories of Loads of the Facilities in the Building
Facility Load(W) Percentage %
Illumination 46332 4.3
uv AC 578220 54.2
Office Accessories 289794 27.2
Office Comfort 3645 0.3
Service Facilities 119145 11.2
Production Facilities 29762 2.8
1066898 100
The Total Connected Load in KW=I,066.898KW
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Table 2: Average Hourly Load of the Buildings per Day
Time(Hour) Load (kW) Time(Hour) Load (kW)
1 181.11 13 260.44
2 182.89 14 279.11
3 82.22 15 276.89
4 73.55 16 346.00
5 5l.l1 17 398.00
6 114.00 18 218.44
7 107.33 19 178.89
8 180.00 20 268.44
9 343.11 21 258.22
10 351.78 22 242.89
11 397.78 23 255.78
12 270.89 24 184.89
Total 5,503.80
Maximum Load is 398kW and is at 5pm (17th hour). At this time, the staff in the Energy House is still in
the office while National Mirror workers have also commenced the production work for the publication of
the second day newspaper edition. This justifies the figure for the maximum load which is equivalent to
Power Consumes in KWh daily.
Table 3: PHCN Bill for Year 2011 for Mirror and Energy House
SIN Months Energy Mirror's Total Bill
House (W) House (N1
1 January 926,460.00 603,000 1,529,460.00
2 February 411,751.40 700,000 1,111,75l.40
3 March 405,431.40 750,000 1,155,431.40
4 April 600,500.90 850,000 1,450,500.90
5 May 757197.70 900,000 1,657,197.70
6 June 757197.70 900,000 1,657,197.70
7 July 295,174.64 720,000 1,015,174.64
8 August 434,973.21 1,490,000 1,924,973.21
9 September 501,064.41 997,000 1,4?8,064.4 1
10 October 1,252,296.26 1,300,000 2,552,296.26
1 1 November 876906.03 900,000 1,776,906.03
12 December 785730.96 950,000 1,735,730.96
8,004,684.61 11,060,000 19,064,684.61
Generators Fixed Cost: Using equation (5) to solve for Depreciation gives N2, 932,500 while operational
costs is calculated by summing the relevant figure of the monthly cost and are tabulated in the table 4.
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Table 4: Operational Cost on the Generators for Year 2011
SIN Months Maintenance Cost of Cost of Operators Operational
Cost (N1 Repair (N1 fuel (N1 Allowancet'N) Cost(N1
1 January 309,54l.66 0 4114800 30,000 4,454,341.66
2 February 309,54l.66 0 4241800 30,000 4,581,341.66
3 March 309,541.66 0 4191000 30,000 4,530,541.66
4 April 309,54l.66 700,000 4216400 30,000 5,255,941.66
5 May 309,541.66 99,750 4653000 30,000 5,092,291.66
6 June 388,609.38 73,000 4653000 30,000 5,144,609.38
7 July 388,609.38 0 5075000 30,000 5,493,609.38
8 August 388,609.38 0 5075000 30,000 5,493,609.38
9 September 280,000.00 0 4950000 30,000 5,260,000.00
10 October 280,000.00 2,000 4,500,000 30,000 4,812,000.00
II November 280,000.00 0 4805000 30,000 5,115,000.00
12 December 0.00 0 5037500 30,000 5,067,500.00
3,553,536.43 874750 55512500 360,000 60,300,786.44
Total Cost of Energy Supplied by generators is sum of fixed cost and operational cost totaling W 63,
232,786.44. Total Cost of Energy due for year 2011 is the sum o(PHCN Bill and Generator Cost of Power
supplied which gives N 82, 297,47l.050
4. RESULTS AND DISCUSSION
The power supply by the generators and PHCN are on average of 16hours and 8 hours daily respectively
The number of hours the power was supplied by the PHCN 365.':1/3 = 121liccu's and cost W 19.
064,684.61 for the period of 20 II. The number of hours the power was supplied by the generators
365X2/3 = 244h'out"s and cost N 82, 297,471.050 for year 2011. Moreover, to find actual energy
wasted from the generator and its concomitant cost, power capacities of individual generator over the year
are considered and the result of the effect and the east estimate implication are tabulated in table 5 and
shown in figure 2.
Table 5: Power Distribution from Generators
Generators Working Energy Energy consumed Un-utilized
III KY A Days Supply(KWh) III the working Energy
_(KW) in working days days(KWh) _ '(KWh)
1250(1000) 86 2,064,000 473,326.80 1,590,673.20
800 (400) 5 48,000 27,519 56,481
500(400) 153 1,468,800 842,08l.40 626,718.60
Total 365 3,580,800 1,342,927.20 2,273,872.80
Cost (N) 63,232,786.44 39,836,655.46 23,396,130.98
From the hourly-load daily consumption, average energy consumes is 5,503.8K Who
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Fig 2: The Pie Chart Showing Energy Utilization Status
III Erlcrgy Ulili,:ed
I!!i Un-Uti ized Enerav
5. CONCLUSIONS
The finding from the result of the auditing reveals how huge money is wasted on the un-utilized energy
and facilities that could be replaced with energy saver equipment The present situation arose from lack of
energy planning and regular assessment of the energy requirement within the building,
Most of the illumination equipments are incandescent bulb, 2-feet and 4-feet fluorescent tubes with power
rating of lOOW, 18W and 36W respectively, These equipments could be replaced with modem energy
savers bulbs with 20W power rating and still achieved the sarrie illumination effect HV AC equiprnents
usage should be based on need, If actions are taken on the above recognized ECO, the PHCN bill will
dropped,
In this research, maximum of 398KW was found to be required by the building at any time in a day, but
the generating plant within the complex are capable of supplying not less than 400KW at any time with
high operational cost Therefore to curtail the energy wastage from the 12S0kV A generator of superfluous
capacity, two generators of capacities SOOKVA (400kW using power factor 0.8) and SSOkVA (440kW
using power factor 0.8) will be sufficient for the energy needed by the buildings throughout a year
provided no additional energy demand arise, The SSOkVA should be used in the evening when we have
the maximum load to gi ve tolerance to the demand,
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