Analysis of Energy Utilization in Selected Industries in ... · objectives of this study are: A) to...

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Analysis of Energy Utilization inSelected Industries inSouthwestern Nigeria

O.S. Oyedepo, M.S. Adaramola, M.K. Odunfa and O.T. Aremu

ABSTRACT

This article presents an analysis of energy use and energy saving opportunities in selected industries in southwest Nigeria. The study is based on the realization that enormous potential exists for energy sav-ing improvements in the existing energy using industrial equipment. A walkthrough energy audit provided data for the power rating, operation time of energy consuming equipment and machineries and power factor. The data were then analyzed to investigate the breakdown of end-use equipment and machineries’ energy use. The results of the energy audit in the selected processing and producing industries showed that the electric motor accounts for a major fraction, 40-70%, of total energy con-sumption. Based on the available data, the food processing industry had the highest energy consumption per year at 5,039.45 TJ/yr., while the ceramic industry had the lowest average annual energy consumption at 109.43 TJ/yr. The annual energy consumption variances for specific sectors during the period under consideration industry-wide were: food processing industry, 28-108 MJ/kg; distillation and bottling industry 3.72-3.96 MJ/kg; chemical industry, 76.55-92.80 MJ/kg; and ceramic industry, 7.71-7.93 MJ/kg. The energy used ratio for all of the selected industries is far from unit (1). This indicates an ineffective utilization of energy in the industries, which implies that more energy is expended in the unit production of finished product. The study established that en-ergy is not sufficiently utilized in the companies studied, so this article suggests possible strategies for efficient energy usage in the selected industries.

Key words: Energy saving, energy efficiency, energy utilization, energy use ratio, industry

48 Energy Engineering Vol. 112, No. 6 2015

INTRODUCTION

Energy use in the industrial sector varies widely among countries and depends principally on the level of technology used, the maturity of plants, the sector concentration, the capacity utilization and the structure of subsectors [1]. In the industrial sector, energy is consumed for a wide range of activities, such as processing and assembly, space conditioning, and lighting. In aggregate, the industrial sector uses more energy than any other end-use sector, consuming about one-half of the world’s total delivered energy [2]. Energy has been the key to economic development worldwide, but in the way it is sourced, produced and used, two major drawbacks have emerged. First, the overall energy system has been very inefficient. And second, major environmental and social problems, both local and global, have been associated with the energy system [3]. Energy efficiency is a major key in this regard. An estimated 10-30% reduction can be achieved at little or no cost by improving efficiency of energy use in the industry [4]. The need to conserve energy in the manufacturing industry is of paramount importance, thus making the cost of energy of immediate interest to managers and engineers in this sector. The efficiency of energy utilization in a manufacturing industry requires knowledge of the en-ergy performance of the machines and plant directly associated with the production process [5-6]. It is important to account for total consump-tion, cost and to recognize how energy is used for each commodity such as steam, water, air and natural gas. The energy manager focuses his professional attention on how to reduce energy consumption per unit of production, i.e. energy efficiency [7]. The whole purpose of energy ef-ficiency is to minimize the amount of energy used to get a desired effect. There are various principles that can be followed in energy management that focus on the reduction of energy productivity and they include: the historical energy use review; energy audits that are reviews of current practices; thorough analysis of energy use using such things as engineer-ing analysis, computer simulations, and availability studies; aggregation of energy uses, and energy conservation to mention but a few [8]. The use of energy pervades every aspect of modern society, but it is not efficiently used in many industries. In view of the fact that there are continually increasing fuel costs, energy efficiency studies are rap-idly becoming more important. Huge amounts of money can be saved

49

in accumulated energy costs when energy is properly managed. Based on this fact, several studies of industrial energy efficiency within and outside Nigeria have been performed in the last few years [9-21], and the results from the studies have been fairly consistent—that there is a read-ily achievable, cost-effective, reduction in industrial consumption using good energy management practices and energy-efficient equipment. Despite numerous studies published on energy audit and energy analysis results for different industries within and outside Nigeria, no study has identified and quantified estimates of energy usage break-down in the industrial sector. There is lack of similar studies in the energy intensive and related industries in Nigeria. Therefore, the prime objectives of this study are: A) to investigate energy utilization in chemi-cal, ceramic, food and distillation and bottling industries in western zone of Nigeria, B) to identify the sources of energy waste in the selected industries and C) to offer effective ways of efficient energy conservation strategies in the industries surveyed. Some of the information provided in this study can be used by the selected and similar industries to man-age the energy consumption efficiently and sustainably.

MATERIALS AND METHOD

Study Area The data for the study were collected from four processing compa-nies located in southwestern Nigeria. Brief descriptions of these indus-tries follow:

Case Study I—Chemical industry (Alum production) The selected chemical industry was incorporated in November 2000 and produces 72,000 metric tons of solid equivalent aluminium sulphate (alum) and sulphuric acid annually. At the time of the walk-through energy audit, production was down to about 60%, as the com-pany was not producing sulphuric acid. Therefore, energy audit was carried out only for the aluminium sulphate (alum) plant. The main uses of alum are in water and effluent treatment, and in papermaking. Other industrial applications include tanning, pharma-ceuticals and electroplating. Raw materials used to produce alum are mainly sulphuric acid and bauxite or other source of aluminium hydrox-ide (such as kaolin). Bauxite has alumina (aluminium oxide) as a major


component containing about 50-55% of the total composition. Other minerals are magnesium oxide, ferric oxide, titanium oxide all contain-ing the remaining 50-45%. The sources of electricity in this industry include a 1250 KVA gas generator that runs for 24 hours—except when it is under main-tenance—and two diesel generators, a 1000 KVA and a 153 KVA, that supply electric power to the plant. The company is also connected to the national grid through a 500 KVA transformer. The standard power factor in the company is 0.94.

Case Study II—Ceramic Industry The selected ceramic industry produces household tiles of several shapes for domestic consumption and export to neighboring West Afri-can countries. It produces more than 14 million kg of tiles in a year. The major raw materials used for the production of ceramic tiles are kaolin and feldspar. The source of electricity in this factory is mainly from three 580 KVA gas generators. Two of these generators are run simultaneously for 24 hours per day and the third generator is on standby. Due to inconsis-tent power supply by the Power Holding Company, PLC (PHCN), the company is not connected to the national grid. The standard power fac-tor in the company is 0.8.

Case Study III—Food Processing Industry This company is essentially a food processing company with a total yearly output of 24,000 tons. The plant produces two types of food savory seasonings, type 1 and type 2. Raw materials for type 1 season-ing include salt, m.s.g., spices, h.v.p and fats. Type 2 seasoning includes salts, sugar, ribotide, flavor, fats, caramel, citric acid and water. The main source of electricity in the company is from six genera-tors: four 1000 kVA gas generators and two 1000 kVA diesel generators. In addition, electricity is supplied to the company through an external power generating company, as the company is not connected to the na-tional grid. The standard power factor in the company is 0.8.

Data Collection The aim of an energy audit is to collect, analyze, quantify and iden-tify opportunities for reducing energy consumption for a given process. The primary energy resources that were used in the selected industries

51

can be categorized into three types of energy: electrical, thermal and manual. During the walkthrough energy audit, records of all equipment on the line (the production floor) were counted and the power rating of the electrical devices was obtained from equipment’s technical specifica-tion sheets. The total working days in a year for each operation was esti-mated in consultation with the production manager and the manager of each unit. The other important data collected per annum over a five-year period (2006-2010) for the chemical industry and a three-year period (2008-2010) for the ceramic industry are the:

• Amount of electricity, diesel and gas consumed

• Number of male and female workers and their respective working periods in hours

• Number and technical specifications of the steam boilers, coolants, and chillers’ operating condition

• Production figures

• Power factors and miscellaneous energy consuming equipment like computers, televisions, printers, photocopiers, and scanners

In addition to the above information, the plant manager and main-tenance engineer were interviewed to obtain more information about the production processes and equipment as well as to investigate how the selected industries emphasize energy conservation or awareness of en-ergy conservation in their facilities. Additional and useful data were also collected from company and government publications, both published and unpublished.

Evaluation of energy used For each selected industry, the total energy input used for each unit operation is determined from the following equation [22]:

Et = Ep + Ef + Em (1)

where Et is the total energy, Ep is the total energy power input, Ef is the total thermal energy input and Em is the total manual energy input. The procedures used for the estimation of the electrical, thermal and manual energy inputs are described below:


Electrical Energy The electrical energy input by electrical equipment was obtained as the product of the rated power of equipment and the duration of opera-tion and it is expressed as [23]:

Epi = ηpt (2)

where Epi is the estimated electrical power input from each electrical piece of equipment, p is the rated power of the system, t is the time of operation in hours and η is the system efficiency, which is assumed to be 80%. The total electrical energy input is then determined from:

Epi = ∑ni Epi (3)

where n is the number of pieces of electrical equipment.

Thermal Energy The thermal energy input was calculated based on the quantity of fuel used to generate steam in the boiler, depending on both the quantity and type of fuel used. The thermal energy for each boiler is estimated as the product of the quantity of fuel and the calorific value of the fuel and it is expressed as [24]:

Efi = CfW (4)

where Efi is the estimated thermal energy input by each boiler, W is the amount of fuel in liters, and Cf is the calorific value of the fuel. The total thermal energy input is then determined from:

Efi= ∑ni Efi (5)

where n is the number of boilers.

Manual Energy Manual energy input depends on the number of workers and their gender. According to Odigboh [25], at maximum continuous energy consumption rate of 0.30 kW and a conversion efficiency of 25%, the physical power output of a normal human labor in the tropical climates is approximately 0.075kW sustained for 8-10 hour workday. Therefore,

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the manual energy input by a male worker and a female worker are de-termined respectively from [23, 26]:

Emm = 0.075Nmtm (6)

Emf = 0.068Nftf (7)

where Emm is the manual energy input by a male worker, Emf is the man-ual energy input by a female worker, Nm is the number of male workers, Nf is the number of females, tm is the time used by male workers and tf is the time used by females. The total manual energy input is then deter-mined from:

Em = Emm + Emf (8)

Energy Used Ratio The energy used ratio is defined as the ratio of the total energy in-put to the total energy content of finished product. It is expressed as:

Em =Et/EFp (9)

where Ei is the energy used ratio and, EFp is the total energy content of finished product, which can be evaluated from:

EFp = Mfp × ECP (10)

where Mfp is the mass of finished product and ECP is the energy content of a unit of product.

RESULTS AND DISCUSSION

Annual Energy Consumption and Production Output The total energy consumed annually by selected industries is the summation of the amount of electricity, natural gas, diesel, liquefied petroleum gas (LPG), gas oil and manual labor used after conversion to energy (Appendix A). Tables 1-4 show the annual energy consumption and produc-tion output for the food processing industry, distillation and bottling company, chemical industry and ceramic industry respectively. The


highest energy consumption and highest production recorded in the selected industries are 5,452,467.24 GJ and 197,760 tons, 479,223.16 GJ and 128,740 tons, 1,955,783.46 GJ and 25,550 tons and 111,355.57 GJ and 14,045.25 tons respectively. The highest consumptions were all recorded in the year 2010 except for ceramic industry that has the highest energy consumption in 2011. On the average, the food processing industry has the highest energy consumption per year at 5,039.45 TJ/yr. The ceramic industry has the lowest average annual energy consumption at 109.43 TJ/yr. This shows that food processing and the manufacture of chemi-cals are complex and energy-intensive, often requiring large quantities of thermal energy to convert raw materials to useful products. The summaries of the percentage total of energy consumed for the period under consideration for the selected industries are presented in Tables 5-8. Table 5 shows the percentages of energy used pattern in the food processing industry. From Table 3, it is seen that manual energy expended in operating machines and lifting of loads was found to be the least-consumed energy, accounting for an average of 0.01% of the total energy input for the five-year period of study. The diesel fuel energy was expended in operating diesel generators and boilers. Diesel fuel was the highest energy consumed, and on average it accounted for about 99.13% of the total energy input for the period under consideration. Table 6 pres-ents the summary of the percentages of total energy consumed in the distillation and bottling company for the period under consideration. Diesel fuel energy expended in operating diesel engine and boiler was also the highest consumed source of energy, and it accounted for 95.25% on average. The percentage of energy used pattern in the chemical in-dustry is presented in Table 7. The highest consumed source of energy is LPG, which accounted for an average of 99.33% of the lowest total en-ergy consumed in the industry. Manual energy is source that accounted for the lowest amount of energy consumed at about 0.01% of total energy consumed. The low percentage of diesel consumption observed during visits to this industry was due to high price of diesel fuel, which forced the company to switch over to LPG in running electricity generating set. Table 8 presented the percentage of energy sources consumed in ceramic industry. The highest energy source consumed within the period under consideration is natural gas, which accounted for 99.75% of total energy consumed. Manual energy source and electricity from the national grid are the least consumed energy sources and they both accounted for 0.04% of the total energy consumed.

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56 Energy Engineering Vol. 112, No. 6 2015Ta

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Table 9: Annual Specific Energy Consumption for Selected Industries

In all the selected industries, the percentage of electricity supplied from the national grid varies from 0.04-1.78% on average. This low proportion of electricity supplied from national grid is due to poor per-formance of the power sector in Nigeria, which has forced many manu-facturing industries in the country to generate electricity on their own. The effects of this are increases in cost of production and poor quality of products from Nigerian industries.

Specific Energy Consumption (SEC) Energy is used for such things as operating machines, air condi-tioning, illumination, compressors, pumps, and boilers in processing and manufacturing industries. Specific energy consumption (SEC) is an important factor that determines the energy situation in a typical indus-try. The total amount of energy consumption and also the deviations of the SEC for each section from the world averages provide adequate information for policy makers to determine the priorities in industrial section. Table 9 shows the annual specific energy or energy productivity consumption, which is the unit energy consumed per unit production in MJ/kg, of each selected industry. As shown, the variations of annual specific energy for the period under consideration are: food process-ing industry, 28-108 MJ/kg; distillation and bottling industry, 3.72-3.96 MJ/kg; chemical industry, 76.55-92.80 MJ/kg; and ceramic industry, 7.71-7.93 MJ/kg. The level of annual specific energy consumption dur-ing production processes depends on the complexity of the production stages, the energy contents of the finished products and level of energy management strategies adopted in the industry.


Table 10 presents the average specific energy consumption in alum production in the chemical industry and ceramic industry in selected countries for comparison purposes. On average, the specific energy con-sumption in alum production of this present study is comparable with that of India at 94.70 MJ/kg, which is higher than other countries but lower than the world average specific energy consumption of 103 MJ/kg. Thus, it can be concluded that energy use in this factory has been relatively efficient. The average specific energy in ceramic tiles produc-tion of this present study is higher than in other countries. Considering the technological and logistic gaps between Nigeria and developed countries, Nigerian manufacturing/processing indus-tries have opportunities to strengthen their operations and minimize energy losses and waste to reduce specific energy consumption. This requires a multi-pronged strategy to follow technological discipline and implement incremental innovations at every stage of processing plant operations.

Table 10: Specific energy used in alum and ceramic tiles production in differ-ent countries

Energy Used Ratio Table 11 shows the energy used ratio in the selected industries for the period under review. The energy used ratio in all the selected indus-tries is far from unit (1). This indicates an ineffective utilization of energy in the industries, which implies that more energy is expended in the unit

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production of finished product. High proportions of energy input are wasted on the factory floor. The energy used ratio in the selected industries signifies an ineffec-tive use of energy with a fluctuating pattern, which could be attributed to such things as diesel leakages, generation of more electric energy (or steam at high temperature and pressure) than needed in the plant, the use of worn out electric motors, poor maintenance of electric appliances, aging machine and equipment.

Table 11: Energy Used Ratio

Daily Electric Energy Consumption Electricity use in industry is primarily for electric drives, electro-chemical processes, space heating, lighting and refrigeration. In this study, Figures 1-8 present the patterns of daily electrical energy con-sumption by various industrial equipment used for different operations in the selected industries. Among the electricity consuming equipment in all the industries surveyed, electric motors consumed the highest electric energy. The proportion of electricity consumed by electric motors depends on the complexity of the industry. The percentages of electric energy consumed by electric motors in the industries surveyed were: chemical industry, 71%; ceramic industry, 77%; distillation and bottling industry, 47%; and food industry, 40%. Electric drives of one type or another use major percentages of industrial electricity. Examples of electric drives include electric motors, machine tools, compressors, refrigeration systems, fans, and pumps. Improvements in these applications would have a significant effect on reducing industrial electrical energy consumption. Motor efficiency can be improved in some cases by retrofits such as modifications, better


lubrication, improved cooling, and heat recovery, but generally requires purchasing of more efficient units.

Energy Management Opportunities in the Selected Industries One of the aims of the walkthrough audit is to identify bad prac-tices, inefficient equipment and poor energy habits to save power con-sumed. Walkthrough energy audits carried out at the food processing in-dustry, distillation and bottling company, chemical industry and ceramic industry revealed energy saving opportunities in the following sections.

Figure 1: Percentage of electric energy consumed by various equipment in the chemical industry

Figure 2: Percentage of electric energy consumed by electric mo-tors in alum production process

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Figure 3: Percentage of electric energy consumed by various equipment in distillation and bottling industry

Figure 4: Percentage of electric energy con-sumed by electric mo-tors in non-alcoholic production process

Lighting A walkthrough audit was conducted during visits to assess the illumination requirement of the selected plants and scope of improve-ment of illumination quality and illumination level, with an objective of cutting down electrical energy consumption. During the walkthrough, it was observed that some of the lighting points were on even though the sunlight was bright enough to provide illumination. Energy consumed through lighting can be reduced in the selected industries by:


Figure 5: Percentage of electric energy consumed by various equipment in the ceramic industry

Figure 6: Percentage of electric energy consumed by electric motors in the ce-ramic tiles production process

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i. Providing electronic control to conserve daytime power waste for lighting. Energy conservation of the order of 10% can be achieved by making arrangement to switch off lights automatically when they are not required.

ii. Replacing lower-efficiency lighting with more efficient, energy saving types such as mercury lamps with HP sodium lamps, and

Figure 7: Percentage of electric energy consumed by various equipment in the food industry

Figure 8: Percentage of electric energy consumed by electric motors in food production process


replacing all standard fluorescent tubes with high-efficiency tubes such as the T* series

iii. Painting the factory walls and ceilings with white or lighter colors and using the light reflectance to improve the brightness of the workplace

iv. Using electronic ballast in place of copper ballast

v. Using reflectors in the ring frame area, which are removed. The use of reflectors will improve illumination level at the work plane

vi. Cleaning light fixtures and lamps periodically

TurningoffEquipmentWhennotinUse Adopting energy efficiency and implementing conservation mea-sures can result in significant energy savings. The selected industries surveyed in this study leave heavy energy consuming equipment on when they are not in use, particularly during breaks. Each motor left on, no matter how small, results in a large amount of wasted energy when considered over a long period. This particular analysis considered sav-ings that could be made if machines and equipment are switched off when not in use.

Electric Process Heat Electricity is widely used as a source of process heat due to the ease of control, cleanliness, and unit capacities range from watts to mega-watts, safety, and low initial cost. Typical heating applications include resistance heaters, such as metal sheath heaters, ovens, furnaces, and boilers, electric salt bath furnaces, infrared heaters, induction and high-frequency resistance heating, dielectric heating, and direct arc electric furnaces. In the industries surveyed, boilers were observed to be losing much heat because they are not properly lagged. Energy can be saved in these industries by:

i. Replacement of aging boilers with new and much smaller boilers to reduce energy waste

ii. Investing in high-precision burner controls for continuous correct air-fuel ratio management

iii. Recovering flash steam from condensate and using the recovered low-pressure steam elsewhere

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69

iv. Proper lagging of pipes carrying steam from boilers to the factory to reduce heat lost to the environment

v. Installing the latest types of heat-reclamation equipment such as economizers and air heaters for flue gas and heat exchangers and heat pumps for boiler blow down in the chemical and food industries

vi. Attaching a metering device to monitor the quantity of gas con-sumed in the boiler

vii. Managing the quantity of fuel and possibly reusing exhaust hot gas in the kiln units in the ceramic industry

Electrical Drives It was observed at the industries visited that some electric motors are weak and generate excessive noise because they have been rewound more than twice. Also, it was observed that some of the motors were dirty, dusty and poorly ventilated. Some energy can be saved by:

i. Reconfiguring electrical motors from delta to star connections, which will make it run at less than 33% of the rated output

ii. Replacing old electric motors with new ones

iii. Performing proper housekeeping and operation of electric drives, as good ventilation reduces energy loss due to heating

iv. Installing variable speed drives and soft-start options on electric mo-tors

Heating, Ventilation and Air conditioning (HVAC) System Heating, ventilating, and air-conditioning (HVAC), are an important use of energy in the industrial sector. Environmental needs in an indus-trial operation can be quite different from residential or commercial op-erations. At the selected industries surveyed, it was observed that air con-ditioning and refrigeration equipment were dirty thus dissipating much heat. It was also observed that there was no minimum temperature setting for air conditioners and refrigerators so that staff can use it for regulating their temperatures. In these industries, energy can be saved by:

i. Cleaning heat exchangers regularly for easy heat transfer

ii. Placing heat exchangers out of direct access to sunlight or heat dis-sipating objects


iii. Setting cooling temperatures for the entire company to avoid waste iv. Fitting doors with springs to trap cold air for self-control v. Installing a new ventilation system using a rotary heat exchanger

to provide fresh air of constant temperature in the factory—The warm exhaust air heats the incoming air in the exchanger and the temperature is controlled by the number of exchanger revolutions.

ElectricGenerator In the course of the walkthrough energy audits, it was observed that the electric generators used at selected industries generate more en-ergy than needed in the industry, which results in waste of energy such as fuel and high production costs. Energy waste can be reduced by: i. Getting smaller generators for load shedding and shifting, as this

will minimize energy waste in the selected industries. It was a com-mon practice in the industries surveyed that had up to two to four big generators that only a single generator was servicing the entire plant. In times of low production, this single generator is still used to generate power to the plant resulting in a lot of wasted energy, as it is not fully utilized. Moreover, it was observed that the capacity of the generators in the selected industries generated more energy than was needed in the industries.

ii. Replacing diesel generators with gas generators, as gas is cheaper, cleaner and burns readily in air

CONCLUSIONS

The judicious use of energy by industries is a key lever for ensur-ing a sustainable industrial development. The cost effective application of energy management and energy efficiency measures offers industries an effective means of gaining both economic and social dividends, while also reducing negative environmental effects of energy use. Unfortu-nately, industries in developing countries are lagging behind in the adoption of energy efficiency and management measures, and therefore are missing the benefits of their implementation. This article examines the pattern of energy consumption in chemi-cal, food processing, ceramic and distillation and bottling industries lo-cated in southwestern zone in Nigeria. The study identified the sources

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of energy consumption, patterns of energy consumption and suggested ways of energy saving in the selected industries. It was also found in the study that the major sources of energy in these industries are diesel and gas fossil fuels, while contributions from manual energy are insignifi-cant. The major source of electrical energy in the companies investigated was mainly from diesel or gas generators, due to low voltage or epileptic power supply from the national grid. Through the method of a walkthrough energy audit, the power rat-ing, operation time of energy-consuming equipment and machineries and power factor were collected. The data were then analyzed to investigate the breakdown of end use equipment and machineries energy use. The results of the energy audit in the selected producing industries showed that the electric motor accounts for 40-77% of total energy consumption. Since the electric motor takes up a substantial amount of the total energy used in the selected industries, energy-savings strategies such as the use of high efficient motors and variable speed drive (VSD) can reduce en-ergy consumption of the motors used. Based on the available data, the food processing industry has the highest annual energy consumption at 5,039.45 TJ/yr., while the ceramic industry has the lowest average annual energy consumption at 109.43 TJ/yr. The annual specific energy consump-tion (SEC) variations for the period under consideration by sector are: the food processing industry from 28-108 MJ/kg; the distillation and bottling industry from 3.72-3.96 MJ/kg; the chemical industry from 76.55-92.80 MJ/kg; and the ceramic industry from 7.71-7.93 MJ/kg. The energy used ratio in all the selected industries is far from unit (1), which indicates the ineffective use of energy in the industries, which implies that more energy is expended in the unit production of the finished product. The study con-cluded that energy is not sufficiently utilized in these companies. Hence, significant amounts of energy can be saved in the selected industries by applying the suggested energy saving strategies. To curtail unnecessary waste of energy and to reduce cost of en-ergy consumption, the following factors must be critically looked into in these industries:• Procuring test equipment for energy monitoring in the factory• Investing significant capital to lower energy consumption• Conducting audits to identify the causes of energy waste• Maintaining and controlling must be done properly to improve the

energy productivity

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————————————————————————————————ABOUT THE AUTHORS Dr. Oyedepo, S.O., is a corresponding author and senior lecturer in the Department of Mechanical Engineering, Covenant University, Nigeria. He can be reached through email: [email protected] or by cell phone: +2348055537865

Dr. Adaramola, S.M., is an associate professor in the Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, Norway. He can be reached through email: [email protected]

Dr. Odunfa, M.K., is a lecturer in the Department of Mechanical Engineering, University of Ibadan, Nigeria. He can be reached through email: [email protected]

Aremu, O.T., is a graduate of the Department of Mechanical En-gineering, Covenant University, Nigeria. He can be reached through email: [email protected]

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