Petrol and diesel utilisations in the Nigerian road transportation sector have been assessed, using exergy efficiency and improvement potential as parameters. The mean petrol engine exergy efficiency was 13.05%, while that of diesel engines was 10.79%. The average improvement potential of petrol engines was 2.07×1011 MJ, which was 75.6% of average input exergy. Diesel engines had an average improvement potential of 5.15×1010 MJ, which was 69.2% of average input exergy. Practical constancy of the exergy efficiencies of the engines left input exergy values as the sole determining factors of improvement potentials of the systems. Petrol fuel was found to be utilised, away from sustainable path, more than diesel fuel. This observation was found attributable to subsidisation of petrol downstream sector and simultaneous deregulation of the diesel downstream sector as well as the preponderance of petrol engines in the road transportation sector. In conclusion, it was recommended that a mechanism be put in place to check the unsustainable petrol fuel utilisation in the transport sector

Ajala, M. T.

Akinleye, A. O.

Alao, W. A.

Badmus, I.

Olalere, N. A.

English

LAUTECH Journal of Engineering and Technology (LAUJET)

Badmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  101  SUSTAINABLE ENERGY ANALYSIS OF NIGERIAN ROAD TRANSPORTATION SECTOR: EFFECTS OF INFLUENCED FUEL DEMAND PATTERNS Badmus I.1, Alao W. A.2, Ajala M. T. 2, Olalere N. A.2, Akinleye A. O.2 1Department of Mechanical Engineering  2Department of Industrial Maintenance Engineering  Yaba College of Technology, Yaba, Lagos, Nigeria Email: ismaila.badmus@yabatech.edu.ng   ABSTRACT  Petrol and diesel utilisations in the Nigerian road transportation sector have been assessed, using exergy efficiency and improvement potential as parameters. The mean petrol engine exergy efficiency was 13.05%, while that of diesel engines was 10.79%. The average improvement potential of petrol engines was 2.07×1011 MJ, which was 75.6% of average input exergy. Diesel engines had an average improvement potential of 5.15×1010 MJ, which was 69.2% of average input exergy. Practical constancy of the exergy efficiencies of the engines left input exergy values as the sole determining factors of improvement potentials of the systems. Petrol fuel was found to be utilised, away from sustainable path, more than diesel fuel. This observation was found attributable to subsidisation of petrol downstream sector and simultaneous deregulation of the diesel downstream sector as well as the preponderance of petrol engines in the road transportation sector. In conclusion, it was recommended that a mechanism be put in place to check the unsustainable petrol fuel utilisation in the transport sector.  Keywords: Improvement Potential, Exergy Efficiency, Road Transportation, Fuel Demand, Fuel Subsidy, Sustainable Energy   1. Introduction Road transport is the main mode of transportation in many developing countries. In Nigeria, road transportation alone consumes an average of 90% of the total energy used by the transport sector. Besides, 77% of total petrol consumed in the country is used in the transport sector [ECN, 2016].  However, energy utilisation efficiencies are generally low, and the information in Table 1, by Maduekwe et al [2020], is instructive:  Table 1: Nigerian Road Fuel Economy Vehicle Type Fuel Type Vehicle Fleet Size (%) Fuel economy (km/litre) Saloon and Station Wagons Petrol 99 11 Diesel 1 11 Motorcycles  Petrol 100 30.7 Vans and Pickups Petrol  75 7.6 Diesel  25 7.6 Tankers, Trailers, Tractors, Tippers Diesel  100 3.5 Lorries, Trucks Diesel  100 3.5 Minibuses, Omnibuses  Petrol  50 3.9 Diesel  50 3.5  Badmus et al [2012] also worked on analysis of Nigerian transportation system energy consumption, but only energy and exergy analyses were made, and the time scope was from 1980 to 2010. There are several ways of assessing a system’s energy utilisation sustainability. Some of the parameters commonly used are exergy efficiency, depletion number, sustainability index and improvement potential [Dincer and Zamfirescu, 2018]. While depletion number and sustainability index are separate functions of a single variable, the exergy efficiency, the improvement potential is a function of both the exergy efficiency and the exergy input rate.   Ordinarily, and as it is elsewhere, demands for petrol and diesel as transportation fuels are different [Nwachukwu and Mba, 2016]. However, in Nigeria, due to public pressures, successive governments have always subsidised the pump prices of petrol as well as household kerosene, leaving diesel fuel, otherwise known as automotive gas oil, to market forces [Onyekwena et al, 2017; Adeoti et al, 2016]. This has resulted in the pump prices of the former always being lower than those of the latter, with one sometimes doubling the other. Expectedly, this has also skewed the demand for transportation fuel in favour of petrol. In fact, Adegoriola and Suleiman [2020] flatly asserted that the present transportation fuel consumption pattern in Nigeria had been largely influenced by the government policy through partial deregulation of downstream sector of the petroleum industry.  Indeed, on the average, Gujba et al [2013] posited not long ago that over 61% of travel was by petrol vehicles and the rest by diesel. The effects of this transportation fuels LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107 Badmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  102  demand pattern on energy utilisation sustainability in the sector are examined in this paper.   2. Methodology 2.1 Exergy efficiency ψ =  . . . (1) The relationship between energy efficiency and its exergy efficiency is given by [Badmus, 2021]:  ψ = η/φf . . . (2) In Eq. (2), φf is the exergy factor of Szargut and Styrylska as enunciated in Szargut et al. [1988]. The fuel exergy factor used for both petrol and diesel fuels in this work is 1.07 [Szargut, 2005]. The heating values have been taken from Garg et al. [2006], and they are 44150 MJ/tonne for petrol, and 42910 MJ/tonne for diesel. When analysing a system of vehicles, as in our case, the system efficiency (ψm) is given by: 𝜓 =  ∑∑   . . . (3) The subscript ‘i’ in Eq. (3) is for the ith vehicle in the system, ‘ψi’ is the exergy efficiency and ‘ϵ’ is its exergy input.  In this paper, vehicle energy efficiencies in Table 2, adapted from Badmus [2021] will be used:  Table 2: Thermal Efficiencies of Road Vehicles in Nigeria (%) Vehicle Petrol Engine Diesel Engine Cars 13.33 15.47 Light Duty Vehicles 8.44 16.88 Heavy Duty Vehicles 11.78 9.12 Motorcycles 32 -------  2.2 Improvement Potential Obviously, maximum improvement in the exergy efficiency of a process or a system is attained when exergy loss is least. Consequently, van Gool [1992] in Dincer and Zamfirescu [2018] suggested the concept of an exergetic ‘improvement potential’, P, when analysing different processes or systems:  P = (1- ψ)(Exin – Exout) =(1- ψ)(1- ψ)Exin   = (1- ψ)2Exin . . . (5)   The Improvement Potential is a function of two variables, the exergy efficiency, ψ, and input Exergy, Exin. The function varies quadratically with ψ and linearly with Exin. When ψ attains a maximum value of 1 or 100%, the Improvement Potential vanishes. This means that, at this maximum attainable efficiency, there is no room for further improvement as the entire input exergy has been fully utilized.  Conversely, when ψ is nil, the entire input exergy is fully degraded. Then, the improvement potential is at climax, being equal to the entire exergy input. Between these two extremes, the improvement potential is a fraction of the input exergy.  An overall change in improvement potential, P(φ, E), is given by: ∆𝑃 =  ∆𝐸 +  ∆𝜑 . . . (6) But  = (1 −  𝜑)  . . . (7) And = 2𝐸(𝜑 − 1) . . . (8)  While the partial change in improvement potential with respect to input exergy is a positive function of exergy efficiency only (Eq. 7), the one with respect to exergy efficiency is a negative function of both input exergy and the system exergy efficiency (Eq. 8). This is because, in practice, φ is always less than unity (100%). For sustainability, improvement potential should be decreasing. Its maximum value for any combination of exergy input and exergy efficiency is attained when the value of ΔP is zero. Then, ∆𝐸 =  ∆   ∆ = ∆     . . . (9) Hence, when the actual input energy change, ΔE, is less than ΔEmax, improvement potential will decrease. When it is more, the improvement potential will increase. In other words, when relative input exergy change, ΔErelative (= ΔE - ΔEmax) < 0, improvement potential will decrease. Both the value and algebraic sign of relative input exergy change are very important in determining direction of improvement potential change.  For any given efficiency change, relative to a particular initial efficiency, the right hand side of Eq. (9) gives the maximum fractional change in input energy that should take place. Energy utilisation is sustainable if the actual fractional input exergy is less than the right hand side of Eq. (9). However, it is not sustainable if it is more. The equation expects no input exergy change, following an unchanging system exergy efficiency.           Badmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  103  3. Results and Discussion  Table 3: Road Transportation Fuel Consumption from 1990 to 2019 in Metric Tonnes   Year Cars Petrol LDV Petrol  HDV Petrol Motorcycles Petrol Total Petrol Cars Diesel LDV Diesel HDV Diesel  Total Diesel Petrol Consumed (%) 1990 3287824 711706.9 17465.2 349304 4366300 71483.7 691009.1 1620297 2382790 64.69 1991 3289639 712099.7 17474.84 349496.8 4368710 71514 691302 1620984 2383800 64.70 1992 3313238 717208.2 17600.2 352004 4400050 56046 541778 1270376 1868200 70.20 1993 4018272 869825.1 21345.4 426908 5336351 101031.9 976641.7 2290056 3367730 61.31 1994 4246928 919321.6 22560.04 451200.8 5640010 69310.5 670001.5 1571038 2310350 70.94 1995 3109416 673087.3 16517.48 330349.6 4129370 67992 657256 1541152 2266400 64.56 1996 3000810 649577.8 15940.56 318811.2 3985140 67953.3 656881.9 1540275 2265110 63.76 1997 3293887 713019.4 17497.41 349948.2 4374352 63624.81 615039.8 1442162 2120827 67.35 1998 2658232 575420.6 14120.75 282415 3530188 54297.48 524875.6 1230743 1809916 66.11 1999 2374655 514035.5 12614.37 252287.4 3153592 47740.11 461487.7 1082109 1591337 66.46 2000 1957500 423730 10400 207970 2599600 61550 590880 1399230 2051660 55.89 2001 2936700 635700 15600 312000 3900000 63730 611830 1448840 2124400 64.74 2002 3571870 773190 18970 379480 4743510 66880 642040 1520380 2229300 68.03 2003 3587630 776610 19060 381160 4764460 63650 611010 1446900 2121560 69.19 2004 3373480 730250 17920 358400 4480050 45830 439950 1041820 1527600 74.57 2005 3554050 769340 18880 377590 4719860 56640 543760 1287660 1888060 71.43 2006 3415380 739320 18140 362860 4535700 27600 264910 627330 919840 83.14 2007 3642670 788520 19350 387000 4837540 23170 222390 526640 772200 86.23 2008 3906040 845530 20750 414980 5187300 25380 243680 577050 846110 85.97 2009 3980190 846000 20760 415210 5262160 18910 181520 429860 630290 89.30 2010 4469520 565460 13880 277530 5326390 14710 141210 334380 490300 91.57 2011 4696940 506270 12420 248480 5464110 16360 157030 371850 545240 90.93 2012 4924360 446560 10960 219170 5601050 11320 108670 257330 377320 93.69 2013 6534950 1414600 34710 694280 8678540 47350 454560 1076410 1578320 84.61 2014 7153720 1548550 38000 760020 9500290 53850 516920 1224110 1794880 84.11 Badmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  104  2015 6534950 1414600 34710 694280 8678540 47350 454560 1076410 1578320 84.61 2016 7157340 1549330 38020 760410 9505100 65270 626600 1483830 2175700 81.37 2017 7428196 1607963 39459.21 789184.2 9864802 32940.15 318421.5 746643 1098005 89.98 2018 11104090 2403674 58985.87 1179717 14746467 26108.31 252380.3 591788 870276.6 94.43 2019 5987527 1296105 31806.25 636125 7951563 25781.04 249216.7 584370 859367.7 90.25    From Table 3, average percentage of petrol fuel consumed during the period was 76.47%. Minimum was 55.89% in the year 2000, and the maximum was 94.43% in 2018. Hence, even the minimum percentage petrol fuel consumption during the period covered by this work was more than 50%. Out of all the categories of carriers, petrol cars recorded the absolutely highest energy consumption of 4.90246×1011 MJ (2018) during the period considered in this paper, while petrol HDV recorded the absolutely lowest of 4.5916×108 MJ (2000).   The two categories of carriers also recorded highest and lowest mean values of 1.95011×1011 MJ and 9.80009×108 MJ respectively. Mean energy utilisation of motorcycles during the period was 1.96005×1010 MJ, which was more than each of similar values for petrol HDVs and diesel cars. This suggests that use of motorcycles was more rampant than use of petrol HDVs and diesel cars and diesel LDVs in the country. While cars consumed most petrol, HDVs consumed most diesel fuels.  Throughout the period covered by this work, the exergy efficiencies of petrol engines system were consistently higher than those of the diesel engines. Secondly, both systems have practically constant efficiencies (Fig. 2). The implication of this is that change in exergy efficiency (Δφ) is always zero within each system, from year to year. Hence, exergy efficiencies could not contribute to improvement potential changes. Invariably under this circumstance, the improvement potential becomes a linear function of exergy input only, as shown in Fig. 4 for petrol engines. The only exception is for petrol engines between 2008 and 2013. During this period, the petrol engines system efficiencies went down, before picking up again. Based on the exergy efficiencies alone, diesel engines should have higher improvement potentials. However, throughout the period, exergy utilisations by the petrol engines were consistently higher than those by diesel engines, being close only once, in the year 2000 (Fig. 1).   Petrol engines exergy utilisations ranged from a minimum of 1.22806×1011 MJ (2,599,600 metric tonnes) in the year 2000 to a maximum of 6.9663×1011 MJ (14,746,467 metric tonnes) in 2018. The corresponding (minimum and maximum) values for diesel engines were 1.73242×1010 MJ (377,320 metric tonnes) in 2012, and 1.54625×1011 MJ (3,367,730 metric tonnes) in 1993 (Table 3). During the periods when the exergy efficiencies were constant in Fig. 2, Eq. 9 expected an exergy input of, at most, zero value for sustainability. However, Fig. 1 shows that this was not the case, as exergy was consumed indiscriminately. The result of uncontrolled, unsustainable energy utilisation is shown in Fig. 3. The total exergy input in the year 2000 is the lowest, resulting in the lowest exergy improvement potential (Fig. 3).  In terms of changes of input exergy values with changes in exergy efficiencies along sustainable energy utilisation path (Eq. 9), Fig. 5 indicates that petrol engines have greater deviations than diesel engines. Indeed, petrol engines have a total deviation of 1.69268×1011 MJ, average deviation of 5642265734 MJ, minimum deviation of -3.2099×1011 MJ and a maximum deviation of 2.30612×1011 MJ, resulting in a deviation range of 5.51607×1011 MJ. The corresponding values for diesel engines are -7×1010 MJ, -2.3×1009 MJ, -4.9×1010 MJ, 6.88×1010 MJ and 1.18×1011 MJ. The average improvement potential of petrol engines is 2.07×1011 MJ , which is 75.6% of average input exergy. Diesel engines have an average improvement potential of 5.15×1010 MJ, which is 69.2% of average input exergy. This indicates that petrol engines have a higher improvement potential than diesel engines.  Badmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  105    Fig. 1: Engines Annual Exergy Inputs   Fig. 2: Engines Annual Exergy Efficiencies  Fig. 3: Engines Annual Improvement Potentials  01E+112E+113E+114E+115E+116E+117E+118E+111985 1990 1995 2000 2005 2010 2015 2020Exergy Input (MJ)YearPetrol EnginesDiesel Engines024681012141985 1995 2005 2015 2025Exergy Efficiency (%)YearPetrol EnginesDiesel Engines01E+112E+113E+114E+115E+116E+111980 1990 2000 2010 2020 2030Improvement Potential (MJ)YearPetrol EnginesDiesel EnginesBadmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  106   Fig. 4: Petrol Engines Improvement Potentials variation with Input Exergy   Fig. 5: Deviations of Actual Input Exergy Changes from the Maximum Allowable Values   4. Conclusion Petrol and diesel engines sustainable fuel utilisations have been assessed using exergy improvement potential as the main parameter. Exergy efficiencies were practically constant throughout the period of the assessment. Improvement potential depended on the exergy inputs of the engines, with petrol engines having larger potentials than the diesel engines. Petrol fuel was also found to be more utilised (with a total change deviation of 1.69268×1011 MJ from the maximum for sustainability) than diesel fuel (with a total change deviation of -7×1010 MJ). This is largely attributable to government subsidies on petrol retail prices and deregulation of the downstream sale of diesel as well as preponderance of petrol engines in the sector. It is necessary to put a mechanism in place to check the unsustainable petrol fuel utilisation in the transport sector. This may be in terms of reducing customs import duties on efficient motor vehicles and outright ban of importation of old, inefficient vehicles. Foreign direct investments in the area of establishing vehicle assembly plants in the country could also be encouraged.  References Adegoriola, AE and Suleiman, IM [2020]: Adopting Gas Automobile Fuels (LPG & CNG) into the Nigerian Transportation System, Journal of Economics and Sustainable Development, ISSN 2222-1700 (Paper) ISSN 2222-2855 (Online), Vol. 10, No. 14, doi:10.7176/JESD/10-14-02, www.iiste.org   Adeoti, JO, Chete, L, Beaton, C and Clarke, K [2016]: Compensation Mechanisms for Fuel Subsidy Removal in Nigeria, GSI Report, International Institute for Sustainable Development, www.iisd.org/gsi Badmus, I, Osunleke, AS, Fagbenle, RO and Oyewola, MO [2012]: Energy and exergy analyses of the Nigerian Transportation Sector from 1980 to 2010, International Journal of Energy and Environmental 01E+112E+113E+114E+115E+116E+110 2E+11 4E+11 6E+11 8E+11Petrol Engines Improvement Potential (MJ)Petrol  Engines Exergy Input (MJ)-4E+11-3E+11-2E+11-1E+1101E+112E+113E+111985 1990 1995 2000 2005 2010 2015 2020Deviation of Actual Input Exergy Change from the Maximum Sustainable Value (MJ)YearPetrol EnginesDiesel EnginesBadmus I.  et al./LAUTECH Journal of Engineering and Technology 2021 15 (2) 2021: 101-107  107  Engineering, Vol. 3, Issue 23, http://www.journal-ijeee.com/content/3/1/23, doi: 10.1186/2251-6832-3-23  Dincer, I and Zamfirescu, C. (2018): Sustainability Dimensions of Energy, Comprehensive Energy Systems, Volume 1, pages 101-152, doi:10.1016/B978-0-12-809597-3.00104-8, Elsevier Inc Energy Commission of Nigeria (ECN) [2016]: National Energy Balance 2012-2013  Garg, A, Kazunari, K, Pulles, T [2006]: Volume 2: energy. In: IPCC guidelines for national greenhouse gas inventories. IGES, Japan Gujba, H, Mulugetta, Y, and Azapagic, A [2013]: Passenger transport in Nigeria: Environmental and economic analysis with policy recommendations, Energy Policy, Vol. 55, pages 353 – 361, http://dx.doi.org/10.1016/j.enpol.2012.12.017,  www.elsevier.com/locate/enpol  Maduekwe, M, Akpan, U and Isihak, S [2020]: Road Transport Energy Consumption and Vehicular Emissions in Lagos, Nigeria: An Application of the LEAP Model, Transportation Research Interdisciplinary Perspectives, Vol. 6, http://dx.doi.org/10.1016/j.trip.2020.100172  Nwachukwu, M. U and Mba, H. C [2016]: Analysis of the Trend of Highway Transportation Fuel Consumption in Nigeria, Tropical Environment, Volume 13, Number 1, Pages 133-145 Onyekwena, C, Adedeji, A, Akanonu, PC and Momoh, A [2017]: Energy Subsides in Nigeria: Opportunities and Challenges, Centre for the Study of the Economies of Africa, CSEA, Abuja, Nigeria, January, 2017  Szargut, J [2005]: Exergy Method, Technical and Ecological Applications, WIT Press, Southampton, Boston, www.witpress.com  Szargut, J, Morris, DR, Steward, FR [1988]: Exergy analysis of thermal, chemical, and metallurgical processes. Hemisphere Publishing Corporation, Washington DC, USA  van Gool, W (1992): Exergy Analysis of Industrial Processes, Energy, Vol. 17, No. 8, pages 791 – 803. 

SUSTAINABLE ENERGY ANALYSIS OF NIGERIAN ROAD TRANSPORTATION SECTOR: EFFECTS OF INFLUENCED FUEL DEMAND PATTERNS

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SUSTAINABLE ENERGY ANALYSIS OF NIGERIAN ROAD TRANSPORTATION SECTOR: EFFECTS OF INFLUENCED FUEL DEMAND PATTERNS

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