Economic Viability of Railway Electrification System in Pakistan
Author: Samar Hanif
Electrical Engineering Department University of Engineering and Technology Lahore, Pakistan.
This Manuscript of mine was accepted at the International Conference on Engineering & Emerging Technologies 2019-ICEET held in Superior University Lahore, Pakistan.
Abstract—Pakistan’s economy is not developing at that speed as it should be. The import to export ratio is getting bigger with time. One way to affect this ratio is to reduce fuel consumption as much as possible. A state-owned enterprise, Pakistan Railways is going at a loss for the last couple of years. The government must take sensible necessary decisions to have positive effects on it. Pakistan Railways consumes millions of gallons of oil on regular basis to drive the trains. This paper presents two topologies i.e. fuel-based rail engines and AC electric rail engines and concludes the best of them. Electric rail engines taking power directly from the transmission line are more economical than fuel initiated ones. The reason for giving power directly from the upper head power line is because, in diesel operated rail engine we generate electrical power inside the rail engine and use it to drive motors, so why not take the power directly from the transmission line.
I. INTRODUCTION
Pakistan has been facing many economic and energy problems for the last couple of years. Unfortunately, Pakistan’s exports are increasing with the passing years and imports are not increasing with that ratio. Therefore the balance of goods is disturbed. The below graph shows the increase in Pakistan’s imports with the passing times.
Figure 1: Pakistan's imports with passing years on the x-axis and Cost USD on y-axis[1]
One of Pakistan’s biggest imports is petroleum products. The lower currency exchange rate of Pakistan directly affects all the goods. US dollar worth against Pakistani Rupees (PKR) is continuously increasing with passing years. In the last ten years exchange rate of Pakistani Rupees has increased from 80 PKR for 1 USD to 133 PKR.[2] Therefore import of petroleum products in USD significantly affects the prices of others goods, produced or undergone transportation. Since Pakistan has to import all of the oil and petroleum products, therefore, making an industry (especially the transport industry) independent of oil as much as possible is a good step toward its benefits. Pakistan Railways(PR) has been suffering from a significant annual loss.
PR’s goods carrying trains used to be the significant source of income than the passenger trains, but now over the years goods trains are being reduced as they are not as cost-effective as they used to be. Currently, all of Pakistan Railways’ trains are driven by diesel input rail engines. Pakistan Railways’ engines are consuming a significant amount of oil on regular basis. The fuel used in the rail engines is first given as an input to a diesel engine present inside the rail engine. This diesel engine then drives an electrical generator/AC alternator fitted alongside which produces electricity. Typically in a 3000 horsepower rail engine, a diesel engine along with an electrical generators/AC alternator of around two megawatts is fitted inside the rail engine.
Figure 2: A 2000hp ALCO 251 diesel engine model.
Figure 3: A diesel engine along with an electrical generator fitted inside a rail engine.
The electricity produced from these diesel generators inside the rail engine is then used to drive the DC traction/AC induction motors. In most PR’s rail engines an AC alternator produces electricity. Then a rectifier converts it into DC which then drive DC traction motors. However, now the newly imported PR’s rail engines use an AC alternator to produce electrical power and drive induction motors.
Figure 4: Image of a traction motor used in PR's engines for traction purposes
In a PR’s engine six AC induction/DC traction motors, a rating of typically around 700hp each are attached to six wheelsets of the rail engine.
Figure 5: A traction motor attached to a wheelset of the rail engine
Production of electricity from oil is not a good practice in Pakistan. As already discussed oil prices increases with the dollar rate. Now let’s see how economically is to produce electricity from diesel generators? Larger machines are considered to be more efficient therefore let’s consider a 2250 kW diesel generator. It consumes 159.6 gallons per hour at its full load[5]. Which means 604.1 litres/hr. Hence this diesel generator produces 3.7kWh/litre. The average per litre diesel price is 0.80USD [6].
So electricity price comes out to be 0.216USD/kWh. The operating cost for the hydroelectric power plant is less than .01USD[7]. And the electricity from a coal power plant is less than 0.08USD/kWh[8]. The below graph shows a good cost comparison of three energy productions. The electricity cost from oil is excluding the maintenance cost of the diesel generator.
Figure 6: The bar graph showing cost comparison for three electricity productions. 1- Coal 2- Oil 3- Hydroelectric.
Hydroelectric and solar productions of electricity are the most economical form of electricity production. These types of production have very less operating costs. A good step towards the long-term solution to the energy problems in Pakistan is to increase the hydroelectric production of electricity. Also, Pakistan has vibrant hydropower resources of around 59796 MW [9]. As the water crises issue has gained importance nowadays, a significant increase in hydroelectric forms of electricity production is expected in the upcoming years. Currently, Pakistan is producing only 35% of its total electricity production from oil-based power plants Pakistan’s electricity production percentage from different resources is given in the table below.
Table 1: percentage of electricity produced in Pakistan from different resources. [9][15]
|
Gas |
29% |
|
hydro |
30% |
|
Oil |
35.2% |
|
nuclear |
6% |
Even though the diesel engine has the highest thermal efficiency among all other practical engines, still, diesel engines are only 45% efficient[11][12]. Besides cost, onboard electricity production in rail engines has many other negative sides. These types of rail engines make a lot of noise while running, which causes noise pollution. Due to burning diesel, they produce exhaust gasses that pollute the environment.
Typically power plants also have separate sections to process the hazardous gasses or waste to convert it into an environment-friendly matter. And the power plant spends a considerable amount of its electricity production in this processing section. No such setup is present in diesel locomotives. The exhaust gasses contain oxides of nitrogen (NO) and carbon. Diesel exhaust has been declared as Group 1 carcinogen, which mainly causes lung and bladder cancer. In fact, diesel exhaust contains many other substances that cause cancer[14].
II. TOPOLOGICAL DESIGNS AND ECONOMIC ANALYSIS
As described earlier onboard electricity production in a rail engine is a less efficient method to drive the trains than the electric locomotives. Most of the European countries are expanding their rail electrification network. Also, we saw using electricity from a hydro/power plant is more economical. Figure7 shows both topological engine designs. Now we compare the alternative topologies.
We can drive the locomotives from the electricity which is transmitted through conductors along the railway path. Electric locomotives do not have to carry the prime movers all the time. Therefore, they have:
•Less axle load and more traction forces.
•Less turn-around time as compared to diesel locomotives.
•Quick acceleration and deacceleration
•No need to go anywhere for refueling.
Although, Pakistan Railways will have to build a new infrastructure for power lines along the existing path but at the most trafficked routes this investment can be paid back in a couple of years. ET system introduced in 1970 in Pakistan over Lahore-Khanewal Section (286Kms) paid back its cost of 142.000 million including the cost of 29 electric locomotives in 8 years. Today ET system over Lahore-Karachi Section can provide savings in expenditure and an increase in earnings of about Rs. 30.000 billion per annum. As 2.2MW is fixed for 3000HP locomotives, if 100
Figure 7: Rail engines simple working shown for both topological design, the upper picture for diesel rail engine, the lower picture for electric traction engine.
Although, Pakistan Railways will have to build a new infrastructure for power lines along the existing path but at the most trafficked routes this investment can be paid back in a couple of years. ET system introduced in 1970 in Pakistan over Lahore-Khanewal Section (286Kms) paid back its cost of 142.000 million including the cost of 29 electric locomotives in 8 years. Today ET system over Lahore-Karachi Section can provide savings in expenditure and an increase in earnings of about Rs. 30.000 billion per annum. As 2.2MW is fixed for 3000HP locomotives, if 100 ET locomotives are used, up to 200MW electricity is required for the ET project over the Lahore-Karachi Section, which is less than 1% of the total installed capacity of the country.[3]
Besides generating electricity onboard in the railway engines, Pakistan Railways is also generating electricity from oil in power vans separately to meet the electricity demand in the trains. Nowadays all of the load inside the Pakistan Railways’ trains e.g. air conditioner, lights, fans is AC load. And separate 3 phase power is generated to meet this load demand. Typically one or two diesel generators of around 1 megawatt are present in the power van. Pakistan Railways electrification system will give benefits in this section as well. Economical electricity can be drawn from the same overhead power line and supplied to the whole train.
Diesel engines also require tuning and significant maintenance costs. On the other hand, electric traction system maintenance cost is comparatively very less. The speed of electric rail engines is also comparatively high.
Pakistan Railways’ passenger trains have an abysmal record of being late on the schedule. If a train departs 2 hours late due to some reasons (e.g. Cross with another train, or waiting for more passenger cars from another train whose arrival is awaited), during these whole two hours the engine was running, consuming a significant amount of fuel. If you go on a typical survey, standby engine running fuel consumption is very common in Pakistan Railways.
To calculate fuel consumption, consider an ideal 3000hp diesel engine with 40% thermal efficiency. For generating a 3000 horsepower constant output (ignoring mechanical losses) to drive a 2.2MW electrical generator, the amount of input energy required can be calculated from the definition of thermal efficiency[4] as:
Taking, “heating value” of diesel fuel = 42500kJ/kg (40282.0693Btu/kg), and density = 0.832 kg/L. To supply input energy at the rate of 19087500Btu/h, the engine has to burn fuel at a rate of
Hence 1-litre diesel produces electricity = 3.8 kWh (Ideally)
As there are more losses present in diesel rail engines on the contrary we have comparatively fewer line losses and transformer losses in ET locomotives. Today we can build a transformer with nearly 100% efficiency[16] and by increasing the transmission voltage we can achieve around 99% efficient transmission[17].
There are also rectification losses in diesel locomotives that use AC alternators to drive the DC traction motors.
Figure 8: losses comparison from input to output and hence efficiency comparison of both topologies.
Pakistan Water And Power Development Authority (WAPDA) can provide roughly 3-4 times cheap solutions to Pakistan Railways for driving trains. Currently, WAPDA is offering Rs. 14.47/kWh tariff rate to Pakistan Railways particularly for traction purposes[10]. On the other hand, Pakistan State Oil (PSO) company is providing fuel at the rate of Rs. 92.58/liter[13]. The below bar graph shows the cost of electricity per unit generated in a diesel locomotive including the maintenance cost of diesel locomotive vs the WAPDA’s 2018 tariff for railway traction. This graph elaborates how cost-ineffective is a diesel locomotive as compared to an ET locomotive when it is covering the distance on the railway track, but when we consider the total transportation distance covered from one city to another city, other cost ineffective things come into play like standby fuel consumption of diesel locomotives, fuel burnt during braking and re-acceleration of the trains.
Figure 9: Cost comparison of per unit electricity produced in diesel locomotives and WAPDA's offer 2018.
III. CONCLUSION AND FUTURE WORK
It is concluded that the onboard electricity production from diesel is not economical and cause noise and air pollution. On the other hand, electric traction(ET) provides an economical solution to the transportation industry. ET has less maintenance cost and no noise or air pollution. DC distribution system is currently in the research phase. In the future economical design of the DC network can be considered for PR’s electrification. Furthermore, during an unexpected or intentional stop of trains many litters of fuel are wasted, regenerative braking system’s implementation in ET can provide benefits in this regard. During deacceleration, the kinetic energy of the trains can be converted into electrical energy and upload to the railway’s grid through the power line above, to be used by the other trains during acceleration.
REFERENCES
[1] International Monetary Fund ( available online: www.imf.org )
[2] International Monetary Fund. The latest data is available online (www.google.com).
[3] Pakistan Railways Headquarters Office, Lahore, Pakistan. No.259-ET-/DIS/RES.
[4] Yunus A. Cengel and Michael A. Boles. Thermodynamics An Engineering Approach, chapter 6.
[5] www.dieselserviceandsupply.com/ Diesel_Fuel_Consumption.aspx
[6] Global Petrol Prices, available online (www.globalpetrolprices.com)
[7] www.e-education.psu.edu/eme801/node/530
[8] Huaneng Shandong Ruyi (Pakistan) Energy (Pvt.) Limited. Available online ( www.nepra.org.pk )
[9] Private Power and Infrastructure Board (PPIB) available online ( www.ppib.gov.pk )
[10] Schedule of electricity tariff w.e.f 22 March 2018. Pakistan Railways Headquarters Office, Lahore, Pakistan.
[11] US EPA. 2004, available online ( www.epa.gov/ otaq/models/ ngm/may04/ crc0304c.pdf )
[12] November 21, 2010, at the Wayback Machine. Freedom CAR & Vehicle Technologies Program. US Department of Energy, Aug. 2003. www1.eere.energy.gov/ vehiclesandfuels/ pdfs/basics/ jtb_diesel_engine.pdf
[13] 2nd supply order no.10/0004/00-0/1-2018. July 2018, Pakistan Railways Headquarter, Lahore, Pakistan.
[14] International Agency for Research on Cancer (IARC). Retrieved June 12, 2012, available online (www.iarc.fr )
[15] Ministry of Finance, Revenue and Economic Affairs available online (www.finance.gov.pk)
[16] John J. Grainger, William D. Stevenson, JR. Power System Analysis, Chapter 2.
[17] Danish Khan (2014). Comparison of transmission losses and voltage drops of GIL(Gas Insulated transmission line ) and overhead transmission lines.