Implementing Sustainable Locomotive Traction Technology Options Environmental Sciences

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This paper reviews commonly known locomotive traction technologies for sustainable implementation under the possible adoption of the Carbon Pollution Reduction Scheme (CPRS) by the current Australian Government. The technologies of interest within this review are bio-fuels and hybrid locomotives. Bio-fuels seem to be a possible substitute/additive for diesel in railway locomotives. Issues regarding sustainability and costs (capital and operational) hinder the commercialization of bio-fuels however unless the government provides appropriate incentives to encourage their uses. For hybrid locomotives, most of the technologies except regenerative braking are in developing stages, signifying the issue of technical feasibility. As a result, no costs (capital and operational) and greenhouse gas emission levels for these technologies exist for an economic analysis.

Regenerative braking technology, in principle, has potential applications on freight and passenger trains that have hybrid power systems. The main concern of regenerative braking is the amount of energy that can be recovered which translates into cost savings from improved output efficiency and lower greenhouse gas emissions. Nevertheless, the collection of relevant data for regenerative braking remains a problem, thereby limiting the usefulness of an economic study.

This paper reviews commonly known locomotive traction technologies for implementation given the possibility of an adoption of a Carbon Pollution Reduction Scheme (CPRS) by the Australian Government. The actions of the Australian government with regard to climate change are examined in the next section. Following this is an explanation of the possible impact generated by the government's action on the railway industry. The paper then reviews the various locomotive traction technologies that could reduce carbon emissions and improve efficiency which will be of interest to railway operators. Finally, conclusions are presented.


In 2007, the Australian Government ratified the Kyoto Protocol [] , committing to reduce greenhouse gas (GHG) emissions to 25 percent below 2000 levels by 2020 and at least 60 percent below 2000 levels by 2050. To put forth their commitment into action, the Australian Government is contemplating the introduction of a CPRS. The CPRS is an emission trading scheme that uses a cap and trade mechanism, of which the cap will be reduced in future years to achieve its emission target levels.

The Australian Government believes that the CPRS is the cheapest and most effective way of tackling climate change (Department of Climate Change and Energy Efficiency 2009). To signal its intention for the initiation of the CPRS, a Green paper [] and a White paper [] have been released by the Australian Government in July 2008 and December 2008 respectively. The CPRS may or may not be established but given the commitment of the Australian Government to reduce emissions, it is likely consider other schemes should the CPRS fail to materialize.

Australian businesses such as railway operators that emit CO2 will be directly affected. Other Australian businesses that emit little to no CO2 will also be indirectly affected through the increase in price of other goods and services. Businesses should therefore consider the option of implementing technologies that reduce greenhouse gas emissions as part of their decision making.

Generally, railway operators have the choice of either to purchase emission permits in order to pollute or invest in new technologies that will decrease CO2 emissions. An advantage of investing in new technologies is that they are environmentally friendlier and improves efficiency, which reduces operating costs in the long run. Another advantage is that unused permits could be sold to other companies (not limited to rail operators) that require them. Purchasing emissions permits over the long term is not sustainable as the price of permits is volatile and increasing. This will reduce business profits and make the prediction of future revenues difficult.

While some businesses do not have the finances to invest in new technologies and have to settle with purchasing permits, other businesses that are financially able should consider the option of investing in greener technologies as part of their long term investment plans. The next section examines potential rail traction technologies that interest railway operators in light of the Australia Government's commitment towards reducing greenhouse gases.


Railway locomotives in Australia are either powered by diesel or electrification. Due to increasing petroleum prices and the possible implementation of the Australian government's scheme to clamp down greenhouse emissions, a change towards greener technology may be beneficial for railroad operators. Railway traction technologies vary widely with focus on different aspects of railway locomotives. These aspects can be classified into three categories; i) power or tractive effort and as a by-product, reduces carbon emission, ii) energy regeneration, and also as a by-product, lowers carbon emission and iii) substituting fossil fuels to minimize carbon emission. Although these technologies have different purposes, they share a common characteristic of decreasing carbon emissions. The rest of the section examines these technologies in detail.


Bio-fuel is a renewable energy source produced from natural materials. The most common bio-fuels are ethanol and bio-diesel. Ethanol is a petrol additive/substitute that can be produced from corn, wheat or sugar beet, cellulosic biomass resources such as herbaceous and woody plants, agricultural and forestry residues and a large portion of municipal and industrial solid waste streams. Biodiesel, a synthetic diesel fuel from oil seeds, is produced from vegetable oil, animal fats or waste cooking oil. These two forms of bio-fuels are seen as possible substitutes of petroleum fuels (Demirbas 2009).

Source: WTRG Economics

Figure 1: Crude Oil Prices based on 2008 US dollars (1947 - August 2009)

Figure 1 shows the crude oil price from 1947 to August 2009. The world price line of crude oil is extremely volatile. From 2000 onwards, the oil price increased at an accelerating rate until 2007 where the global financial crisis occurred and the oil price plunged to approximately 50 US dollars per barrel in August 2009. The figure also shows that the oil price is dependent on supply and demand interactions. The events shown in the figure are shocks to supply or demand sides which affects the oil price greatly. Setting aside Figure 1, the oil price is expected to increase in the very long run due to increasing demand (population growth) and decreasing supply [] . The increasing and volatile oil price, coupled with the establishment of the Kyoto Protocol in 1997, are possible reasons that the world is looking towards petroleum fuel substitutes.

Source: Demirbas (2009)

Figure 2: World Production of Ethanol and Biodiesel (1980 - 2007)

Figure 2 displays the world production of ethanol and biodiesel from 1980 to 2007. The production of both bio-fuels is growing at an increasing rate from year 2000 onwards, with ethanol production growing at a much faster rate than biodiesel. The figure seems to suggest that the world is turning to ethanol and biodiesel as possible substitutes/additives for petroleum fuels.

Bio-fuels production costs vary widely depending on factors such as feedstock, conversion process, scale of production and region (Demirbas 2009). Since ethanol is produced from food crops, there is competition between the production of food and the production of ethanol. For biodiesel, the use of oil produced from oil seeds for cooking is a competitor (Demirbas 2008A; Demirbas 2008B; Demirbas 2008C). Demirbas (2009) argues that one of the main benefits of using bio-fuels is that it is sustainable. However, the International Union of Railways (UIC) conducted a study in 2007 and found that there are some uncertainties about the sustainability of bio-fuels. The UIC states that the issue of sustainability relates to bio-fuels impacts on energy use, the emission of other conventional air pollutant such as nitrogen oxide, land use, impacts on biodiversity and ecosystems, impacts on water and the production and disposal of waste products. The UIC's study also shows that biodiesel is feasible for railway traction unit engine use but this is not without its disadvantages. The first potential disadvantage is an increase in fuel consumption and decreased power. The second disadvantage is that biodiesel blends in excess of 30% may increase maintenance costs. In relation to the cost of bio-fuels, both the UIC and Demirbas (2009) mentioned that the cost of biodiesel is significantly higher than diesel and requires the aid of the government if bio-fuels are to be developed commercially.

Although bio-fuel seems to be a possible substitute/additive for diesel in railway locomotives, the issue of sustainability is questionable. The cost of bio-fuels deters people from using it as well. Therefore, unless the government provides appropriate incentives to encourage the use of bio-fuels, it is not an attractive option for railway operators.

Hybrid Locomotives

A hybrid locomotive consists of a hybrid power plant in which fuel cells comprise the prime mover and an energy source which provides auxiliary power (Miller et al. 2006). The energy source can come from storage devices such as batteries, flywheels or super capacitors. Fuel cell [] by itself is also a technology that is improving through time. Furthermore, a rail vehicle can implement regenerative braking if it has the capability of using the traction motors as generators or alternators to recover potential or kinetic energy of the vehicle. Storage device technologies, fuel cell technologies and regenerative braking are examined below.

There are various battery technologies on the market with lead-acid technology dominating the automotive industry for over a hundred years. As the market demands for improved cycle life and operation over broader temperature range, nickel-metal-hydride technology developed. The advantage of nickel-metal-hydride over lead-acid is improved cycle life and excludes the use of toxic heavy metals for production. Another battery technology, lithium-ion also provides improved cycle life under pulsing or under deep discharge when compared with lead-acid. In addition, lithium-ion technology provides higher specific energy, uses less expensive electro active materials and outperforms nickel-metal-hydride at high and low application temperatures. However, unresolved issues with the safety of large cells and reliable battery-pack management mean that lithium-ion technology is not ready for commercialization. (Miller et al. 2006)

Table 1: Battery Parameters

Battery Type

Specific Power

(W kg-1)

Specific energy

(W h kg-1)

Cycle Life

Life (years)

Cost Target ($/kW h)



















Source: Miller et al. (2006), p. 858

From Figure 3, lithium-ion batteries have potentially the best performance but due to the issues mentioned as above, they are not commercially viable compared to nickel-metal-hydride batteries. Besides the three battery technologies, there are other batteries that are undergoing research but none of them come as close as lithium-ion technology towards commercialization due to operational issues.

Flywheels [] have existed as one of the oldest form of energy storage device. The advantage of a flywheel over battery is its capability of handling higher power. The main disadvantages are its structural requirements that contain safety issues in the event of a catastrophic failure under higher rotational rates. Flywheel requirements of size and capacity for a fuel cell hybrid locomotive are still in the early commercialization stage and are likely to be more expensive than batteries (Miller et al. 2006).

Super capacitors have higher power density, higher cycle life than batteries. Conversely, the downside of super capacitor is its lower energy density against batteries. There are other hindrances towards implementation on locomotives. The first hindrance is the higher cost compared to batteries or flywheels (Romo et al. 2005). The second hindrance is related to a safety issue concerning locomotive operators as super capacitors contain toxic and flammable dielectric fluids (Romo et al. 2005). These hindrances prevent super capacitors from application on hybrid locomotives.

Fuel cell is a technology that has gathered much interest owing to its wide range of output power and has the potential to be a carbon-neutral energy source (Meegahawatte et al. 2010). An example would be fuel cells running on hydrogen that emits zero carbon emissions. However, this depends on the source of hydrogen extraction. Currently, steam reforming is the preferred method of extracting hydrogen with almost 50% of the world's hydrogen being produced through it (Meegahawatte et al. 2010). Another method of obtaining hydrogen is obtained by the electrolysis of water using electricity from traditional power plants (Meegahawatte et al. 2010). And through the de-carbonization of electricity grids using renewable energy, such as solar or wind power, and carbon capture and storage programs, carbon emission can be neutralised. The key challenge for fuel cell hybrid locomotives is the extraction and delivery of hydrogen, which relates to its feasibility. As the technical feasibility of hydrogen fuel cell hybrid locomotive has not been fulfilled, there are no costs attached to it at the moment. It is expected that future fuel cell costs will be reduced as there is an anticipation of mass fuel cell production when they are ready for commercialization (Miller et al. 2006).

Regenerative brakes, in principle, have potential applications on passenger trains and freight locomotives that have hybrid power systems because the necessary power-management system is already in place. The main concern relates to how much of the available energy can be recovered. When moving at a high speed, the locomotive's power level is at its highest and probably cannot be absorbed by practical hybrid storage systems (Miller et al. 2006). This means that a substantial portion of the high-speed braking energy has to be dissipated by other means. Alternatively, when moving at a low speed, the available energy for recovery is low (Miller et al. 2006). Thus, the use of regenerative brakes depends largely on its capital cost and maintenance cost. These costs should then be evaluated against the amount of savings (in terms of reduced carbon emission level and output efficiency) that the regenerative brakes offer. One major problem is the collection of relevant data for analysis.

Most of the hybrid technologies besides regenerative braking are still in developing stages. Thus, there are no known costs attached to them. Furthermore, the level of carbon emissions for each technology is also unknown until they have proved to be feasible. Regenerative braking seems to be a feasible option for specific locomotives but it depends on the capital cost, maintenance cost, the amount of carbon emissions it reduces and the amount of output efficiency it increases. An analysis of regenerative braking on trains is able to determine its usefulness for specific railway operators. However, the collection of relevant data remains a problem.


The Australian government has determined that a CPRS is the cheapest and most effective way of reducing greenhouse gas emissions. The possibility of CPRS implementation forces railway operators to abate carbon emissions depending on their financial ability. As such, technologies such as bio-fuels, storage devices, fuel cells and regenerative braking were reviewed for possible implementation so that CPRS costs may be avoided. None of the technologies except regenerative braking proved to be technically feasible as most of them are in developing stages. Lastly, although regenerative braking is a possibility for implementation, the collection of relevant data for analysis is difficult and therefore, limits the usefulness of an economic study.


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