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Using electricity to power road freight

First publishedin ITS International
2014 September October
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Real life electrified road system eHighway
The eHighway system uses a series of gantries along the road to carry overhead power lines.

Next year sees the start of the first real-life electrified road system for transporting freight.

Worldwide freight transportation is predicted to double by 2050 but despite expansion of global rail infrastructure only one third of this additional freight transport can be handled by trains. This means that the largest proportion of freight transport will continue to be by road and as a result, experts expect global CO2 emissions from road freight traffic to more than double by 2050.

It is calculated that 64% of freight in the US is delivered by road and that the trucks delivering those goods account for 18% of the country’s NOx production 5% of greenhouse gas emission (see graphs). These challenges, combined with concerns about fuel prices and energy security, highlight the need for solutions that can address not only the expected increase in transport but also employ technology that offset or overcome the environmental and economic problems too.

One sustainable solution to improve transportation systems today and in the future is electromobility. Though the term ‘electromobility’ may bring to mind electric cars, there are other important ways transportation systems can utilise electricity to power vehicles both small and large.

The ‘eHighway’ from Siemens is one potential solution. Its concept uses electricity delivered via overhead lines to electrify road lanes and provide clean and efficient power to trucks - enabling the use of renewable energy and can result in lower CO2 emissions.

The first real-world demonstration project of the technology will take place in California near the Ports of Long Beach and Los Angeles, the two largest ports in America, and is due to begin operation in July 2015. Working with the South Coast Air Quality Management District, Siemens is to install an eHighway system along one mile of a highly-travelled corridor near the ports. Up to four trucks will be running in the one-year demonstration, making multiple trips each day.  As this is the first operational trial of the technology there are no official projections regarding savings on emissions and running costs, so the project’s findings will act as benchmark of what the technology can achieve. 

Technology

Using technology similar to trolley systems or streetcars with overhead contact lines, the eHighway system will use an active pantograph to conduct direct current (DC) electricity to an electric and/or electric-hybrid truck. The drive system will enable full electric operation when connected to the contact line while retaining an engine, or other form stored energy, supplies power when outside of the contact lines.

Unlike rail technology the eHighway contact line system is designed with two poles (one to handle the power in-feed and the other the out-feed) because the current return circuit cannot flow via the road in the same way it can through a rail. Overhead contact lines provide a secure energy supply at speeds up to 96kmh (60mph). A substation connected to the medium voltage grid located near the eHighway provides power to the overhead contact lines and can collect and feed it back energy from regenerative braking system to further increase the efficiency achievable from the technology.

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Scania based vehicle european trial
A Scania-based vehicle participating in a track-based European trial

 An active pantograph atop the truck transfers the energy from the overhead lines to the electric motor and can connect and disconnect with the contact line automatically at statutory speeds.  As soon as the truck-mounted optical scanner recognises an overhead line, the pantograph is ready to connect and it can also be extended automatically or manually from inside the vehicle. This allows significant flexibility as the eHighway trucks can easily switch lanes or pass other vehicles without being permanently fixed to the overhead systems like a streetcar.

Each truck will be equipped with either an all-electric or a hybrid drive systems comprising a drive motor, generator, inverter, on-board energy storage and DC/DC converter. The eHighway system could be combined with most other technology, be it diesel, natural gas (CNG/LNG), battery or fuel-cell for powering the vehicle outside of the catenary.

While details are yet to be finalised the eHighway technology being demonstrated in California looks set to feature a hybrid diesel/electric truck, one powered by a compressed natural gas/electric hybrid drive train and an all-electric truck that runs on battery power outside of the contact line. The option remains for a fourth vehicle with a different configuration to be added to the trial.

Already under development for the project is a diesel-hybrid demonstration vehicle which is being built a partnership between Siemens and Mack Trucks, a subsidiary of Volvo. The vehicle will be based on a conventional Mack Pinnacle highway chassis and equipped with a proprietary and fully integrated hybrid electric driveline. It will be fitted with the fuel-efficient 11-liter Mack MP7 engine which drives the vehicle mechanically through a modified Mack mDRIVE automated manual transmission, and a 150kW integrated AC electric motor/generator.

Mack’s 11-liter engine develops 302kW (405hp) and 2,115Nm (1,560lbft), which is mid-range for this type of vehicle and work. According to Jan Hellaker, Volvo Group vice president of transport solutions: “Besides further reducing exhaust emissions and fuel usage without compromising performance, the MP7 engine delivers a significant weight advantage and helps offset the weight of add-on components required for the eHighway.” 

The trucks will operate in full-electric mode when on the eHighway routes and will automatically switch to the diesel/mechanical drive system where there is no overhead line.

Benefits of eHighway

Siemens expects adopting eHighway technology to result in a number of environmental and economic benefits due to the increased efficiency an electric motor has in comparison with a diesel engine. Typically a diesel engine is 35%-40% efficient while an electric traction motor is around 95% efficient while total efficiency from in-feed at the substation to the wheel is estimated to 80%-85%. So when the test vehicles are powered electricity, roughly twice as much of the input energy reaches the wheels - or put another way, half as much energy is needed to move the same load. It is also a possible to use regenerative braking to further improves the overall efficiency. This translates into significantly reduced operating costs, which can finance the investment costs, especially on frequently used routes.

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real life electrified road system emisions graph
Emissions % of all US Sources

 Using electricity also eliminates the local emissions associated with diesel engines, greatly improving the local air quality. At the same time, the eHighway concept allows the use of renewable electricity in heavy duty road freight, opening up the possibility to greatly reduce the green house gas emissions caused by the freight industry. It is also possible that roadside solar panels and wind turbines could be used to feed the overhead power lines which would reduce the carbon footprint still further.

Contact line systems have been proven to work reliably and cheaply across the world for more than a century, strengthening the case that this technology can be used successfully for other modes of transportation. Furthermore, the system can be installed along existing roads, greatly reducing investment and maintenance costs, and without disrupting traffic – an important consideration in severely space constrained and heavily trafficked areas like ports. Two studies estimate the cost of installing gantries and sub-station connections to be in the region of $5 – 6 million per km  ($8 - $9.6 million per mile). 

Electrifying Applications

The California eHighway project focuses on heavy-truck transport in key logistical hubs like ports but there are a number of other potential applications for electrified road freight. Mining is another example of trucks transporting goods on a small but regularly travelled route that may not warrant a separate rail connection. An eHighway concept in this setting could result in similar reductions in costs and emissions as the port demonstration.

Electrification is potentially applicable for almost any routes highly-travelled by trucks or other heavy-duty vehicles and over the coming decade will provide an ever increasing market for eHighway vehicles. Economies of scale will reduce prices and open the way for truck operations on moderate or diverse duty cycles. Regional or national highways may be considered for eHighway applications and with the expected standardisation of the vehicle technology, the challenge will shift to the traffic management.

This would include organising the billing and enforcement required to operate an eHighway system open to all suitable vehicles.
Looking to the Future

The California project is crucial to understanding how electricity can answer today’s transportation challenges and to demonstrate zero emission road freight. Installing the technology in a real-world scenario allows it to be evaluated with a view of how it can be scaled up beyond connecting the ports to possibly the surrounding freeways and other cities.

In the future it might then be possible to electrify the highway network. These electric trucks would be able to charge their on-board storage from the powerline while on the move to make deliveries away from the electrified route – a concept that could have significant potential in densely populated nations. It also may not be so far off that we’ll see highway signs for HOV, Exit Ramps and also an ‘E’ lane.

Meeting greenhouse gas reduction targets and efficiently serving the transportation needs of a dynamic economy can only be achieved with new solutions. Using electricity is a key way to bring the transportation systems of yesterday into the present and to test the ideas of tomorrow.

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