AN OVERVIEW
For the logistics industry, there is no way around thinking and acting sustainably about the future of road freight transport. Manufacturers are working intensively on new drive systems for their trucks that run on alternative fuels and use new technologies, as the time for diesel engines is running out. The focus is on liquefied natural gas (LNG), hydrogen, fuel cells and electric motors.
As of 2022, around a third of greenhouse gas emissions in the transport sector are caused by commercial vehicles, with heavy trucks with diesel engines being responsible for the majority of CO2 due to their high mileage. Although emissions per tonne-kilometre have fallen since 1995 thanks to more efficient engines, improved exhaust gas purification technology and higher-quality fuel, the total volume of goods traffic on the roads has risen by around 74% in the same period, according to the Federal Environment Agency.
The German government’s 2030 climate protection program has therefore set the target that by the end of the decade, around a third of heavy goods vehicles should be powered by electric drives or electricity-based fuels.
HOW QUICKLY CAN THE EXCHANGE SUCCEED?
Commercial vehicles for heavy goods transport on the road achieve very high mileages per year, which is why their useful life is short. The Federal Ministry for Digital and Transport Affairs therefore sees the replacement of conventional truck fleets with alternative drive systems as an effective measure against CO2 emissions from diesel vehicles.
The well-known management consultancy Boston Consulting Group has conducted a study on this topic. According to the study, around 35 percent of all newly registered light trucks up to six tons and 26 percent of heavy trucks over 15 tons will have drives other than diesel engines in 2030.
Bain & Company, another major US management consultancy, comes to different conclusions. The company conducted a survey of 565 fleet managers in Germany, Spain, France and the UK, 60 percent of whom stated that they would buy vehicles that run on hydrogen or electricity, or at least have hybrid technology, by 2025. The target is a 50 percent share of vehicles with alternative drive systems. This will put truck manufacturers under a lot of pressure and they will have to change their current business models.
However, the publishers of the study believe that the European truck industry is in a comfortable starting position, as its efforts in recent years have resulted in greater customer loyalty. The reasons for this can be seen in a reduction in operating costs, an increase in reliability and a more targeted focus on customer needs.
Currently, trucks with battery electric motors, hydrogen and fuel cells as well as hybrid drives (diesel and overhead line) are rarely found in practical use on the road. In the case of light commercial vehicles (LCVs) with a gross vehicle weight of up to 3.5 tons, larger numbers with electric motors and batteries are already on the market. Heavy-duty commercial vehicles (HDVs) weighing 3.5 tons or more, on the other hand, are mostly still in development or have not yet progressed beyond the pre-series stage. At the same time, the necessary infrastructure of charging stations and overhead lines leaves a lot to be desired. Their network needs to be massively expanded in order to guarantee nationwide coverage in the future.
The Bain & Company study also provides interesting information in this regard. Currently, the total cost of ownership of a truck is still in the foreground, with reliability and service in second and third place. In the future, however, those responsible will focus first on range, followed by driving performance, efficiency and reliability.
WHICH DRIVES ARE CURRENTLY BEING TESTED?
Truck manufacturers are experimenting with various ways of getting their products on the road completely or largely emission-free. These include
- Liquefied natural gas and bio-liquefied natural gas (LNG and bio-LNG)
- hydrogenated vegetable oils (HVO)
- Hydrogen and fuel cells
- Electric motors
- Hybrid solutions with diesel burners and overhead lines
The following sections describe the various drives, their development status and their advantages and disadvantages.
LIQUEFIED NATURAL GAS, LIQUEFIED PETROLEUM GAS, AND BIO-LIQUEFIED PETROLEUM GAS
Liquefied petroleum gas (LPG) and liquefied natural gas (LNG) are among the best-known solutions for replacing diesel. The fossil fuel mainly consists of
- from methane (LNG)
- or from butane and propane (LPG).
Bio-liquid gas can be obtained from different types of biomass such as waste and food waste. The biomass is fermented anaerobically, i.e. without the addition of oxygen, and then purified. The end product is pure methane and a small amount of CO2.
LNG, LPG and bio-LNG allow long ranges and are considered to be somewhat more environmentally friendly, as they achieve a high level of efficiency in combustion engines and produce fewer emissions than diesel. The gases are cooled down to temperatures between -161 °C and -164 °C and liquefied in this way. This reduces the volume to just one six-hundredth of the original amount, making these alternatives ideal for transportation over long distances. In addition, the technology, which is based on diesel engines, is already ready for series production and enables ranges of up to 1,600 kilometers.
Compared to diesel, the various gases offer a number of advantages. For example, greenhouse gas emissions can be reduced by up to 22 percent. Bio-LNG can be supplied in many countries and existing biomass has great potential for its production. In addition, the network of filling stations throughout Europe is already quite well developed and continues to grow. However, natural gas is a fossil fuel whose resources will eventually be exhausted. The additional technology required makes these vehicles more expensive than conventional diesel-powered commercial vehicles.
HYDROGENATED VEGETABLE OILS
Hydrogenated vegetable oils (HVO) are very similar to conventional diesel and can be used in most engines. Therefore, there are no increased vehicle costs. HVO is produced from various organic oils such as palm oil, pine oil, animal fats and other vegetable waste oils. HVO can be used on its own or mixed with fossil diesel. The CO2 emissions of the fuel are lower due to its production from bio-oils, but the energy content is just as high as that of diesel. Another advantage is that the existing filling station network can be used.
However, there are also disadvantages. The availability of raw materials, i.e. bio-oils, is limited. The production of palm oil and waste from palm oil production is particularly controversial. This is because large areas of rainforest are cut down and destroyed to grow the plants and extract the oil. On the one hand, this has a negative impact on the global climate and, on the other, biodiversity in these regions suffers greatly.
HYDROGEN AND FUEL CELLS
Trucks with fuel cells are a realistic option in the medium to long term. There are two options that can reduce the CO2 emissions of trucks by up to 100 percent. They are either powered by a fuel cell, in which gaseous hydrogen reacts with oxygen to generate electricity that powers an electric motor. Or the hydrogen is used as fuel for an internal combustion engine.
The drive is particularly environmentally friendly because only water vapor is released as exhaust gas and no emissions of CO2, nitrogen oxides or particulate matter are produced. The major truck manufacturers are working on advancing the technology and are also cooperating with other companies, for example from the fuel industry.
Compared to fuel cell technology, a combustion engine with hydrogen offers the advantage that no large energy storage system is required. The cooling capacity can also be lower. A combustion engine also places lower demands on the purity of the hydrogen.
Unfortunately, the technology also has a catch. According to a study by the Fraunhofer Institute, trucks with hydrogen and fuel cells only have a range of 300 to 400 kilometers. In contrast, a 40-ton truck with a conventional diesel drive can travel up to 2,500 kilometers. However, this is not the only hurdle that hydrogen propulsion still has to overcome, as it is only sustainable if it is produced using renewable energy sources, the keyword being green hydrogen. However, the most important energy sources, such as coal and natural gas, are currently still fossil fuels. Overall, hydrogen production requires a great deal of energy and is difficult to calculate due to strongly fluctuating prices.
TRUCKS WITH ELECTRIC MOTORS
The greatest difficulty with electric drives for trucks is the current battery technology, as it cannot yet offer a satisfactory range. A breakthrough is therefore still a long way off. 18- and 25-ton trucks from leading German manufacturers have a range of around 200 kilometers including charging. The common and widely used lithium-ion batteries are expensive, heavy and do not have a long service life. Despite this, the BMDV is also providing considerable funding for electric trucks.
Because the advantages of electric vehicles speak for themselves. Electricity can be generated from numerous sources of primary energy. These include fossil fuels such as natural gas and coal, but also renewable sources such as wind and hydropower or solar energy. Electricity can power fully electric trucks or be used in plug-in hybrid electric trucks. The impact on the climate is generally lower than that of diesel vehicles.
The other technology in electrically powered trucks is also impressive. For example, the drivetrains work very efficiently. In addition, around 30 percent fewer moving parts are installed in an electric truck than in trucks with a combustion engine. This significantly reduces the need for servicing and maintenance. Finally, operation is also much quieter, so that they offer advantages in urban areas and at night.
However, electrification also has its disadvantages. The infrastructure of electric charging stations for trucks has so far been poor, as the charging points must have an output of at least 150 kW in order to be suitable for electrically powered trucks. Significant increases in investment are required here in order to create a satisfactory network. In addition, the cost of purchasing new equipment is currently higher than for conventionally powered trucks.
OPERATION WITH OVERHEAD LINES AND DIESEL
In the federal states of Hesse, Baden-Württemberg and Schleswig-Holstein, there are test routes for trucks equipped with a diesel engine and an electric and battery drive. The batteries can be recharged while driving under an overhead line so that the vehicles can drive emission-free off-road and only have to fall back on the diesel engine when the battery is empty. Whether this technology will ever be suitable for everyday use remains to be seen in further tests. The greatest difficulty is likely to be providing the broadest possible infrastructure, i.e. equipping all freeways or at least the most important routes in Germany with overhead lines.
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