Road transport is to become independent of fossil fuels. But how will this be implemented, and what will it cost? Focusing on three scenarios, the “Defossilizing the Transportation Sector” study conducted by the Research Association for Combustion Engines (FVV) provides a basis for informed discussion.
Text: Johannes Winterhagen
To ensure the global average temperature does not increase by more than two degrees Celsius by the end of the 21st century, current scientific research has shown that a total of 1100 billion tonnes of CO2* can still enter the atmosphere – not a huge amount considering that current annual emissions total more than 40 billion tonnes. As such, the transport sector, which is currently still almost completely dependent on fossil fuels, is facing a huge challenge. While it should continue to provide prosperity, it must also become climate-neutral in a relatively short time.
In the foreseeable future, electricity generated primarily from solar and wind energy will be available as a climate-neutral energy source. There are three paths which enable this electricity to be utilized in road transport.
In the “Defossilizing the Transportation Sector” study, a working group at FVV analysed the three paths that are technically feasible with regard to the economic costs to be expected. At times, over 40 experts from different sectors were involved in precisely calculating the engineering basis for these costs – such as the efficiency of specific powertrains or possible loads in the power grid. To keep results comparable, the working group decided to solely analyse scenarios in which a single energy source could cover 100% of the demand. The required amount of kinetic energy in road transport – i.e. the energy at the wheel – was kept consistent at 143 terawatt hours per year for all three scenarios.
Energy chains for climate-neutral mobility
The hydrogen pathway
The electric pathway
The synthetic fuels pathway
No surprise here: the direct use of electrical energy results in the greatest efficiency. As such, only between 249 and 325 terawatt hours of electricity must be generated in order to maintain our current level of mobility. This equates to the average annual yield of 11,000 to 15,000 offshore wind turbines in the 5 megawatt class in the North Sea. However, it does not take into consideration the energy required to heat the interior – energy which is generated as waste heat in combustion engine applications. Experts in the FVV working group also assume that the availability of charge electricity during dark periods (times without sun radiation and wind) can only be ensured in a climate-neutral manner via reconversion of sustainably generated energy sources (e.g. synthetic methane in a gas power plant).
The economic investment required for a 100% electric scenario is determined by the infrastructure for electricity distribution and charging. The core question for the distribution networks is how far time-controlled charging can compensate for the network expansion. The investment requirements for car traffic are between 0 and 77 billion euros. This is joined by costs for the required AC charge points at home and at work, as well as the quick charge stations on motorways. Experts expect to see a hybrid solution for lorries which combines overhead power lines on motorways with high-performance batteries for all other routes. The infrastructure required here will cost up to 21 billion euros.
Bigger means more efficient. This applies both to engines and to electrolysis systems in which sun and wind energy are used to manufacture hydrogen. However, alongside the large-scale manufacturing analysed in the study, a local hydrogen generation structure was also observed, for which the “transport costs” are mainly generated through the expansion of the electricity networks. Initial findings showed that the efficiency advantages of centralised generation are significant. The electricity requirements are between 502 and 574 terawatt hours, which can increase up to 703 terawatt hours in a local structure. Furthermore, decentralised (local) generation requires the corresponding expansion of the electricity network, which can cost up to 90 billion euros.
According to experts, between 5,000 and 10,000 hydrogen filling stations, each with eight filling points, should be sufficient to guarantee complete mobility with fuel cell vehicles in Germany. Investment costs of more than three million euros are to be expected for a single filling station with eight filling points, each capable of charging at least six vehicles per hour.
There is no such thing as ‘the’ synthetic fuel. As there are multiple methods available to enrich regeneratively created hydrogen with carbon, the experts from the FVV working group analysed a total of seven fuels in eight scenarios. An important factor for overall efficiency beyond the manufacturing process is how the carbon is generated. In the long term, the only conceivable method in a climate-neutral world is to separate it from the air, which requires additional energy and costs. In a transitional period, however, using CO2 from industrial processes is a viable option. The study shows that synthetic methane can be produced with an efficiency of 65% in this manner. The worst overall efficiency is found in the production of OME when coupled to CO2 separation from the air, at just 31%. In the best-case scenario, this results in additional required electricity generation of 625 terawatt hours – a figure which is 2.5 times higher than the electricity requirements in the purely electric scenario.
The combustion engine as an energy converter has a decisive impact on the energy balance of synthetic fuels. The study was based on the fuel consumption from the best current passenger car and truck engines. Further potential for improvement – such as the “admixing” of electricity in hybrid powertrains – was not considered.
»The results of the study show that synthetic e-fuels can be competitive, irrespective of their less favorable effciencies across the entire energy chain.«
In reality, 100% scenarios are neither useful nor desirable. The results from the FVV study, which are sound from an engineering standpoint, provide different indicators for the design of future energy and traffic policies, as well as the respective research funding. The most important findings from the study include the following:
Taking the least expensive scenario as the basis in each case, the route-related mobility costs are almost equal as long as cost parity can be achieved between a passenger car with a combustion engine (diesel), battery-electric drive and fuel cells. The minimum costs in the electric scenario are 29.4 cents per kilometre, while the best value achieved by hydrogen is 29.9 cents per kilometre. The least expensive synthetic fuel is synthetic methane at 28.4 cents per kilometre.
From a purchasing standpoint, the total costs alone are decisive. These comprise many factors not considered in the study, such as taxes and insurance premiums. When the usual depreciation is applied, the acquisition costs and not the price for energy sources dominate the total costs. When converted to individual users, the costs for the establishment and expansion of the infrastructure are almost negligible for synthetic fuels, but not when battery-electric vehicles are used.
From an economic standpoint, however, significant investments are required. They vary from 270 billion euros for the least expensive scenario (synthetic methane) to at least 360 billion euros for 100% electric, and at least 380 billion euros for 100% hydrogen. The calculations are based on the year 2050, with costs being significantly higher in the beginning. The greatest risks are found for the hydrogen scenario with decentralised generation.
The experts involved in the study calculated the costs and efficiency based on the technology available today. However, as the work progressed, it became apparent that there is significant potential for further development in several areas, such as the efficiency of electrolytic hydrogen generation during fluctuating electricity loads. However, as the economic optimum will probably only be achieved through hybrid scenarios, it would appear sensible to promote research which is open to a wide range of technologies.
According to the experts, the key to developing energy paths for a largely greenhouse gas-neutral and environmentally friendly transportation system lies in energy generation, not in the vehicle itself. Finding the best powertrain mix, with which individual mobility requirements can be fulfilled in passenger and goods transport, requires technology-neutral conditions. Legislators in Germany and Europe should therefore ensure that the industry has enough room for a wide variety of innovations.
1 | Research Association for Combustion Engines (FVV): Energy paths for road transport in the future - Options for climate-neutral mobility in 2050 (Executive summary | briefing paper). Frankfurt/Main, 2018
2 | Research Association for Combustion Engines (FVV): Defossilizing the transportation sector - Options and requirements for Germany (Full study | specialist paper). Issue R586, Frankfurt/Main, 2018
Road traffic is to be virtually climate-neutral by 2050. However, this goal can only be achieved if renewable energies are used in the transport sector. A working group at the Research Association for Combustion Engines (FVV) has therefore analyzed various energy paths. The resulting study examines the use of electricity, hydrogen and synthetic e-fuels as energy sources in road transport, taking both technical and economic factors into consideration.
FOLLOW-UP OF THE STUDY
* Note: To improve comprehensibility, this text refers solely to CO2. As other gases also increase the greenhouse effect, their impact on the climate is generally converted to CO2 equivalents.