How efficient are e-fuels really?
Facts and figures on the efficiency and costs of synthetic fuels.
Professors, engineers and experts answer frequently asked questions:
Always stay up to date with eFuels?
eFuels efficiency: How efficient are eFuels?
If we look at the overall system efficiency of e-fuels, it is – contrary to many media portrayals – in no way inferior to that of electric drives. The most common mistake here is to base the efficiency analysis only on the electric motor – i.e. without considering the entire system before and after the motor.
However, if you look at efficiency from the wind gust (wind wheel) to the spinning wheel (well-to-wheel, wtw), rather than just from the engine to the wheel (tank-to-wheel, ttw), the efficiency comparison between electric cars and internal combustion cars with e-fuels is at a similar level. See the graphic from the Karlsruhe Institute of Technology (KIT) from the lecture “Sustainable Drive Systems” by Prof. Thomas Koch.
Here, it is important to always make realistic assumptions, such as the fact that industrial e-fuels production takes place in sun- and wind-rich regions of the world and not in Germany. This is because e-fuels can be transported over long distances thanks to their liquid form and can be easily stored in tanks – in stark contrast to the charging current of e-cars.
In addition, it should also always be remembered that efficiency is only one aspect of the overall picture and other factors such as infrastructure, availability of raw materials and political decisions also play a role.
eFuels costs: How much does 1 liter of synthetic diesel cost?
At present, eFuels are mainly produced in small quantities for research purposes.
The price of eFuels, which is often quoted, is therefore naturally still very high.
However, this will change with the ramp-up of eFuels production on an industrial scale (keyword: economies of scale).
eFuels manufacturers such as Saudi Aramco are already assuming that a price of 80 cents/liter of eFuels will be achievable in a few years. One of the reasons for this is the favorable price of electricity in Saudi Arabia, which is only one cent per kilowatt hour.
What are eFuels?
Put simply: eFuels, also known as synthetic fuels, are fuels produced using renewable electricity and carbon dioxide (CO2). First, electrolysis splits water into hydrogen and oxygen. The hydrogen is then combined with CO2 to produce hydrocarbons. These can be used as eFuels.
Refueling with eFuels: Can any combustion engine refuel with eFuels?
Yes, eFuels can be used in existing combustion engines as they have similar chemical properties to traditional fossil fuels. They can be designed to have similar combustion properties to gasoline, diesel or kerosene.
Why is it essential to use eFuels in road transport too?
eFuels can play an important role in reducing greenhouse gas emissions in road transport. Here are some reasons why their use in road transport is also essential:
Modern driving: eFuels are made from carbon dioxide (CO2) and hydrogen, which can be obtained using renewable energy. This means that the CO2 released when eFuels are burned was previously removed from the atmosphere.
Compatibility with existing infrastructure: eFuels can be used in existing combustion engines and fossil fuel infrastructure. This could facilitate the transition to a low-carbon economy, as it would not be necessary to replace all existing infrastructure immediately.
Energy efficiency and range: eFuels can offer higher energy efficiency and range compared with electric vehicles, particularly in heavy vehicles or applications requiring longer range.
Complementary technology: eFuels could complement electric vehicles, particularly in areas that are difficult to electrify, such as heavy goods transport, long-distance vehicles or certain forms of public transport.
Important to consider:
Restricting eFuels to relatively small, cost-sensitive sectors such as shipping and aviation would hinder their ramp-up, while producing aviation fuel automatically also yields fuels for road transport as co-products. When considering optimal resource use, the synthetic by-products such as e-petrol, e-diesel and e-heating oil that arise during e-kerosene production should therefore also be used.
eFuels production: How are eFuels produced?
The production of eFuels, also known as synthetic fuels, generally involves three main processes:
Water electrolysis: Initially, electricity from renewable energy sources is used to break down water into hydrogen and oxygen. This process is called electrolysis. The hydrogen produced is the basic raw material for the production of eFuels.
CO2 capture: In parallel with hydrogen production, CO2 is captured from the atmosphere or from industrial emissions. CO2 capture technologies, also known as carbon capture, can help to supply the CO2 required for the production of eFuels.
Synthesis: Finally, the deposited carbon and the hydrogen obtained by electrolysis are combined to produce eFuels. This process is achieved through various chemical processes, including methanation, which is the production of synthetic methane, and Fischer-Tropsch synthesis, to produce synthetic hydrocarbons such as diesel or kerosene.
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