By the middle of this century, stopping at a charging station may be just as normal for most drivers as stopping at a gas station is today. However, electric motors are not the right drive system for all means of transportation. For example, according to our present knowledge, ships and very large airplanes probably will continue to need liquid or gaseous fuel for a long time.
The Future of Mobility
Sustainable Fuels for Conventional Engines
In tomorrow’s largely CO2-free transportation systems there will no longer be room for fossil fuels such as gasoline and diesel. That’s why researchers and scientists are working at full speed to develop new climate-friendly alternatives.
From Fields to Fuels
Biofuels can be produced from biomass — i.e. from parts of plants — and if this can be done sustainably their impact on the climate will be smaller than that of fossil fuels. In Germany, for example, gas stations have for years been offering E10 fuel — gasoline that contains a 10% portion of ethanol. All the same, our energy problems will not be solved in farmers’ fields, because the production of adequate amounts of plant-based fuel would require tremendous expanses of farmland. Environmental associations are urgently warning us about the environmental consequences of turning even more natural ecosystems into arable land.
From Electricity to Gas
By contrast, hydrogen, a combustible gas that can be produced from water by means of electrolysis, could be a genuine alternative. Hydrogen can be used either directly as a fuel in fuel cell vehicles or processed into synthetic liquid fuels. Furthermore, if electrolysis itself is powered by renewable energy sources, then its climate impact is neutral. .
Here’s another benefit: The operators of climate-friendly energy sources such as solar and wind installations also profit from hydrogen production, because hydrogen can be used to store the excess energy they produce. By transforming their electrical energy into hydrogen gas, excess energy becomes storable and thus can be used in other sectors. A special form of this technology, proton exchange membrane (PEM) electrolysis, is particularly suitable for capturing “green” electricity. It can be very flexibly adapted to the typical fluctuations of power from wind and solar installations, and it can also be operated at partial load.
From Hydrogen to Liquid Fuel
However, liquid fuels are more practical than gaseous hydrogen, particularly because they are compatible with the existing liquid fuel infrastructure. That’s why it might make sense to subject the hydrogen that is generated through electrolysis to an additional transformation — for example, to methanol, a chemical compound that, like ethanol, could compete with diesel and gasoline as a transport fuel. However, the disadvantage is that this additional step is less flexible and therefore requires complicated interim storage of the gas. For this reason, Siemens and Friedrich Alexander University of Erlangen-Nuremberg in Germany are jointly conducting the “Green Liq” research project, whose aim is to develop a new reactor concept for generating this kind of CO2-neutral liquid fuel, which enables operation at flexible loads.
However, even this fuel would not be entirely free of disadvantages. When energy is transformed from electricity to hydrogen, about half of the energy is lost. The direct use of electrical energy is therefore a more energy-efficient method for using renewable energy sources locally. As a result, further groundbreaking research is still needed in order to take optimal advantage of green energy in the field of mobility.