Nina Holenstein

Transportation represents with 41% CO2 emissions from energy combustion one of the major CO2 contributors in Switzerland (in 2016). To reduce these emissions, we need a shift towards alternative methods or behavioral change. This can be done by reducing the demand of transportation, changing the type of energy carrier or using synthetic fuels. But are these really suitable solutions? Or are new ideas like the approach from Synhelion, where they create liquid with the help of solar, the solutions for the future of mobility?

 Reducing demand
Driving less sounds like the simplest way to reduce CO2 emissions from the transportation sector. But if we have a look at the emission curve from mobility, the demand for transportation is still on the rise! So how could we reduce this demand? Mobility pricing would be one option. Maybe also motivate the people to choose different modes like rental bikes or car sharing. All nice ideas and reducing the demand is possible the way with the highest potential to mitigate CO2. But there is an uncertainty. Because it requires changed behavior at the individual level which is really hard to achieve. Another possible solution to really reduce the demand is to have a “CO2 budget” for each person. Everybody would have the same amount of CO2 which they are allowed to use over one year. One can sell their CO2 budget if they do not use that amount of CO2. Others could buy CO2 budgets so they can use more CO2 for example for a flight or for longer car drives. This strategy would probably reduce the demand of mobility a lot because people would have to plan their CO2 budgets and in some cases they would need to change their behavior so they can save money by not using CO2 but selling their budget.

Changing the type of energy carrier
Liquid energy carriers are the easiest to handle, refuel the fastest and have the best energy density. Therefore, from an engineer’s perspective diesel and gasoline are the most reasonable carriers. So why should we move away from them? The problems with gasoline and diesel are local pollutant emissions, finite oil reserves and global warming through to CO2 emissions. Therefore, from the climate perspective it is necessary to change the type of energy carrier from fossil fuels to alternative carriers.

Internal Cumbustion Engines (ICE) or Battery Electric Vehicle (BEV)?
Internal Cumbustion Engines are powered by gasoline, diesel, biofuels or synthetic natural gas. As we now know that in favor of the climate, we need to quit using fossil fuels, gasoline and diesel fall away as good solutions.
So, what about biofuels? Growing biomass and processing it to liquid fuels sounds like a good idea but if one calculates the amount of space it needs, it shows that it is not a high-scale solution. It also not fits with the second Sustainable Development Goal (SDG) “zero hunger” as the land we would use for growing energy crops would take away the available land to grow crops to feed the rising human population.
Synthetic natural gas on the other hand could meet the scale of future global demand for fuels. With the Carbon Capture and Utilisation (CCU) method it would be even possible to get to netto-zero emissions from the transportation sector. This for example by using plants like the ones from Climeworks. They capture CO2 out of the air with a filter, heating it up, store the concentrated CO2 and release the CO2-free air back into the atmosphere. By combining the CO2 with H2 it is possible to produce synthetic fuels. But from where does the H2 comes from? That is probably one of the main negative points of the production of synthetic fuels. The production of H2 relies on water electrolysis, electricity storage for continuous operation and other additional steps which are all associated with a lot of energy! Therefore, it can be quite expensive and not so CO2 neutral as hoped so. For the last point it depends from where the energy comes from, renewables or other energy sources. In figure 1 it is shown how such synthetic fuels are processed.

Figure 37.1 – Figure 1: The process of “Power-to-Liquid”

Battery Electric Vehicles are powered by rechargeable batteries and are probably the most known alternatives from all the “future mobilities”. Fuel cell electric vehicles are another alternative where fuel cells instead of a battery are used. But the problem for these two electric vehicles with the energy demand is similar like with synthetic liquid fuels. The electric vehicles need to recharge their batteries constantly and therefore need a lot of electricity. The fuel cell electric vehicle even more because again, H2 needs to get produced first. So the question is, would the actual amount of renewable energy be enough to cover the demand of electricity for electric cars on a large-scale?

Changing to renewables
In the graphic below (figure 2) the comparison between the different powered vehicles is shown for driving a distance of 180,000km total in the year 2017. The emission of CO2 per kilometre rises for all the alternative solutions battery electric vehicle, fuel cell electric vehicle and ICEV-SNG, as the CO2-intensity of electricity rises as well. Whereas for the ICEV powered by fossil fuels the emission per kilometre stays all the same. So if we compare the amount of CO2 emissions per kilometre for the different vehicles for Switzerland with a CO2-intensity of electricity of approximately 120 g CO2eq/kWh, all the alternative solutions are better than using a car powered with petroleum. However, in the EU with a CO2-intensity of electricity of nearly 400 g CO2eq/kWh only the emission of the battery electric vehicle is lower than the fossil fuels powered cars. So if one lives in a country with a lot of renewables and no CO2 connected energy sources, the CO2-intense of electricity is very low and alternatives like battery electric vehicles are a very good solution to reduce CO2 emissions. Whereas one lives in a country with energy sources like coal power, the CO2-intensity of electricity rises fast and especially VECH-SNG are no good solutions.

Figure 37.2 – Figure 2: Comparison of different energy carriers

In conclusion, substitution of the energy carrier is effective but shifts the problem to the energy sector where it needs a lot of energy! Therefore, it is as important as never before to change to renewable energies and stop using CO2 connected energy sources like coal. This way we could perfectly use synthetic fuels which even gets us to netto-zero emissions in the transportation sector.

Better solutions?
The science never gets to a stop and the innovations continue. Really similar to the production of synthetic liquid fuels with power is the Synhelion approach. Here the solar is used as the main energy deliver. A thermochemical route uses the entire solar spectrum and therefore gives high-temperature heat. This heat gets directly to the chemical reactors and reduces the highly energy required steps of electrolysis and electricity storage for continuous operations to get H2. It goes on with similar steps like in the production of synthetic fuels with power. In the end this integration of thermal storage makes it possible to produce fuel for 24 hours. With less power and less CO2 emissions, the Synhelion approach gives a new opportunity for the “future of mobility”.

Figure 37.3 – Figure 3: The process of “Solar-to-Liquid”

Conclusion
To conclude one can say, that for the future it is crucial to mitigate our CO2 emissions and as the transportation sector is a major contributor we must include CO2 reduction methods in transportation. As it is hard to change people’s behavior, the reduction of mobility demand is difficult to achieve. Substitution of the energy carrier such as battery electric vehicles, fuel cell electric vehicles or ICEV-SNG are effective but it shifts the problem to the energy sector. So to use these methods efficiently we need like the seventh SDG says “affordable and clean energy”. This means that we need to extend our renewable energy sources as much as possible. Lastly, the Synhelion approach which gets liquid fuels with the help of solar would be a good solution as well if not even better because of its reduction of CO2 emissions and electricity. In the end we have so many different inventions which all have the same aim. So to achieve our goal to reduce CO2 emissions we need to work together and combine all the different solutions, the big ones as well the small ones.

References text:

Thalmann Philippe& Vielle Marc, Lowering CO2 emissions in the Swiss transport sector, https://sjes.springeropen.com/articles/10.1186/s41937-019-0037-3, retrieved on 03.04.2020.

Diermann Ralph (2017), Technik-Mythos: Wasserstoff revolutioniert die Energieversorgung, https://www.heise.de/newsticker/meldung/Technik-Mythos-Wasserstoff-revolutioniert-die-Energieversorgung-3638549.html, retrieved on 03.04.2020.

Swiss competence center for energy research (2019), Perspectives of Power-to-X technologies in Switzerland, http://www.sccer-hae.ch/resources/WP_P2X/SCCER-JA_2019_WhitePaperP2X-SupplementaryReport.pdf, p.20-21.

Climeworks (2020), Our customers, energy, fuels and materials, https://www.climeworks.com/our-customers/energy-fuels-and-materials/, retrieved on 03.04.2020.

Synhelion (2020), Technology, https://synhelion.com/#home, retrieved on 03.04.2020.

References figures:

Swiss competence center for energy research (2019), Perspectives of Power-to-X technologies in Switzerland, http://www.sccer-hae.ch/resources/WP_P2X/SCCER-JA_2019_WhitePaperP2X-SupplementaryReport.pdf, p. 21.

Synhelion (2020), Why Synhelion Technology?, https://synhelion.com/#home, retrieved on 03.04.2020.

References Lectures:

“The Energy Challenge”: Giacomo Pareschi, Efficient Mobility, Its role for future energy systems, 03.03.2020.

“The Energy Challenge”: Marco Mazzotti, Climate change, energy system, CO2 emissions, CCS and CCU, 24.03.2020.