Hydrogen: an opportunity to reduce CO2 emissions in transportation
Through a range of options, hydrogen offers the path to a sustainable, carbon neutral or even carbon-free age of mobility in both the short- and long-term. Ilona Dickschas from Siemens Gas and Power explains.
There is growing pressure around the globe to reduce the environmental impact of transportation. The transportation sector is not only a major contributor to climate warming but also the fastest growing, according to the World Health Organization (WHO). Figures show that energy use is higher for the transport sector than any other end-use sector.
While many see the electrification of road transportation as the solution to reduce emissions, data collected by the International Energy Agency shows that road transport emissions have increased despite electric vehicles (EV) being produced on a large scale by now. It is due to the fact that EVs bring along several problems that have yet to be solved, especially compared to gasoline fuelled transportation: limited range (roughly half as long as gasoline tanks), long recharging times (around eight hours in typical EVs with a 60kWh battery) and costly components consisting of a variety of rare earth metals which exploitation processes produce CO2 emissions in and of itself. These challenges have led to other technologies being reassessed, and one that is growing in importance is hydrogen with several companies like Siemens making an effort to provide applications in this field.
Setting up the infrastructure for the future of transportation
A hydrogen car does not face the same challenges as an EV. It can be refuelled in much the same time as its gasoline counterpart and the range is similar. Where an EV utilises electricity from a battery, a hydrogen-powered car uses electricity from a fuel cell. When the fuel cell is filled with hydrogen from the vehicle’s fuel tank, it mixes hydrogen with oxygen to create H2O in an electrochemical process. This reaction generates electricity which is then used to power the electric motors, much like with an EV. Although EVs and hydrogen cars currently suffer from a lack of charging infrastructure, this will mature once the number of vehicles on the road reaches a critical level. There are already several hydrogen powered cars available with many more due on the roads soon.
The transportation sector is not only a major contributor to climate warming but also the fastest growing
According to the eleventh annual assessment by H2stations.org, there were 369 hydrogen refuelling stations available around the world at the start of 2019. In Germany, 20 new public refuelling stations started operation in 2019 bringing the total up to 80. Japan has the most at 96 public stations with the United States third at 42 stations.
Despite hydrogen’s clear benefits, it is likely that the future will see a mix of both EV and hydrogen powered cars. For urban travelling, the range and slow charging time for EVs is not an issue with the average daily urban drive in Germany being around 25km, meaning that the cars can be charged at home overnight. The real win for hydrogen comes when you look at longer driving scenarios. For heavy-duty vehicles such as trucks and buses it is impractical to have a large enough battery for the thousands of kilometres they must travel. The only practical solution for a smaller carbon footprint in transportation is a fuel cell truck. Fuel cell trucks are already being manufactured while different companies are working on ways of producing, storing and delivering green hydrogen.
Hydrogen in action
It is not just road travel where hydrogen can have an impact; it is also beginning to make inroads in rail transportation. To further progress its hydrogen train portfolio, Siemens is collaborating with Canadian fuel cell manufacturer Ballard Power Systems to develop a modular and scalable traction system with fuel cells that can be integrated onboard its Mireo train platform. The technology is particularly appealing to areas of Europe that have not yet benefited from electrification of the rail network because of high cost. Moving from diesel trains to fuel cell trains that link with a network of fuel cell buses would provide a cost-effective solution to reduce carbon emissions.
Hydrogen is not the only solution, but is part of the remedy when combined with electrification
There are applications where hydrogen and fuel cells can also play a significant role in the oceans. However, the heavy fuel demand for larger ocean-going vessels and the long distances they travel make it impractical for alternative propulsion. But when you get into coastal waters with local shipping such as ferries then the opportunities abound. Here, there are already electric ferries powered by batteries and it seems these applications would make perfect sense for hydrogen-powered boats.
Pros and cons of electric and hydrogen
The crux of much of the discussion comes down to the power itself – electricity and hydrogen. One of the major quandaries is that moving to electric cars will only be carbon-free if the electricity that charges the batteries comes from renewable sources. The same charge can be laid at the door of hydrogen. Its production from water electrolysis is traditionally an energy intensive process and this, in the past, has been one of the major hurdles that has prevented the technology becoming mainstream.
Figures show that energy use is higher for the transport sector than any other end-use sector
In general, if you use an electric car with a battery you directly use the power coming from the grid to charge the battery. If you use the electricity to generate hydrogen, then there is an additional step required of transporting that fuel to a filling station before using it to charge the fuel cell. This additional step could be a challenge or an advantage. A battery is charged on demand from the grid, whether there is overcapacity or not. Hydrogen can be generated at the most cost-effective time. It would generally require its own renewable generation system but can also utilise spare renewable energy that is not required for the grid. The hydrogen produced can then be stored until it is required by the vehicle.
The normal tried and trusted method of producing hydrogen is using the steam reforming process, in which steam reacts with natural gas to produce synthetic gas or syngas (CO, H2). The steam reforming process is highly energy intensive and it has traditionally relied on natural gas as its energy source. However, that hurdle has been overcome with Siemens’ introduction of industrial applications for generating e-Hydrogen via electrolysis of water with the energy required for this process coming from renewable sources that are completely free of CO₂ emissions from the beginning.
In order to produce e-Hydrogen, Siemens has developed the Silyzer portfolio family: an innovative electrolysis system based on PEM technology. PEM takes its name from the proton exchange membrane, which is permeable to protons (H+) but tight for gases and electrons. In other words, this kind of membrane acts as an electrical isolator between the anode and cathode side as well as a physical separator, preventing hydrogen and oxygen from remixing.
The technology is ready for deployment, although work is still ongoing in increasing the efficiency and economics of the hydrogen production process
Compared to alkaline electrolysis, PEM technology is ideal for working with fluctuating wind and solar power sources, as it allows a highly dynamic mode of operation and can be rapidly turned on and off without preheating. This method allows optimum efficiency at high power densities and good product gas quality even at partial loads. The operation is low-maintenance and reliable without the use of chemicals or foreign substances. The Siemens hydrogen generation plant is a facility that integrates key technologies to produce e-Hydrogen. This innovative solution could serve, connect, transform and reduce carbon emissions in multiple industries.
Synthetic e-Fuels as a bridging option
As discussed earlier, one of the challenges that is common to both EV and fuel-cell cars is the lack of a comprehensive charging or refilling and propulsion infrastructure. This will require a huge investment to deliver and it is difficult to see that investment materialising until there is the demand from a high volume of vehicles. A short to mid-term solution is required that can make use of the existing infrastructure.
The perfect solution could be energy rich e-fuels that are generated from renewable electricity. These e-fuels can be mixed with conventional fuels and eventually replace them as a primary source of energy and raw materials in transportation. They are synthesised from e-hydrogen with CO2 from unavoidable emissions, e-methane (CH4, via the Sabatier process), e-methanol (CH3OH) or via the Fischer-Tropsch process electricity-based jet fuels or diesel. In addition, e-gasoline can be produced via a special process from e-methanol. Although the final use of these carbon-based e-fuels emits CO2, the overall balance is largely carbon neutral.
The future for hydrogen
Given the clear advantages that hydrogen offers, it begs the question of why we have been so slow to move forwards with the technology. The technology is ready for deployment, although work is still ongoing in increasing the efficiency and economics of the hydrogen production process, especially in terms of the electrolysers, and there is the challenge with infrastructure. But that aside, it has been a lack of desire, both political and social.
Public demand for hydrogen systems has grown dramatically during the past year, and particularly the past few months, and pressure on politicians is now huge. They urgently need to find alternative energy solutions for mobility and invest in them. Aside from that political desire, there are fiscal reasons to look to more environmentally-friendly solutions. It is proposed that in Germany the automotive manufacturers will have to pay for the CO2 emissions of all the cars they manufacture. That is increasing the pressure on car makers because that charge will be significant and grow every year.
Hydrogen is not the only solution, but is part of the remedy when combined with electrification. Working in tandem they can deliver a carbon free solution to enable us to maintain the mobility that we are accustomed to whilst significantly improving our environmental performance.