Recently, there has been an incredible amount of hype surrounding the hydrogen economy. Is this hype justified or is it another misguided development in energy and resource policy?
The hydrogen economy pivots around hydrogen as an energy carrier. It is touted as a means to overcome resource scarcity in fuels and combustibles and to open up new options for energy storage.
The (unsustainable) state of the world
In the transformation of the energy economy, we are facing a fundamental challenge. Until now, it was easy to extract primary energy from the earth in the form of fossil fuels: oil, coal and gas, and use them more or mostly unaltered as an energy source. In the case of crude oil, some refining was necessary depending on the end product, and ship diesel, petrol, or kerosene were ready for use, especially in transportation.
We must now say goodbye to this way of working if we do not want to pollute the atmosphere with more CO2 (and methane) and if we want to achieve our climate goals.
This means the fundamental and revolutionary challenge will be that we generate primary energy from renewable sources (wind, solar, tidal, geothermal) and then convert this energy into an energy carrier. A difficult undertaking because we need to manufacture or convert a substance from electrical, thermal or mechanical energy so that we can transport, handle, transfer and store the energy it contains and then release it again at the push of a button.
And yes, one option is to produce hydrogen: Using electrical or thermal energy to split water through electrolysis and use the hydrogen as an energy carrier. That already works and could be scaled up, in particular in the more long-term time frame.
The (dismal) economics of a hydrogen economy
But there are a few serious disadvantages. Hydrogen is unsuitable as an energy carrier because its density is one of the lowest of all materials on earth and its volatility is very high. And it doesn't matter whether it is gaseous or liquid. This means that the energy density obtained is very low and the tanks have to be very large, leak-proof and safe. All quite complex.
The next problem is the ridiculously high electrical energy consumption for the production of hydrogen and the very low energy efficiency of the overall process, which makes it unattractive both energetically and economically.
Let's take a look at the processes for mobility e-fuel and fuel cell drives as examples. Consider 100% primary energy, which is obtained as electricity from wind or solar power. This electricity is used to split water into hydrogen. For this purpose, we can estimate the conversion efficiency into direct current of suitable voltage as 90% and the efficiency of the electrolysis process as 80%. Now we have obtained hydrogen, from the 100% primary energy there is still 72% left. Now there are two separate paths, for e-fuel and fuel cells.
The calculation for e-fuel:
Energy efficiency in conversion to methanol and then to petrol: 45%.
Efficiency in combustion engine: 40%
Useful power at the wheel: 72% × 45% × 95% × 40% = 12% of the original energy.
It doesn't look much better with fuel cell:
Liquefy hydrogen for transport and storage: 85%
Compressing to 700bar for the vehicle's tank: 90%
Fuel cell efficiency: 40%
Efficiency of electric motor: 95%
Useful power at the wheel: 72% × 85% × 90% × 40% × 95% = 21% of the original energy.
For comparison: battery vehicles today already achieve efficiencies of 70–75% of the primary energy.
One can now argue, as is often done, that we have wind and solar power surplus and thus have a clever storage option here and that efficiency does not play a role. One can only reply that we do not have any energy left over.
If we look at the fact that, for example, Germany has a total energy consumption of 13106 petajoule in 2018 and only 1804 petajoule is generated from renewable sources, everything else from fossil sources and nuclear power, then inefficient use of energy is not permissible. We should do everything we can to get a smart grid with efficient storage before we spend precious primary energy senselessly on inefficient processes.
But how will the vehicles of the future run if e-fuels and fuel cells are not the solution?
A more pragmatic proposal
For light vehicles like passenger cars, it will be battery. That is already a fixed goal. Trucks have a much longer road ahead, figuratively and literally, and might never really run on batteries. Should we then scrap all the vehicles with combustion engines and write off the energy consumed in their manufacture?
Certainly not. We have to be pragmatic here and keep them running for the time being. Yes, with fossil fuel. And compensate for the CO2 emissions so that the overall accounting balanced out to zero.
What should be done to achieve this? Capture CO2 directly and store it? Also an inefficient and rather unsafe process. Planting trees? This certainly not the thing that helps long term, as we already pointed out in this newsletter. The carbon will soon be released again once the trees decay or burn.
The safest option is to use hydrothermal carbonization to produce storable carbon from bio-based residues and to store it permanently in a stable form. This can protect us from inefficient processes during the conversion period.
In the long run, a hydrogen or better methanol economy will certainly also make a contribution. But neither offer an attractive short-term prospect. Here, compensation should play a much more important role – of course only if it is reliable, permanent and secured with accountable certificates.
“Creating the new hydrogen economy is a massive undertaking” The Economist (2021).
Gerben Hieminga, Nadège Tillier “High gas prices triple the cost of hydrogen production” ING Think (2021).
Dirk Asendorpf “Die Mär vom Wasserstoff” Die Zeit (2004).
Christoph Heinemann, Peter Kasten “Die Bedeutung strombasierter Stoffe für den Klimaschutz in Deutschland” Öko-Institut (2019).
Jens Perner, Michaela Unteutsch, Andrea Lövenich “The future cost of electricity-based synthetic fuels” Agora (2018).