The long road to green hydrogen
10,000 wind turbines for the steel industry alone
By 2050, not only mobility should function in a CO2-neutral way, but our entire industrial society. Electricity generated from renewable sources, for example, will allow battery-electric cars to run on a CO2-neutral basis. Even if all cars in Germany were to run on electricity in 2040, for example, only about 25 percent more electricity would be needed than today.
With hydrogen and fuel cell drives, CO2-neutral operation would also work in principle if the hydrogen itself were produced by electrolysis from renewable electricity. But this is exactly where the problem lies: “Due to the poor efficiency chain, starting from the off-shore wind farm to the electric motor in the car, including liquid distribution and high-pressure refueling, the demand for primary energy for the production of hydrogen for fuel cells in passenger cars is about five to six times higher than for battery vehicles,” writes for example our podcast guest Prof. Martin Doppelbauer in his strategy paper. This means that the electricity required to run all 47 million passenger cars in Germany on hydrogen would be about 1.5 times greater than the total electricity produced today. That can’t work, especially since in the future not only about 50, but 100 percent of the electricity will have to come from renewable sources.
What we need hydrogen for
But energy transmission or storage doesn’t work purely electrically everywhere. Aircraft, for example, cannot carry as many batteries as they need. Hydrogen fuels could be the alternative. Hydrogen offers a much higher energy density. One kilogram of hydrogen contains almost as much energy as three kilograms of gasoline, and one liter of Super carries almost nine kWh of energy. The 700-kilogram battery of an Audi E-Tron is therefore roughly equivalent to a tank of ten liters of gasoline. After all, the efficiency of the e-car is three times as high as that of the combustion engine, so in this respect the E-Tron still has about 30 liters of gasoline in its tank.
However, the calculation also shows that if you have to take a lot of energy with you, you need a carrier other than batteries, and hydrogen can basically be produced with (green) electricity, the energy of which is then stored in it. Taking hydrogen with you, however, is not trivial. At normal temperatures and atmospheric pressure, one kilogram of hydrogen occupies more than eleven cubic meters of volume – hence its use in e-fuels.
But even for stationary processes, hydrogen is a decarbonization option. For example, for steel production, where enormously high temperatures and thus large amounts of energy are required. Currently, steel production mainly uses coke (coal). In Germany, it emits around 70 million tons of CO2 (equivalent) per year. An alternative to the common iron ore reduction in the blast furnace using carbon is the direct reduction of iron ore using hydrogen. Complete substitution of coal or coke would create an additional hydrogen demand of 2.4 million tons per year in Germany. The German Energy Agency believes that “today’s hydrogen demand and that needed for direct reduction in the future can be successively covered by green hydrogen.”
How is hydrogen produced?
Industry already produces large quantities of hydrogen for fertilizer production and for refineries. There, it is needed as an auxiliary material for the production of gasoline and diesel. In 2019, according to Statista, there were a total of about 117 million metric tons of hydrogen worldwide. 69 million metric tons were created from natural gas, and the remaining 48 megatons as a byproduct of chemical processes.
Gray hydrogen is anything but EO2-neutral
However, steam reforming of hydrogen from natural gas produces ten tons of CO2 per ton of hydrogen (about 400 grams per kWh of H2, according to one study). This hydrogen is therefore called gray. It is of no use for CO2 neutrality in the future. Unless the CO2 produced during steam reforming is separated and stored, pressed underground, for example in former gas deposits. The hydrogen is then called blue – because some residual CO2 emissions always remain, it is not green. What’s more, natural gas as a feedstock already has significant emissions attached to it through extraction, processing and transportation. “These upstream emissions account for about 25% of the total emissions from natural gas,” according to an evaluation of several studies (p. 8 there). Currently, blue hydrogen is considerably cheaper (by a factor of about three) than green hydrogen, which is why it has good chances, especially as a transitional solution, despite the higher CO2 emissions and the limited deposits of CO2. Price forecasts vary between 20 and 60 percent additional costs for green hydrogen in 2030.
This plant in India mixes natural gas with green hydrogen, which improves the CO2 balance.
How much energy does green hydrogen need?
If the economic disadvantages of green hydrogen can be eliminated politically with the appropriate prioritization, there is no getting around the increased demand for electricity. One kilogram of hydrogen contains 33.33 kWh of energy. The efficiency of electrolysis varies between 60 and 85 percent, depending on the technology and operation. To produce one kilogram of hydrogen by electrolysis, therefore, an average of about 50 kWh of electrical energy is currently required. The 2.4 million metric tons of hydrogen needed for steel production in Germany would therefore require about 120 terawatt hours (TWh) of electrical energy, about one-fifth of annual electricity production, as Germany produced an average of 608.83 TWh p.a. over the last three years. Nevertheless, the German Energy Agency believes that “today’s hydrogen demand and that needed for direct reduction in the future can be successively covered by green hydrogen.” In fact, wind energy alone already accounted for 23.5 percent of the German electricity mix in 2020.
Daimler
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Audi
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Dino Eisele
Hans-Dieter Seufert
Hyundai
Dino EiseleOn the other hand, estimates for 2030 assume a hydrogen demand for steel production of three million tons; this would be equivalent to 150 TWh of electrical energy. This corresponds to the annual output of 3333 MHI Vestas V164 offshore wind turbines. Currently, there are only 1200 offshore wind turbines in the German North and Baltic Seas. Onshore, there are almost 29,000, the most powerful of which, the Nordex N149, produces only a third of the yield of the offshore Vesta. Accordingly, the 150 TWh would require 9740 such wind turbines on land. Nevertheless, it might make sense to produce the electricity for hydrogen generation on land. At the very least, it would be advantageous if the electrolysis took place where the steel is produced. Then one would save the transport of the light and volatile gas – which brings us to the next point.
The production of hydrogen by means of electrolysis requires electricity; if this comes from volatile renewable sources such as wind power or solar energy, it can be stored in hydrogen.
Where is the hydrogen to be generated?
As mentioned, hydrogen is produced in a CO2-neutral manner during the electrolysis of water – in simple terms, electricity is applied to a pool of water, thereby splitting it into hydrogen and oxygen. In this way, electrical energy is converted into chemical energy (in the hydrogen), with the efficiency losses described at the beginning. If the hydrogen is to serve as a storage medium for electrical energy, as is the case with fuel cell vehicles, the losses during reconversion are added, and in total the efficiency is then rather below 40 percent.
Steel production with green hydrogen in direct reduction plants is CO2-neutral. Until sufficient climate-neutral hydrogen is available, the use of natural gas in direct reduction plants can already significantly reduce emissions compared with the coal-based blast furnace method. Thyssenkrupp Steel, for example, plans to start up the first large-scale direct reduction plant in 2024. The more green hydrogen – Thyssen reckons it will need 700,000 tons or 3,000 wind turbines in the long term – available by then, the greener the steel.
Solar power from the desert – hydrogen too?
No wonder, then, that scenarios for hydrogen production are also developing elsewhere, where there is space for wind turbines or solar plants, land is correspondingly cheap, and the cost of regenerative energy production is correspondingly lower. In the Sahara, for example. One such idea is already a good ten years old: “Desertec” proposed solar power plants in the Sahara and overland pipelines to Europe. A new position paper takes up the idea again. Instead of expensive power lines, the idea is now to use electricity to produce hydrogen.
However, electrolysis requires a lot of water – ten liters per kilogram of hydrogen. Water and sunny deserts are largely mutually exclusive. That’s why Desertec proposes installing seawater desalination plants, of course also powered by wind and solar energy. Even under the most unfavorable conditions, the cost share for this should not exceed 2 percent of the total costs; any surplus production could help local irrigation projects.
Solar and wind energy need a lot of space.
Hydrogen transport as a drawback
Producing hydrogen where there is space for renewable energy generation, however, subsequently requires transporting the gas to Europe for steel production, for example. The study relies primarily on existing infrastructure pipelines – for natural gas. If volatile and light hydrogen is to be pumped through them, however, some modifications are necessary.
Hydrogen could also be converted into ammonia for transport. This could then be transported to Europe by ship. The study calculates a prospective price of less than $2 per kilogram, and roughly estimates that transport would cost another $2 per kilogram. In addition to the transport costs to Europe, there are then the local costs and the corresponding infrastructure. In addition, studies speak of an energy loss of 15 to 25 percent in the reconversion of ammonia. Losses due to conversion – the problem is reminiscent of the one described at the beginning.
Survey
Hydrogen cars – they can be refueled quickly.
On battery-electric cars – they will soon have enough range and will take no longer to charge than internal-combustion vehicles to refuel.
Conclusion
Due to the efficiency of the process chain, hydrogen as an energy carrier is unlikely to be a viable option for powering cars in the future. The amount of renewably generated electricity required for this is simply too large.
For the decarbonization of industrial processes such as steel production, however, hydrogen is urgently needed, and large-scale production is unavoidable. Without new CO2 emissions, this can only be achieved with large quantities of regeneratively generated electrical energy. The temptation to produce this and the hydrogen in distant regions, for example, like crude oil, is great. But costs and CO2 emissions during transport suggest that autarky, or the production of energy, hydrogen and end products such as steel, is the more promising principle in this case.
Once the mass production of green hydrogen is established, there may eventually be something to produce e-fuels to power internal combustion engines.