Pilot plant demonstrates iron-based hydrogen storage feasibility

Photovoltaics are set to satisfy over 40% of Switzerland’s electrical energy wants by 2050. However solar energy is not all the time out there when it is wanted: there’s an excessive amount of of it in summer season and too little in winter, when the solar shines much less usually and warmth pumps are operating at full tilt. Based on the Swiss federal authorities’s Power Technique, Switzerland needs to shut the winter electrical energy hole with a mixture of imports, wind and hydropower in addition to alpine photo voltaic crops and gas-fired energy crops.

One solution to decrease the necessity for imports and gas-fired energy crops in winter is to supply hydrogen from low-cost solar power in summer season, which may then be transformed into electrical energy in winter. Nevertheless, hydrogen is extremely flammable, extraordinarily risky and makes many supplies brittle.

Storing the fuel from summer season till winter requires particular pressurized containers and cooling know-how. These require lots of energywhereas the numerous security precautions that have to be adopted make constructing such storage services very costly. What’s extra, hydrogen tanks are by no means utterly leak-proof, which harms the setting and provides to the prices.

Now researchers at ETH Zurich led by Wendelin Stark, Professor of Useful Supplies on the Division of Chemistry and Utilized Biosciences, have developed a brand new know-how for the seasonal storage of hydrogen that’s a lot safer and cheaper than current options. The researchers are utilizing a widely known know-how and the fourth most plentiful component on Earth: iron.

The findings are published within the journal Sustainable Power & Fuels.

Chemical storage

To retailer hydrogen higher, Stark and his workforce are counting on the steam-iron course of, which has been understood for the reason that nineteenth century. If there’s a surplus of solar energy out there in the summertime months, it may be used to separate water to supply hydrogen. This hydrogen is then fed into a stainless-steel reactor full of pure iron ore at 400 levels Celsius. There, the hydrogen extracts the oxygen from the iron ore—which in chemical phrases is just iron oxide—leading to elemental iron and water.

“This chemical process is similar to charging a battery. It means that the energy in the hydrogen can be stored as iron and water for long periods with almost no losses,” Stark says.

When the vitality is required once more in winter, the researchers reverse the method: they feed scorching steam into the reactor to show the iron and water again into iron oxide and hydrogen. The hydrogen can then be transformed into electrical energy or warmth in a fuel turbine or gas cell. To maintain the vitality required for the discharging course of to a minimal, the steam is generated utilizing waste warmth from the discharging response.

Low-cost iron ore meets costly hydrogen

“The big advantage of this technology is that the raw material, iron ore, is easy to procure in large quantities. Plus it doesn’t even need processing before we put it in the reactor,” Stark says. Furthermore, the researchers assume that enormous iron ore storage services might be constructed worldwide with out considerably influencing the worldwide market worth of iron.

The reactor during which the response takes place does not have to meet any particular security necessities both. It consists of chrome steel partitions simply 6 millimeters thick. The response takes place at regular stress and the storage capability will increase with every cycle.

As soon as full of iron oxide, the reactor may be reused for any variety of storage cycles with out having to switch its contents. One other benefit of the know-how is that the researchers can simply increase the storage capacity. It is merely a case of constructing larger reactors and filling them with extra iron ore. All these benefits make this storage know-how an estimated ten occasions cheaper than current strategies.

Nevertheless, there’s additionally a draw back to utilizing hydrogen: its manufacturing and conversion are inefficient in comparison with different sources of vitality, as as much as 60% of its vitality is misplaced within the course of. Which means as a storage medium, hydrogen is most tasty when enough wind or solar energy is offered and different choices are off the desk. That’s particularly the case with industrial processes that may’t be electrified.

Pilot plant on the Hönggerberg campus

The researchers have demonstrated the technical feasibility of their storage know-how utilizing a pilot plant on the Hönggerberg campus. This consists of three chrome steel reactors with a capability of 1.4 cubic meters, every of which the researchers have full of 2–3 metric tons of untreated iron ore out there available on the market.

“The pilot plant can store around 10 megawatt hours of hydrogen over long periods. Depending on how you convert the hydrogen into electricity, that’ll give you somewhere between 4 and 6 megawatt hours of power,” explains Samuel Heiniger, a doctoral scholar in Stark’s analysis group. This corresponds to the electrical energy demand from three to 5 Swiss single-family properties within the winter months. At current, the system remains to be operating on electrical energy from the grid and never on the solar energy generated on the Hönggerberg campus.

That is quickly set to vary: the researchers wish to increase the system such that by 2026, the ETH Hönggerberg campus can meet one-fifth of its winter electrical energy necessities utilizing its personal solar energy from the summer season. This may require reactors with a quantity of two,000 cubic meters, which may retailer round 4 gigawatt hours (GWh) of inexperienced hydrogen.

As soon as transformed into electrical energy, the saved hydrogen would provide round 2 GWh of energy. “This plant could replace a small reservoir in the Alps as a seasonal energy storage facility. To put that in perspective, it equates to around one-tenth of the capacity of the Nate de Drance pumped storage power plant,” Stark says. As well as, the discharging course of would generate 2 GWh of warmth, which the researchers wish to combine into the campus’s heating system.

Good scalability

However may this know-how be harnessed to supply seasonal vitality storage for Switzerland as a complete? The researchers have made some preliminary calculations: offering Switzerland with round 10 terawatt hours (TWh) of electrical energy from seasonal hydrogen storage techniques yearly sooner or later—which might admittedly be lots—would require some 15–20 TWh of inexperienced hydrogen and roughly 10,000,000 cubic meters of iron ore.

“That is about 2% of what Australia, the biggest producer of iron ore, mines yearly,” Stark says. By the use of comparability, in its Power Views 2050+, the Swiss Federal Workplace of Power anticipates complete electrical energy consumption of round 84 TWh in 2050.

If reactors have been constructed that would retailer round 1 GWh of electrical energy every, they might have a quantity of roughly 1,000 cubic meters. This requires round 100 sq. meters of constructing land. Switzerland must construct some 10,000 of those storage techniques to acquire 10 TWh of electricity in winter, which corresponds to an space of round 1 sq. meter per inhabitant.