QAZAQ GREEN.  The scientists at the University of Salamanca in Spain have offered a method for producing steel using only renewable energy sources and hydrogen. To do this, they developed a model of an energy complex combining solar and wind power plants with several energy storage systems. Calculations show that such a system can supply a steel mill with electricity and hydrogen year-round without coal, oil, or natural gas, Global Energy Prize reported.

The steel industry is considered to be a sector where decarbonization is incredibly challenging. The International Energy Agency estimates that this industry accounts for about 7% of global CO₂ emissions. Today, coal and coke are primarily used for steelmaking. They not only provide energy but also help extract iron from their ore.

One of the leading alternatives is the direct reduction of iron with hydrogen. In this process, hydrogen replaces coal and binds the oxygen contained in the iron ore. The result is iron re-melted in an electric arc furnace.

But this approach has a serious problem. Hydrogen production requires a large amount of electricity. But if you get it solely from the sun and wind, how can you ensure a continuous plant operation at night, in windless weather, and in winter when energy production declines?

To address this challenge, the researchers proposed combining several technologies. Electricity is generated by solar panels and wind turbines. Part of the energy is used directly to power the plant, while the surplus – for hydrogen production from water through electrolysis. To store energy reserves, the scientists have incorporated batteries, compressed hydrogen tanks, and the so-called liquid organic hydrogen carriers, which are special substances capable of storing hydrogen in a chemically bound form. These liquids enable creation of seasonal energy reserves. In the summer, when solar power plants generate excess electricity, hydrogen is stored in a liquid carrier. In the winter, it can be extracted again and used to power a metallurgical plant.

The researchers modeled operation of such a system for a steel mill with an annual capacity of 1 million tons and performed calculations for 48 provinces in mainland Spain. This allowed them to compare how different climatic conditions affect the plant performance.

It turned out that regions with high wind levels have a significant advantage. Although wind conditions vary from hour to hour, wind power generation is generally less dependent on the season than solar energy. Therefore, such regions require fewer large-scale seasonal energy storage facilities. In sunny regions, the situation is quite opposite. To get through the winter, it is necessary to build up large hydrogen reserves and construct more generating capacity.

At the same time, the calculations have revealed another peculiarity. To ensure a plant’s uninterrupted operation using only renewable energy sources, such as solar panels and wind power, we have to build significantly more capacity than required on average. As a result, there is a massive surplus of electricity during certain periods. In some scenarios, the surplus was nearly five times the plant’s annual energy needs. However, in the future, this energy could be redirected toward production of chemical products, synthetic fuels, or other energy-intensive processes.

For now, the cost remains the main obstacle. According to the scientists’ calculations, the cost of electricity and hydrogen for producing green steel currently amounts to approximately 500–600 euros per ton of the product, which is several times higher than when using traditional technologies. At the same time, solar power plants and hydrogen production equipment account for the bulk of the expenses. As technologies advance, their costs will decrease, and the introduction of carbon dioxide emission fees will make traditional metallurgy less profitable. Therefore, in the long term, hydrogen-based steel production could become a competitive alternative to the available technologies.