The challenge

​One of the most important societal challenges nowadays is that we will have to say goodbye to fossil fuels and obtain our energy from renewable sources. Fortunately, solar panels are becoming more and more efficient, and the number of windmills is multiplying. However, there is one problem: we do not control whether the sun shines or whether the wind blows. As a result, sometimes there will be renewable energy when it is not needed, and sometimes there will not be enough renewable energy when it is required. The main problem does not lie in the generation of sustainable energy but does so in storing it. Currently, there are no promising solutions to large-scale energy storage and especially the industry which needs high-temperature heat has a hard time to 'go green', because electricity is not able to provide them with these high temperatures.

The solution

You can use iron powder and rust powder to create a circular system in which energy can be stored and released. Iron powder reacts with air in a combustion chamber and energy is released in the form of heat. In this combustion process, the iron is converted into rust. The rust particles are separated from the hot air flow, and the clean heat flow can be used for a diverse range of processes. The leftover rust particles are captured and can be converted back to iron powder again in a sustainable way. Currently, a cycle in which green hydrogen (hydrogen which is made using renewable energy, for example solar or wind energy) is used seems the most promising way of reduction. The advantages of iron especially come into its own at large scales. Moreover, iron powder had a few unique features that alternative energy storage methods like batteries and hydrogen do not possess: - Iron is really compact, if you would fill a glass with iron powder, it will contain 30 times more energy than a battery of the same size (and 5300 times more than hydrogen at standard temperature and pressure) - Iron is one of the most abundant metals on earth. Lithium used for lithium-ion batteries is mined in countries like China and Congo, and is becoming scarce. Iron is widely available, and will therefore be relatively cheap. - The energy you stored in iron five years ago, would still come out of it today, especially if stored in a oxygen-free environment. Batteries lose energy over time and hydrogen (because this molecule is so small) is hard to store as well. Iron is suitable for long-term energy storage. - Burning iron does not involve the creation of CO2 - An iron powder-based system is easily scalable.

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