Tough cylinder

Indian Oil Corporation and IIT-Kharagpur are jointly developing a new material to make cylinders for storing hydrogen, IOC’s Director – R&D, SSV Ramakumar, told Quantum . Hydrogen is difficult to store, as it reacts with the cylinder walls, forming compounds and weakening them. This ‘hydrogen embrittlement’ can cause (an invisible) explosion — you won’t know until the heat touches you. The “special material” under development is at least a third cheaper than conventional cylinders. Prototypes are undergoing tests. Eventually, they will develop a type-III (carbon composite with metal liner) or a type-IV (carbon composite with polymer liner) cylinder that can hold hydrogen at over 650 bars pressure. Right now the permissible pressure is 300 bars. “We have applied to the Petroleum and Explosive Safety Organization (PESO) for permission to raise the pressure,” Ramakumar said.

Good framework

Physical storage is not the only option for hydrogen. You can store it chemically, for example, in the form of methanol or formic acid. You can also embed it into metals (as metal hydrides — IIT-Guwahati specialises in this) or into some specially designed materials. But an in-thing seems to be the use of a ‘metal-organic framework’ — materials made of metals and organic compounds. The metal atoms are ‘linked’ by the organic molecules to form a cage-like structure with a large hollow inside that can hold hydrogen atoms. “Intense research is going on all over the world in MOF for hydrogen storage, including at IOC,” says the oil company’s R&D Director SSV Ramakumar. Efficient storage is key to hydrogenisation of the economy.

Power-packed paste

Researchers from the Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Dresden, Germany, have come up with a hydrogen-based fuel that is ideal for small vehicles. Called POWERPASTE, it is based on solid magnesium hydride. “POWERPASTE stores hydrogen in a chemical form at room temperature and atmospheric pressure to be then released on demand,” says Marcus Vogt of Fraunhofer IFAM. POWERPASTE decomposes at 250 degrees C, so the vehicle is good to stand in the hot sun for hours. Moreover, refuelling is simple — instead of heading to the filling station, riders merely have to replace an empty cartridge with a new one and refill a tank with mains water. The starting material of POWERPASTE is magnesium, abundant in earth. Magnesium powder is combined with hydrogen to form magnesium hydride at 350 degrees C and 5-6 bar pressure. An ester and a metal salt are then added to form the finished product. Onboard the vehicle, the paste released from the cartridge mixes with water, hydrogen is released “in a quantity dynamically adjusted to the requirements of the fuel cell”, says a press release from Fraunhofer IFAM. The cartridge packs more energy than a 700-bar high-pressure tank, it says, adding that the paste can also power drones in flight for hours.

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