Hydrogen: the future energy carrier.
Hydrogen as an energy carrier does not cause any harmful emissions, in particular no carbon dioxide, if it is obtained from renewable energies (wind, sun, water). Hydrogen is the main component of our planet and is available in water in bound form, for example. Even our body consists of about 10% of hydrogen.
Storing hydrogen in pressure tanks…with our researches, we are looking for a clean future.
In hydrogen storage tanks, the hydrogen is stored by means of high pressure of up to 800 bars. For this purpose, the gaseous hydrogen is first cooled and then compressed with multi-stage compressors to the desired pressure. By compressing the hydrogen, the energy density in the existing volume is increased. The additional energy required, for compression for the refueling of hydrogen-powered passenger cars, is about 12% (at 700 bars) of the stored hydrogen energy content. As a hydrogen storage tanks, special high pressure and low-diffusion tanks are used as containers. Since hydrogen is the smallest molecule on our planet, special attention is paid to the inner coating of the container. The pressure tanks are TÜV certified. Tanks up to 1200 bars are feasible or producible.
Hydrogen – element information & properties
Properties of Hydrogen: Hydrogen is the element with the lowest density. Molecular hydrogen (H2) is about 14.4 times as light as air. Liquid hydrogen weighs 70.8 grams per liter. Its melting point is 14.02K (-259°C), the boiling point at 21.15K (-252°C). Hydrogen is poorly soluble in water and other solvents. For water, the solubility is 18.2 ml/L at 20°C and atmospheric pressure. Because of its chemical and physical properties, the handling of hydrogen differs from the previously used energy sources. Hydrogen forms an inflammable mixture with the ambient air when released, at a level of 4% to 75%. An explosive mixture (oxyhydrogen) forms hydrogen only at a level of 18%. Because hydrogen is the lightest of all elements, it volatilizes in an open environment before it can form an explosive mixture, or burns out in hot environments at the 4% concentration level. Compared to many hydrocarbons, hydrogen has a low combustion enthalpy and thus a low volume-related energy density (about 1/3 of natural gas). This requires three times the size of a tank or three times the pressure of natural gas to store equivalent amounts of energy. However, due to the low molar mass, there is a comparatively high mass-to-energy density (e.g. more than twice the mass-based energy density of natural gas). Due to its small molecular size, hydrogen diffuses relatively well through a variety of materials, making many materials unsuitable for the tank shell. High temperatures and high internal pressure increase the diffusion process. Durch Wasserstoffversprödung werden metallische Tankhüllen zusätzlich belastet. Bei Hüllen aus Kunststoff tritt dieser Effekt nicht auf.
Hydrogen gas contains more energy per unit of weight than any other chemical fuel, but significantly less energy per unit volume. Hydrogen, like electrical energy, is not primary energy, but must be produced like primary energy. The technical problems with the storage of hydrogen are technically already solved today.
Energy densities in comparison
Based on mass (in kWh/kg):
– hydrogen: 33.3
– natural gas: 13.9
– gasoline: 11.1-11.6 (40.1-41.8 MJ/kg)
– diesel: 11.8-11.9 (42.8-43.1 MJ/kg)
– LOHC (N-ethylcarbazole): ): 1,93
– Li-ion battery: 0,2 (approx., depending on the type)
Based on volume (in kWh/l):
– hydrogen gas (normal pressure): 0,003
– hydrogen gas (20 MPa/200 bars): 0,53
– hydrogen gas (70 MPa/700 bars): 1,855 car refueling
– natural gas (20 MPa): 2,58
– gasoline: 8,2–8,6
– diesel: 9,7
– Li-ion battery: 0,25–0,675