FAQ Hydrogen Facts

No. The usage of hydrogen as an energy carrier is based on chemical reactions, i.e. reactions in the electron cloud. In contrast, the energy release of a hydrogen bomb is based on the fusion of nuclei as it happens inside the sun – the extreme temperatures and pressures needed for this can under no circumstances be reached in the daily use of hydrogen.

The plant is equipped with safety valves for pressure relief. Additionally, explosion protection zones are defined, in which the electric appliances are designed in accordance with 94/9/EC (ATEX Directive). This means they are especially designed for use in explosive areas.

No. Hydrogen can be handled and stored safely – this has been proven over the last century by the industrial gas industry.

No. Hydrogen itself is not explosive. It can only explode in combination with an additional oxidizing agent (air, pure oxygen, chlorine, etc.) and an ignition source (a spark).

That depends on the process used. By combusting hydrogen, it delivers heat. Used in fuel cells, hydrogen is converted to electricity and heat. At “Energiepark Mainz” hydrogen can either be fed into the natural gas grid or transported in a high pressure gas pipe to the combined-cycle gas turbine power station of Kraftwerke Mainz-Wiesbaden. At the power station it can be converted into green electricity and district heating.

Hydrogen converts into a liquid at minus 253°C.

Hydrogen can be stored as a gas or as a liquid. To store a reasonable amount the hydrogen either has to be compressed or liquefied at cryogenic temperatures, i.e. minus 253 °C. Small volumes of compressed hydrogen gas are commonly stored in pressurized cylinders at either 200 or 300 bar with between 10 and 50 liters of volume per cylinder. They are mainly used for laboratory and welding applications and also as small refueling solutions for the demonstration of hydrogen-powered vehicles. As a liquid, hydrogen can be stored without pressure, however, the tanks need to have a heat insulation to minimize vaporization. Hydrogen can also be stored in natural or artificial caves as well as in the natural gas grid if the grid fulfils all technological requirements.

Hydrogen is the smallest atom, therefore it is also the gas with the lowest density. The volumetric energy density of hydrogen corresponds to about one third of the energy density of natural gas. Therefore, processes to increase the volumetric density are used when storing hydrogen. With regards to its weight, however, hydrogen has the highest energy density of all fuels: almost three times as high as the one of gasoline or diesel. That is one of the reasons why hydrogen is used as fuel for space travel.

Today hydrogen is an important industrial gas, i.e. for the refining of fuels, for the production of fertilizer and methanol, for the hydrogenation of fats, for steel production, metal processing, as well as in the production of flat glass. In the future hydrogen will additionally be used to store energy in centralized and decentralized facilities. Furthermore it can serve as energy carrier for various stationary, mobile and portable applications. And there are many more possible applications: Fuel cell vehicles, fuel cells as small backup heating stations and power plants, mobile emergency power generators, mini fuel cells for electric devices like laptops, etc.

PEM is the abbreviation for proton exchange membrane. This membrane is a crucial part of the electrolytic cell in a PEM-electrolyzer. The membrane separates the anode, where the oxygen is collected, and the cathode, where the hydrogen gas is generated.

Today more than 80% of the hydrogen worldwide is produced from hydrocarbons. Until now electrolysis is less common to produce hydrogen due to its lack of economic efficiency. It is mostly used where cheap electricity is available, natural gas is not available or where only small amounts of hydrogen are needed.

Electrolyzers can be categorized as follows:

• alkaline electrolysis with liquid alkaline electrolytes
• acidic electrolysis with a solid polymer electrolyte and
• high temperature electrolysis with a solid oxide as electrolyte

At “Energiepark Mainz” the acidic electrolysis is implemented in an innovative PEM-electrolyzer from Siemens. The necessary water is fed as a liquid (low temperature process), in contrast to the high temperature process with steam infeed.

In the future hydrogen will be produced to a greater extent using electricity from renewable energy sources. At “Energiepark Mainz”, wind energy will play an essential role. Furthermore biogas and various fuels like glycerin and solid biomass will help to produce green hydrogen in the future.

No. Hydrogen is to become a substantial and permanent element of a sustainable energy industry.

The most important sectors for the use of hydrogen are oil refining and the production of ammonia. It also plays an important role in the production of methanol. Furthermore, hydrogen is a base material for fertilizers and synthetic materials. Hydrogen is also used for fat hardening, in steel production, as well as in the glass and semiconductor industries.

Yes. For example, the former town gas, which was also used for gas lamps – also in Mainz – contained 50 percent hydrogen.

Especially in the chemical industry, hydrogen has been produced and used for more than 100 years. As early as 1808, the first large-scale use of hydrogen was established for the street lighting system in London. Experience shows that hydrogen can be stored, distributed and converted safely.

Hydrogen is an abundant element in the universe. 90 percent of all atoms are hydrogen atoms. They add up to three quarters of the total mass in the universe.

A hydrogen-air mixture is always lighter than air alone, therefore it will rise upwards. As a result there is no danger that the gas mixture will build deposits in cellars, trenches, underground garages, in the canalization system, etc.

To prevent explosive mixtures, the facilities are designed to be permanently technically leak proof and flange connections designed especially for hydrogen are used to minimize the number of detachable connections. Furthermore, in buildings a steady air exchange is ensured and the facilities are equipped with safety valves and pressure reliefs. Additionally explosion prevention zones are defined. In these zones, electrical and other equipment needs to be in accordance with 94/9/EC (ATEX Directive) for the use in potentially explosive atmospheres.

The chemical industry has been operating hydrogen plants for more than 100 years now, with excellent experiences to ensure the safety of these plants, i.e. with the support of project partners like Linde. There is no indication that hydrogen represents a higher risk than natural gas.

It is true that hydrogen can cause material fatigue. This phenomenon, known as hydrogen embrittlement, was already discovered at the end of the 19th century and has been the subject of research ever since. Today’s engineers have this problem under control. We know which materials are suitable and what stresses they can be subjected to. Worldwide, more than 2000 km of hydrogen pipelines and plenty of hydrogen vessels and other equipment are operated safely. At “Energiepark Mainz” hydrogen is feed into the natural gas grid, which has no risk of hydrogen embrittlement.

Just like natural gas or gasoline vapor, a hydrogen-air mixture can explode. But the hydrogen rate in the air must at least reach 4 percent to ignite. If the hydrogen level makes up more than 75 percent, the gas-mixture cannot ignite, because of a lack of oxygen. In contrast to gasoline and natural gas, hydrogen has significant buoyancy in atmospheric conditions due to its low density, which reduces the risk of an ignition in open air. Within buildings, gas detectors are installed which, in the unlikely event of a gas release with a concentration of 1.6% of hydrogen or higher, will immediately shut down the system and bring it to a safe state so that the hydrogen concentration cannot increase anymore.

At “Energiepark Mainz” hydrogen is stored to balance the dynamic production of renewable energies. After a short residence time in onsite pressurized storage tanks, the hydrogen will be picked up by tank trucks or fed into the natural gas grid.

For hydrogen-powered vehicles, an industrial standard of 700 bar has been established. Vehicles for the transport of compressed hydrogen, so called “trailers”, usually work with a maximum pressure of 200 bar.

By converting electricity from renewable energies (i.e. wind, solar power) into hydrogen, it is possible to store the energy and use it when it is required: i.e. at night, when the sun is not shining or when there is no wind and the wind turbine is not operating. In this combination, we can even use renewables to provide base load power. Furthermore, hydrogen opens up new ways for using green electricity, i.e. by using hydrogen as substitute for natural gas by feeding it into existing pipelines, as fuel for fuel-cell vehicles, or as raw material for the hydrogen processing industry.

Hydrogen (chemical symbol H) is a gas. As a molecule, hydrogen occurs only in small amounts in nature. Mainly it is chemically bound. It can be produced by using energy. It is the lightest element in the periodic table (atomic number: 1).