Ready for hydrogen: What companies can do today

Dr. Anne Giese, Head of the Industrial and Combustion Technology Department at the Gas- und Wärme-Institut e. V. (GWI), provides the answers. The doctor of engineering has been researching and working on solutions for a safe and efficient energy supply for over 20 years. In addition to her work at the GWI, she is involved in expert committees of the German Technical and Scientific Association for Gas and Water (DVGW), is a member of the board of the German Association for Combustion Research (DVV) and is active as an expert in industrial joint research.

Dr. Anne Giese: Anyone wishing to switch from natural gas to hydrogen as an energy source must be aware that the properties of the new energy source differ significantly. Hydrogen provides only about one-third of the energy content of natural gas per volume. This means that in order to generate the same heat output in the furnace, approximately three times the amount of gas must flow through the pipes. This alone makes it clear that existing infrastructure, from pipes and fittings to blowers and air preheaters, must be carefully checked and, if necessary, adapted.

What's more, hydrogen is a particularly small and light molecule. Even tiny leaks can cause gas to escape. That's why it's important to ensure that systems are completely leak-proof. Measurement, control and regulation technology must also be adapted to the new conditions to ensure that operation remains reliable and safe. In some cases, this also applies to the burners themselves: as the flame shape can change due to the altered gas and air volume flows, the burner geometry must be checked and adjusted if necessary.

Dr. Anne Giese: The use of hydrogen can usually have an indirect effect on the lining of furnaces, their service life or even the end product itself via the increased water vapour content in the exhaust gas. In industries such as glass, porcelain and aluminium, effects have already been observed that require adjustments to raw materials or processes. It is not possible to make general statements here. Each plant must be considered individually.

Dr. Anne Giese: Another point concerns exhaust gas aftertreatment. Hydrogen burns hotter than natural gas, which can produce more nitrogen oxides (NOx). These are air pollutants whose levels are regulated. However, with known and adapted measures, the limit values can be reliably complied with. In addition, the use of hydrogen produces more water vapour in the exhaust gas. Since the limit values generally apply to ‘dry exhaust gases’, the measured values are only comparable to those of natural gas combustion to a limited extent and should be converted to a different reference system. The GWI has developed proposals for practical solutions in collaboration with partners.

The switch to hydrogen is technically feasible for many industrial furnaces, often even easier than for gas turbines in power plants. Nevertheless, companies should leave nothing to chance and thoroughly examine their own situation. Especially for small and medium-sized enterprises, there are many experts at research institutes, universities and engineering firms who can assist them in this process.

Dr. Anne Giese: There are two important questions when it comes to both electrification and the use of hydrogen. Which energy source is best suited to a given process, and is there the right infrastructure in place to reliably supply the energy? The dimensions are enormous – industrial process heat in Germany alone accounts for around 500 terawatt hours. This is roughly equivalent to today's total electricity consumption. If we were to electrify all these heating processes, the electricity grid would have to be massively expanded. The gas network, on the other hand, already exists and can be used for hydrogen relatively quickly.

Another argument: many industrial plants run continuously, day and night, often for decades. Shutting them down or slowing them down is simply not possible without risking production losses or even damage. A secure supply based solely on electricity from renewable energies such as wind and solar is not yet realistic. In addition, the carbon footprint always depends on how the electricity is generated. If it is produced in a gas-fired power plant, it is often more harmful to the climate to use the electricity than to burn the gas directly in the furnace.

Dr. Anne Giese: Electrically generated heat does not always reach the required temperature or heat flux density, i.e. the amount of heat per area and time required for certain processes. In high-temperature processes, this can mean that plants have to be much larger or can produce less. At the same time, additional chemical reactions take place in many furnaces that influence product properties: for example, colour changes in glass, differences in hardness in metals or moisture absorption in food. Such processes often depend on the furnace atmosphere and cannot be easily replicated electrically.

What's more, not all materials respond well to electric heating. Ceramic materials and bulk goods are difficult to heat evenly. And even with aluminium, the picture is mixed: pure scrap can be melted down electrically, but with contaminated material, such as traces of paint or oil, a gas flame is essential to ensure quality and yield.

For low temperatures up to around 300 °C, electrification, for example with heat pumps, can be very efficient. At higher temperatures, however, hydrogen – alone or in combination with electricity – often remains the more robust and flexible solution. Ultimately, it is always necessary to assess on a case-by-case basis which technology is best suited to the respective process and location.

Dr. Anne Giese: The switch to hydrogen is not an all-or-nothing project. Many steps can be taken today to ensure that the actual transition runs smoothly later on. Numerous plant manufacturers and suppliers have now made their products ‘H2-ready’, and the first industrial furnaces of this type are already in use.

For companies, this means four things in particular:

First, existing systems should be checked: Which components are hydrogen-compatible, and where are modifications necessary? Anyone investing in new technology should ensure that it is designed for operation with hydrogen, even if natural gas is still used initially. It is equally important to consult with the local energy supplier: When will hydrogen be available locally, and are there alternatives such as a dedicated electrolysis plant? Finally, it is also worthwhile to involve the regulatory authorities at an early stage in order to clarify any questions regarding emissions or limit values.

In short, companies that act now are laying the groundwork to switch to hydrogen quickly and directly when the time is right.

Dr. Anne Giese: There is no universal recommendation. The processes, products, locations and investment scope of companies vary too greatly. It is important to keep an open mind about the options. In addition to electrification and hydrogen, other energy sources such as biomass or biogas can also be interesting and often quickly implementable solutions, especially in rural areas. Hybrid systems are also gaining in importance. They can switch flexibly between electricity and gas or hydrogen. This makes them more technically sophisticated and often more expensive, but opens up new business models, such as demand side management. This involves flexibly adjusting energy consumption to price and availability.