H2 in the home | #explore

19. October 2023

Winter is approaching, and, with that in mind, many people are now asking whether green hydrogen could possibly also be used to heat their homes. And if so, what technical conditions need to be met for this kind of conversion. And would H₂-based heating be financially viable for homeowners too? With these and other questions in mind, we spoke to Thomas Kattenstein, a hydrogen expert at TÜV NORD subsidiary EE ENERGY ENGINEERS.

#explore: Mr Kattenstein, whenever there have been heated discussions (pun intended!) about the so-called “Heating Act”, hydrogen has always been brought into play as a possible option. What is the current state of the art? Do we already have gas heating systems which are H₂-ready?

Thomas Kattenstein: Yes indeed, our current natural gas heating systems are already easily capable of dealing with the addition of up to 20 percent hydrogen. OK, so you can’t yet buy appliances that can be powered by hydrogen alone. But all the major manufacturers are developing and trialling systems like these, which ought then to be ready for larger scale market launch in 2024 to 2025.

How do these appliances differ from classic gas heating systems?

Hydrogen burns hotter than natural gas and has a different flame, which is why H₂ heating systems use different burner technology and components that can cope with higher temperatures. Burning hydrogen also generates more water vapour, which needs to be taken into account when you build such systems. At the end of the day, we’re looking at modest adaptations, comparable with the conversion from L-gas to H-gas in natural gas heating systems that’s been underway since last year, especially in northern Germany.

What conditions must the infrastructure meet – for instance concerning the tank in your garden and the pipes in your house?

Well, it’s true that the liquid natural gas tanks in use today won’t be an option any longer. You wouldn’t be able to store enough hydrogen in them to last the winter. But, with buildings already connected to the gas main, you would instead be able to replace natural gas with green hydrogen. 95 percent of all gas pipes in the distribution network could quickly and easily be converted to carry hydrogen, according to the grid operators. The gas pipelines in the transport networks are also compatible. But since hydrogen, as the smallest molecule, is more volatile than natural gas, it might in some cases be necessary to replace gas taps or the like. You would above all need new compressors to compress the hydrogen to feed it into the network. This conversion may well be the biggest factor in the conversion of the gas networks, in terms of both time and expense.

How would this kind of conversion unfold? Could it be that some households in the same local gas network might continue to use gas while others would use hydrogen?

When hydrogen was first being discussed more widely in public about ten years ago, most of the thinking was to add hydrogen to natural gas to gradually make the industrial sector, transport and heating more climate friendly. Now there is a general consensus that the steel and chemical industries, for instance, will need large quantities of pure hydrogen to significantly reduce their CO₂ emissions. Instead of adding hydrogen to natural gas, these players would completely switch to green hydrogen. And that would also apply to the building heat supplied using the same gas network. This is why an entire section of the gas network would switch from natural gas to hydrogen on one specific date. Every heating system connected to this grid would have to be H₂-ready by this date. In other words, you wouldn’t have one household using natural gas with another using hydrogen, since this just wouldn’t work in practice.

How efficient is hydrogen compared to other sustainable forms of heating like heat pumps?

Heat pumps have a clear edge when it comes to efficiency, as the amount of heat energy they generate outweighs the electrical power that feeds them. When designing a heat pump, the annual performance coefficient is at least three. This means that they use one kilowatt of electricity to produce three kilowatts of heat energy. In other words, they have an efficiency of 300 percent. If you use the same quantity of electrical power to produce hydrogen, you first have to use about 30 percent of the energy for electrolysis, the process which produces hydrogen. And then you have distribution losses in the boiler, resulting in an efficiency figure of 50 to 60 percent. Which means that heat pumps are five to six times more efficient than hydrogen. Although, it must be said, you can’t use a heat pump to heat every type of building; for instance, modernising some old buildings to make them fit for a heat pump would consume so much energy that it simply wouldn’t be financially worthwhile. In such cases, an option would be to use green hydrogen for heating! It’s going to be flowing through our gas network in the future in any case. On the one hand, to supply major industrial consumers. But also because, as we continue to expand our use of renewables, we’re going to need hydrogen as a storage medium for those times when the sun doesn’t shine and the wind doesn’t blow. Batteries are a good option as temporary energy stores to stabilise the grid. But if you want to store large amounts of energy for longer, then hydrogen will be your medium of choice.

About Thomas Kattenstein:

Thomas Kattenstein is the director of the hydrogen competence centre at EE Energy Engineers. The graduate civil and energy technology engineer and his colleagues are in the vanguard of hydrogen expertise. They have been advising policymakers and business for over 20 years on the possible deployment of our universe’s smallest element – starting with the question of which sites are suitable for the construction of electrolysers courtesy of their proximity to renewable energy sources and potential buyers, and moving on to feasibility studies and the design of specific electrolysis plants, right through to preparations for the approvals procedure and coordination with the authorities.

The HydroHub, the TÜV NORD GROUP’s hydrogen initiative, pools all the expertise from the operational divisions in consulting and engineering, such as EE ENERGY ENGINEERS, Encos and the DMT Group.

Green hydrogen is currently produced only in small quantities and at high prices. Will it be available for heating in sufficient quantities and at affordable prices any time soon?

There’s no doubt that supplying major consumers in industry and transport with green hydrogen will initially take priority over making it available for domestic heating. But if we also import hydrogen via pipelines from Scandinavia, Scotland and North Africa as well as producing our own, things could happen very quickly. We might easily end up with prices of between two and four euros per kilogramme of hydrogen. If we got it down to two euros, that would amount to six or seven cents per kilowatt hour. And the cost of natural gas and oil will be significantly higher than this, in no small part due to the increasing price of CO₂. So, it would not be a good idea to quickly buy yourself a new oil heating system before the Heating Act comes into force. With these costs per kilowatt hour, heating with hydrogen could also compete with heat pumps. Although it should be said that heat pumps will become cheaper to run, especially as the cost of electricity will continue to fall as more and more renewables come on stream. But the lower purchase costs for an H₂ heating system should compensate for this.

Which role will green hydrogen play in the sustainable heating system of the future?

In percentage terms, the heat pump will probably win out, followed by district heating and hydrogen. District heating will become more and more important in major cities and densely populated areas – increasingly so with the waste heat produced by industrial plants or decentralised electrolysers. We’re a long way away from fully exploiting the potential of these. When it comes to new buildings and upgrades, the heat pump is generally the medium of choice; hydrogen will come into its own in buildings for which no district heat is available and where the cost of upgrading the building will make fitting a heat pump prohibitively expensive. In rural areas, biogas or wood pellet heating systems may also play a role.

Existing structure can be used: According to the network operators, almost all gas pipelines in the distribution network can be converted to hydrogen.