Current debates around the role of hydrogen in decarbonising the heating sector ignore some important factors, argues Alix Chambris, vice-president of global public affairs and sustainability at Viessmann. 

Decarbonising the built environment poses major challenges around generating, storing and transporting energy. To meet our climate goals, we must intensify our efforts to tackle these problems head on. Germany, for example, has committed to reducing its heating sector emissions by a further 40 per cent on current levels by 2030, compared to 18 per cent over the last decade.  

The speed and scale of change required means we really need to understand the issues in full, within the context of the entire energy system. Partial analyses and isolated measures, for example focussing on end-use energy efficiency of products alone, are unhelpful.  

Multi-faceted approach  

Buildings and the heat market are heterogeneous, emissions from buildings are hard-to-abate, roadmaps for a net-zero building stock must ensure that nobody is left behind. It means: there are no ‘one-size-fits-all’ solutions. We therefore need a balanced mix of energy sources and technologies to meet the needs of all users, those able to pay and on low incomes, while also ensuring we move forward on all fronts rapidly and simultaneously, rather than waiting for future technology developments to manifest.  

Climate-neutral heat supply requires a considerable transformation that cannot be achieved overnight. Many European countries’ building stock is decades old, with the vast majority using gas- or oil-based heating systems. A one-sided focus on switching to electric heat pumps ignores the technical and economic hurdles involved.   

Example Germany: the electricity system is in transformation from “firm” generation provided by coal and nuclear, to wind and solar. It was shown that a mix of electrons and green molecules in heating fits that pathway best – despite the fact that, in “isolation”, heat pumps have a better end-use efficiency than a boiler run on green molecules. One reason: each heat pump adds load that has to be covered by the electricity system also in periods with low output from wind capacities, and low outside temperatures. Mutually reinforcing gas and electricity infrastructures are preferable, compared to a scenario “electricity only, gas connections to buildings dismantled”. In my view the “load” and energy system aspects are often a blind spot in the debate around hydrogen in heating. 

It therefore makes sense to explore the use of hydrogen, which requires fewer adaptations to infrastructure and appliances and has the potential to be entirely carbon neutral.  

The hydrogen debate 

Renewable hydrogen is now widely recognised as a crucial building block for achieving climate goals, complementing efficiency measures and other  renewable energies. The ramp-up of the H2 economy is now gaining pace: projects with more than 115 GW of electrolyser capacity for clean electricity-based hydrogen by 2030 are currently planned in EU countries and the UK alone. And this is only the start. 

Both the German Hydrogen Strategy and the country’s EU-mandated Long-term Renovation Strategy refer to the use of hydrogen to decarbonise the heating sector. However, some stakeholders argue that hydrogen use should be restricted to only industry and transport.  

They reason that, unlike heating, some industrial and long haul transport operations lack economically and technically viable low-carbon alternatives. Hydrogen is viewed as a scarce commodity not to be squandered on heating homes when other solutions, like heat pumps and improvements to the energy efficiency of the building envelope, are available. 

However, this argument overlooks several factors. 

Plentiful and transportable 

Renewable energy does not necessarily occur where heat is consumed.  

Worldwide there is considerable potential for renewables, greatly exceeding future energy demand. Existing gas infrastructure can be easily repurposed to import hydrogen or hydrogen-based gases (which are easy to transport and store) from renewable sources in regions with better climatic or geological conditions, thereby making a valuable contribution to decarbonisation.  

Furthermore, depending on progress in energy efficiency and the market penetration of alternative technologies – hybrids of a heat pump and a gas boiler to name just one – in the built environment, the demand for hydrogen in heat supply will be significantly lower than the current share of natural gas.  

In the longer term, there is no scarcity of renewable hydrogen. 

Stable demand 

The heating sector can provide stable demand straight away, by blending hydrogen into the existing gas grid. In Germany, it can already directly absorb about 70% of the government’s 2030 volume target for domestic production of renewable hydrogen.  

Thus, the heating sector can provide immediate security for investments in hydrogen production, transport and distribution, bolstering its ramp-up in other industries.  

Moving on from here, for me it is obvious: we need flexibility for optimising the hydrogen value chain and the energy system. A key ingredient is combustion heating technologies that are prepared for operating on variable compositions of green gases. All Viessmann heating appliances will be ready for 100% H2 in the near future, the capability to process admixtures is standard already today. 

Seasonality 

Energy demand in the heating sector is characterised by seasonal variations, plus rare periods of extreme cold (‘1-in-20 winters’). While gas infrastructure is designed to meet peak demand and can be adapted to increasing hydrogen shares, seasonality represents an enormous challenge for national power supplies once heating is electrified, even if efficiency is optimised.  

Five million additional heat pumps in Germany would lead to a peak-load increase of up to 55%. Meanwhile, 35% of current firm electricity-generation capacity is scheduled for decommissioning by 2030 – and we can expect that the new government will accelerate the exit from coal. When you consider that the country’s electricity-storage capacity is 6000 times smaller than that of its gas-storage capacity, you can see the scale of the problem.  

More research needed 

Thanks to its use of existing gas systems, switching to hydrogen can reduce total costs of heating decarbonisation, reducing financial burdens on households and governments and making it more accessible to low-income groups – providing diverse options for staged renovations that can be tailor-made to heterogeneous individual circumstances and preferences of households. However, studies analysing the minimum total cost of different technologies in the heating market show diverse results. 

Hence, further research is clearly needed. This is unsurprising, given the rapidity of developments around green hydrogen in recent years. 

For all these reasons, policy makers should not limit technology options today, for example by proscribing gas-heating systems which in future can be increasingly served by renewable, carbon-neutral hydrogen-based gases.  

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