Applications & Pathways

Aviation is the backbone of our modern society. In 2019 around 4.5 billion passengers travelled through the air. However at the same time aviation was also responsible for around 5% of anthropogenic causes of global warming. The impact of the COVID-19 pandemic on the aviation sector in the short term is clearly very high but the long-term effects are still unknown. However with the increase in global GDP the number of travelers is expected to increase between three- to four-fold by the middle of this century. While other sectors of transportation are making steady progress in decarbonizing aviation is falling behind. This paper explores some of the various options for energy carriers in aviation and particularly highlights the possibilities and challenges of using cryogenic fuels/energy carriers such as liquid hydrogen (LH2) and liquefied natural gas (LNG).

New energy vehicles (NEVs) especially electric vehicles (EVs) address the important task of reducing the greenhouse effect. It is particularly important to measure the environmental efficiency of new energy vehicles and the life cycle analysis (LCA) model provides a comprehensive evaluation method of environmental efficiency. To provide researchers with knowledge regarding the research trends of LCA in NEVs a total of 282 related studies were counted from the Web of Science database and analyzed regarding their research contents research preferences and research trends. The conclusion drawn from this research is that the stages of energy resource extraction and collection carrier production and energy transportation maintenance and replacement are not considered to be research links. The stages of material equipment and car transportation and operation equipment settling and forms of use need to be considered in future research. Hydrogen fuel cell electric vehicles (HFCEVs) vehicle type classification the water footprint battery recovery and reuse and battery aging are the focus of further research and comprehensive evaluation combined with more evaluation methods is the direction needed for the optimization of LCA. According to the results of this study regarding EV and hybrid power vehicles (including plug-in hybrid electric vehicles (PHEV) fuel-cell electric vehicles (FCEV) hybrid electric vehicles (HEV) and extended range electric vehicles (EREV)) well-to-wheel (WTW) average carbon dioxide (CO2 ) emissions have been less than those in the same period of gasoline internal combustion engine vehicles (GICEV). However EV and hybrid electric vehicle production CO2 emissions have been greater than those during the same period of GICEV and the total CO2 emissions of EV have been less than during the same period of GICEV.

Immediate and widespread changes in energy generation and use are critical to safeguard our future on this planet. However while the necessity of renewable electricity generation is clear the aviation transport and mobility chemical and material sectors are challenging to fully electrify. The age-old Fischer-Tropsch process and natural gas industry could be the bridging solution needed to accelerate the energy revolution in these sectors – temporarily powering obsolete vehicles acting as renewable energy’s battery supporting expansion of hydrogen fuel cell technologies and the agricultural and waste sectors as they struggle to keep up with a full switch to biofuels. Natural gas can be converted into hydrogen synthetic natural gas or heat during periods of low electricity demand and converted back to electricity again when needed. Moving methane through existing networks and converting it to hydrogen on-site at tanking stations also overcomes hydrogen distribution storage problems and infrastructure deficiencies. Useful co-products include carbon nanotubes a valuable engineering material that offset emissions in the carbon nanotube and black industries. Finally excess carbon can be converted back into syngas if desired. This flexibility and the compatibility of natural gas with both existing and future technologies provides a unique opportunity to rapidly decarbonise sectors struggling with complex requirements.

The power management strategy (PMS) is intimately linked to the fuel economy in the hybrid electric vehicle (HEV). In this paper a hybrid power management scheme is proposed; it consists of an adaptive neuro-fuzzy inference method (ANFIS) and the equivalent consumption minimization technique (ECMS). Artificial intelligence (AI) is a key development for managing power among various energy sources. The hybrid power supply is an eco-acceptable system that includes a proton exchange membrane fuel cell (PEMFC) as a primary source and a battery bank and ultracapacitor as electric storage systems. The Haar wavelet transform method is used to calculate the stress (σ) on each energy source. The proposed model is developed in MATLAB/Simulink software. The simulation results show that the proposed scheme meets the power demand of a typical driving cycle i.e. Highway Fuel Economy Test Cycle (HWFET) and Worldwide Harmonized Light Vehicles Test Procedures (WLTP—Class 3) for testing the vehicle performance and assessment has been carried out for various PMS based on the consumption of hydrogen overall efficiency state of charge of ultracapacitors and batteries stress on hybrid sources and stability of the DC bus. By combining ANFIS and ECMS the consumption of hydrogen is minimized by 8.7% compared to the proportional integral (PI) state machine control (SMC) frequency decoupling fuzzy logic control (FDFLC) equivalent consumption minimization strategy (ECMS) and external energy minimization strategy (EEMS).

In April 2018 the International Maritime Organisation adopted an ambitious plan to contribute to the global efforts to reduce the Greenhouse Gas emissions as set by the Paris Agreement by targeting a 50% reduction in shipping’s Green House Gas emissions by 2050 benchmarked to 2008 levels. To meet these challenging goals the maritime industry must introduce environmentally friendly fuels with negligible or low SOX NOX and CO2 emissions. Ammonia use in maritime applications is considered promising due to its high energy density low flammability easy storage and low production cost. Moreover ammonia can be used as fuel in a variety of propulsors such as fuel cells and can be produced from renewable sources. As a result ammonia can be used as a versatile marine fuel exploiting the existing infrastructure and having zero SOX and CO2 emissions. However there are several challenges to overcome for ammonia to become a compelling fuel towards the decarbonisation of shipping. Such factors include the selection of the appropriate ammonia-fuelled power generator the selection of the appropriate system safety assessment tool and mitigating measures to address the hazards of ammonia. This paper discusses the state-of-the-art of ammonia fuelled fuel cells for marine applications and presents their potential and challenges.

This paper presents a case study of a lithium battery and fuel cell integrated powertrain system for a renewable energy vehicle. The performance analysis includes evaluating the energy consumption of the vehicle and the efficiency of the power generation components. When driven solely by the lithium battery at average speeds of 15 km/h and 20 km/h it was observed that speed significantly influences the travel distance of the vehicle with higher speeds resulting in lower mileage. The energy efficiency rates were found to be 89.3% and 85.7% at speeds of 15 km/h and 20 km/h respectively indicating an 18.1% decrease in efficiency from low to higher speeds. When the lithium battery is solely charged by the hydrogen fuel cell the efficiency under test conditions reaches approximately 32.5%. In the “FC + B + SC” driving mode which combines the use of the lithium battery fuel cell and solar panel to power the vehicle the travel range can be extended to 50.62 km and 42.05 km respectively representing an increase of over 50% with overall efficiencies of 63.8% and 60.7% respectively. This hybrid powertrain system exhibits rapid dynamic response high energy and power density and enables longer travel distances for the renewable energy vehicle.

The Jet Zero strategy sets out how we will achieve net zero aviation by 2050.<br/>It focuses on the rapid development of technologies in a way that maintains the benefits of air travel whilst maximising the opportunities that decarbonisation can bring to the UK.<br/>The Jet Zero strategy includes a 5-year delivery plan setting out the actions that will need to be taken in the coming years to support the delivery of net zero aviation by 2050. We will be monitoring progress and reviewing and updating our strategy every 5 years.<br/>The strategy is informed by over 1500 responses to the Jet Zero consultation and the Jet Zero further technical consultation to which we have issued a summary of responses and government response.<br/>The Jet Zero investment flightpath is part of a series of roadmaps to be published over the course of 2022 for each sector of the Prime Minister’s Ten point plan for a green industrial revolution.<br/>It showcases the UK’s leading role in the development and commercialisation of new low and zero emission aviation technologies. It also highlights investment opportunities across systems efficiencies sustainable aviation fuels and zero emission aircraft.

Meeting the Paris Agreement will most likely require the combination of CO2 capture and biomass in the industrial sector resulting in net negative emissions. CO2 capture within the industry has been extensively investigated. However biomass options have been poorly explored with literature alluding to technical and economic barriers. In addition a lack of consistency among studies makes comparing the performance of CO2 capture and/or biomass use between studies and sectors difficult. These inconsistencies include differences in methodology system boundaries level of integration costs greenhouse gas intensity of feedstock and energy carriers and capital cost estimations. Therefore an integrated evaluation of the techno-economic performance regarding CO2 capture and biomass use was performed for five energy-intensive industrial sub-sectors. Harmonization results indicate that CO2 mitigation potentials vary for each sub-sector resulting in reductions of 1.4–2.7 t CO2/t steel (77%–149%) 0.7 t CO2/t cement (92%) 0.2 t CO2/t crude oil (68%) 1.9 t CO2/t pulp (1663%–2548%) and 34.9 t CO2/t H2 (313%). Negative emissions can be reached in the steel paper and H2 sectors. Novel bio-based production routes might enable net negative emissions in the cement and (petro) chemical sectors as well. All the above-mentioned potentials can be reached for 100 €/t CO2 or less. Implementing mitigation options could reduce industrial CO2 emissions by 10 Gt CO2/y by 2050 easily meeting the targets of the 2 ◦C scenario by the International Energy Agency (1.8 Gt CO2/y reduction) for the industrial sector and even the Beyond 2 ◦C scenario (4.2 Gt CO2/y reduction).

With the rapid promotion of renewable energy technologies and the trend to a low-carbon society the positive impacts of an integrated energy system that realizes various forms of energy-utilizing improvement and carbon reduction have fully emerged. Hydrogen with a decarbonized characteristic being integrated into the integrated energy system has become a viable option to offset the intermittency of renewables and decline the fossil fuel usage. An optimal planning model of a wind–photovoltaic–hydrogen storage-integrated energy system with the objective of total economic and environmental cost minimization by considering various energy technology investments is proposed. Case studies are developed to compare the economic and environmental benefits of different energy investment scenarios especially hydrogen applications. The cost–benefit analysis was carried out to prove that hydrogen investment is not a cost-competitive option but can alleviate the burden of carbon emissions somehow. Finally sensitivity analysis of key parameters of sale capacity carbon tax and renewable penetration level was performed to indicate the rational investment for a wind–photovoltaic–hydrogen storage-integrated energy system.

Hydrogen fuel cell vehicle industry is in a rapid development stage. Studying the domestic spatial distribution of hydrogen fuel cell vehicle industry across a country especially the spatio-temporal evolution of the innovation level and position of each region in innovation network will help to understand the industry’s development trends and characteristics and avoid repeated construction. This article uses social network analysis and patent citation information of 2971 hydrogen fuel cell vehicle related invention patents owned by 218 micro-innovators across 25 provinces of China from 2001 to 2020 to construct China’s hydrogen fuel cell vehicle innovation network. Based on the dimensions of knowledge production knowledge consumption and network broker the network positions of sample provinces in three periods divided by four main national policies are classified. The main findings are as follows. 1) In China the total sales of hydrogen fuel cell vehicle and the development of supporting infrastructure are balanced and a series of national and local industrial development polices have been issued. 2) China’s hydrogen fuel cell vehicle innovation network density the proportion of universities and research institutes among the innovators and the active degree of the eastern provinces are all becoming higher. 3) The provinces in optimal network position are all from the eastern region. Shanghai and Liaoning are gradually replaced by Beijing and Jiangsu. 4) Sichuan in the western region is the only network broker based on knowledge consumption. 5) Although Zhejiang Tianjin Hebei Guangdong and Hubei are not yet in the optimal position they are outstanding knowledge producers. Specifically Guangdong is likely to climb to the optimal network position in the next period. The conclusions will help China’s provinces to formulate relevant development policies to optimize industry layout and enhance collaborative innovation in the hydrogen fuel cell vehicle industry.

Alongside the rapid expansion of wind power installation in China wind curtailment is also mounting rapidly due to China’s energy endowment imbalance. The hydrogen-based wind-energy storage system becomes an alternative to solve the puzzle of wind power surplus. This article introduced China’s energy storage industry development and summarized the advantages of hydrogen-based wind-energy storage systems. From the perspective of resource conservation it estimated the environmental benefits of hydrogen-based wind-energy storages. This research also builds a valuation model based on the Real Options Theory to capture the distinctive flexible charging and discharging features of the hydrogen-based wind-energy storage systems. Based on the model simulation results including the investment value and operation decision of the hydrogen energy storage system with different electricity prices system parameters and different levels of subsidies are presented. The results show that the hydrogen storage system fed with the surplus wind power can annually save approximately 2.19–3.29 million tons of standard coal consumption. It will reduce 3.31–4.97 million tons of CO2 SO2 NOx and PM saving as much as 286.6–429.8 million yuan of environmental cost annually on average. The hydrogen-based wind-energy storage system’s value depends on the construction investment and operating costs and is also affected by the meanreverting nature and jumps or spikes in electricity prices. The market-oriented reform of China’s power sector is conducive to improve hydrogen-based wind-energy storage systems’ profitability. At present subsidies are still essential to reduce initial investment and attract enterprises to participate in hydrogen energy storage projects.

This study analyzes the optimal sizing design of a stand-alone solar hydrogen hybrid energy system for a house in Afyon Turkey. The house is not connected to the grid and the proposed hybrid system meets all its energy demands; therefore it is considered a zero-energy building. The designed system guarantees uninterrupted and reliable power throughout the year. Since the reliability of the power supply is crucial for the house optimal sizing of the components photovoltaic (PV) panels electrolyzer storage tank and fuel cell stack is critical. Determining the sufficient number of PV panels suitable electrolyzer model and size number of fuel cell stacks and the minimum storage tank volume to use in the proposed system can guarantee an uninterrupted energy supply to the house. In this study a stand-alone hybrid energy system is proposed. The system consists of PV panels a proton exchange membrane (PEM) electrolyzer a storage tank and a PEM fuel cell stack. It can meet the continuous energy demand of the house is sized by using 10 min of averaged solar irradiation and temperature data of the site and consumption data of the house. Present results show that the size of each component in a solar hydrogen hybrid energy system in terms of power depends on the size of each other components to meet the efficiency requirement of the whole system. Choosing the nominal electrolyzer power is critical in such energy systems

In this paper the design of fuel cells for the main energy supply of passenger transportation aircraft is discussed. Using a physical model of a fuel cell general design considerations are derived. Considering different possible design objectives the trade-off between power density and efficiency is discussed. A universal cost–benefit curve is derived to aid the design process. A weight factor wP is introduced which allows incorporating technical (e.g. system mass and efficiency) as well as non-technical design objectives (e.g. operating cost emission goals social acceptance or technology affinity political factors). The optimal fuel cell design is not determined by the characteristics of the fuel cell alone but also by the characteristics of the other system components. The fuel cell needs to be designed in the context of the whole energy system. This is demonstrated by combining the fuel cell model with simple and detailed design models of a liquid hydrogen tank. The presented methodology and models allows assessing the potential of fuel cell systems for mass reduction of future passenger aircraft.

With little time left for humanity to reduce climate change to a tolerable level a highly scalable and rapidly deployable solution is needed that can be implemented by any country. Offshore wind energy in international waters is an underused resource and could even be harnessed by landlocked countries. In this paper the use of sailing wind turbines operating autonomously in high seas to harvest energy is proposed. The electrical energy that is generated by the wind turbine is converted to a renewable fuel and stored onboard. Later the fuel will be transferred to shore or to other destinations of use. The presented idea is explored at the system level where the basic subsystems necessary are identified and defined such as energy conversion and storage as well as propulsion subsystems. Moreover various operating possibilities are investigated including a comparison of different sailing strategies and fuels for storage. Existing ideas are also briefly addressed and an example concept is suggested as well. In this paper the proposed sailing renewable energy conversion system is explored at a higher level of abstraction. Following up on this conceptual study more detailed investigations are necessary to determine whether the development of such a sailing renewable energy conversion system is viable from an engineering economic and environmental point of view.

For this episode we speak to Amanda Lyne the Managing Director of ULEMCo and the Chair of the UK Hydrogen and Fuel Cell Association (UKHFCA). Below are a few links to some of the content discussed on the show and some further background reading.

The podcast can be found on their website

The fuel cell game is not new and for many it is has been a long time coming. Few know this better than Ballard Power Systems the third ever founded Fuel Cell company that has operated since the 1970s. On the show we ask Nicolas Pocard about Ballards history and why this time the market is different for fuel cell companies.

The podcast can be found on their website

To limit global temperature increase below +2°C societies need to reduce greenhouse gas emissions radically within the next few decades. Amongst other mitigation measures this requires transforming process-emission intensive industries towards emission neutrality. One way to this end is the renewables-based electrification of industries. We present results of a recent coproduction process which brought together stakeholders from industry policy administration and science to co-create climate-neutral transition pathways for the steel and electricity sectors in Austria. The results summarized here are the definition of reliable pathways and the identification of associated risks pertaining to pathway implementation including a macro-economic quantification. We find that risks to implementation (barriers) are at least as important as risks of implementation (negative consequences). From the quantitative analysis we find that provided that barriers can be reduced macroeconomic costs of the transition are only moderate and that stakeholders might overestimate risks when neglecting economy-wide feedbacks.

Hydrogen fuel cells are systems that can be successfully used to partially replace internal combustion propulsion systems. For this reason the article presents an operational analysis of energy flow along with an analysis of individual energy transmission systems. Two generations of the Toyota Mirai vehicle were used for the tests. The operational analyses were carried out on the same route (compliant with RDE test requirements) assessing the system’s operation in three driving sections (urban rural and motorway). Both generations of the drive system with fuel cells are quite different which affects the obtained individual systems operation results as well as the overall energy flow. Research was carried out on the energy flow in the fuel cells FC converter battery and electric motor using a dedicated data acquisition system. The analyses were carried out in relation to the energy of fuel cells battery energy and recovered braking energy. It was found that in the urban drive section of the second-generation system (due to its much larger mass) a slightly higher energy consumption value was obtained (by about 2%). However in the remaining phases of the test consumption was lower (the maximum difference was 18% in the rural phase). Total energy consumption in the research test was 19.64 kWh/100 km for the first-generation system compared to 18.53 kWh/100 km for the second-generation system. Taking into account the increased mass of the second-generation vehicle resulted in significantly greater benefits in the second-generation drive (up to 37% in individual drive sections and about 28% in the entire drive test).

The ignition of hydrogen in compression ignition (CI) engines by adding noble gas as a working gas can yield excellent thermal efficiency due to its high specific heat ratio. This paper emphasizes the potential of helium–oxygen atmosphere for hydrogen combustion in CI engines and provides data on the engine configuration. A simulation was conducted using Converge CFD software based on the Yanmar NF19SK engine parameters. Helium–oxygen atmosphere compression show promising hydrogen autoignition results with the in-cylinder temperature was significantly higher than that of air during the compression stroke. In a compression ignition engine with a low compression ratio (CR) and intake temperature helium–oxygen atmosphere is recognized as the best working gas for hydrogen combustion. The ambient intake temperature was sufficient for hydrogen ignition in low CR with minimal heat flux effect. The best intake temperature for optimum engine efficiency in a low CR engine is 340 K and the engine compression ratio for optimum engine efficiency at ambient intake temperature is CR12 with an acceptable cylinder wall heat flux value. The helium–oxygen atmosphere as a working gas for hydrogen combustion in CI engines should be consider based on the parameter provided for clean energy transition with higher thermal efficiency.

The crisscross progress of transportation and energy carries the migrating track of human society development and the evolution of civilization among which the decarbonization strategy is a key issue. Traffic carbon emissions account for 16.2% of total energy carbon emissions while road traffic carbon emissions account for 11.8% of total energy carbon emissions. Therefore road traffic is a vital battlefield in attaining the goal of decarbonization. Employing clean energy as an alternative fuel is of great significance to the transformation of the energy consumption structure in road transportation. Hydrogen and ammonia are renewable energy with the characteristics of being widely distributed and clean. Both exist naturally in nature and the products of complete combustion are substances (water and nitrogen) that do not pollute the atmosphere. Because it can promote agricultural production ammonia has a long history in human society. Both have the potential to replace traditional fossil fuel energy. An overview of the advantages of hydrogen and ammonia as well as their development in different countries such as the United States the European Union Japan and other major development regions is presented in this paper. Related research topics of hydrogen and ammonia’s production storage and transferring technology have also been analyzed and collated to stimulate the energy production chain for road transportation. The current cost of green hydrogen is between $2.70–$8.80 globally which is expected to approach $2–$6 by 2030. Furthermore the technical development of hydrogen and ammonia as a fuel for engines and fuel cells in road transportation is compared in detail and the tests practical applications and commercial popularization of these technologies are summarized respectively. Opportunities and challenges coexist in the era of the renewable energy. Based on the characteristics and development track of hydrogen and ammonia the joint development of these two types of energy is meant to be imperative. The collaborative development mode of hydrogen and ammonia together with the obstacles to their development of them are both compared and discussed. Finally referring to the efforts and experiences of different countries in promoting hydrogen and ammonia in road transportation corresponding constructive suggestions have been put forward for reference. At the end of the paper a framework diagram of hydrogen and ammonia industry chains is provided and the mutual promotion development relationship of the two energy sources is systematically summarized.

The use of drop-in capable alternative fuels in aircraft can support the European aviation sector to achieve its goals for sustainable development. They can be a transitional solution in the short and medium term as their use does not require any structural changes to the aircraft powertrain. However the production of alternative fuels is often energy-intensive and some feedstocks are associated with harmful effects on the environment. In addition alternative fuels are often more expensive to produce than fossil kerosene which can make their use unattractive. Therefore this paper analyzes the environmental and economic impacts of four types of alternative fuels compared to fossil kerosene in a well-to-wake perspective. The fuels investigated are sustainable aviation fuels produced by power-to-liquid and biomass-to-liquid pathways. Life cycle assessment and life cycle costing are used as environmental and economic assessment methods. The results of this well-towake analysis reveal that the use of sustainable aviation fuels can reduce the environmental impacts of aircraft operations. However an electricity mix based on renewable energies is needed to achieve significant reductions. In addition from an economic perspective the use of fossil kerosene ranks best among the alternatives. A scenario analysis confirms this result and shows that the production of sustainable aviation fuels using an electricity mix based solely on renewable energy can lead to significant reductions in environmental impact but economic competitiveness remains problematic.

Considering the imperative reduction in CO2 emissions both from household heating and hot water producing facilities one of the mainstream directions is to reduce hydrocarbons in combustibles by replacing them with hydrogen. The authors analyze condensing boilers operating when hydrogen is mixed with standard gaseous fuel (CH4 ). The hydrogen (H2 ) volumetric participation in the mixture is considered to vary in the range of 0 to 20%. The operation of the condensing boilers will be numerically modeled by computational programs and prior validated by experimental studies concluded in a European Certified Laboratory. The study concluded that an increase in the combustible flow with 16% will compensate the maximum H2 concentration situation with no other implications on the boiler’s thermal efficiency together with a decrease in CO2 emissions by approximately 7%. By assuming 0.9 (to/year/boiler) the value of CO2 emissions reduction for the condensing boiler determined in the paper and extrapolating it for the estimated number of boilers to be sold for the period 2019–2024 a 254700-ton CO2/year reduction resulted.

Hydrogen fuel cell technology is securing a place in the future of advanced mobility and the energy revolution as engineers explore multiple paths in the quest for decarbonization. The feasibility of hydrogen-based fuel cell vehicles particularly relies on the development of safe lightweight and cost-competitive solutions for hydrogen storage. After the demonstration of hundreds of prototype vehicles today commercial hydrogen tanks are in the first stages of market introduction adopting configurations that use composite materials. However production rates remain low and costs high. This paper intends to provide an insight into the evolving scenario of solutions for hydrogen storage in the transportation sector. Current applications in different sectors of transport are covered focusing on their individual requirements. Furthermore this work addresses the efforts to produce economically attractive composite tanks discussing the challenges surrounding material choices and manufacturing practices as well as cutting-edge trends pursued by research and development teams. Key issues in the design and analysis of hydrogen tanks are also discussed. Finally testing and certification requirements are debated once they play a vital role in industry acceptance.

The reduction of harmful emissions from the international shipping sector is necessary. On-board energy demand can be categorised as either: propulsion or auxiliary services. Auxiliary services contribute a significant proportion of energy demand with major loads including: compressors pumps and HVAC (heating ventilation and air-conditioning). Typically this demand is met using the same fuel source as the main propulsion (i.e. fossil fuels). This study has analysed whether emissions from large scale ships could feasibly be reduced by meeting auxiliary demand by installing a hydrogen fuel cell using data from an LNG tanker to develop a case study. Simulations have shown that for a capacity of 10 x 40ft containers of compressed hydrogen the optimal fuel cell size would be 3 MW and this could save 10600 MWh of fossil fuel use equivalent to 2343 t of CO2. Hence this could potentially decarbonise a significant proportion of shipping energy demand. Although there are some notable technical and commercial considerations such as fuel cell lifetime and capital expenditure requirements. Results imply that if auxiliary loads could be managed to avoid peaks in demand this could further increase the effectiveness of this concept.

Hydrogen is commonly mentioned as a future proof energy carrier. Hydrogen supporters 6 advocate for repurposing existing natural gas grids for a sustainable hydrogen supply. While the 7 long-term vision of the hydrogen community is green hydrogen the community acknowledges that 8 in the short term it will be to large extent manufactured from natural gas but in a decarbonized 9 way giving it the name blue hydrogen. While hydrogen has a role to play in hard to decarbonize 10 sectors its role for building heating demands is doubtful as mature and more energy efficient alter- 11 natives exist. As building heat supply infrastructures built today will operate for the decades to 12 come it is of highest importance to ensure that the most efficient and sustainable infrastructures are 13 chosen. This paper compares the source to sink efficiencies of hydrogen-based heat supply system 14 to a district heating system operating on the same primary energy source. The results show that a 15 natural gas-based district heating could be 267% more efficient and consequently have significantly 16 lower global warming potential than a blue hydrogen-based heat supply A renewable power-based 17 district heating could achieve above 440% higher efficiency than green hydrogen-based heat supply 18 system.