international journal of hydrogen energy xxx (xxxx) xxx Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he Short Communication Transition toward emission-free energy systems by 2050: Potential role of hydrogen Pawan Kumar Pathak a, Anil Kumar Yadav b,*, Sanjeevikumar Padmanaban c a School of Automation, Banasthali Vidyapith, Rajasthan, 304022, India Department of Electrical Engineering, NIT Hamirpur, Hamirpur (HP), 177005, India c Department of Electrical Engineering, Information Technology and Cybernetic, University of South-Eastern Norway, Porsgrunn, Norway b article info abstract Article history: Hydrogen has a potential role in helping the world for obtaining net-zero emission/emis- Received 31 October 2022 sion-free energy systems by 2050 and restrict global warming by 1.5 C because it can Received in revised form subside 80 gigatons (GT) of CO2 by 2050. This causes the utilization of 660 million metric 1 December 2022 tons (MT) of low-carbon hydrogen and renewables up to 2050, almost equal to 22% of global Accepted 5 December 2022 energy demand. In the coming decades, the need for very high clean hydrogen production Available online xxx to fulfill the decarbonization role for net zero emission. About 4.5 to 6.5 terawatts (TW) of renewable power, about 3e4 TW of electrolysis, 40e280 MT of minimal carbon hydrogen Keywords: production reforming capacity, and 1e1.25 GT of CO2 storage infrastructure in a year are Greenhouse emission required for supplying 660 MT of end uses. In such circumstances, 15e25% of total Hydrogen pathway renewable energy is required for hydrogen till 2050 e a 10X enhancement over the present Emission-free energy systems installed capacity (2.8 TW). Net-zero emission © 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Energy sectors Introduction One of the malignant impacts of the greenhouse effect is a constant elevation in the Earth's atmospheric temperature. Yearly peak CO2 emission is breaking new records due to five sectors: industry, energy, agriculture, building, and transportation. If we want to limit future warming, we need “deep and rapid” emission cuts across these sectors. A very adverse environmental impact can be seen due to the utilization of fossils and greenhouse emissions. The major global emission by five sectors: industry, energy, agriculture, building, and transportation, is depicted in Fig. 1 [1,2]. Hydrogen can obtain emission-free energy systems via the decarbonization process [3,4]. Hydrogen has higher specific (energy/unit mass); a very high temperature is achieved during hydrogen combustion and can be stored in large quantities [5,6]. Hence, hydrogen is considered a versatile energy vector that may be utilized in various hard-to-decarbonize fields where electricity may not be suitable. To trigger the decarbonized energy system, hydrogen is essential. It helps integration of renewable-driven * Corresponding author. E-mail address: anilei007@gmail.com (A.K. Yadav). https://doi.org/10.1016/j.ijhydene.2022.12.058 0360-3199/© 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article as: Pathak PK et al., Transition toward emission-free energy systems by 2050: Potential role of hydrogen, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2022.12.058 2 international journal of hydrogen energy xxx (xxxx) xxx Fig. 1 e Worldwide greenhouse gas emission by sectors [1,10]. energy because it can provide resilience, energy storage, and transport a high volume of energy via ships and pipelines [7,8]. It may be obtained from electricity and converted into or used as chemicals, fuels, and power; hence electricity-driven hydrogen will reshape and connect current chemical, gas, power, and fuel markets [9,10]. A special report by International Energy Agency (IEA) on the roadmap for the global energy sector to achieve net zero by 2050 was published in 2021 [10]. Hydrogen production is obtained via renewable sources such as wind, biomass, solar, algae, geothermal, and traditional non-renewable sources such as coal, natural gas, nuclear and thermochemical processes [11,12]. Various types of hydrogen production with the level of greenhouse gas footprint are depicted in Fig. 2. A vivid hydrogen generation scheme with the cost analysis of each source is demonstrated in Ref. [11]. To obtain emission-free shipping, a comparative analysis of three critical candidates: hydrogen, methanol, and ammonia, is performed [13]. A bibliometric assessment with future direction for sustainable energy production via hydrogen electrolyzer is revealed in Ref. [14]. The case studies are performed from the global literature to benchmark the statical electrolyzer analysis, modes of operation, outstanding issues, critical challenges, and future research. Chemical and biological methods (bio-hydrogen production) as the future of hydrogen energy are briefed in Ref. [15]. The economic evaluation of bio-hydrogen production in the view of production, transportation, and storage is also performed. The results showed that bio-hydrogen might be an excellent possibility for renewable-based hydrogen production. Low-gradient combustion has become an alternative scheme to reduce the carbon footprint when combined with hydrogen as a blended compound or fuel. Recent enhancement in low gradient combustion as hydrogen fuel blend is demonstrated in Ref. [16]. A detailed comparative analysis of renewable Fig. 2 e Various types of hydrogen production with greenhouse footprint. Please cite this article as: Pathak PK et al., Transition toward emission-free energy systems by 2050: Potential role of hydrogen, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2022.12.058 international journal of hydrogen energy xxx (xxxx) xxx electricity and fossil fuel-driven hydrogen based on cost and emission is performed in Ref. [17]. According to this literature [17], various national hydrogen techniques define both renewable-based and fossil fuels with carbon capture and storage (CCS) as ‘low-emission’ and/or clean hydrogen. However, the carbon footprint is higher in fossil fuel-driven hydrogen than in renewable-based hydrogen, as presented in Fig. 2. In 2020 International Renewable Energy Agency (IREA) published a report on the cost reduction of green hydrogen to meet the 1.5 C climate goal by scaling up electrolyzer [18]. In November 2021, Hydrogen Council (McKinsey & Company) published a report on hydrogen for net-zero [19]. In this detail, global hydrogen demand and the pathways to achieve an emission-free energy system by 2050 are demonstrated. By 2050, North America, Europe, and China will be the largest hydrogen markets, with 60% global demand. Hydrogen is rarely present in its natural condition; it must be obtained from other materials, causing energy. In the present scenario, producing low-carbon hydrogen is a very challenging task. The detailed production methodologies of grey, blue, and green hydrogen are revealed in Fig. 3. These three forms of hydrogen are gaining much attention in the present scenario. The grey hydrogen is made of methane via steam methane reformation, a carbon-intensive process containing a carbon footprint of 10 kg CO2/kg H2. The grey hydrogen production process produces CO2 in the atmosphere, while the production of blue hydrogen captures the CO2. So, these two hydrogen forms are unsuitable for achieving emission-free energy systems. Moreover, the production of green hydrogen is obtained via electrolysis of water and renewable energy; hence, it contains zero carbon. ✓ Blue and grey hydrogen depends on the supply of fossil fuels. ✓ Blue hydrogen depends on CCS technology. ✓ Green hydrogen depends on renewable energy and supply. 3 ✓ Supply of the critical care elements and electrolyzer build rates are required for green hydrogen. ✓ Hydrogen production via fossil feedstocks causes greenhouse emissions even when CCS technology is used. ✓ Hydrogen produced via electrolysis does not create greenhouse emissions. Presently, most of the hydrogen is grey (fossil-based), so to achieve the goal of zero emission by 2050, much focus is required on low carbon (blue) hydrogen and renewable (green) hydrogen. By 2050, 20%e40% of the supply, that corresponds to 140 MTe280 MT of hydrogen will be provided by low carbon hydrogen [10]. In comparison to present grey capacity, the above-mentioned capacity is around two to three times higher and will necessitate huge infrastructure for the storage of 1.5 GTe2.5 GT of CO2 a year. Moreover, 60%e80% of the supply that corresponds to 400 MTe550 MT of hydrogen will be provided by renewable driven green hydrogen by 2050 [10,18]. For this, immense power, 4.5 TW to 6.5 TW renewables and electrolysis capacity of 3 TW to 4 TW will require. For emission-free energy systems by 2050, hydrogen demand will reach 140 MT by 2030, of which 75 MT will be clean hydrogen [10]. Moreover, blue and green hydrogen supply must inflate to help emission-free energy sectors. The full potential of hydrogen may be utilized if proper action is taken over three areas: trigger demand, enable access via infrastructure, and close the gap between traditional and hydrogen decarbonization methods. Key Features of Hydrogen: ✓ Hydrogen can store very high energy over a long period of time. ✓ In pipelines, storage of hydrogen can be done via “line packing,” i.e., a high volume of hydrogen is stored by boosting the pressure in pipelines. ✓ The energy system's resiliency will be enhanced via end uses of hydrogen. Fig. 3 e Green, blue, and grey hydrogen production process. Please cite this article as: Pathak PK et al., Transition toward emission-free energy systems by 2050: Potential role of hydrogen, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2022.12.058 4 international journal of hydrogen energy xxx (xxxx) xxx ✓ It can enable global and regional energy transmission. ✓ Compared to electrical grids, 10 to 20 times more energy can be transmitted via pipelines. ✓ Hydrogen may be shipped over long distances. Hydrogen pathways in energy sectors By 2050, 660 MT of hydrogen will require for the end uses to achieve the target of an emission-free energy system [10,19]. Sector-wise hydrogen demands in MT are revealed in Fig. 4. Hydrogen is essential for the decarbonization of industries, e.g., feedstocks for food, glass, fertilizers, and steel, in form of synthetic fuels for maritime vessels and aviation, for power generation, e.g., as backup power, in case of ground mobility provides fuels for heavy-duty trucks, coaches, passenger vehicles for long range, trains and lastly for high grade (temperature > 400 C) industrial heating [5,6,19]. Rapid acceleration and firm commitment are essential to achieve emission-free energy systems. It is estimated that Fig. 4 e Hydrogen demand by sectors: end uses. 75 MT capacity of clean/green hydrogen is required by 2030, which is an acceptable target [10]. With this amount of clean/ green hydrogen, ammonia refining and methanol-based 25 MT of grey hydrogen, ground mobility based 50 billion liters of diesel, and steel production based 60 MT of coal can be replaced. The most significant segments for hydrogen's enduse applications by 2050 will probably be feedstock, industrial heating, mobility, and building heating correspond to 90% of the total demand (660 MT) [10,18]. The hydrogen pathways to achieve emission-free energy systems are revealed in Fig. 5, and the significant sectors associated with hydrogen end uses are: Mobility Currently, 19% of global emission is due to mobility, which will be the most significant segment of hydrogen and use with 285 MT of demand by 2050 [10]. The mobility sector inculcates maritime, aviation and ground mobility. The most challenging areas for decarbonization of mobility and uses are containerships and long-range flights, and the combination of biofuels and hydrogen is the unique scalable pathway for the decarbonization of these areas. Moreover, around 4% of global emission is produced by aviation and maritime; these are the long-range and high-power end applications and will partly depend on hydrogen-driven fuels for decarbonization. To obtain complete decarbonization in maritime fields, liquid hydrogen and hydrogen-driven fuels like methanol, ammonia, or e-methane are the potential green fuels [10]. CO2 captured from direct air or CO2 obtained from biogenic sources in combination with hydrogen will be promising synthetic fuels (e-kerosene) for aviation and intercontinental flights [10,18,19]. These two end applications will become essential consumers of liquid hydrogen and correspond to 110 MT of hydrogen demand with 13 GT abetment of CO2 by 2050 [10,18,19]. Fig. 5 e Hydrogen pathways in energy sectors. Please cite this article as: Pathak PK et al., Transition toward emission-free energy systems by 2050: Potential role of hydrogen, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2022.12.058 international journal of hydrogen energy xxx (xxxx) xxx 5 Industrial Heating Steel Due to the high utilization of natural gas and coal, industrial heating is one of the significant emission sources. Many decarbonization schemes are available such as direct electrification, biomass, hydrogen combustion, and post-combustion carbon storage. Hydrogen has the potential to decarbonize industrial heat, mainly for high-grade heating applications like aluminum remelting, glass making, and cement plants. By 2050, these sectors will require 70 MT of hydrogen demand to achieve emission-free systems, particularly for high-grade industrial heating [10,19]. The steel plant is the world's highest carbon emission industry; around 8% of annual global emissions are due to the blast furnace process. Very few decarbonization pathways are available for the steel melting process. Which makes it the most challenging task for decarbonization and for the complete decarbonization process relies only on hydrogen. For this purpose, around 35 MT of hydrogen demand by 2050 is necessary for the decarbonization of steel industries, accounting for the 12 GT emission suppression through 2050. Aromatics Power Sector According to the data available till 2019, the power sector accounted for 30% of worldwide emissions [10]. The critical decarbonization pathway is the high penetration of renewable generation capacity in the power sector. Wind and solar power are inherently volatile, but the power sector causes long- and short-term balancing. Hydrogen can play a critical role for the decarbonization process of 1%e3% of power demand in a completely decarbonize based grid because it may give the options of seasonal storage, long-duration storage, and peak shaving and will be crucial for grid stabilization. Around 65 MT of green hydrogen will require for grid power generation by 2050 [10]. In order to reduce the carbon footprints of aromatics, the decarbonization process is very necessary, but the decarbonization of benzene, toluene, and xylene (BTX) production is at an initial stage. Aromatics production via hydrogen routes like methanol-to-aromatics, which includes CO2 captured from the air or biogenic sources with clean hydrogen, is presently in testing mode and underdeveloped. It is expected that the decarbonization of aromatics will boost after 2030 when technology commercialization occurs. Around 40 MT of hydrogen will require for methanol to aromatics by 2050. BTX can work as a carbon sink for plastic production (e.g., nylon) by long-duration storage of captured CO2. The low carbon BTX may contribute to negative CO2 emission if air-captured CO2 or biogenic CO2 is utilized and the plastic is not burnt. Building Heating Around 5% of global emissions produce by heating commercial and residential buildings and are the last hydrogen end applications to scale due to high infrastructural investment requirements, as it will cause pipeline-based hydrogen distribution networks. Blending hydrogen in the present natural gas grid can provide an early step for the entire hydrogenbased pipeline networks. The key advantages of blending hydrogen in the natural gas grid are: a step toward a carbon neutral future, a significant reduction in greenhouse gas footprint, enhancement of the air quality of hydrogen blended fuel cell electric vehicles by reducing oxide of nitrogen and sulfur dioxide, renewable driven end products to consumers, etc. Moreover, the significant disadvantages and challenges of hydrogen blending are integrity management, limited availability of hydrogen, material durability, leakage, higher cost, higher risk of asthma, etc. By 2050, 40 MT of hydrogen will be required for building heating in the US, parts of China, and Europe, where natural gas is utilized for building heating [10]. Present Feedstock Hydrogen can play a critical role in decarbonizing present feedstock applications such as refining, methanol, and ammonia. These uses account for 2%e3% of worldwide emissions presently. For the complete decarbonization of these sectors by 2050, 105 MT of hydrogen, i.e., around 15% of total demand, will require [10,18,19]. Boosting hydrogen projects To achieve emission-free energy systems, private and government sectors have vital roles to play. Scaling through 2030 is very crucial to achieve the emission-free target by 2050. Around 40 National hydrogen strategies have been declared or are in developing mode. Due to the war in Ukraine and the hardening gas and oil markets, the results may be seen in the hydrogen market globally. For example, Europe is enhancing its renewable hydrogen target from 5 MTe20 MT by 2030 to replace the dependency on Russian gas. More than 500 projects have been declared with more than $500 billion globally. According to Glasgow Financial Alliance, more than $130 trillion of private capital is committed to transforming the economy for an emission-free future. Around 150 projects have been appended in the last four to five months. The gigascale projects have doubled in the past year. North America (67 projects) and Asia -Pacific (121 projects) have seen very high project growth [10]. To export hydrogen, giga-scale projects have been declared by industry players in Africa, Oceania, Latin America, and the Middle East. These regions are lower-cost energy resources and attractive and strategically balanced locations to fulfill the boosting demand of Europe, Korea, and Japan. Players have declared more than 18 MT of low carbon and renewable hydrogen by 2030 e an enhancement of 12 MT this year. Moreover, 40 GW of electrolysis power has been declared since 2020, and this announced capacity has been fivefold higher since 2019 [14]. North America Please cite this article as: Pathak PK et al., Transition toward emission-free energy systems by 2050: Potential role of hydrogen, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2022.12.058 6 international journal of hydrogen energy xxx (xxxx) xxx What to do now? ✓ ✓ ✓ ✓ ✓ Invest in early and rapid pilot projects. Drive down costs for enabling transition. Government support and industry adoption. Bridge the gap between investments. Finalize the hydrogen business model as soon as possible. What to do shortly? Fig. 6 e Hydrogen investments by 2030. has declared 3.5 MT of hydrogen capacity by 2030; around 85% will be low-carbon hydrogen. The public and private sectors need to meet to fulfill and complete these ongoing projects urgently to achieve an emission-free future. Boosting capital investments announcement for hydrogen Around $160 billion of total direct investments have been seen globally as the high growth in hydrogen projects by 2030 (revealed in Fig. 6). Most investments are associated with low carbon and renewable hydrogen production, corresponding to $95 billion, followed by $45 billion for end uses and $20 billion for storage, transmission, and distribution [10,19]. The announced funding's lowest volume involves heating and power applications, while the steel and mobility sectors account for more than 75% of the announced investments. Presently, around 100 projects are in the planning stage with a $64 billion investment, around 126 projects are announced with $76 billion, and 20 projects are committed with $20 billion investments [10,19]. To achieve the emission-free pathway by 2050 and 22% of decarbonization of final demand will cause 75 MT of clean hydrogen by 2030. To achieve this target, industries require direct investments of $700 billion in the hydrogen value chain by 2030. End-use applications will require $200 billion in investments by 2030 to fulfill aimed demand for hydrogen plants and new types of equipment [10,19]. The global hydrogen distribution, shipping, conversion, pipeline, and refining infrastructure will cause $200 billion in investments by 2030, with more than half for the hydrogen mobility infrastructure. The new hydrogen industry and mobility will require a total of $150 billion in investments [10,19]. Conclusion Hydrogen puts forward the probability of moving away from fossils at the cost of its challenges. A successful transition toward an emission-free future will probably depend on hydrogen utilization. If we are planning to limit global warming to 1.5 C-1.8 C by 2050, the coming decades are crucial for action e the 2050 ambition of 80 GT CO2 suppression cannot be fulfilled unless the noteworthy and crucial foundation is laid today. ✓ Enhance carbon abatement budget to meet 2050 emissionfree future. ✓ Address the initial skills gap related to renewable electricity generation. ✓ Wide-scale development for green and blue hydrogen production. ✓ Widening hydrogen supply chain. ✓ Invest in innovation and research to remove the necessity for scarce critical components for electrolysis. Moreover, four short-term opportunities to drive a hydrogen-based clean future: 1. To scale up the utilization of clean hydrogen by making industrial ports as nerve centers. 2. Boosting the present infrastructure, like making highrange natural gas pipelines of millions of kilometers. 3. Expand hydrogen in transport via freight, fleets, and corridors. 4. Launch the maiden international shipping routes for hydrogen trade. Presently, hydrogen is an unprecedented momentum. The world must not miss this unique chance to secure energy and an emission-free future. Pivotal momentum has been achieved, and it is time to act now for an emission-free future. Finally, we can conclude the potential role of hydrogen that “Green hydrogen e the fuel of the future”. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. references [1] Pathak PK, Yadav AK, Padmanaban S, Alvi PA, Kamwa I. Fuel cell-based topologies and multi-input DC-DC power converters for hybrid electric vehicles: a comprehensive review. IET Gener, Transm Distrib 2022;16(11):2111e39. [2] Fan F, Zhang R, Xu Y, Ren S. Robustly coordinated operation of an emission-free microgrid with hybrid hydrogen-battery energy storage. 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