Hydrogen

What is Hydrogen?

Hydrogen (H₂), the first element in the periodic table, is a colorless, odorless, tasteless, non-toxic, and highly flammable gaseous substance. It is the most abundant element in the universe, making up 75% of normal matter by mass and more than 90% by number. It is present in water, organic compounds, and other molecular forms on Earth.. [1,2,3]

How is natural Hydrogen formed?

Hydrogen nuclei formed when the universe began to cool down approximately 380,000 years after the Big Bang, which occurred 13.8 billion years ago. When the universe reached a temperature of about 3,000 K, it formed elemental atoms. Hydrogen, helium, and lithium are the three elements now recognized as the only ones with a cosmological origin [4].

Natural hydrogen has been discovered in many geological environments and studied in recent decades, subsequently discovered hydrogen-rich fluids at midocean ridges. The primary hydrogen sources of these locations include the alteration in Fe(II)-containing rocks; the radiolysis of water due to the radioactive decay of uranium, thorium, and potassium; degassed magma; and the reaction of water and surface-free radicals during mechanical fracturing of silica-containing rocks [5]

What are the uses of Hydrogen?

Hydrogen has various uses across various industries and applications, such as the following:

1. Industrial Applications [2,6,7,8]:

• The production of ammonia, a key component in fertilizer, accounts for a significant portion of global hydrogen usage, representing about 55% of hydrogen consumption worldwide.
• Hydrogen is extensively used in petroleum refining processes, including hydrocracking to break down hydrocarbon molecules, removing contaminants like sulfur, and creating methanol.
• Hydrogen is utilized to turn unsaturated fats into saturated oils and fats, such as in producing hydrogenated vegetable oils like margarine.
• In metalworking, hydrogen is used for metal alloying to enhance properties like strength and corrosion resistance.
• Hydrogen is employed in welding processes, particularly in atomic hydrogen welding, where it is split into atoms to create a flame for melting metals.
• Hydrogen and nitrogen are used in flat glass production to prevent oxidation and defects during manufacturing.
• Hydrogen serves as a reducing and etching agent in electronics manufacturing, contributing to producing semiconductors, LEDs, displays, and other electronic components.

2. Energy Storage and Generation [2,9]:

• Hydrogen offers the unique capability of seasonal energy storage, addressing the challenge of energy demand variations throughout the year. During high renewable energy production periods, hydrogen can be generated and stored for low energy production, like in winter, with reduced sunlight.
• Hydrogen can be used in stationary fuel cells for power generation. When hydrogen reacts with oxygen in a fuel cell, it produces electricity, water, and heat, offering a clean and efficient energy generation process.
• Hydrogen can be burned for electricity generation and heating purposes. While integrating hydrogen into existing natural gas infrastructure presents challenges, advancements are being made to effectively utilize hydrogen in power generation.

3. Transportation:

Hydrogen is increasingly being explored as a key player in decarbonizing transportation due to its potential as a zero-emission fuel. In transportation, hydrogen is primarily used to power fuel cell electric vehicles (FCEVs), considered zero-emission vehicles (ZEVs) as they emit only water and heat as byproducts. Unlike battery electric vehicles (BEVs) that rely on plugged-in batteries for recharging, FCEVs produce electricity onboard through hydrogen. However, emissions can be generated during the production, transportation, and dispensing of hydrogen fuel, depending on the source and method of production. [10,11,12]

How to produce hydrogen?

Hydrogen can be produced from various methods as follows:

1. Steam-Methane Reforming (SMR)

Steam-methane reforming (SMR) is a crucial process for hydrogen production, particularly in industrial settings. This method involves the reaction of methane (CH₄) with high-temperature steam to produce hydrogen (H₂) and carbon monoxide (CO). The process is highly efficient and widely used, with around 95% of hydrogen production in the United States relying on natural gas reforming, mainly through SMR. [13]

The SMR process involves a primary reaction, which is the reaction of methane with steam, represented by the equation: CH₄ + H₂O → CO + 3H₂. This reaction is highly endothermic, requiring a substantial amount of heat. In a subsequent step known as the water-gas shift reaction, carbon monoxide and steam react to form carbon dioxide and additional hydrogen: CO + H₂O → CO₂ + H₂. This reaction helps increase the yield of hydrogen. The reaction is facilitated by a catalyst, typically nickel, which enhances the efficiency of the process. After the initial reactions, the gas mixture undergoes pressure-swing adsorption to remove impurities like carbon dioxide (CO₂), leaving behind pure hydrogen. [14]

2. Electrolysis of water

Electrolysis of water is a process that involves splitting water (H₂O) into its basic components, hydrogen (H₂) and oxygen (O₂), through the passage of an electric current. This method is a key pathway for producing hydrogen, especially when the electricity used is generated from renewable sources like solar or wind power. The electrolysis occurs in an electrolyzer unit, which consists of two electrodes: a positively charged anode and a negatively charged cathode, separated by an electrolyte membrane. During electrolysis, water is oxidized at the anode to produce oxygen gas and positively charged hydrogen ions (H⁺). Simultaneously, water is reduced at the cathode to generate hydrogen gas and negatively charged hydroxide ions (OH^–). The overall reaction can be divided into two half-cell reactions: hydrogen evolution (HER) and oxygen evolution (OER). The efficiency of this process is crucial for the production of high-purity hydrogen. [17,18]

3. Solar Hydrogen Production

Solar hydrogen production is a promising research area involving using solar energy to split water molecules into hydrogen and oxygen. This process can be achieved through two main methods: water electrolysis using solar-generated electricity and direct solar water splitting. [20]

• Water electrolysis using solar-generated electricity involves photovoltaic (PV) cells to convert sunlight into electricity, then powering an electrolyzer that splits water into hydrogen and oxygen. [20,21]
• Direct solar water splitting refers to any process in which solar energy is directly used to produce hydrogen from water without going through the intermediate electrolysis step. Examples of direct solar water splitting methods include high-temperature thermochemical cycles, biomass gasification, and photocatalytic water splitting. [20,21]

5. Thermochemical Hydrogen Production

Thermochemical hydrogen production uses heat and chemical reactions to release hydrogen from organic materials or materials like water. This process differs from other hydrogen production methods, such as electrolysis, which uses electricity to split water into hydrogen and oxygen, or biological processes, which use microorganisms such as bacteria and algae to produce hydrogen. [24]

Thermochemical hydrogen production can be achieved through various processes, including natural gas reforming, biomass gasification, biomass-derived liquid reforming, and solar thermochemical hydrogen (STCH) production. [25]

• Natural gas reforming, or steam methane reforming (SMR), is the most common method worldwide for producing hydrogen (discussed above).
• Biomass gasification is another thermochemical process that utilizes biomass as its source of hydrogen energy. The biomass source reacts with a controlled amount of oxygen or steam, producing CO, CO₂, and hydrogen. The CO reacts with water to form more CO₂ and hydrogen through a similar water-gas shift reaction. When oxygen is unavailable, biomass can undergo a reaction known as pyrolysis to produce hydrogen energy. [25]

Solar thermochemical hydrogen (STCH) production is a promising method for generating hydrogen using concentrated solar energy to drive a series of reactions. This closed-loop process utilizes only water as feedstock and solar heat. [26]

6. Biological Hydrogen Production

Biological hydrogen production refers to generating hydrogen gas (H₂) through biological means, typically involving microorganisms such as bacteria and microalgae. There are three primary biological pathways for hydrogen production: direct or indirect bio-photolysis of water using cyanobacteria, photo-fermentation using photosynthetic bacteria, and dark fermentation that uses various groups of anaerobic bacteria. [28]

• Direct bio-photolysis of water: In this process, microorganisms such as cyanobacteria use light energy to split water molecules into hydrogen and oxygen. This process is typically less efficient than other biological hydrogen production methods due to the competition between oxygen and hydrogen production. [28,29]
• Indirect bio-photolysis of water: This process involves using microorganisms to produce biomass through photosynthesis, which is then converted into hydrogen through dark fermentation or other biological processes. This method can be more efficient than direct bio-photolysis, as it allows for energy storage and subsequent conversion. [28,29]
• Photo-fermentation: This process involves using photosynthetic bacteria to convert organic compounds into hydrogen using light energy. The bacteria use the nitrogenase enzyme to convert organic carbon to hydrogen and carbon dioxide while also fixing molecular nitrogen. [28,29]
• Dark fermentation: This process involves using anaerobic bacteria to convert organic compounds into hydrogen without light. The bacteria produce hydrogen as a byproduct of their metabolic processes, typically using glucose or other sugars as a substrate. [28,29]

The advantages and disadvantages of different methods of producing hydrogen can be summarized below:

Method	Advantages	Disadvantages
Steam-Methane Reforming (SMR)	·  It is highly efficient and yields a substantial amount of hydrogen gas ·  It can utilize various feedstocks ·  It is a mature and well-established technology [15]	·  It emits CO2 as a byproduct ·  It is an energy-intensive, requiring high temperatures and pressures ·  It requires frequent catalyst regeneration or replacement [15,16]
Electrolysis of water	·  It produced zero direct emission ·  It can be in synergy with dynamic and intermittent power generation from renewable sources ·  It can produce high purity hydrogen [17,19]	·  It is capital intensive ·  It is an energy-intensive process requiring significant electrical energy ·  It has low efficiency [17]
Solar Hydrogen	·  It can significantly reduce the carbon footprint in hydrogen production ·  It is flexible to be scaled up or down [22,23]	·  It is expensive, requiring significant capital investment in infrastructure ·  It is an intermittent energy source due to its dependence on sunlight ·  It has low efficiency [22,23]
Thermochemical Hydrogen	·  It can efficiently utilize biomass within a short time scale and yields amount of hydrogen ·  It emits low to no greenhouse gas [26,27]	·  It relies on renewable energy sources, which may not always be available or reliable in certain regions. ·  Genetic modification or breeding of feedstocks may be required. ·  It is expensive, requiring sophisticated equipment and materials. [26,27]
Biological Hydrogen	·  It utilizes various biological processes ·  It has a low carbon footprint ·  It can be carried out at room temperature and atmospheric pressure [29,30]	·  It has a low production rate ·  It has low substrate conversion efficiencies ·  It can produce and accumulate acid-rich intermediate metabolites ·  It requires specific conditions, such as light energy, nutrients, and temperature, to be carried out effectively. ·  It is limited by the availability of suitable organisms that can efficiently produce hydrogen [29,30]

Hydrogen is often categorized based on its production method [31,32,33,34]

• Grey Hydrogen is the most common and cheapest form of hydrogen. It is produced by a steam-methane reforming process that extracts hydrogen from natural gas but does not capture carbon, resulting in a large carbon footprint.
• Blue Hydrogen is similar to grey hydrogen. Blue hydrogen is produced by the same process but with carbon emissions captured and sequestered underground. Although considered clean due to its low carbon content, recent studies have raised concerns about the negative climate impact of blue hydrogen.
• Green Hydrogen is produced using clean electricity from surplus renewable energy sources, such as solar or wind power, to electrolyze water, emitting zero-carbon dioxide. Green hydrogen currently makes up a small percentage of the overall hydrogen due to its expensive production.
• Brown or Black Hydrogen is produced from coal through gasification, with black hydrogen using black coal and brown hydrogen using brown coal or lignite. Both have an even larger carbon footprint than grey hydrogen.
• Pink Hydrogen is generated through electrolysis powered by nuclear energy, and nuclear-produced hydrogen can also be referred to as purple or red hydrogen.
• Turquoise Hydrogen is a new entry in the hydrogen color charts. It is produced using methane pyrolysis to produce hydrogen and solid carbon. Turquoise hydrogen may be valued as low-emission hydrogen if the thermal process is powered with renewable energy and the carbon is permanently stored or used.
• Yellow Hydrogen is a relatively new phrase for hydrogen made through electrolysis using solar power.
• White Hydrogen naturally occurs in underground deposits created through fracking. There are no strategies to exploit this hydrogen at present

What are the challenges in hydrogen production and distribution?

1. Cost competitiveness

The cost competitiveness of hydrogen production is a critical factor for its widespread adoption, as production and infrastructure development require significant investments. The cost of hydrogen must be competitive with traditional fossil fuels to achieve decarbonization in various sectors, such as shipping and steelmaking. [35]

The price of hydrogen is influenced by production, transportation, and end-use efficiency. The production cost of green hydrogen depends on the price of renewable energy, electrolysers, and water used to create hydrogen. Blue hydrogen, produced from fossil fuels with carbon capture and storage, is currently more affordable than green hydrogen. However, this is expected to change in the mid-2020s-2030s due to falling renewable prices and economies of scale with increased deployment. The transportation of hydrogen can increase its cost by 50-100%, depending on the technology used. End-use efficiency is also crucial, as hydrogen has an energy-to-weight density three times greater than batteries storing electricity. This makes it suitable for long-distance heavy haulages such as trucking and aviation. However, batteries are a better candidate for lighter and less used vehicles. [36]

Policy support is necessary for developing green hydrogen projects, realizing market off-take, infrastructure development, and further de-risking. While there is significant policy momentum, current policy support in most locations falls short of supporting announced targets. [35]

2. Infrastructure development

Building a robust hydrogen infrastructure involves the development of production facilities, storage systems, transportation networks, and refueling stations. This requires substantial investment and coordination among various stakeholders, including governments, utilities, and private companies. Hydrogen infrastructure-related efforts primarily focus on expanding pipeline infrastructure by utilities and developing hydrogen hubs for co-located production and distribution of hydrogen to early adopters. However, the visibility of hydrogen demand remains the overarching constraint preventing larger-scale hydrogen infrastructure development, leaving it as a secondary investment area overall within energy infrastructure. [37]

To ensure swift and equitable development, communities must be holistically engaged throughout the project development process to ensure their voices are equally heard, and project developers must accelerate construction timeframes and shorten permitting processes. States and countries must streamline regulations and establish a clear regulatory body. Hydrogen producers, off-takers, and infrastructure developers must strengthen coordination, develop a trained workforce, and deploy tremendous capital. [38]

3. Storage and distribution

Hydrogen has a low volumetric energy density, making it difficult to store and transport. Hydrogen can be stored physically as a gas or a liquid. Gas storage typically requires high-pressure tanks (350-700 bar), and liquid storage requires cryogenic temperatures due to hydrogen’s boiling point in one atmosphere. The primary challenge for hydrogen storage is increasing capacity, durability, and efficiency. [39,40]

Hydrogen distribution faces challenges in fuel storage, as onboard fuel capacity needs to be increased to meet demands for greater driving ranges. Gaseous hydrogen is less dense than gasoline, so it is important to develop robust, lightweight compressed gas containers capable of withstanding high pressures and large enough to meet consumer needs. Expanding hydrogen pipeline networks and converting natural gas infrastructure to transport hydrogen are technical and logistical challenges. Hydrogen distribution also requires monitoring pipelines and increasing liquefaction efficiency. [40]

4. Safety

Hydrogen is no more or less dangerous than other flammable fuels, including gasoline and natural gas. Safety measures, from production to utilization, are crucial across the entire hydrogen value chain to ensure safe handling and storage. Establishing stringent safety standards, protocols, and laws is essential to building public trust and acceptance of hydrogen as a viable and safe energy source. In addition, it is also crucial to implement adequate engineering controls, ventilation systems, leak detection mechanisms, and training programs to mitigate risks effectively. [41,42]

5. Policy and regulations

The challenges in policy and regulation for hydrogen production include outdated federal regulations, unclear jurisdiction for regulating interstate hydrogen pipelines, lengthy time lags between policy announcements and implementation, and the need for harmonized rules and standards for international trade in low-carbon hydrogen. [43]

Clear and encouraging policies and regulations are vital in fostering investment in hydrogen infrastructure and technology development. Governments need to provide long-term incentives, financing, and robust regulatory frameworks to support the growth of the hydrogen economy. These measures are essential to create a conducive environment for stakeholders, including industry players, investors, and governments, to harness the potential of hydrogen in driving the global green energy transition. [44]

6. Public awareness and acceptance

The public’s awareness and acceptance of hydrogen production are generally high, but campaigns are still needed to increase knowledge and acceptance of hydrogen energy. Studies have shown that knowledge about or experience with hydrogen fueling stations improves public acceptance and that the public views hydrogen technology as one of the best ways to combat climate change. Educating the public about hydrogen’s advantages, safety precautions, and environmental benefits is key to dispelling myths and misconceptions surrounding this technology. [45,46]

 

By: Hendra WINASTU, SOLEN Principal Associate – IPC panel coordinator

Edited by: (1) Nguyen Duy Hung, SOLEN Director – IPC program director; (2) Kukuh Jalu Waskita, SOLEN Associate – IPC panel member

Date: 05 April 2024

Article#: SOLEN-IPC-0034

 

 

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