All about Hydrogen

• Hydrogen is the most abundant element.
• Henry Cavendish, a British scientist, first identified hydrogen as an element in 1766.
• Hydrogen is a colorless, odorless, and tasteless gas at room temperature and standard pressure.
• Hydrogen is the lightest element in terms of atomic weight.
• Hydrogen is highly reactive.
• Hydrogen combustion produces water vapor, making it a clean fuel source.
• Global hydrogen demand reached over 94 million tonnes (Mt) in 2021.
• China is the largest hydrogen consumer, with about 28 Mt demanded in 2021.
• The United States is second, and the Middle East is third, consuming around 12 Mt each.
• Europe is the fourth largest consumer; more than 8 Mt in 2021.
• India's hydrogen demand was 8 Mt in 2021.

Properties of Hydrogen

• Atomic symbol: H
• Atomic number: 1
• Molecular form: H₂ (Diatomic molecule)
• Atomic weight: 1.008 u
• State at room temperature: Gas
• Density: 0.08988 g/L (much lighter than air at standard conditions)
• Boiling Point: -252.87°C (20.28 K)
• Melting Point: -259.16°C (14.03 K)
• Energy Density: 120-142 MJ/kg (higher than other fuels by weight, but lower by volume due to its low density)
• Flammability: Highly flammable, it ignites in air at concentrations as low as 4%.
• Explosive Limits: 4% to 75% hydrogen in air.
• Bond Energy (H₂): 436 kJ/mol (strong bond making it stable, but requires energy to dissociate)
• Solubility: Sparingly soluble in water; better soluble in organic solvents.
• Electrical Conductivity: None, can be made conductive under high pressure.
• Color, Odor, Taste: Colorless, odorless, and tasteless
• Isotopes: Protium (¹H), Deuterium (²H), and Tritium (³H)
• Specific Heat Capacity: 14.304 J/g·K at room temperature

Importance of Hydrogen

• Critical element in the global energy transition.
• Supports decarbonization and sustainability.
• Can replace fossil fuels in steel, cement, and chemical manufacturing industries.
• Offers a clean fuel alternative for shipping, aviation, and long-haul trucking.
• Effective as a large-scale energy storage medium.
• Useful for solar and wind energy sources.
• Excess renewable energy produces hydrogen via electrolysis.
• Versatile in electricity generation, transportation, industry, and heating.
• A flexible energy vector in an integrated energy system.
• Green hydrogen (via electrolysis) helps renewable energy overcome variability and intermittency.
• Reduces greenhouse gas emissions when produced from renewable sources.
• Blue hydrogen (from natural gas with carbon capture) reduces emissions compared to fossil fuels.
• Enhances energy security and reduces dependence on oil and gas imports.
• Only produces water vapor when used in fuel cells or combusted.
• Can be integrated into existing natural gas networks or stored in pipelines.
• Acts as a secondary energy carrier, similar to electricity, with efficient storage potential.
• Fuel cells convert hydrogen directly into electricity, with high efficiency and zero emissions.
• Hydrogen-powered vehicles can decarbonize transportation while reducing urban air pollution.

Uses for Hydrogen

• Clean transportation: In fuel cell vehicles, hydrogen-powered buses, trucks, and trains
• Industry: In oil refining, ammonia production, metals manufacturing, and chemicals
• Power generation: in stationary power generation via hydrogen fuel cells
• Energy storage: Stores excess renewable energy for grid stability
• Aerospace: Rocket fuel for space exploration
• Food processing: In hydrogenation processes
• Laboratory and specialty gases: Carrier gas for analysis and research
• Clean energy transition: Vital for decarbonizing various sectors and promoting sustainability

National Green Hydrogen Mission

• India's Green Hydrogen production capacity could reach at least 5 MMT per year.
• Associated renewable energy capacity could add about 125 GW.
• The Cabinet approves Rs 19,744 crore for the mission.
• Targets by 2030 could bring in over Rs. 8 lakh crore investments.
• India could create over six lakh jobs.
• Nearly 50 MMT per annum of CO₂ emissions may be averted by 2030.

Types of Hydrogen

• Blue
• Green
• Brown
• Yellow
• White
• Pink
• Grey

Types of Hydrogen Production

Green Hydrogen

• Produced by electrolysis of water using electric current to break water (H₂O) molecules into hydrogen and oxygen.
• If the electric current is from a renewable source (solar PV or a wind turbine).

Yellow Hydrogen

• It is produced by electrolysis of water.
• If this electric current is produced by a solar power.

Pink Hydrogen

• Produced by electrolysis of water using electricity.
• If the electricity is from nuclear power.

Blue Hydrogen

• Natural gas splits into hydrogen and CO₂ via steam methane reforming (SRM)).
• The CO₂ is captured and stored through carbon capture usage and storage (CCUS), mitigating environmental impacts.

Grey Hydrogen

• Natural gas splits into hydrogen and CO₂ via steam methane reforming (SRM).
• The CO₂ is not captured and is emitted into the atmosphere.

Brown Hydrogen

• Extracted from fossil fuels, especially coal, by coal gasification.
• Produced by gasification of renewable sources, like biomass.

Ministries Involved in National Green Hydrogen Mission

• Ministry of New and Renewable Energy (MNRE): Responsible for promoting green hydrogen production
• Ministry of Power: Involved in the mission's implementation
• Ministry of Environment, Forest and Climate Change (MoEFCC): Role in environmental policies
• Ministry of Petroleum and Natural Gas: Involvement in the transition to hydrogen and its integration into existing energy infrastructure
• Ministry of Finance: Crucial for funding and financial support
• Ministry of Road Transport and Highways: Promotes the use of hydrogen in transportation

Hydrogen Production from Fossil Fuels

• Production from natural gas/ Hydrocarbon reforming via:
  • Steam reforming (steam methane reforming- SMR)
  • Partial oxidation (POX)
  • Autothermal reforming
• Production concepts aren't close to commercialisation.

Steam Reforming (Steam Methane Reforming - SMR)

• Steam reforming is the endothermic conversion of methane and water vapor into hydrogen and carbon monoxide.
• Occurs at 700 to 850 °C at 3-25 bar.
• Product gas contains CO, which becomes CO₂ and H₂ through the water-gas shift reaction (Eq.2).
• CH₄ + H₂O + Heat → CO + 3H₂ (Eq.1)
• CO + H₂O → CO₂ + H₂ + Heat (Eq.2)

Partial Oxidation (POX)

• Partial oxidation of natural gas produces hydrogen through partial combustion of methane with oxygen gas.
• This yields carbon monoxide and hydrogen (Eq.3).
• Heat is produced in an exothermic reaction, allowing more compact design.
• No external heating of the reactor is needed.
• CO is converted to H₂ via equation (2).
• CH₄ + ½ O₂ → CO +2H₂ + Heat (Eq. 3)

Autothermal Reforming

• Hydrocarbon, like methane (CH), from sources like natural gas.
• This involves mixing the hydrocarbon with oxygen (O) and steam (HO).
• Steam methane reforming (SMR) and partial oxidation (POX) can occur in this mixture.
• The mixture is heated to very high temperatures, between 800°C to 1100°C.
• Steam Methane Reforming (SMR): CH4 + H2O → CO + 3H2
• Partial Oxidation (POX): CH4 + 0.502 → CO + 2H2
• These reactions give us a mixture of hydrogen and carbon monoxide.
• Water-Gas Shift Reaction: CO + H2O → CO2 + H2

Production from Coal

• Coal produces hydrogen through gasification processes (e.g., fixed bed, fluidised bed, or entrained flow).
• Carbon converts to carbon monoxide and hydrogen.
• C(s) + H₂O + Heat → CO + H₂ (Eq. 4)
• Additional heat is required due to the reaction being endothermic.
• Hydrogen production from coal is commercially mature.
• More complex than hydrogen production from natural gas.

Biomass Gasification

• A thermochemical process converting biomass into hydrogen gas (H₂) through high heat (700°C to 1,200°C) with limited oxygen.
• Biomass feedstock is shredded/chipped into smaller pieces.
• Thermochemical reactions in the gasifier break down organic compounds into a gas mixture (H₂, CO, CO₂, etc.).
• Products contain impurities like tars, particulates, sulfur compounds, and ammonia.
• Syngas cleanup processes include filtration, scrubbing, and catalytic conversion.
• Syngas undergoes further separation to isolate hydrogen.

Biomass Pyrolysis

• Converts biomass into hydrogen gas (H₂) via thermochemical decomposition in the absence of oxygen.
• Biomass feedstock (wood, agricultural residues, organic waste) is collected, dried, and ground into smaller particles.
• Biomass is subjected to typically 400°C to 800°C temperatures.
• In the absence of oxygen, the biomass breaks down into:
  • Biochar: carbon as soil conditioner
  • Bio-oil: liquid with organic compounds
  • Syngas: gas mixture with hydrogen (H₂), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), etc.
• Cleanup techniques include filtration, scrubbing, and catalytic conversion.
• Purification to separate hydrogen gas (H₂) may use pressure swing adsorption (PSA) or membrane separation.

Biomass Combustion

• Involves burning biomass materials in the presence of oxygen or air
• Aimed primarily at releasing heat energy for direct use or generating electricity rather than hydrogen
• The process typically produces hydrogen as only a byproduct, alongside gases like carbon dioxide (CO₂) and carbon monoxide (CO).
• The hydrogen yield from biomass combustion is relatively low.

Water Splitting Thermolysis

• Thermochemical water splitting, dissociates water into hydrogen and oxygen gases using high temperatures (above 800°C).
• Often requires extreme heat and chemical reactions, using external sources like concentrated solar energy or fossil fuels.
• Water molecules (H₂O) undergo reactions to break apart into hydrogen (H₂) and oxygen (O₂) gases.
• Hydrogen and oxygen gases are collected and separated.
• Production hydrogen without electricity also requires high-temperature environments.

Water Splitting Photolysis (Photoelectrochemical Cells)

• Photoelectrochemical water splitting, uses light energy to split water into hydrogen and oxygen with specialized cells.
• Photoelectrochemical cells absorb photons of light using semiconductor materials as photoanodes.
• Photons create electron-hole pairs in the semiconductor material.
• Drives electrolysis reactions to produce oxygen and hydrogen gas.
• Photolysis provides a renewable way of producing hydrogen from solar energy.

Water Splitting Electrolysis

• Electrolysis involves using electricity to separate water molecules (H₂O) into hydrogen gas (H₂) and oxygen gas (O₂).
• Water Supply for electrolysis can be from pure (H2O), tape water or seawater.
• Electrolyzer setup includes two electrodes: a cathode (negative) and an anode (positive), is also needed.

Electrolyte Selection

• Alkaline Electrolysis: Typically a strong alkaline solution.
• PEM Electrolysis: Solid polymer membrane that conducts protons (H+ ions).
• Solid Oxide: Typically operates at high temperatures.

Electrolysis Process

• Apply an electric current to the electrolyzer to initiate a reaction.
• At the cathode: 2H₂O + 2e- → H₂ (hydrogen gas) + 2OH-
• At the anode: 2H₂O → O₂ (oxygen gas) + 4H+ + 4e-
• Hydrogen and oxygen gases are separated and collected in separate chambers.

Biophotolysis

• Biophotolysis harnesses photosynthetic microorganisms, like green algae or cyanobacteria, to convert sunlight into hydrogen gas.
• Water splits into hydrogen and oxygen using solar energy: 2H₂O + light energy -> 2H₂ + O.
• It is lower in efficacy compared to other hydrogen production processes.

Dark Fermentation

• Dark fermentation uses microorganisms like anaerobic bacteria.
• Breaks down organic materials, such as sugars, starches, or organic waste, into hydrogen and carbon dioxide in the absence of light.
• A wide range of organic feedstocks occurs and more tolerant of impurities in the feedstock compared to other methods.

Photofermentation

• Employs anaerobic purple non-sulfur bacteria, such as Rhodobacter species.
• Combines photosynthetic and fermentation, relying on an organic co-substrate for the highest hydrogen production.
• Photofermentation produces hydrogen from a broader range of organic substrates than dark fermentation, with more efficiency than biophotolysis.

Hydrogen Storage

Compressed Hydrogen Gas

• Compressed to high pressures (350-700 bar) and stored in high-strength tanks.
• For hydrogen-powered vehicles and industrial applications.
• Requires strong and heavy storage tanks.

Liquid Hydrogen

• Cooled and converted at very low temperatures (-253°C or -423°F) and stored in cryogenic tanks.
• It has higher energy density than compressed gas.
• Suitable for some applications like rocket propulsion.
• Maintaining low temperatures and energy costs are challenging.

Metal Hydrides

• These materials absorb/release hydrogen gas reversibly.
• They can Store hydrogen at moderate pressures/ambient temperatures.
• The challenge is finding efficient yet stable storage.

Chemical Hydrogen Storage

• Chemically bonds hydrogen to other compounds that releases hydrogen through chemical reactions.
• Storage yields high energy density.
• Additional processing is required to release hydrogen.
• Examples include ammonia (NH3) and liquid organic hydrogen carriers.

Adsorption

• The process adsorbs hydrogen onto porous materials like activated carbon or metal-organic frameworks.
• Stores hydrogen at moderate pressures/temperatures.
• Suitable for portable applications.

Hydrogen Transportation Methods

Pipeline Transport:

• Hydrogen flows through pipelines like natural gas.
• Used specialized pipelines for hydrogen's reactivity.
• Efficient for a minimal emission long-distance.
• Limited coverage has high upfront infrastructure costs.

Compressed Hydrogen

• Compressed/stored in high-pressure containers (350-700 bar) transported via trucks or ships.
• Suitable for transport over medium distances with flexible trucking/shipping.
• Suffers energy-intensive compression and has limited range compared to liquid hydrogen.

Liquid Hydrogen:

• Cooled/liquefied at very low temperatures (-253°C or -423°F) and densifies the hydrogen.
• Suits long-distance shipping and aerospace.
• Needs cryogenic storage and suffers storage/shipping losses.

Hydrogen Carriers

• Ammonia and liquid organic hydrogen carriers (LOHC) like toluene can binds hydrogen for transport.
• Carriers release hydrogen at the final site.
• They can store more hydrogen with lower pressure .
• Requires energy-intensive release processes and new infrastructure.

Hydrogen Tube Trailers

• High-pressure transport of hydrogen gas is used over shorter distances.
• Reaches locations missing pipeline infrastructures, i.e., industrial facilities/refueling stations on mobile with high-pressure.
• Suffers from a limited storage capacity.

Hydrogen Barges and Ships

• Long-distance transport in gaseous or liquid form over waterways.
• Suitable for great volumes over water however this form relies on loading/unloading with high build costs and safety.

Challenges

• Production often relies on fossil fuels.
• "Green" hydrogen is more sustainable.
• Hydrogen infrastructure, storage, and transportation face technical and logistical challenges.
• The projects require investment and innovation.
• Safety considerations are important due to hydrogen's flammability and potential for leakage.

The Future of Hydrogen

• Future is sustainable and low-carbon.
• Technological advancements are continued.
• Supportive policies and international collaborations are needed.