CHE241 Self-Study Assignment - Green Hydrogen and Fuel Cells PDF

Self-Study Assignment: Green Hydrogen and Fuel Cells Question 1: Complete the following sentences: 1. Green hydrogen is hydrogen produced using renewable energy sources, such as wind, solar, hydropower, or biomass, without releasing CO₂ emissions. 2. Green hydrogen is a clean fuel source for fu...

Self-Study Assignment: Green Hydrogen and Fuel Cells Question 1: Complete the following sentences: 1. Green hydrogen is hydrogen produced using renewable energy sources, such as wind, solar, hydropower, or biomass, without releasing CO₂ emissions. 2. Green hydrogen is a clean fuel source for fuel cells. 3. Hydrogen is recognized for its high gravimetric energy density, i.e., high energy content relative to its weight, which makes it an attractive energy carrier. 4. Hydrogen is categorized into several types based on the energy source and production process. 5. Green Hydrogen is produced from renewable energy sources through methods like water electrolysis, biomass or biological processes, resulting in no net CO₂ emissions. 6. Grey Hydrogen is produced from fossil fuels (such as natural gas) without capturing CO₂, leading to significant greenhouse gas emissions. 7. Blue Hydrogen is produced from fossil fuels (natural gas) along with carbon capture technology in place to mitigate greenhouse gas emissions. 8. Turquoise Hydrogen refers to hydrogen produced through methane (natural gas) pyrolysis, which generates solid carbon rather than CO or CO2 9. Steam Reforming, Pyrolysis, Partial Oxidation, Autothermal, and Dry Reforming are all methods to produce hydrogen from natural gas or methane. 10. Steam methane reforming (SMR) is used for hydrogen production, from natural gas (methane) by reacting methane with steam at high temperature temperatures (700-1000C̊) and in the presence of a nickel catalyst. Δ CH4 + H2O → Ni CO + 3H2 11. Pyrolysis is a process in which methane is thermally decomposed at high temperatures (above 1000C̊) into hydrogen (Turquoise H2) and solid carbon. Δ CH4 → C (solid) + 2H2 12. In Partial Oxidation (POX), an exothermic reaction where methane reacts with a limited amount of oxygen to produce hydrogen. CH4 + ½ O2 → CO + 2H2 13. In Dry Reforming, methane reacts with carbon dioxide instead of water to produce hydrogen and carbon monoxide. Reaction occurs at high temperatures (800–1000°C) and typically requires a catalyst. Δ CH4 + CO2 → Ni 2CO + 2H2 14. Syngas or Synthesis Gas is primarily consisting of carbon monoxide (CO) and hydrogen gas (H2). 15. After production of syngas, the water-gas shift follow-up reaction usually occurs in order to maximize hydrogen production. CO + H2O → CO2 + H2 16. Water electrolysis (reverse fuel cell operation) is an electrochemical process in which electrical current is used to dissociate water (water splitting) into hydrogen and oxygen gases. 2H2O → 2H2 + O2 17. In thermal water splitting, high temperatures (>2500C̊) can split water into hydrogen and oxygen gases. 18. In catalytic water splitting, catalysts are used to lower the required temperature for water splitting into hydrogen and oxygen gases 19. Photobiological water splitting for Bio-hydrogen production can be achieved by certain algae and cyanobacteria which utilize sunlight to drive the process of splitting water into oxygen and hydrogen. Page 1 of 3 20. Gasification of woody biomass is a thermochemical process that converts these carbon-rich materials into syngas, making it a promising method for sustainable energy or a precursor for green hydrogen production. 21. The main challenge for hydrogen storage is its low volumetric energy density or low energy density by volume. 22. Compression is a gaseous hydrogen storage method that involves storing compressed hydrogen under heightened pressure. 23. Liquification is a liquid hydrogen storage method that involves storing hydrogen in well-insulated tanks designed to maintain hydrogen at cryogenic temperatures, typically below − 253 C̊, i.e., below its boiling point. 24. Solid-state hydrogen storage involves physisorption (adhering) of H2 molecules to the surface of porous adsorbent materials like metal-organic frameworks (MOFs) or Carbon Nanotubes (CNTs). 25. Solid-state hydrogen storage involves chemisorption (chemical bonding) of H2 molecules to lightweight elements creating complex hydrides like sodium aluminum hydride (NaAlH4). 26. Hydrogen Fuel cell is an electrochemical device that converts chemical energy supplied as input fuels into electric energy through a reaction with an oxidizing agent (usually oxygen from the air). 27. Hydrogen fuel cell generates electricity by combining hydrogen (H₂) and oxygen (O₂) in an electrochemical reaction. 2H2 + O2 → 2H2O + e ̶ (electricity) 28. Hydrogen fuel cell produces water (H₂O) as the only byproduct, making it an environmentally friendly energy source. Question 2: For each statement below, determine whether true or false. 1. Green hydrogen is also called clean or renewable hydrogen. 2. Hydrogen gas is a versatile energy carrier that can be used for heating, electricity generation and transportation. 3. Hydrogen gas is a feedstock for range of industrial processes, including chemicals, glass, and synthetic fuel. 4. Hydrogen fuel can release a substantial amount of energy per unit mass of about 120-142 MJ/kg which may be considered the highest net calorific value. 5. A possible disadvantage might be the high requirements for tightness of containers and pipelines needed to avoid leakage. 6. Hydrogen produced by pyrolysis is labeled turquoise because solid carbon is easier to store compared to carbon dioxide, avoiding emissions and enabling potential reuse in other industries. 7. Autothermal reforming is a thermally neutral process that combines endothermic steam reforming and exothermic partial oxidation in a single reactor. 8. Water electrolysis is the reverse fuel cell operation. 9. Water electrolysis is an electrochemical process in which electrical current is used to dissociate water into hydrogen and oxygen gases. 10. Bio-hydrogen production can be achieved by certain algae and cyanobacteria through a process called photobiological water splitting, which uses sunlight to split water into oxygen and hydrogen. 11. Purple non-sulfur bacteria can produce bio-hydrogen by metabolizing organic compounds under anaerobic conditions (in the absence of oxygen). 12. In the absence of light, some bacteria can produce bio-hydrogen by breaking down organic compounds through fermentation. 13. Woody biomass conversion via gasification is considered carbon neutral as a promising method for sustainable energy production and green hydrogen production because the carbon emissions released were previously absorbed as CO₂ through photosynthesis and do not contribute additional CO₂ to the atmosphere. Page 2 of 3 14. The main challenge for hydrogen storage is its Low volumetric energy density or low energy density (content) by volume. 15. A large volume is required to store a relatively small amount of energy compared to other fuels like gasoline or natural gas. 16. Solid-state storage of hydrogen offers improved safety and increased volumetric energy density compared to gaseous or liquid hydrogen storage. 17. Hydrogen fuel cells are eco-friendly devices that convert chemical energy from hydrogen fuel and oxygen from air into electrical energy through an electrochemical reaction, with water being the only byproduct. Question 3: What is the scientific term for the following statements? 1. Primarily consisting of carbon monoxide (CO) and hydrogen gas (H2). [syngas or Synthesis Gas] 2. High energy content of hydrogen relative to its weight, makes it a promising energy carrier. [High Gravimetric energy density] 3. The amount of energy produced per unit mass of fuel in MJ/kg unit. [Net calorific value] 4. A technology that involves capturing carbon dioxide (CO2) emissions from industrial sources to storing them underground in a geological reservoir. [Carbon Capture and Storage] 5. Low energy content of hydrogen relative to volume at standard temperature and pressure [Low volumetric energy density] Question 4: Briefly discuss the following topics. [ Short Essay  3-5 lines] 1. Green Hydrogen Production by water electrolysis. Green hydrogen is usually produced by water electrolysis with very low or zero emissions. Water electrolysis is an electrochemical process in which electrical current is used to dissociate water (water splitting) into two gases, hydrogen and oxygen. The overall reaction of water electrolysis is expressed as: 2H2O (l) → 2H2 (g) + O2 (g) 2. Carbon Capture and Storage Technology. CCS is a technology that involves capturing carbon dioxide (CO2) emissions from industrial sources, transporting them, and storing them underground to prevent them from entering the atmosphere. It isolates CO2 permanently from the Earth's atmospheric carbon cycle, typically by injecting it at a depth of several thousands of meters into a geological reservoir, such as a depleted oil or gas field. Page 3 of 3