A Curriculum Comparing Hydrogen Derivatives

Objective
Evaluate which hydrogen derivative is most suitable for:
- Transport
- Industrial use
- Energy storage

You will compare four options:
- Compressed hydrogen (H₂ gas at 700 bar)
- Liquefied hydrogen (LH₂)
- Ammonia (NH₃)
- Methanol (CH₃OH)

Part 1: Given Data -- Use the following information:

• Compressed hydrogen (700 bar)
  Energy density: 120 MJ/kg and 5.6 MJ/L
  Storage: very high pressure
  Infrastructure: low maturity
  Toxicity: low

• Liquefied hydrogen (LH₂)
  Energy density: 120 MJ/kg and 8.5 MJ/L
  Storage: extremely low temperature (−253°C)
  Infrastructure: low maturity
  Toxicity: low

• Ammonia (NH₃)
  Energy density: 18.6 MJ/kg and 12.7 MJ/L
  Storage: mild pressure or refrigeration
  Infrastructure: medium maturity
  Toxicity: high

• Methanol (CH₃OH)
  Energy density: 20 MJ/kg and 15.8 MJ/L
  Storage: ambient conditions
  Infrastructure: high maturity
  Toxicity: medium

Part 2: Questions

1. Transport (cars, trucks, ships)

a. Which fuel has the highest volumetric energy density?
b. Why is volumetric energy density more important than gravimetric energy density in transport applications?
c. Based on the data, which option would you choose for:
- Passenger cars?
- Long-distance shipping?
Justify your answers by considering efficiency, safety, and infrastructure.

2. Industry (steel, chemicals, etc.)

a. Which derivative is already widely used in industry today?
b. Which one would be easiest to integrate into existing systems?
c. Which option minimizes energy losses from conversion?
Conclude which is best suited for industrial decarbonization.

3. Energy Storage (grid-scale)

a. Which fuel is easiest to store over long periods?
b. Which likely has the lowest storage cost based on conditions required?
c. Which is most suitable for seasonal (long-term) energy storage?
Explain the trade-offs between efficiency and practicality.

Part 3: Calculation

A facility needs to store 1,000 MJ of energy.
For each fuel, calculate the required volume in liters using:
Volume = Energy ÷ volumetric energy density

Part 4: Critical Thinking

Write short answers to the following:
1. Why might Ammonia be preferred over hydrogen even though it is toxic?
2. What are the main challenges of using Liquefied hydrogen?
3. Can Methanol act as a hydrogen carrier? Explain your reasoning.

Final Task

For each application (transport, industry, and energy storage), choose the best option among the four and justify your choice with clear arguments.

Bonus (Advanced)

Explain how Power-to-X technologies influence the choice of hydrogen derivatives.

Part 2 : Answers

1. Transport

a. Highest volumetric energy density
Methanol (15.8 MJ/L) has the highest volumetric energy density, followed by ammonia (12.7 MJ/L), liquefied hydrogen (8.5 MJ/L), and compressed hydrogen (5.6 MJ/L).

b. Why volumetric density matters more
In transport, space is limited. Vehicles (cars, trucks, ships) have strict volume constraints, so fuels that store more energy per liter allow longer range or smaller tanks. Gravimetric density matters too, but volume is often the limiting factor, especially for ships and trucks.

c. Best choices

• Passenger cars: Compressed hydrogen (H₂ at 700 bar)
  Reason:

  • Already used in fuel cell vehicles

  • Fast refueling

  • Clean (no toxic emissions)

  • Despite low volumetric density, acceptable for cars with high-pressure tanks

• Long-distance shipping: Ammonia
  Reason:

  • Much higher volumetric energy density than hydrogen

  • Easier to store than liquefied hydrogen (no extreme cryogenics)

  • Existing global transport infrastructure (used in fertilizers)

  • Can be burned directly or used in fuel cells

--> Conclusion: Hydrogen works for light transport; ammonia is more practical for heavy, long-distance transport.

2. Industry

a. Most widely used today
Ammonia is already massively produced and used (fertilizers, chemicals).

b. Easiest to integrate
Ammonia again, because:
- Existing pipelines, storage, and handling systems
- Established global market
Methanol is also widely used and easy to handle.

c. Lowest conversion losses
Compressed hydrogen (H₂ gas):
- No need for conversion (already hydrogen)
- Avoids energy losses from synthesis (e.g., making ammonia or methanol)

--> Conclusion:
- For efficiency → hydrogen is best
- For practical deployment → ammonia is often preferred

3. Energy Storage

a. Easiest to store long-term
Methanol and ammonia are easiest because they are stable liquids under mild conditions.

b. Lowest storage cost
Methanol:
- Stored at ambient temperature and pressure
- No need for expensive tanks or cooling

c. Best for seasonal storage
Ammonia
Reason:
- High volumetric density
- Easier and cheaper storage than hydrogen
- Suitable for large-scale infrastructure

--> Trade-off:
- Hydrogen → high efficiency but hard to store
- Ammonia/methanol → easier storage but energy losses in conversion

Part 3: Calculations

We use:
Volume = Energy ÷ volumetric energy density
Energy = 1,000 MJ

• Compressed hydrogen:
  1000 ÷ 5.6 ≈ 179 L

• Liquefied hydrogen:
  1000 ÷ 8.5 ≈ 118 L

• Ammonia:
  1000 ÷ 12.7 ≈ 78.7 L

• Methanol:
  1000 ÷ 15.8 ≈ 63.3 L

--> Conclusion: Methanol requires the least storage volume, hydrogen gas the most.

Part 4: Critical Thinking

1. Why prefer Ammonia despite toxicity?
- Much easier to liquefy and store than hydrogen
- Higher volumetric energy density
- Existing infrastructure worldwide
- Lower transport cost
Toxicity is a drawback, but industry already manages it safely at large scale.

2. Challenges of Liquefied hydrogen
- Requires extremely low temperatures (−253°C)
- High energy consumption for liquefaction
- Boil-off losses during storage
- Expensive insulation systems

3. Can Methanol act as a hydrogen carrier?
Yes.
- Methanol contains hydrogen chemically bound
- It can be reformed to produce hydrogen when needed
- Easier to transport and store than pure hydrogen

However:
- Reforming requires energy
- Produces CO₂ unless captured

Final Ranking

Transport:
- Best: Ammonia (especially for ships)
- Second: Hydrogen (cars)
- Third: Methanol
- Last: Liquefied hydrogen (too complex)

Industry:
- Best: Hydrogen (efficiency)
- Close second: Ammonia (practicality)
- Third: Methanol

Energy Storage:
- Best: Ammonia
- Second: Methanol
- Third: Liquefied hydrogen
- Last: Compressed hydrogen