---
title: "Hydrogen fuel compared with solar"
subject: "Energy Environment and Society"
chapter: 3
key: "semester_7/energy_environment_and_society:hydrogen-fuel-solar-comparison"
source: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/hydrogen-fuel-solar-comparison
site: BCT Engineering
---

# Hydrogen fuel compared with solar

Energy Environment and Society · Chapter 3: Renewable Energy Sources

- Asked in: 2073 Shrawan
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/hydrogen-fuel-solar-comparison
- Whole chapter: https://www.bctengineer.com/md/semester_7/energy_environment_and_society/chapter-3

## Question

What is hydrogen fuel? Describe about advantages and disadvantages of Hydrogen fuel. Also compare with solar energy.

## Answer

**Hydrogen fuel** is hydrogen gas (H₂) used as an energy carrier to produce heat by burning or electricity in a fuel cell. It is made by electrolysis of water, steam reforming of natural gas, gasification of biomass or coal, etc. 2H₂ + O₂ → 2H₂O. Energy content is about 120 MJ/kg.

#### Advantages
- Clean: only water is formed on use.
- Highest energy per kg of any fuel (about 120 MJ/kg).
- Can be made from water using renewable electricity (green hydrogen) and can store surplus solar or wind power.
- Fuel cells are efficient (40–60%) and quiet.
- Usable in vehicles, industry, power and heating.

#### Disadvantages
- It is not a primary fuel; production needs energy, and most hydrogen today comes from fossil fuels (grey hydrogen).
- Very low volumetric energy density; storage needs high pressure, cryogenic liquefaction or metal hydrides, which is costly.
- Highly flammable and explosive; leaks and embrittlement of metals.
- Missing infrastructure; high cost of fuel cells and electrolysers; low round-trip efficiency.

#### Comparison with solar energy
| Point | Hydrogen | Solar energy |
|---|---|---|
| Nature | Secondary energy carrier | Primary renewable source |
| Availability | Must be produced | Directly available from the sun |
| Storage | Can be stored (in tanks) for long time | Needs batteries; not storable directly |
| Emissions | Clean at use; production may emit CO₂ | No emissions in operation |
| Cost | High (production, storage, fuel cells) | Low and falling (PV) |
| Transport use | Good for vehicles | Indirect (electric vehicles) |
| Intermittency | Not intermittent | Intermittent (day only) |
| Efficiency chain | Low (electricity -> H₂ -> electricity ~30-40%) | PV 15-22% |

They work well together: solar electricity can produce green hydrogen for storage and transport.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why is hydrogen called a secondary energy carrier?
   A. It occurs freely in nature as fuel
   B. It must be produced using energy from other sources
   C. It is made by the sun directly
   D. It is a primary fossil fuel
   Answer: B. Hydrogen is made by electrolysis or reforming, which need energy input. (Key point: Hydrogen as energy carrier)

2. What is the main storage disadvantage of hydrogen?
   A. Very low energy per kg
   B. Very low volumetric energy density, needing high pressure, liquefaction or hydrides
   C. It is inert
   D. It is not flammable
   Answer: B. Hydrogen has high energy per kg (120 MJ/kg) but low per volume. (Key point: Hydrogen disadvantage)

3. Which comparison is correct?
   A. Solar is a secondary carrier; hydrogen is primary
   B. Hydrogen is storable for long and not intermittent, while solar is intermittent and needs batteries
   C. Hydrogen is cheaper than PV
   D. Solar is storable directly
   Answer: B. Hydrogen can be stored in tanks; solar is primary but available in daytime only. (Key point: Hydrogen vs solar)

## Related in Energy Environment and Society

- [Hydrogen fuel advantages and disadvantages](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Ahydrogen-fuel-adv-disadv) — Energy Environment and Society, chapter 3, asked 3×
- [Solar thermal energy and application](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-thermal-application) — Energy Environment and Society, chapter 3
- [Hydrogen production and storage](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Ahydrogen-production-storage) — Energy Environment and Society, chapter 3
- [Fuel cell and its working](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Afuel-cell-working) — Energy Environment and Society, chapter 3, asked 2×
- [Electrochemistry basics, hydrogen production](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Aelectrochemistry-hydrogen-production) — Energy Environment and Society, chapter 3
- [Solid oxide fuel cell](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asofc-construction-working) — Energy Environment and Society, chapter 3, asked 2×

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