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Hydrogen Fuel Cells

Fuel cell applications and the challenges of hydrogen

  • 3 things to know
  • A2 1

Overview

Backup, remote and telecommunications power, fuel cell cars, buses in Belfast, trains, boats and portable generators, backup efficiency, round-trip efficiency and car emissions calculations, and the cost, transport and storage of hydrogen.

What you need to know

Answer each one before you reveal it.

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Key term

A 1.0 kW backup fuel cell runs for 10 hours and uses 0.60 kg of hydrogen, which contains 120 MJ/kg. What is its efficiency?

Key term

Electricity makes hydrogen at 70% efficiency, and a fuel cell turns the hydrogen back into electricity at 50% efficiency. What is the overall efficiency?

Key term

Why are hydrogen fuel cells used for stationary backup power?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Why are hydrogen fuel cells used for stationary backup power?

    Model answer

    A fuel cell starts quickly when the mains supply fails and runs for as long as hydrogen is available. Hospitals and data centres use fuel cells to keep essential equipment running.

  2. 2

    Why do fuel cells suit power generation in remote locations?

    Model answer

    A fuel cell needs no grid connection and has few moving parts, so it needs little maintenance. Hydrogen can be delivered occasionally or made on site from renewable electricity.

  3. 3

    Why are fuel cells used as stand-alone power supplies for telecommunications installations?

    Model answer

    Mobile phone masts need an uninterrupted supply, often at remote sites. A fuel cell gives longer backup than batteries and is quieter and cleaner than a diesel generator.

  4. 4

    A 1.0 kW backup fuel cell runs for 10 hours and uses 0.60 kg of hydrogen, which contains 120 MJ/kg. What is its efficiency?

    Model answer

    The fuel cell is 50% efficient. The electrical output is 1.0 kW × 10 h = 10 kWh, or 36 MJ. The hydrogen supplied 0.60 × 120 = 72 MJ, and 36 ÷ 72 × 100 = 50%.

  5. 5

    How does a fuel cell electric car work?

    Model answer

    A fuel cell stack turns hydrogen from a high-pressure tank into electricity, which drives an electric motor. A small battery stores energy recovered during braking and helps with acceleration.

  6. 6

    Why are fuel cells well suited to buses?

    Model answer

    Buses run fixed routes and return to one depot, so a single refuelling station can serve a whole fleet. Hydrogen buses refuel in minutes and have a long range.

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