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The Understand Energy Learning Hub is a cross-campus effort of the Precourt Institute for Energy.


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Fast Facts About

Principal Energy Uses: Electricity, Transportation

Hydrogen is a versatile energy currency that can be produced from fossil fuels or water. Hydrogen has very low energy density by volume but is extremely energy dense by weight. Although it is currently used primarily as a feedstock for oil refining, chemicals, and fertilizers, hydrogen shows promise as a clean fuel for heavy-duty transportation, steel-making, heating, and energy storage. Hydrogen is often referred to as the “Swiss Army knife of decarbonization”, because it has potential in hard to decarbonize applications.

Today, the vast majority of hydrogen is created from fossil fuels, but renewable hydrogen can be created through electrolysis, the process of using electricity to create hydrogen from water. Electrolysis is more expensive than fossil fuel hydrogen and other fuels, but the relative costs are rapidly decreasing due to technological innovation, government subsidies, investment activity, and commercialization.

Current Status

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Global Pure Hydrogen Demand 

Types of Hydrogen*

Brown Hydrogen 
Hydrogen produced from coal gasification

Grey Hydrogen 
Hydrogen produced from steam methane reforming, a process which converts natural gas into hydrogen and CO2

Blue Hydrogen  
Hydrogen produced from fossil fuels, and the CO2 produced it captured and stored

Turquoise Hydrogen  
Hydrogen produced via methane pyrolysis, a process that splits methane, the main component of natural gas, into hydrogen and solid carbon

Yellow Hydrogen 
Hydrogen produced from grid electricity through electrolysis

Pink Hydrogen 
Hydrogen produced from nuclear energy through electrolysis

Green Hydrogen 
Hydrogen produced from renewable electricity through electrolysis

*All hydrogen is the same. Colors are assigned based on the environmental impact of how the hydrogen was produced. The colors above are listed in order of their environmental impact. (brown is worst, green is best)

The Future

Potential Significant Markets

  • Steel production
  • Trucks, planes, and ships
  • Long term energy storage
  • Building and industrial heating
  • Clean chemicals

Growth of Investment in Hydrogen (VC)

420% growth in VC investment from 2017-2022 
($500 million in 2017 to $2.6 billion in 2022)


  • High energy density by weight
  • Can be a low to no carbon fuel
  • Strong policy support and subsidies for hydrogen production
  • Can be paired with renewables to produce zero carbon fuels
  • No air emissions when using / burning hydrogen, only byproduct is water
  • Potential for long term energy storage
  • Potential to decarbonize steel production
  • Potential to replace carbon fuels in transportation
  • Most abundant element on the planet
  • Reduces reliance on imports of fuels


  • Very low energy density by volume
  • Expensive to produce from clean energy (electrolysis)
  • Difficult to transport and distribute (hydrogen is only liquid at very high pressure and low temperature)
  • One of the most fugitive gases in the world due to small atom size
  • Extremely expensive to build necessary infrastructure for hydrogen transportation and storage (e.g. specially sealed pipelines, refueling stations)
  • Safety concerns of hydrogen fires
  • Hydrogen gas doesn’t exist naturally, must be created from fossil fuels or water
  • Lack of public awareness/understanding


Updated July 2023

Before You Watch Our Lecture on

We assign videos and readings to our Stanford students as pre-work for each lecture to help contextualize the lecture content. We strongly encourage you to review the Essential videos and readings below before watching our lecture on Hydrogen. Include selections from the Optional and Useful list based on your interests and available time.


  • Hydrogen 101. Student Energy. May 18, 2015. (3 min)
    Quick overview of what hydrogen is and the two main ways we make it (since it’s an energy carrier, not an energy resource, we have to make it).
  • How Does a Fuel Cell Work?. Naked Science Scrapbook. October 7, 2011. (4 min)
    Simple demonstration on how fuel cells work.
  • The Truth About Hydrogen. DW Planet A. February 25, 2022. (12 min)
    Explores the drivers and barriers to hydrogen contributing to a decarbonized future.

Optional and Useful

Our Lecture on

This is our Stanford University Understand Energy course lecture on hydrogen. We strongly encourage you to watch the full lecture to understand the potential role of hydrogen in our energy system and to be able to put this complex topic into context. For a complete learning experience, we also encourage you to watch / read the Essential videos and readings we assign to our students before watching the lecture.

Diana Gragg

Presented by: Diana Gragg, PhD; Core Lecturer, Civil and Environmental Engineering, Stanford University; Explore Energy Managing Director, Precourt Institute for Energy
Recorded on: April 28, 2023   Duration: 24 minutes

Table of Contents

(Clicking on a timestamp will take you to YouTube.)
00:00 Introduction and Potential
5:20 What is Hydrogen
13:44 How Do We Generate and Move Hydrogen?
18:07 Where Do We Use Hydrogen?
19:03 Where Are Things Going in the Future?

Lecture slides available upon request.

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Additional Resources About

Government and International Organizations