What is hydrogen?

Hydrogen (H₂) is a molecule made of two hydrogen atoms. It has the highest energy content per unit of mass of any common fuel, but a very low energy density per unit of volume—requiring it to be compressed or liquefied for storage and transport. Hydrogen exists naturally in very small amounts (often called “white hydrogen”) in the atmosphere and in certain geological formations. However, nearly all the hydrogen used today is produced through industrial processes from other primary energy sources—such as fossil fuels, wind and solar, and biomass—making it an energy carrier rather than a primary source of energy. 

How is hydrogen produced?

Today, the most common method for producing hydrogen is steam-methane reforming, which extracts hydrogen from natural gas using steam. A cleaner alternative is “green hydrogen,” produced via water electrolysis, a process that uses electricity to split water into hydrogen and oxygen. This method is becoming more technically feasible, and when powered with renewable energy, avoids the production of greenhouse gases.

Does hydrogen create pollution?

When burned for heat and electricity, most fuels produce pollutant by-products, such as particulate matter, carbon monoxide, and carbon dioxide. Hydrogen, in contrast, produces mostly water as a by-product. How “clean” hydrogen is will depend on the production path used. When it is produced from low-carbon electricity and water, it could be a solution to reducing carbon emissions. On the other hand, producing hydrogen from fossil fuels releases greenhouse gases.

In addition, while hydrogen itself is not a greenhouse gas, it can indirectly contribute to global warming. When leaked into the atmosphere, hydrogen interferes with the chemical processes that break down methane, effectively extending methane’s lifetime and enhancing its warming impact Hydrogen can also produce polluting nitrogen oxides (NOx) due to reactions with nitrogen in the air. 

How is hydrogen for energy storage modeled in En-ROADS?

Using hydrogen produced via electrolysis for energy storage has already been proven to be technologically feasible, but it faces significant barriers to scaling up. These barriers include the cost of hydrogen pipeline and infrastructure construction and safety concerns. 

En-ROADS models hydrogen produced through electrolysis as a form of energy storage that can help meet long-term energy needs, such as storing renewable electricity for use when the sun isn’t shining or the wind isn’t blowing. The hydrogen produced is captured and stored to be used when needed. 

To simulate a breakthrough in the use of hydrogen for storage in En-ROADS, use the “Green hydrogen production subsidy” slider in the Renewables advanced view. This incentivizes the production of hydrogen via dedicated wind and solar electricity: 

To learn more about hydrogen as a form of energy storage, the importance of energy storage, and which parameters you can test in En-ROADS, read the FAQ: "How do I simulate energy storage for wind and solar?"

Hydrogen as an energy carrier and as an industrial feedstock

Beyond its use for long-term storage of energy from wind and solar, hydrogen—in particular, green hydrogen—can also be used in three other sectors and ways: 

• In Industry, for energy and as a feedstock: Using hydrogen to replace natural gas in boilers and other settings where high heat is needed or as feedstocks in chemical processes, such as separating iron from iron ore. 
• As an energy carrier in transport: Converting hydrogen into synthetic fuels (e.g., ammonia, methanol) for aviation and shipping. 
• As an energy carrier in buildings: Burning hydrogen in boilers for heating in residential and commercial spaces. 

To learn more about these uses of hydrogen, read the Hydrogen in En-ROADS Explainer.