Hydrogen Energy: Tomorrow’s Clean Fuel

What Is Hydrogen power? How is it produced? What are its main uses? What are the main advantages and disadvantages? What's the difference between brown, grey, blue and green hydrogen? We answer these question and others. We also examine how green hydrogen from electrolysis can boost the appeal of wind and solar power and might help to decarbonize our entire energy system.
Hydrogen Car
Test driving a hydrogen car, Annapolis, Maryland. Photo: © MDGovpics/Flickr

Hydrogen energy has been around since the 1970’s, but after decades of false starts, it seems finally poised to take off. This is due to technological improvements, falling production costs and a global push towards sustainable energy with few or no emissions.

To combat global warming, we need to massively ramp up production of renewable energy, and at the same time to improve the flow of wind and solar power to the grid. Hydrogen power could help us to do both.

What Is Hydrogen Energy?

Hydrogen power comes from hydrogen gas (H2), a highly flammable odorless gas, which is the most abundant chemical substance in the universe. But there’s a catch.

The catch: H2 is not a freely available fuel like coal, or solar energy or wind power, or marine energies like tidal and wave power. This is because hydrogen is never found on its own. It is always bonded to other atoms and must be separated to be used. What’s more, the process of extracting hydrogen is energy intensive.


Hydrogen is usually separated from other chemicals through the application of heat – a process known as reforming. Currently, most hydrogen is made this way using natural gas. The gas is heated with steam to form syngas (a mixture of hydrogen and carbon monoxide). The syngas is separated to give hydrogen.

Hydrogen produced this way is not renewable, because it relies on a fossil fuel for production. Indeed, this method is responsible for 830 million tonnes of carbon dioxide (CO2) emissions per year. The equivalent of United Kingdom and Indonesia’s emissions combined. 1

Coal Gasification

Another way of extracting H2 is coal gasification. Coal is burned in a reactor at a very high temperature of between 1,200 and 1,500 °C, the coal releases gas that separates and reforms to produce H2 and carbon monoxide (CO). Similar methods also use peat or charcoal to produce heat.

Biomass gasification, is a process that uses heat, steam, and oxygen to convert biomass to hydrogen and other products, without combustion. Since live biomass removes CO2 from the atmosphere, the net carbon emissions of this method are typically quite low, especially if it incorporates carbon capture and storage in the long term. 2  To date, this method has proven limited.


Hydrogen can also be produced by water and electricity, a process called electrolysis. This is where an electrical current is used to split water into its components of oxygen and hydrogen. Where the electricity provided comes from renewable energy, it is said to produce green hydrogen. This type of hydrogen emits no CO2 emissions and is renewable.

How Much Hydrogen Power Is Produced?

Today, global energy consumption of hydrogen power is about 4 percent. But experts predict this figure will grow to 22 percent by 2050, given the right political and investment support. 3

While hydrogen energy can be produced from a wide variety of sources, including water and biomass, today about 95 percent of worldwide hydrogen actually comes from fossil fuels. (IRENA, 2019).

Natural gas is currently the primary source of hydrogen production, accounting for about three quarters of the annual global production of 70 million tonnes. This accounts for about 6 percent of global natural gas use. Coal is the next source, due to its dominant role in China, and a small fraction is produced from the use of oil and electricity.

Most of what is produced is consumed by the chemical industry. 4

The latest hydrogen revival however, has centered on green hydrogen.

Green Hydrogen from Electrolysis Can Help to Decarbonize Our Entire Energy System

Green hydrogen, produced from water by electrolysis, powered by electricity from renewable sources like wind power and solar energy is a clean burning molecule, unlike oil and gas alternatives. It doesn’t cause air pollution or greenhouse gas emissions.

Experts say, if we are serious about taking climate action, we have no choice but to invest in green hydrogen infrastructure.

This is because green hydrogen offers a sustainable way of channeling large amounts of renewable electricity to sectors for which decarbonization is otherwise difficult – namely, industry, heating and transport. It is one way of decarbonizing the whole energy system.

Types of Hydrogen: Color Chart

There are different methods for producing hydrogen and these have been categorized by color. This is how we judge how renewable a particular hydrogen facility is.

Experts also use this color system to debate whether the market should move directly to green hydrogen, or whether the transition to decarbonization could accommodate a role for brown, grey or blue hydrogen.

ColorProduction Process
Hydrogen made by using coal. This method releases emissions into the air.
Hydrogen made from natural gas. This method also produces emissions. It’s how the vast majority of hydrogen is produced today. If the natural gas used is extracted by fracking, this method could pose other environmental dangers.
Hydrogen made from natural gas, but where the emissions are captured using carbon capture and storage.
Hydrogen made from methane, but where the emissions are captured using carbon capture and storage. No more carbon-neutral than blue hydrogen.
Hydrogen made from electrolysis powered by renewable electricity. This is where most of the interest is.

The Debate

The argument for moving directly to green includes, reaching an end-goal of providing clean emission free energy that can be used in heat, transport and industry sooner. Electricity is the main cost of green hydrogen and the cost of that renewable electricity is coming down. There is a lot of support for green hydrogen and the scale and number of projects is growing.

The argument against a direct transition goes something like this: diverting renewable electricity to producing hydrogen will delay emission reductions from electricity generation. Furthermore, electrolysers are not yet developed enough to handle large scale production, and green is much more expensive currently than blue hydrogen. While green hydrogen is the agreed goal, it may be that different colors of hydrogen have a stepping stone role in getting us there.

For example, while green hydrogen would cut emissions to almost zero, the blue alternative through the use of carbon capture and storage (CCS) technologies could reduce CO2 production by about 50 percent. And according to some estimates about 90 percent of emissions produced during methane reformation process can be captured using CCS. 5

Is Hydrogen Energy Renewable?

Only green hydrogen – made by electrolysis using renewable grid electricity – can be considered renewable. As the levels of intermittent energies such as wind and solar power increase, there should be plenty to go around.

Currently, green hydrogen accounts for less than 1 percent of total annual hydrogen production. 6 But the number and size of operations is predicted to rise significantly, driven by a rapid scaling up of electrolysers. In 2020 Japan’s claimed to have the biggest green hydrogen facility in the world with a 10 MW electrolyser. However, there are already plans for a 250 MW renewable hydrogen electrolyser in Copenhagen by 2027. 7

How Green Hydrogen Works

Green hydrogen is the extraction of hydrogen from water through the process of electrolysis. It is also called electrolytic hydrogen.

With electrolysis, all you need to produce large amounts of hydrogen is water, a big electrolyser and plentiful supplies of electricity. If the electricity is generated from renewable sources like wind or solar, the hydrogen is effectively green. The only carbon footprint comes from the engineering infrastructure.

The resulting hydrogen gas can be transported by special trucks and even pipes to where it is needed, like refueling stations. Usually it is transported as liquid hydrogen in insulated tanks. To be liquefied, hydrogen must be cooled to below −253°C (−423°F). The downside is that liquefaction consumes more than 30 percent of the energy content of the hydrogen.

Electrolysis is still expensive, but the market is expected to grow after receiving significant attention and investment recently. 4

In 2020, the EU issued a report: “A hydrogen strategy for a climate-neutral Europe.” The report says “hydrogen is essential to support the EU’s commitment to reach carbon neutrality by 2050 and for the global effort to implement the Paris Climate Agreement while working towards zero pollution.” 8

What Is Hydrogen Used For?

Hydrogen use today is dominated by industry. The chemical industry uses it to make ammonia for agricultural fertilizer (the Haber Process). It is also used in oil refining, methanol production and steel production. More recently, NASA has relied upon hydrogen for its missions and other activities. Virtually all of this hydrogen is supplied using fossil fuels, so there is significant potential for emissions reductions from clean hydrogen.

While hydrogen is already widely used in some industries, it has yet to realize its potential in supporting the clean energy transition. In order to achieve this, the hydrogen must be (1) primarily green and (2) adopted in sectors where renewables are almost completely absent, namely transport, heating and power generation.

Transport: Hydrogen Fuel Cell Vehicles

This diagram shows the basic components required for a hydrogen powered car. Some of these components are shared with a Battery Electric Vehicle (BEV) such as the traction motor and battery.

How A Hydrogen Fuel Cell Car Works. Components and diagram.
Image: US Dept of Energy

Inside the car, the hydrogen combines with oxygen from the atmosphere and is fed into a fuel cell. Here a reaction occurs which generates electricity. The only by-product is heat and water. This electric charge is used to power the battery which in turn powers the motor.

How this works in practice: As a driver, you pull into a filling station which sells hydrogen fuel. You connect the dispenser to the vehicle, fill, disconnect, pay and finally drive away with a full tank. Refueling takes about the same amount of time as refueling a regular gasoline power car.

This raises the question: If both an electric and hydrogen car are powered by electricity, why bother with a hydrogen car? The reason is, hydrogen fuel cells have a much faster refuel time. Also, hydrogen fuel cells are more space efficient than lithium batteries, meaning they have longer ranges than electric vehicles. This is why hydrogen is an interesting alternative for the trucking, shipping and possibly aviation industry.

Yet adoption of hydrogen vehicles has been slow. In 2019, there were 18,000 hydrogen vehicles on the road globally, compared to 7.2 million electric cars. One of the main problems is lack of fueling stations. As of 2020 there were only 407 hydrogen fueling stations worldwide. The majority are in Europe, followed by Asia and finally North America. 9

Besides the lack of infrastructure, green hydrogen fuel loses 70 percent of it’s efficiency between the time of production, through transportation, distribution and being re-transformed into electricity in a fuel cell. 10

What’s more, hydrogen vehicles are expensive, and there are not many options available. The Toyota Mirai – hydrogen fuel cell family car – currently leads the market in the United States.

Elon Musk calls hydrogen technology “mind boggingly stupid” and claims “success is simply not possible.” But perhaps he judges too soon. 11

Hydrogen Energy For Heating Buildings

Hydrogen is a low-carbon alternative to natural gas, and can provide heating and hot water to homes.

Recently the UK announced a plan to power a town in Fife, Scotland entirely by hydrogen. 12 The initiative will use offshore wind to provide electricity to an electrolysis plant, which will in turn produce the hydrogen. The 300 inhabitants will be provided with free hydrogen boilers, heaters and cooking appliances to be used for more than four years in the largest test of whether zero carbon hydrogen can help the country tackle the climate crisis and reach its sustainability goals.

At the same time, a recent study in Germany found that hydrogen is not a great option when it comes to heating buildings. It compared the use of special hydrogen boilers to regular heating pumps that used electricity directly. It found that the amount of green electricity needed to produce green hydrogen for the purpose of a hydrogen boiler was 500 to 600 percent greater. It concluded that the direct use of green electricity from the grid is a better option for decarbonized heating. 13

As a Storage Solution For Renewable Power

The biggest problem of wind and solar energy is their intermittency. Sometimes the wind doesn’t blow or the sun doesn’t shine. To ensure a reliable power supply, these energies must be stored so that they can be available when needed. 

The problem is, electricity is difficult to store and, so far, no feasible, cost effective, grid-scale storage technology has emerged. This is why electricity from renewables still needs to be backed up by conventional generation – to provide power on demand.

For example, California makes a lot of renewable electricity. So much so, that in the spring of 2020, it curtailed (i.e. restricted the delivery of energy from a generator to the electrical grid) between 150,000-300,000 MWh of excess power per month. Yet it also experienced its first rolling blackouts in August because the grid didn’t have enough energy.

So, while we are producing more and more renewable power, we now need to find a way to store it. This includes long-duration energy storage, which is able to store power for weeks or months.

It is this intermittency issue which has given hydrogen a new lease of life, because green hydrogen is emerging as a key contributor to the renewable power storage sector. (For details of its main rival, ‘pumped storage’, see: Hydropower Renewable Hydroelectricity.)

Thus, for example, the excess electricity produced at wind and solar energy sites, which can’t be supplied directly to the power grid, can be used to power electrolysis, with the hydrogen stored for later reuse. This ensures that all the renewable wind and solar energy is used, with none wasted.

The hydrogen produced can be stored on site, in underground caverns, such as salt caverns. Storing fuel in this type of cavern isn’t new, but hydrogen’s growing role in decarbonization has refocused attention on the concept. For example, The U.S. Strategic Petroleum Reserve has stored emergency crude oil in underground salt caverns for a long time and says they cost 10 times less than above ground tanks.

Caverns can be created in salt domes by drilling into the salt dome and injecting the rock with water, which dissolves the salt. The resulting brine is extracted, leaving a large cavity. The next step is to inject liquefied hydrogen which can be reconverted to electricity when needed.

Salt caverns are considered the best way to ensure hydrogen purity and hermetic (sealed) storage. Certain application such a fuel cells, require very pure hydrogen.  14

What Are The Advantages of Hydrogen Energy?

Potentially Renewable

Hydrogen itself is abundant, which means unlike most energy sources, it will never run out. It can be renewable when produced by renewable electricity or biomass. It is a very clean fuel source for transport where the only by-products are water and heat. No greenhouse gases or emissions of particulate matter are produced by the use of hydrogen fuel cells.

Energy Storage

Hydrogen can be stored as a gas or a liquid and will never dissipate until it is used. Compare that to other storage types like batteries which use the energy stored in them over time and need to be periodically recharged even without use.

Does Not Harm the Environment

Hydrogen does not cause damage to the environment or to human health unlike nuclear energy, coal, and other fossil fuels. See, for example: What are the environmental effects of fossil fuels?

What Are The Disadvantages of Hydrogen Energy?

It’s Expensive

Producing hydrogen from low-carbon energy is expensive at the moment. However, the IEA predicts the cost could fall 30 percent by 2030 as a result of declining costs of renewables and the scaling up of hydrogen production. Furthermore, costly fuel cells, refueling equipment and electrolysers will all benefit from mass manufacturing.

Lack of Infrastructure

The slow development of hydrogen infrastructure is holding back the wider adoption of hydrogen vehicles. Lack of fueling stations requires better planning and coordination among governments, industry and investors. But even if hydrogen suddenly became cheap today, it would still take years to become widely used since vehicles themselves and service stations would need to be customized to conform to hydrogen requirements. 

There also needs to be common international trading standards for the safety of transporting and storing large volumes of hydrogen and for environmental transparency on the different type of hydrogen supplies (blue, green or grey?).

Watching climate change intensify, many experts are beginning to worry that the huge infrastructure changes needed – for example, to support the mass uptake of renewables – may prove too much for today’s fragile global consensus. With UN climate talks at an impasse and subsequently delayed further by the coronavirus pandemic, the challenges facing negotiators are mounting up.


Hydrogen is a highly flammable gas which makes it risky to work with. It also has no smell so sensors are required to detect leaks.

As hydrogen is lighter than gasoline, this makes it harder to store and transport. It needs to be converted to liquid and stored under high pressure at a low temperature.

High Carbon Emissions

Right now, hydrogen production is almost entirely dependent on coal and gas, and the carbon emissions of CO2, methane and nitrous oxide they produce, are well documented.

The only sustainable paths forward are: (a) to ramp up production of green hydrogen, and (b) to speed up development of carbon capture technology in order to decarbonize fossil-fuel based hydrogen production.

Future Prospects Of Hydrogen Power

The European Commission predicts the share of hydrogen in Europe’s energy mix will rise from 2 percent today, to 13-14 percent by 2050. 8

In the United States, demand for hydrogen could quadruple, from 41 million metric tons per year by 2050, up from 10 million today. 15

Still, there is likely to be a gradual transition from brown and grey hydrogen to blue and green varieties.

For example, CCS might be suitable for regions with low-cost natural gas, and in the short term CCS might also be a good fit for large-scale applications in industry, given the relatively small scale of deployment for electrolysis. 16

The very latest use of hydrogen in energy development is nuclear fusion, a very costly quest for low carbon energy which involves the fusion of two isotopes of hydrogen.

Further Reading


  1. The Future of Hydrogen.” IEA Report June 2019 []
  2. Hydrogen Production: Biomass Gasification.” []
  3. BNEF Hydrogen Council []
  4. IRENA. “Hydrogen from Renewable Power.” September 2019. [][]
  5. Independent Commodity Intelligence Services: EU hydrogen strategy 2020. []
  6. “The future for green hydrogen” Wood Mackenzie []
  7. “Rapid scaling of electrolyzers accelerates wind hydrogen savings.” Reuters []
  8. “A hydrogen strategy for a climate-neutral Europe.” European Commission, July 2020. PDF: https://ec.europa.eu/energy/sites/ener/files/hydrogen_strategy.pdf [][]
  9. “Update on the global transition to electric vehicles through 2019.” The International Council on Clean Transportation. 2020 []
  10. Green Hydrogen Cost Reduction Report. Scaling Up Electroysers to Meet the 1.5°C Climate Goal. IRENA 2020.[]
  11. “Elon Musk says the tech is ‘mind-bogglingly stupid,’ but hydrogen cars may yet threaten Tesla.” CNBC. Feb 2019. []
  12. “Scottish homes to be first in world to use 100% green hydrogen”. The Guardian, November 2020. []
  13. “Green hydrogen or green electricity for building heating?” Fraunhofer Institute for Energy Economics and Energy System Technology. 2020. []
  14. “Salt Caverns: Underground and pipeline hydrogen storage.” M. Panfilov, in Compendium of Hydrogen Energy, 2016. []
  15. “The Technical and Economic Potential of the [email protected] Concept within the United States.” October 2020 U.S. Department of Energy’s National Renewable Energy Laboratory. []
  16. Green Hydrogen Cost Reduction. Scaling Up Electrolysers To Meet The 1.5°C Climate Goal. PDF: https://irena.org/-/media/Files/IRENA/Agency/Publication/2020/Dec/IRENA_Green_hydrogen_cost_2020.pdf []
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