Green hydrogen: the future of clean energy?

• Hydrogen can serve as an energy carrier just like fossil fuels do.
• Green hydrogen is an emission-free energy source for heavy industries and long-haul transport.
• The high cost of making green hydrogen is slowing its adoption.

Green hydrogen is hydrogen that is produced by splitting water by electrolysis, using electricity that has been generated using renewable energy. This process produces only hydrogen and oxygen. We can use the hydrogen and vent the oxygen to the atmosphere with no negative impact. This is one of the cleanest ways to generate hydrogen, which can then be used as fuel.

Burning of hydrogen produces water and no carbon emissions, making it an ideal fuel to power our industrial requirements. However, the use of green hydrogen is not economically feasible yet. In this explainer, you will learn about green hydrogen and how it could play a major role in the carbon emission-free future that we want to pursue.

With most countries around the world looking for ways to achieve their net zero goals, alternate sources of energy such as wind and solar have picked up steam. Companies are building the biggest wind turbines ever, and solar farms are increasing in size rapidly. However, both these energy forms suffer from intermittency problems – they do not always generate power continuously or on demand.

For a long time, fossil fuels have provided the energy security needed by industries and nations alike, and until renewable sources of these forms of energy scale up to meet demand, a carbon-free fuel could be used to fill the gap or act as a backup when renewables do not deliver.

Since fossil fuels are currently delivered and in use all over the planet, their replacement must also have the same reach, and for hydrogen, this means massively scaling up its production.

How is hydrogen produced?

In its elemental form, hydrogen serves as an energy carrier. It can transport energy from one place to another, just like we do with fossil fuels. There are several methods of producing hydrogen, but we will discuss two major ones.

• Thermal process

This method typically involves the use of high temperatures on a hydrocarbon fuel to release hydrogen. The process called steam reforming can be applied to a wide variety of hydrocarbon fuels such as diesel, natural gas, gasified coal, or biomass.

• Electrolytic Processes

Hydrogen can be produced by splitting water molecules in an electrolyzer in a process called electrolysis. The process is the opposite of what happens in a fuel cell, where hydrogen combines with oxygen to form water and release energy. In electrolysis, energy is used to split the water molecule.

Making hydrogen production green

Steam reforming currently accounts for around 95 percent of all hydrogen production in the U.S. today. Most of the hydrogen manufacturers use methane (CH₄), found in natural gas, as the starting material for steam reforming, where the carbon atom is split from the hydrogen using high heat under moderate to high pressure (3- 25 bar) in the presence of a catalyst.

In addition to hydrogen, the process also creates carbon monoxide and a small amount of carbon dioxide, which is undesirable since it increases our carbon emissions. It is also an energy-intensive process. Electrolysis, on the other hand, does not produce any by-products other than hydrogen and oxygen, depending on the fuel used to power the electrolysis process.

Depending on the fuel type used to produce the gas, hydrogen is classified into different types, such as green, yellow, brown, grey, blue, etc. Grey hydrogen is the most abundant type of hydrogen. It is produced by steam reforming, but without capturing the greenhouse gases made in the process, so it produces carbon emissions. Coal is also commonly used to produce hydrogen gas, which is then known as black or brown hydrogen.

Blue hydrogen is produced from natural gas, but the CO2 generated during the manufacturing process is captured and stored permanently underground. In blue hydrogen production, hydrogen is still produced using fossil fuels; however, the emissions from the process are captured using industrial carbon capture and storage (CCS), making it cleaner than black and grey hydrogen.

Green hydrogen is the cleanest form of hydrogen production. It is energy produced from renewable sources, which can be a mix of hydro, wind, and solar power (hydrogen produced using solar power is sometimes referred to as yellow hydrogen). Although the installation of renewable energy farms is on the rise, only 0.1 percent of overall hydrogen production is actually green today.

Why do we need green hydrogen?

To understand the need for the production of green hydrogen, we must also understand the other types of hydrogen production techniques, such as blue or turquoise hydrogen (produced using a process called methane pyrolysis to produce hydrogen and solid carbon).

Another energy source being explored for the production of hydrogen is nuclear power. Hydrogen produced using nuclear power is called pink hydrogen or sometimes also referred to as red hydrogen. This process does not create carbon emissions but may contribute to a future problem of producing nuclear waste that will need to be dealt with.

Green hydrogen, on the other hand, provides the best of both worlds since it delivers an eco-friendly fuel in an eco-friendly way. As countries look to transition to greener sources of energy, hydrogen is expected to play an important role. To ensure that we make this shift without adding more carbon dioxide to the atmosphere and further warming the world, some have argued that we need to speed up production and adoption of green hydrogen now.

Where can green hydrogen be used?

Green hydrogen can be a replacement energy source in almost every application where fossil fuels are currently used. Aviation and shipping, for instance, are facing challenges with electrification since currently available technology cannot support long-haul trips with heavy loads. In such a scenario, hydrogen, which packs three times as much energy as the same weight of gasoline, and nearly seven times that produced by coal, could be an alternative. Using green hydrogen will also ensure that these trips are emission-free.

Apart from this, hydrogen used in fuel cells is a source of electricity that can be deployed anywhere on the planet. It only needs oxygen to work and produces water as the by-product. Hydrogen produced at a green site can be transported to even remote areas of a country in the same way as fossil fuels are today, using existing transportation systems, and used to power vehicles, homes, and even industries.

Instead of using batteries to store energy, hydrogen can be used as a carrier and oxidized when in need of energy, such as electricity or heat.

How much does green hydrogen cost to make?

Due to its advantages, hydrogen could be poised to become a viable energy source for the world. However, its adoption has been rather slow, and this has been largely due to the relatively high financial cost of generating and using the fuel.

As per estimates from the Center of Global Energy at Columbia University, 70 million tons of hydrogen are produced every year in the U.S. alone. This demonstrates that the technical challenges of transporting and using hydrogen have been well understood and addressed. In these networks, it is the gray or blue hydrogen that is largely transported, and that's because green hydrogen can cost three times as much as gray hydrogen to produce.

The cost of electrolyzers is one of the major factors contributing to the high price of green hydrogen, which can vary between $3.5 to $6 per kilogram. In comparison, gray hydrogen costs around $1.5 per kilogram to produce, while blue hydrogen costs around $2-$3 for the same weight.

In addition, because hydrogen has a low volumetric energy density, it is generally stored onboard a vehicle as a compressed gas – otherwise, not enough would fit on the average vehicle to ensure long-range travel. Most current applications use high-pressure tanks capable of storing hydrogen at either 5,000 or 10,000 pounds per square inch (psi). So, there is also the cost of installing tanks and ensuring their safety.

Governments must work to bring in policies that can reduce the cost of producing green hydrogen as it will help in the development of new technologies and clean up the environment as well.