Green hydrogen – what is it and how is it produced? What applications does it have?

Green hydrogen is set to be a game changer in the energy transition strategies of Europe, the US, China, Japan, and Australia, as well as many other countries. Until a few years ago, little was said about this fuel. So why today is it being called a key tool for decarbonization and put at the center of discussions about the future of energy worldwide? What is green hydrogen? How is it produced and what applications does it have? We answer all these questions in today’s article.

In 2015, as part of the Paris Agreement, 197 countries pledged to continue their efforts to keep the Earth’s average temperature increase below 2°C compared to the pre-industrial era. The agreement has sparked ambitious climate targets in many countries, as well as the European Union’s long-term strategy to become the world’s first continent to achieve carbon neutrality by 2050. This means that the European economy is to manifest the same level of emissions reductions that will be released into the atmosphere (net zero).

Green hydrogen in the European Union

One element of the strategy is the Fit for 55 package announced in 2021, a package of proposed legislative changes with the main goal of reducing emissions by 55% by 2030 and achieving neutrality by 2050. An important step was also published in 2020. European Union hydrogen strategy. Among its key goals was

  • to achieve in the EU an installed capacity of electrolyzers of 6 GW by 2024, which could produce about 1 million tons of hydrogen per year;
  • achieving an installed capacity of 40 GW of electrolyzers in the EU by 2030, which would produce 10 million tons of hydrogen per year. This was to meet the projected demand for hydrogen in various sectors of the European economy.

The geopolitical situation quickly revised the European Commission’s original plans. In 2022, in response to Russia’s aggression against Ukraine and the need for Europe to cut off fuel imports from Russia, the EC published the REPowerEU plan, which raised the hydrogen demand target for the European economy to 20 million tons by 2030, half of which is to be met from imports.

This was driven by the need to diversify energy sources and thus increase the share of RES in the EU’s energy mix. In addition to the obvious advantage of hydrogen as a carbon-free source, the fact of energy security, which hydrogen realizes by stabilizing and increasing the efficiency of renewable sources, is also important.

Green hydrogen – what is it?

It’s not without reason that we first highlighted the EU’s goals, which place the production of hydrogen from renewable energy at the center. This is green hydrogen, alternatively also called renewable hydrogen or pure hydrogen.

It is produced by electrolysis of water, which involves the separation, under the influence of an electric voltage, of a water molecule into its components – hydrogen and oxygen. The condition is that the energy used in this process is renewable. Only then can we speak of the emission-free nature of the fuel.

Currently, hydrogen accounts for about 2% of the EU’s energy mix. However, about 95-96% comes from fossil fuels. Through this, 70-100 million tons of CO2 are released into the atmosphere each year. Electrolytic hydrogen still accounted for about 2% of the share of total hydrogen production in Europe in 2022. At the same time, it should be noted that only a fraction of this was accounted for by electrolysis, which was powered by RES. The energy for electrolysis came mainly from the grid, hence it is difficult to determine the carbon footprint it may have generated (strong dependence on the energy mix of individual countries). Member states therefore face a huge task in the coming years to achieve the targets set by the EU.

Electrolysis – green hydrogen production

Electrolysis is a well-recognized process for obtaining hydrogen, and the technology itself has been developed since the 18th century. In this method, the flow of electric current between electrodes through an electrolyte causes chemical processes to take place at the boundary of media, i.e. between a solid conductor (electrode) and a liquid conductor (aqueous solution).

In an alkaline electrolyzer, reaction (1) occurs at the anode, while reaction (2) occurs at the cathode:

1. 4OH- –> H₂O + O₂ + 4e-

2. 2H₂O + 2e- → H₂ + 2OH-

For an electrolyzer made with PEM technology, the reactions at the anode (3) and cathode (4) are as follows:

3. 2H₂O → 4H+ + 4e- +O₂

4. 4H+ + 4e- → 2H₂

Using an AEM electrolyzer, the expected reaction for the anode (5) and cathode (6) is described by formulas

5. 4OH → 2H₂O + O₂ + 4e-

6. 4H₂O + 4e- → 2H₂ + 4OH-

The energy intensity of the electrolysis process depends on the electrolyzer technology used, oscillating between 45-70 kWh/kg H₂. Thus, the efficiency of the process averages 45%-70%.

Areas of application for green hydrogen

Hydrogen has been used for years in many sectors of the economy. With this, we are talking about hydrogen from conventional fuels, which is used in the chemical industry (production of ammonia, methanol, oxo alcohols), petrochemical industry (hydrotreating, reforming, and hydrocracking processes), food industry (included in the list of substances approved for use in food production and processing), as well as metallurgy, jewelry, and glass industries. Their decarbonization is possible by eventually replacing emitting hydrogen, with that produced from RES.

In recent years, new and particularly promising areas of green hydrogen exploitation have also been recognized – transportation, power generation, heating, and heavy industry.

Hydrogen in transportation – independence of fuel production

It is widely believed that transportation will be the first area to transform the increased use of green hydrogen. The particular potential of the new fuel is seen especially in those modes of transportation whose electrification is difficult, uneconomic, or technically impossible – trucks and long-haul transport, non-electrified rail routes, maritime transport, and even aviation.

The advantages of hydrogen as a fuel for transportation are its high efficiency and achievement of long ranges, short refueling times, and fully environmentally friendly nature. Hydrogen vehicles also do not require the use of large batteries, which, in the case of long-haul and freight transportation, worsen the ergonomics of the vehicle and require longer recharging, worsening the economics of transportation. Green hydrogen can also be used to produce RFNBOs (non-biological renewable fuels), including e-ammonia, which is increasingly being cited as a fuel for ships, e-methanol and even e-kerosene as aviation fuel.

Electrolyzers also allow production to take place directly or near depots, airports seaports, or refueling stations, creating a dedicated hydrogen hub for transportation purposes. This reduces the need to transport fuel, increasing users’ independence.

Green hydrogen in the energy sector – increasing RES efficiency

The transformation of the energy sector is to consist primarily of increasing the existing share of RES in the energy mix. In October, the RED III directive upheld the target for this share to be at least 42.5% by 2030, with member states required to strive for 45%. This brings with it the challenge of the volatility and variability of power generation, characteristic especially of solar sources, which are characterized by variability not only on a seasonal level but also daily.

Crucial for Power-to-Gas installations is the production of gas (hydrogen) with significant energy potential. Using unstable RES sources to produce clean hydrogen during times of electricity oversupply will increase their efficiency, by producing fuel or substrate for transportation, industrial, or other energy purposes, such as thermal power generation. Unlike batteries, the technology also allows for long-term energy storage in the form of hydrogen and its subsequent use during periods of lower supply and high demand, or its conversion back into energy using fuel cells (with the current state of technology, however, this process involves certain energy losses).

Heat production – green hydrogen for heating buildings

Hydrogen has the potential to decarbonize the heating and district heating sector and supplement the need for clean heat alongside other alternative technologies, such as heat pumps. Worldwide, projects are already underway to add hydrogen to residential buildings for heating and utility purposes. With that said, we are talking about H2 Ready boiler technology, which operates on a mixture of hydrogen and natural gas, which translates into the occurrence of certain emissions.

SES Hydrogen Energy is developing a hydrogen boiler that will enable the elimination of CO2 emissions, as well as NOx, SOx, and particulate matter. How is this possible? The device uses only hydrogen and pure oxygen in the combustion process, not a mixture or atmospheric air. As a result, the only products of combustion are energy and steam. SES Hydrogen Energy’s hydrogen boiler is a solution aimed at medium- to large-scale applications – in system energy, industry, and local heating hubs for commercial buildings, residential buildings, and housing estates.

The full hydrogen boiler plant includes RES sources and hydrogen production and storage modules, providing a local heating hub of small or medium scale. On-site hydrogen production for heating ensures the creation of a local ecosystem, making heat consumers independent of what happens in the energy and fuel market, and thus heat at a stable price in the long term.

Hydrogen in industry – application opportunities

In addition to transportation, power, and heating, the role of hydrogen as a tool for decarbonization is seen in industry. This is a particularly demanding sector due to the high energy intensity that characterizes heavy industry and metallurgy.

As recently as 2020, global demand for hydrogen in the industrial sector was 94 Mt, equivalent to about 2.5% of global energy demand, at which point it is not used as an energy feedstock, but primarily as a substrate and intermediate in the manufacturing processes of target products.

Industry is considering the use of hydrogen not only as a fuel and raw material but also as an energy carrier. Green hydrogen is already being used in the steel industry, among others, as an alternative to fossil fuels in processes other than direct combustion. Such a process is, for example, the production of high-quality steel using the DRI (direct reduction) method, where conventional fuels – coal or coke – are replaced by hydrogen.

Analyzing the potential of using hydrogen as a fuel and energy storage in the indicated economic sectors, including the most demanding energy and industrial sectors, it is not difficult to understand why green hydrogen is expected to be a tool for decarbonizing the world’s economies in the next decades.

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