The first thing to consider when examining hydrogen is that it can only store energy, not produce it. This is why hydrogen is considered an energy carrier and not a source. These ‘carrier’ qualities are what make it a good option in the renewable energy industry normally impeded by ‘intermittency’, or the fact that natural elements like sunlight and wind are not always available. Hydrogen has the benefit that it can be dispatched to different parts of the planet and converted to energy on the spot. A bit like portable sunshine.

The ‘dispatchability’ of fossil fuels like oil and natural gas is why they are still actively consumed as a source of energy, since they can provide energy quickly to meet peak demand. The downside of fossil fuels however, is that carbon gets emitted into the atmosphere when the energy conversion takes place. If not absorbed again via natural or man-made sequestration processes, that carbon gradually acts like a blanket that traps heat around the earth, increasing sea temperatures and consequently affecting weather patterns in ways that impact on human livelihood.

Compare that process to hydrogen: The advantage of the energy that gets created when hydrogen (H2) links with oxygen (O), for example in a car’s fuel cell, is that the only by-product is water (H20). Although that might sound like an elegant solution, the problem lies in creating hydrogen. Since pure hydrogen is rarely found on earth, it requires energy to produce it. That energy can be created by either renewable means such as wind or solar power (green hydrogen), using fossil fuels such as natural gas and coal (grey hydrogen), or by capturing the carbon that gets produced via fossil fuels (blue hydrogen).

Green hydrogen is produced by splitting the hydrogen from the water molecule via the renewable-energy powered process of electrolysis. According to the International Energy Agency, just 0.1% of the world’s dedicated hydrogen production today comes from water electrolysis due to its significantly higher cost. But declining costs for renewable electricity, in particular from solar PV and wind, will likely see an increase in electrolytic hydrogen in the future. Grey hydrogen accounts for around 95% of the hydrogen produced today, and there are also other ‘colours’ in the spectrum that make up the rest.

But even though green hydrogen is considered the cleanest option of all, it still needs to be shipped or piped around. That is the case even if it is ultimately used in a car’s fuel cell, for example. Shipping can also involve the use of fossil fuels, and leaks from pipes are not only hazardous due to the invisible manner in which hydrogen burns, the element is in itself considered by many scientists as an ‘indirect’ greenhouse gas more potent than carbon dioxide. According to Steven Hamburg, chief scientist at the Environmental Defense Fund (EDF), the way in which hydrogen interacts with and then extends the life of methane in the atmosphere is a problem.

This interaction causes hydrogen to “stick around and continue contributing to the greenhouse effect,” Hamburg said in an interview with the EURACTIV media network. Packing and unpacking the hydrogen as ammonia is one way to reduce the risk here. But according to the EU’s 2021 Joint Research Center report, that process also has the highest costs. One common and more affordable means of transporting hydrogen to the EU, particularly in the absence of pipelines, is to transport the hydrogen as a liquid in super-insulated, cryogenic tanker trucks, for example from Chile, North Africa or Australia. After liquefaction, the liquid hydrogen is dispensed to delivery trucks and transported to distribution sites where it is vaporized to a high-pressure gaseous product for dispensing, similar to natural gas.

Even this approach results in some hydrogen escaping into the atmosphere. A certain low percentage of leakage is always to be expected via pipelines according to a report released by the Frazer-Nash Consultancy. But a report commissioned by the UK government suggests that even in bad leakage scenarios, hydrogen’s usage is still preferable for the environment compared to the CO2 that would otherwise be produced. The UK report also found that there is no single optimal hydrogen delivery solution across every transport scenario: The most cost effective way to deliver renewable hydrogen depends on distance, amount, final use, and whether there is infrastructure already available.

This brings into question whether other energy carriers with higher efficiency such as rechargeable batteries, pumped-storage hydroelectricity and molten salt, can be used instead. Like hydrogen, each of these has strengths and weaknesses, with the general advantage that energy storage allows greater grid flexibility as distributors can buy electricity during off-peak times and deploy it to the grid when it is in greater demand. How green hydrogen rates against these alternative carrier options will be the focus of a future Insight Article.