No one believed Jules Verne when he predicted that we’d be harnessing most of our energy from water in the future.
But now in the midst of an energy and climate crisis, harnessing green hydrogen from water seems like one of the most promising solutions to solve our woes.
The 500 billion dollars invested in over 350 large-scale hydrogen projects worldwide is proof that there is enormous potential.
In this article, we explain what green hydrogen is, how the fuel cell works, and how it could decarbonise many of the most emitting industries.
Contents
Why is hydrogen used as a fuel?
Hydrogen is the most common element in the universe and the building block of living organisms (carbohydrates) and water (H2O), where it resides happy, and in a stable form.
But when it is forcefully separated from these stable molecules, hydrogen readily bonds with itself, forming H2 molecules that may be stored away in sealed, pressurized tanks as hydrogen fuel.
And the magic happens within a fuel cell, in which hydrogen fuel (H2) reacts with oxygen to produce heat, electricity and water.
What is a Hydrogen Fuel cell?
Hydrogen fuel cells are crucial because, without them, hydrogen fuel (H2) would be useless as we wouldn’t be able to harness any useful energy from it (apart from an explosion!).
There is a plethora of hydrogen fuel cell designs, but what they have in common is that they all use oxygen in the air to react with hydrogen fuel to produce heat, electricity and water. What varies is the efficiency and the proportion of heat, electricity or water output for the desired use case.
Generally, fuel cells have a positive (+) and negative (-) terminal, which are separated by an electrolyte. Hydrogen fuel is injected into the positive terminal, where it is split into H+ ions that go into the electrolyte and electrons (e-) that join a circuit and create an electric current.
The H+ ions eventually make it to the negative (-) terminal, where they can re-join their lost electrons by reacting with oxygen to create water (H2O) and the potential difference to keep pulling electrons from the first reaction.
This simple yet effective reaction is what makes using hydrogen as fuel totally clean, as its sole emissions are harmless water vapour. But what about the production of the hydrogen fuel that feeds the cells? Is that clean too?
What is Green Hydrogen?
The process of producing hydrogen fuel is one that requires energy. If this energy in the form of heat or electricity is not low-carbon energy it means that the process in its entirety is not climate positive.
Unfortunately, the current reality is that most (>90%) of the hydrogen fuel that is being produced is derived from fossil fuels like natural gas, coal and oil. This is colloquially referred to as ‘Blue’ hydrogen.
The good news is that hydrogen can also be produced with very little emission from clean-burning Pyrolisis of methane and water electrolysis, both of which can be powered using any source of electricity.
When this comes from clean sources like solar, wind, geothermal, hydro and nuclear (debatable), it is deemed as Green Hydrogen.
However, this is where green-washing often happens as the emissions of its entire life-cycle have to be included: i.e. transportation, distribution, and storage. These processes may be carbon-intensive, making the green transition in these areas as crucial as the hydrogen itself.
What is the problem with green hydrogen production?
Green Hydrogen production requires any surplus low-carbon electricity or heat that isn’t being used to feed national grids and heating systems which are normally a top priority.
However, this surplus is small and only happens when low demand coincides with above-average wind or sunshine. So using only this surplus for the production of green hydrogen is not feasible as the supply wouldn’t be reliable.
But given how important hydrogen fuel can be to solve the problems batteries cant solve for some heavy industries and aviation, green hydrogen is necessary, so another solution is necessary.
How will Green Hydrogen be produced in the future?
The renewables/national grid problem means that there has to be a base-load of clean energy entirely dedicated to producing green hydrogen
In the UK, it has been argued that green hydrogen could be produced from biomass energy supplied by Drax Power Station, and mixed with any surplus renewable energy, which can be redirected using a smart grid (which we think needs blockchain to work properly!).
In Germany, experiments with Concentrated Solar Power (i.e. using an array of mirrors to concentrate solar heat into one single point) and smart grids have been taking place with some success.
The key takeaway here is that the success of green hydrogen also depends on our ability to keep scaling green energy.
What is Green Steel?
The steel industry is a vital component of modern society and is present in everything, from furniture to electronics to buildings.
With global demand still increasing, the IEA believes that the steel industry is expected to grow by 33% by 2050.
On the flip side, steel-making is a carbon-intensive industry that contributes to 9% of global emissions, as its core process requires a mixture of coke and coal, as well as heating a blast furnace to >1600C, which is difficult to do without fossil fuels.
But recent innovation in Sweden has yielded a method of producing steel called HYBRIT which entirely replaces coal and coke with hydrogen as a reducing agent, significantly reducing emissions.
Other industries like cement, beverages and metallurgy that rely on fossil fuels for their processes are exploring green hydrogen fuel as a replacement, with the key being that hydrogen may be the only alternative to making some of these clean (i.e. electricity alone cannot process iron into steel).
Green hydrogen for the aviation industry?
Another industry that cannot simply replace gasoline with batteries is aviation, as batteries would make them prohibitively heavy.
Hydrogen is actually significantly more energy dense than any other fossil fuel, which means that it doesn’t need to carry as much fuel weight compared to current aircraft.
However, hydrogen fuel takes on four times the volume of kerosene, meaning a radical design change from current aeroplanes is necessary, which also needs to be compatible with much of the existing aviation infrastructure (e.g. airport terminals, boarding bridges, runways).
Many small companies like ZeroAvia are trialling new aeroplane designs, and larger ones like Airbus have already gone public regarding their hydrogen endeavours, especially since the entire aviation supply chain would need to adapt to support these new aircraft.
Many experts conclude that we will need to ditch the current fuselage-wing design and replace it with a ‘Flying Wing’ in which the entire fuselage becomes a voluminous, flight-efficient wing.
Airbus is expecting to have its ZeroE planes in the air as early as 2035, so hopefully, the Green hydrogen infrastructure will be ready by then.
Green hydrogen for the automobile industry?
Road transportation contributes about 15% of global CO2 emissions, making it another high-priority industry to decarbonise.
Currently, Electric Vehicles (EVs) are all the rage and are spearheading the road transportation revolution, but doing so at a cost. There are environmental concerns regarding battery recycling, China’s supply chain monopoly and long re-charging times.
In contrast, hydrogen vehicles take less than 5 minutes to refuel and are significantly lighter than EVs or diesel cars, without mentioning that they have no carbon emissions as they are powered by a fuel cell.
The issue is that green hydrogen is a very limited resource, so many argue that its use must be prioritised for industries that have no other way of reducing emissions, like green steel-making and aviation.
Also, since hydrogen must be produced, distributed and stored, it is actually less energy-efficient than EVs that directly feed their energy from the grid.
This is evident in the table below, which summarizes the energy efficiency of different fuels when considering their entire life cycle (manufacture, transport, distribution, etc.). Source: DW Documentary
| Fuel | Efficiency (Considering entire life cycle) |
|---|---|
| Diesel | 20% |
| Hydrogen | 27% |
| Li-Ion Batteries | 64% |
But this may change with improvements in hydrogen fuel distribution. In Germany, the existing natural gas pipelines are being experimented with for long-distance hydrogen fuel transportation that would make it even greener.
In terms of road freight transportation, brands like Daimler have built prototype trucks that utilize hydrogen fuel cells that can travel over 1000km without refuelling. These could go into production as early as the mid-2020s, providing additional low-carbon alternatives.
Can green hydrogen help reduce my energy bills?
Unfortunately, energy suppliers don’t sell green hydrogen, and there is no green hydrogen tariff available. The infrastructure is not yet built, and there are very few businesses that can store hydrogen on their premises.
However, you can reduce your energy bills by becoming more energy-efficient or by comparing and switching your business energy suppliers using AquaSwitch.
FAQs
Here we answer some of the internet’s frequently asked questions about green hydrogen and fuel cells:
What is a hydrogen fuel cell bus?
This is simply a hydrogen-powered bus that carries passengers without any operational carbon emissions.
Hydrogen fuel-cell bus experiments have been taking place around the world over the last 20 years, and currently, a fleet of 20 hydrogen-powered double deckers is operating in London.
What type of energy is released by a hydrogen fuel cell?
As mentioned here, hydrogen fuel cells produce energy in the form of electricity and heat, with water being the “waste” product.
Are hydrogen fuel cells rechargeable?
Hydrogen fuel cells are analogous to a combustion engine in a traditional diesel car and not a battery.
Despite having a positive (+) and negative (-) terminal, fuel cells are not where the fuel is stored but where it is produced.
Fuel is stored in a hydrogen fuel tank, which is refuelled.
Can a hydrogen fuel cell explode?
Hydrogen fuel cells themselves do not contain much volatile hydrogen at any one time but are still liable to catch fire as hydrogen is a flammable gas. However, this is no different to combustion engines that burn petrol to create energy, so it can be done safely.
How green is blue hydrogen?
This is a good question despite sounding more appropriate for a pub quiz.
The short answer is no, blue hydrogen is not green, as ‘blue’ hydrogen is another name for hydrogen derived from fossil fuels, which currently composes >90% of hydrogen demand.
How “green” it is, depends on the fuel mix used to produce and distribute the fuel. For example, hydrogen produced from coal burning is less green than hydrogen produced from natural gas with installed carbon capture equipment.
Are hydrogen cars green?
Yes, hydrogen cars can be considered “green” because they have no direct carbon emissions.
How much does green hydrogen cost?
According to a study by KPMG, the current price of Green Hydrogen is $2.5 per kg. We have not found any credible sources that state this in kWh for comparison to other fuels.
