Hydrogen, viewed as a key element in the decarbonisation of the global cement sector, is costly and difficult to transport. Verano Energy looks at how ammonia can help.
Hydrogen has the potential to decarbonise a wide range of heavy industries including cement production, power, chemicals and steel. This means that demand for hydrogen is going to be huge. In its Net-Zero Emissions scenario the International Energy Agency (IEA) expects demand to increase five-fold from 2020 to 2050.
However, there are a few important limitations to overcome for hydrogen to become competitive. The first challenge is to produce sufficient supply of renewable ‘green’ hydrogen. The next is to be able to store it in large quantities and then to establish the required infrastructure to trade and transport it. This is where ammonia comes into play. Consisting of one nitrogen and three hydrogen atoms, the ammonia molecule (NH3) has the potential to support the hydrogen fuel economy in all three domains.
Making hydrogen competitive
Today, most hydrogen is produced from fossil fuels through steam methane reforming, generating 830Mt/yr of CO2. Carbon-free ‘green’ hydrogen, conversely, is produced using electrolysers to split water into hydrogen and oxygen. This is expensive and energy-intensive, but when the energy used is from renewable sources - hydro, wind or solar - then it provides a versatile, fossil-free energy carrier.
But how can hydrogen be made more competitive? Firstly, by using renewable energy rich sources such as solar photovoltaic panels in Chile, Saudi Arabia and Australia, where it will be extremely competitive to produce. Secondly, as we ramp up renewable energy production, we should deploy electrolysers to produce hydrogen from ‘excess’ renewable energy that cannot be used immediately. Unfortunately, the intermittence of renewable energy means that there are periods of very high energy production that do not match demand. The supply from renewables, particularly solar, becomes so high that the amount of electricity generated threatens to overwhelm the grid capacity.
Although battery energy storage systems are being developed, they are not yet capable of capturing and storing this amount of excess energy. The result is curtailment. This is where grid operators shut down access to the grid or adopt pricing mechanisms to generate negative pricing to reduce production. Some estimates put renewable energy curtailment as high as 20% of capacity.
Rather than curtailing excess renewable energy, the solution would be to use this excess to produce green hydrogen. By installing electrolysers at major substations that are connected to renewable plants, green hydrogen production can act as a load balance. It would be cost competitive, because the renewable energy would otherwise be wasted, and it allows renewable operators to be paid for every megawatt hour they produce. No energy is lost.
In this way, green hydrogen production would incentivise further growth in renewables. However, it must not detract from the availability of electricity for other essential and more effective uses – it must be additional. The transition to green hydrogen and the acceleration of renewable energy generation must work together.
Hydrogen could also play a useful complementary role to current energy storage solutions. Batteries are a cost-effective way to store energy on a daily or potentially weekly basis. However, curtailment is usually seasonal and it will never be cost-effective to store six months’ worth of energy using batteries, at least not with the ones that exist today. If renewable energy is going to replace fossil fuels, we will need seasonal or even annual storage as well as international trade of renewable energy. Green molecules are perfect for this.
NH3 will enable the hydrogen economy
While most of the hydrogen produced will be fed into existing pipelines and traded regionally, some regions such as Latin America, the Middle East and Northern Africa have the potential to produce more clean hydrogen than needed. Other regions, for example Japan, Korea or Hawaii, will have insufficient renewable sources and will need to import hydrogen.
But transporting hydrogen over long distances is not efficient and doesn’t make economic sense. The transportation of hydrogen in large quantities from one continent to another would require a whole new liquefaction and distribution infrastructure of ports, terminals and storage. This is where ammonia provides a competitive solution.
A recent report published by the International Renewable Energy Agency estimates that over half of the global trade in hydrogen will be in the form of ammonia. This is because hydrogen is liquified at -252°C. It is extremely reactive, requiring specific corrosion resistant materials, which makes storage and transportation excessively expensive. Ammonia on the other hand can be condensed to liquid at -33°C, making it much easier to store and transport. The infrastructure already exists, with terminals at 120 ports around the world.
Moreover, the process technology to condense hydrogen and transform it into ammonia has a very high efficiency rate. Installing ammonia crackers alongside centres of green hydrogen production and consumption will support the development of a hydrogen fuel economy. These crackers are still not commonly available, but their theoretical efficiency is high. Efforts should be made to develop them quickly at scale.
Energy storage is another benefit, the relevance of which has been highlighted in the energy crisis caused by the war in Ukraine. Ammonia can be stored for as long as necessary, providing an important reserve of energy security. Cheap large storage tanks remove the need to have production and consumption closely aligned.
Renewable energy storage concept
We can think of green ammonia as the backbone of a renewable, hydrogen-based economy, using a renewable power storage concept. In the concept, ‘excess’ renewable power is converted to different types of energy storage depending on the quantity available and the duration over which it needs to be stored.
For example, if a country were to generate excess solar energy, it would first be stored in batteries. When those are full, it would start to convert excess renewable into hydrogen, for medium-term storage and possible sale to other countries via regional pipelines. Once it has reached its hydrogen capacity, it would then start to convert the hydrogen into ammonia, for long term storage and trans-continental sale. While there are energy losses to consider, the prospect of green ammonia trade is a game-changer for the renewable sector. It will enable any nation worldwide to use an alternative to fossil-based energy systems, regardless of their solar exposure or prevailing wind conditions.
Other uses
Continued research and development open up additional uses for ammonia, including as a fuel, especially in shipping. Although it is less flammable, the energy density of ammonia is 1.5 times higher than liquid hydrogen. Collaborative efforts are underway to develop safe, reliable and environmentally-friendly marine engine technology. A European consortium aims to have a zero-emissions vessel running on ammonia by 2025.
Power generation offers another application, where ammonia could be used as a fuel to replace coal, heavy fuel oil or diesel. Admittedly, this is not the most efficient way to use ammonia and hydrogen. The only valid reason we would do this is to accelerate the adoption of green hydrogen and take advantage of existing infrastructure. Japan is looking to develop a co-firing coal and ammonia-fired power plant. Direct ammonia turbines using hydrogen as an accelerant to improve firing are currently under development. Ammonia turbines could provide a more cost-effective net-zero alternative to carbon capture or battery storage, especially for nations which currently operate diesel turbines. Research in this field to resolve the issue of NOx emissions, needs to be rapidly ramped up.
Finally, green ammonia can be used as a building block to produce other chemicals, including fossil free fertilisers. Various projects are underway which consider alternative ways of combining carbon and hydrogen to build plastics. These could involve carbon capture and utilisation to produce hydrocarbons rather than releasing CO2 into the atmosphere.
The ‘crude’ of the hydrogen economy
Green ammonia’s role in the energy transition is going to be huge. It will work together with renewable energy as we transition away from fossil fuels to meet our net zero targets. However, capacity needs to be massively scaled-up to reduce costs and be more competitive. Once this is achieved, ammonia would become the global renewable energy commodity, acting as the backbone of the hydrogen economy much like crude oil does today. The fact that it can be transported globally - at a known price governed by market forces - will enable us to convert the renewable sector from the national to the global scale, enabling more efficient use for all. Green ammonia will have the flexibility to be used as an energy carrier, as a fuel and as a building block for other chemicals. It will be the ‘crude’ of the hydrogen economy.