The Energy Diary: hydrogen and ammonia, partners in decarbonising power generation
Hydrogen is often characterised as a panacea for decarbonising activities, from power generation to transport. The reality is more complex, as ANGEA Senior Advisor Neil Theobald writes in the October installment of The Energy Diary – his monthly column on major issues in the global energy transition.
Being clear about the difference between energy sources and energy carriers is important in the transition discussion. Energy sources provide energy without relying on some other energy form to create them.
Examples of energy sources are fossil fuels and the sunlight that drives solar, wind and hydroelectric power generation. Nuclear fission and fusion are also primary source of energy. Energy carriers include electricity, hydrogen, ammonia, batteries and pumped hydroelectric storage. Of course, fossil fuels are also technically energy carriers in that they carry the energy from prehistoric sunlight, but for simplicity they can be assumed to be primary sources in our current environment.
Any analysis of options for energy transition must go back to the primary energy source to understand whether those options are viable or even desirable. For example, in electric vehicles, the source of the electricity is a critical part of the evaluation, along with the infrastructure requirements for transmission of the power and emissions embedded in the manufacturing of the vehicles and batteries. Only by assessing the emissions of the full production and utilisation chain can effectiveness be assessed. If the power is still generated by high emissions coal , then the main impact of EVs will be to transfer emissions from the vehicle to the power station. This may be desirable for urban air-quality but have much more limited impact on overall emissions.
Confusion between energy sources and energy carriers seems most common when discussing hydrogen. How often have we heard stories that hydrogen-powered “fill in the blanks” will transform our economy and reduce emissions? The first question should be where the hydrogen is going to come from. Hydrogen as a gas is rare on Earth, and most current production comes from hydrocarbons as part of industrial processes. Hydrogen can also be produced from water via electrolysis. This variety of sources has led to the categorisation of hydrogen by colours to account for different levels of greenhouse gas emissions – for example, green hydrogen is produced from renewable power, grey hydrogen usually from natural gas and blue hydrogen from natural gas but with underground storage of the carbon dioxide emissions (carbon capture and storage).
Unfortunately, hydrogen is not a user-friendly energy carrier. As a gas, it has high energy content by mass but its low density means it carries only a third of the energy of natural gas per cubic metre. Physically increasing its density can involve storage at high pressure, which raises costs and the complexity of equipment. Another way to increase density is by cryogenic liquefaction, but for hydrogen this requires cooling to a temperature of -253°C compared to -162°C for natural gas (LNG), again greatly adding to complexity and cost. While limited demonstrations of liquefied hydrogen shipping have been undertaken, the feasibility of large-scale liquefied hydrogen export to replace existing liquefied natural gas exports is low.
But there are alternative ways to transport hydrogen. It can be used to manufacture ammonia, which has existing global production of 180 million tonnes a year, mostly for conversion into fertiliser. Ammonia is shipped at scale as a liquid in vessels that already exist. The technology for ammonia-fuelled gas turbines to generate power is developing rapidly with the potential for 100 per cent ammonia firing by the middle of this decade. For boiler-based power generation, the potential for 20 per cent ammonia co-firing will be proven in the next few years with 50 per cent possible early next decade. This has the potential to significantly assist decarbonisation efforts in power generation, particularly in Asia where many economies remain reliant on coal and gas-switching remains an ongoing process.
So ammonia is an existing, well understood, long-distance transportation option for hydrogen. But what about the production of the hydrogen itself? While in the longer term green hydrogen from renewable power and electrolysers is expected to become economically viable, in the medium-term as a bridging solution, blue hydrogen is the most attractive. Technologies to produce blue hydrogen/ammonia and capture associated CO2 and store it underground already exist and are proven, and the cost is expected to be significantly below green hydrogen for some time.
Some people may object to blue hydrogen/ammonia on the basis it extends the production of fossil fuels, however with the storage of the bulk of produced CO2 it provides a pragmatic way to significantly decarbonise power production with technology that is largely existing or in advanced stages of development.
The energy transition is so challenging that it requires all technology options to be pursued, including those that bridge to a renewables-based longer term future.
Neil Theobald has more than 40 years’ experience in the oil and gas industry, including 17 years at Chevron, where he was Vice President, Global LNG, Gas Supply & Trading. He has been a Senior Advisor to ANGEA since 2021.
ANGEA is an industry association representing LNG and natural gas producers, energy buyers, suppliers and companies in APAC. Based in Singapore, it works in partnership with governments and societies across the region to deliver reliable and secure energy solutions that achieve national economic, energy security, social and environmental objectives and meet global climate goals.