The past year witnessed several announcements of hydrogen initiatives with countries such as France and Germany approving strategies of 8.2 and 10.6 billion dollars respectively for the development of carbon free hydrogen. Meanwhile, Saudia Arabia plans to become one of the world's largest green hydrogen producers by 2025 with its 5 billion dollar plant Helios, powered by renewables in the city of Neom. Globally, more than 200 hydrogen projects have been announced from production to end use with an estimated investment of more than USD 300 billion just through 2030.
Hydrogen has been getting a lot of interest around the globe from governmental bodies, intergovernmental organizations, and several key players coming from the energy sector, the industrial sector, and the transportation sector. This note is intended as an introduction to hydrogen : what's its importance currently and why is it increasingly seen as key to future energy systems.
Hydrogen as an input to industrial processes
Although the increased attention to hydrogen is recent, hydrogen is a well-known and abundant compound that is already being used around the world with a total demand reaching 115 Million tons as reported by the IEA for the year of 2019.
So far, the demand for hydrogen has been mainly directed towards industrial purposes within the chemical and petrochemical sectors and the production of steel from iron. The IEA’s The Future of Hydrogen reports that oil refining is the activity that utilizes hydrogen the most with a demand estimated at 38Mt/year followed by the production of ammonia (80-90% of which is used in fertilizers, the remaining covers household cleaning products and industrial and manufacturing uses such as refrigeration) at 31 Mt/year, then methanol production and iron and steel at 12 Mt/year and 4 Mt/year respectively.
For 70 million tons of this demand, hydrogen is utilized for oil refining and ammonia production in its pure form with some minor additives. The remaining 45 million tons are hydrogen present in a mixture of gases and is used for other industrial processes such as methanol production and steel production (IEA, The Future of Hydrogen).
Hydrogen Production : past and present
Up to 99% of hydrogen is produced through well established technologies broken down as follows: 50% from natural gas mainly using Steam Methane Reforming (SMR) process, 30% from the cracking of oil products, 18% from coal gasification, whereas the remainder is the production of hydrogen as a biproduct or using electrolysis (IEA, World Energy Outlook 2018).
These processes are carbon intensive, the most intensive being coal gasification at 19 tons of CO2 emitted for every ton of hydrogen produced (19 tCO2/tH2), followed by the cracking of oil products at 12tCO2/tH2, and 10 tCO2/tH2 using SMR. The IEA, The Future of Hydrogen estimates that hydrogen in its pure form leads to emissions of nearly 830 MtCO2/yr.
Another way of understanding CO2 emissions from traditionally applied technologies is to see it in relation to energy content of hydrogen: 1 kWh from hydrogen (~30 gr H2) leads to emissions of 570g CO2/kWh from coal sourced hydrogen, 360g CO2/kWh from oil products, and 300g CO2/kWh from SMR.
Hydrogen as a vector for large scale decarbonization
In 1998, the Hydrogen Technology Advisory Panel (HTAP), in the United States, identified hydrogen as an important energy option in their review of the state of hydrogen technologies. At the time, the cost of hydrogen from electrolysis, inefficient fuel cell technologies and inexistent enabling technologies led to hydrogen losing traction in the market.
As renewable energy costs are decreasing and fuel cell technologies and electrolysis are improving, green hydrogen is getting closer every day to economic parity. With stronger incentives to reduce CO2 emissions, abundance and versatility of hydrogen, the chemical compound is regaining momentum.
Due to its high specific energy content (~33 kWh/kg) compared to traditional fuels such as diesel (~13 kWh/kg), natural gas (~15 kWh/kg), and gasoline (~13 kWh/kg) hydrogen is a good energy carrier, enabling it to replace traditional fuels in their respective applications while leaving a much smaller carbon footprint.
Due to the ample knowledge of hydrogen’s properties, its utilization in a wide range of applications has been mastered.
Low carbon hydrogen production
In order to overcome the issue facing emissions from well established technologies such as SMR and coal gasification, the pairing with carbon capture, utilization and storage (CCUS) technology is considered. With the aim of achieving a 90% capture rate from CCUS, emissions could fall to 2 and 1 tCO2/tH2 for coal gasification and SMR respectively (IEA, The Future of Hydrogen).
Another means of production of hydrogen is electrolysis, which is a well established process that is not yet widely used. The electrolysis process does not produce CO2. The electricity used in the process is the main source of CO2 in such a process.
When using low carbon electricity, hydrogen produced through electrolysis is carbon neutral.
For example, using renewable energy sources for electrolysis, known as green hydrogen, or nuclear power, known as pink hydrogen, are arguably two carbon neutral technologies to produce hydrogen.
Emerging uses for green hydrogen
Due to its versatility, the deployment of green hydrogen is emerging in the transportation sector and in buildings and power generation to reduce the carbon footprint of these sectors.
In transportation, hydrogen has been successfully deployed in heavy duty vehicles from construction forklifts to large trucks for freight transport in France, China, Japan, and the United States as reported by H2-Share. Also, hydrogen fuel cell electric vehicles (FCEV) are emerging in the commercial vehicles market with Toyota among other car manufacturers making their own models. Overall, there are more than 10,000 light vehicles currently on the streets worldwide.
As for rails and trains, a couple of hydrogen fueled trains have been deployed in Germany as part of decarbonizing their rail industry and switching from diesel. The UK have taken similar steps with Breeze and Hydroflex aiming to fit their diesel trains with hydrogen fuel cells and storage. Meanwhile France plans on decarbonizing their unelectrified rails with hydrogen trains.
A much less mature technology is hydrogen driven shipping, with only some projects and concepts being planned and announced. By the end of 2021 a cargo vessel and a ferry both powered by hydrogen are expected to be launched as part of the Flagship project in Europe.
As for aviation, the HyPort project is deploying hydrogen infrastructure for vehicles around the Toulouse airport. The project consists of constructing hydrogen stations in order to fuel vehicles that service the airport.
For actual flight using hydrogen, several aspects are to be considered regarding how hydrogen is being used whether as a gas, liquid, or source for synthetic fuels. Hydrogen has a greater specific energy (142 MJ/kg vs 43 MJ/kg), but a lower energy density (3-11 MJ/l vs 35 MJ/l) than kerosene which may lead to changes in plane design and airport infrastructure. Another consideration is the usage of hydrogen in fuel cells or in gas turbines or to produce synthetic kerosene.
Global emissions from buildings mounted to 3 GtCO2 for the year 2019. 80% (2.4 GtCO2) of which is attributed to space and water heating from the combustion of fossil fuels (IEA, Energy Technology Perspectives 2020).
Blending hydrogen into existing natural gas networks, heating with methane produced from hydrogen, heating using electricity generated from hydrogen by fuel cells, or heating using hydrogen boilers are proposed solutions to decrease the carbon footprint of buildings.
For example, hydrogen can be blended into existing natural gas infrastructures with ratios reaching up to 20% in order to reduce carbon emissions. This has been deployed in both France (GRHYD) and the UK (HyDeploy).
Power generation and grid services
In times of excess renewable energy, hydrogen produced from electrolysis can be stored in salt caverns or in the form of ammonia for long term and seasonal storage and to avoid curtailment. Converting electricity to hydrogen and hydrogen back to electricity has an overall efficiency of almost 40%.
Hydrogen power generation solutions such as: co-firing ammonia in coal power plants, using hydrogen rich gases in gas turbines, or the direct utilization of hydrogen in fuel cells can offer flexibility to support the grid during peak hours. This is particularly of interest in systems where the marginal cost of base power is significantly lower than that of peak power.
Hydrogen for power is also a good alternative for island systems, presenting multiple advantages compared to hybrid generation options : lower carbon footprint, economic competitiveness and resilient logistics.
In Denmark, electrolysis is used to support the grid and store excess energy in the form of hydrogen at the Hybalance plant which is then used in industry and transport.
The Hyflexpower project by Engie aims to use electricity to produce hydrogen similar to what has been done in the HyBalance project and then utilize this hydrogen to produce power again. In the first phase, hydrogen will be mixed with natural gas. For the next phase, power will be produced from 100% hydrogen without natural gas.
According to the IEA’s Net Zero by 2050 scenario, these emerging uses of hydrogen may lead to an increase in demand of around to 141 MtH2 per year by 2030. This emerging market's size is estimated at ~210 bn€ of annual revenues.
Recent developments have shown a growing interest in hydrogen production and utilization. The IEA envisions up to 150 Mt of low carbon hydrogen being produced by the year 2030 on the road to achieving carbon neutrality by 2050. Hydrogen's specific energy allows it to be a good candidate to replace hydrocarbons in hard to abate sectors like transport, building, and power generation. Mass production through low carbon processes is a near term development. Hydrogen's abundance, its versatility and the well mastered processes required to produce green hydrogen have made it a promising fuel for the future.