Solving the Hydrogen Transport Problem

Solving the Hydrogen Transport Problem

Marcus Brücher

If there is anything 2022 has taught us, it is that the success of the Energy Transition does not solely hinge on reducing greenhouse gas (GHG) emissions. It also depends on creating a secure, affordable, and equitable energy system for all.

 Achieving this feat requires a diverse and balanced energy mix. While a world dominated by renewables is undoubtedly the future, the transformation cannot happen overnight.

 With more than 10% of the global population lacking access to reliable power and global energy demand projected to increase by nearly 50% over the next three decades, we must come to terms with the uncomfortable truth that hydrocarbons (particularly natural gas) will have to be part of the equation for the foreseeable future. 

Hydrogen also has an important role to play. The International Renewable Energy Agency (IRENA) projects that hydrogen and its derivatives could account for up to 12% of worldwide energy consumption by 2050 [1]. 

Sustainably meeting this demand will require an accelerated build-out of renewable energies and electrolyzer capacity for “green” hydrogen production. Carbon capture, utilization, and storage (CCUS) technologies will also be needed to expand the range of use cases for “blue” hydrogen.

 However, there is another piece to the puzzle if we are to realize the full potential of hydrogen as a clean energy carrier: reliable and efficient transport infrastructure.

 Hydrogen Transport Options

It is logical to expect that in the future, a large portion of hydrogen production will occur long-distances away from its point of end-use. This is particularly the case with green hydrogen, as electrolysis plants typically must be near a renewable generating source, which often tend to be in remote or even offshore locations.

 The task of transportation is not simply a matter of getting hydrogen from point A to point B. But rather doing it in a sustainable manner so that any emissions reductions achieved from its use – whether that be for mobility, industrial use, power generation, etc. -- are not offset by the mode of transport.

 Today, there are several proven methods of transporting hydrogen, including:

•  Rail / Truck - While storage in high-pressure gas containers or insulated liquid containers for transportation by rail or truck is feasible, it is not cost-efficient for moving large volumes. The liquefaction process, which requires cooling hydrogen to -253°C (only 20°C above absolute zero), consumes as much as 30% of its energy content [2]. Additionally, some of the hydrogen is lost via “boil off” when using small tanks with large surface-to-volume ratios.
•  Liquid eFuels – A more economical option is to further process the hydrogen to create liquid eFuels. ·     

eMethanol (CH3OH), in particular, holds enormous potential as a decarbonization agent and is produced by chemically combining CO2 with green hydrogen. Its potential lies in the fact that the CO2 used can be obtained via carbon capture processes. This both avoids the emission of further CO2 and uses it as a resource and raw material for a new energy carrier. Utilizing CO2 from Direct Air Capture (DAC) is also possible, though it is very energy intensive.

Similarly, eAmmonia (NH3) is formed by combining green hydrogen with nitrogen obtained from air separation (green Ammonia) or from reforming of natural gas (blue Ammonia). With about 175 kilograms of hydrogen per ton, Ammonia represents a highly efficient transport medium. Additionally, it can be transported using established infrastructure (i.e., seaborne tankers, trucks, rail, etc.). These factors have led many shipping/marine operators to consider it as a potential long-term replacement for traditional fuel oil.

• Liquid Organic Hydrogen Carriers (LOHCs) – LOHCs are organic compounds used as a storage medium for hydrogen. Hydrogen is absorbed by the LOHC at the point of generation, transported, and then released via a chemical reaction at its point of end-use. 
• Pipeline - Among all transport options, pipelines remain the most economical for moving large volumes of hydrogen reasonably long distances. This is largely due to the high calorific value and compressibility of hydrogen, which gives it a high energy density. 

Converting Natural Gas Pipelines for Hydrogen

 Although it is not widely known, pure hydrogen pipeline systems of several thousand kilometers in length have been in operation for decades.

 While new systems will be needed to accommodate increased hydrogen supply in the coming years, the high cost, time, and regulatory complexities associated with building new pipelines has led many stakeholders across the industry to explore the possibility of converting existing natural gas infrastructure for hydrogen operation.

 The transport energy density of hydrogen is only slightly lower than that of natural gas. As a result, blending natural gas with hydrogen or replacing it entirely would have little impact on the energy transport capacity of the line. However, modifications, particularly to rotating equipment, may be necessary to handle the hydrogen-natural gas admixture.

 Compression Requirements

 For pipelines transporting 100% hydrogen, modern reciprocating (i.e., piston) compressors are currently the most energy efficient solution, as compression efficiency is not compromised by the lower molecular weight of the gas. By increasing drive power and the number of cylinders in the compressor, and operating units in parallel, transport capacities as high as 750,000 Nm³/h can be achieved economically.

Siemens Energy has more than 2 million horsepower of reciprocating compression installed in hydrogen-rich services, including tail gas, feed gas, and make-up services, as well as pipeline and storage. 

For higher flows, multiple reciprocating compressors are required, which increases investment costs and footprint. In such cases, it may be possible to meet requirements using one or more turbocompressors, despite their lower energy efficiency.

 Siemens Energy experience with hydrogen turbocompressors is extensive. With our STC-SVm platform, we have fostered a design that is capable of high rotational speeds. This allows for a smaller and lighter compressor unit with fewer stages than legacy machines, making it particularly advantageous for the types of high-flow hydrogen applications that will be required in the coming years.

Many existing turbocompressors in pipeline applications today can be operated with a low content of hydrogen in the gas stream. However, as the percentage of hydrogen by volume increases, modifications to the machine are necessary to ensure safe and efficient operation.

 Generally speaking, no major changes to compressor hardware are required for admixtures with less than 10% hydrogen by volume. Even up 40% hydrogen content, the compressor housing can be kept. Although modifications/adjustments to impellers, feedback stages, and gears are likely needed.

 For pipelines with greater than 40% hydrogen content, replacement of the compressor is the most practical solution.

 Looking to the Future

 Hydrogen is poised to play a pivotal role in the global Energy Transition. However, its potential as a decarbonization agent will be severely hindered without a safe and efficient transport network.

 While several modes of transportation are needed to accommodate the wide range of end-use applications, establishing an expansive hydrogen economy is not possible without long-distance pipelines.

Many of the technical challenges that exist around converting existing natural gas infrastructure for hydrogen operation can be solved using today’s technologies.

 Success will ultimately come down to execution and this starts by acknowledging the reality that no single entity can drive transformation alone. A truly collaborative effort between operators, OEMs, government, regulators, etc. is required to move projects forward and ensure that we do not fall behind on the quest for net-zero.

 References:

 1.    International Renewable Energy Agency (IRENA)

2.    U.S. Office of Energy Efficiency and Renewable Energy (EERE)

3.    Adam, Peter. "Opportunities and Challenges in Converting Existing Natural Gas Infrastructure for Hydrogen Operation." Paper presented at the Abu Dhabi International Petroleum Exhibition & Conference, Abu Dhabi, UAE, November 2021. doi: https://doi.org/10.2118/208033-MS