Transporting and Distributing Green Hydrogen: A Case Study on Singapore
Tan Wooi Leong
Managing Director, Surbana Jurong
Derek Wong Sun Soon
Senior Director (Energy & Industrial), Surbana Jurong
Leong Hoi Hoong
Business Development Director, Surbana Jurong
Tay Seow Beng
Director (Energy & Industrial), Surbana Jurong
The need to transition to green renewable energies to tackle climate change is clear.
In the pursuit of alternative energy sources, green hydrogen has emerged as a promising source of clean energy, adaptable to all types of transport and storable for long periods of time. However, the green hydrogen economy will not succeed without a safe and efficient infrastructure for transportation of hydrogen.
The processes around the production, handling and storage of hydrogen are well established in the industry. However, the evolution of the infrastructure, particularly in the transportation of hydrogen, presents new challenges in selecting suitable materials to build the pipelines. The critical questions confronting the industry include the best choice of pipeline materials, as well as the best corridor routes to transport green hydrogen in a safe manner.
Transporting hydrogen gases through pipes is the most efficient way for a large throughput. High-pressure gaseous hydrogen is the most common transportation mode at the present. Long-distance transmission pipelines are used to convey high-pressure hydrogen between the production unit and station. Short distance distribution pipelines are used to transport medium and low-pressure hydrogen between the hydrogen station and end-users.
Factors to Consider in Hydrogen Pipeline Material
The hydrogen pipeline material’s susceptibility to hydrogen and the external environment must be considered for safety and efficiency purposes. Exposure to hydrogen can deteriorate the mechanical properties of metals and easily create material fatigue, causing metals to crack under low stress. Three consequences of hydrogen exposure to materials, especially metals, are:
- a decrease in material toughness,
- a decrease in ductility, and
- an increase in the crack rate.
The reduction in the ductility of a metal due to the hydrogen absorbed by it is known as hydrogen-assisted or hydrogen-induced cracking, or hydrogen embrittlement. Hydrogen embrittlement is a degradation mechanism for metals; its severity depends on the temperature. While the embrittlement effect occurs between -100 to +100 degrees Celsius, the effect reaches the maximum around room temperature. Most metals are relatively immune to hydrogen embrittlement at above approximately 150 degrees Celsius. Non-metallic materials such as Reinforced Thermoplastic Pipe (RTP) and Fibre Reinforced Polymer (FRP) have been developed to transport low-medium pressure hydrogen to manage the effects of hydrogen on metals.
The external environment or varying conditions during the transportation process of hydrogen may result in the unexpected degradation of pipeline materials. To ensure a safe handling of hydrogen, operators must consider the impact of the external environment on hydrogen. For example, in wet-dry coastal and industrial areas, chlorides combined with humidity and sunlight may lead to stress corrosion cracking of stainless steel. It may therefore be necessary to reinforce stainless steel or build proper shelter for metal surfaces. Buried pipelines may also require special considerations dependent of soil conditions.
International standards such as the European Industrial Gas Association (EIGA) Doc121/04, provide guidance on the selection of suitable materials for various conditions, pressure and composition of hydrogen.
Factors to Consider in Planning Hydrogen Corridor routes
Hydrogen is more prone to leakage problems compared to other gases due to its small molecular size. International standards such as by the American Petroleum Institute (API) specify the welding requirements, selection and installation of pressure-relieving devices for the safe handling of hydrogen. There are also guidelines provided by the European Industrial Gas Association (EIGA), for aboveground and underground hydrogen pipelines.
Hazard analysis and risk assessment must be performed to determine the route and corridor of the hydrogen pipeline. Every new hydrogen transportation pipeline system must be designed, constructed and operated in such a way that the additional risk to people, property and the environment is within acceptable limits. To this end, a safety analysis should be performed on every new pipeline system or significant modification to an existing system. The safety analysis is a proven way to assess the risks of the pipeline system to the environment, the risks to the pipeline from its environment, as well as to define the measures to be applied during the design, construction and operation of the pipeline, to reduce the probability of occurrence and the consequences of abnormal events.
The safety analysis’ level of detail is based on the population density around the pipe route, the potential severity of an incident, and the likelihood of an incident occuring. The method typically used in a safety evaluation is to determine the individual risk and to show that it is within acceptable limits. Local regulations should be referenced before performing safety analyses and determining acceptable limits.
The EIGA Doc121/04 provides the typical safety distances for hydrogen control and isolating or metering stations.
A preventive maintenance programme should also be put in place for the hydrogen pipeline corridor. Periodic checks should be carried out to ensure the integrity of the pipelines and cathodic protection system are functioning as intended.
Case Study: Hydrogen Gas Pipeline for Carbon Emission Reduction in Singapore
Singapore is aiming to significantly reduce its carbon emission levels to around 60 MtCO2e by 2030 and achieve net zero emission by 2050, as part of its Long-Term Low-Emissions Development Strategy (LEDS).
The Singapore government has been pushing hard for the implementation of solar panels on almost every available rooftop, as well as vacant land and reservoirs in this tiny island state. The authorities have also pushed industries to adopt greener energy such as green hydrogen. This has provided good business opportunities for industrialists in the production, storage, transportation and dispensing chain of hydrogen. The next section will discuss the transportation of hydrogen from a source country to Singapore and its distribution within Singapore.
Hydrogen Carrier for Transportation of Hydrogen
For a successful transition to greener energy with green hydrogen, the transportation of hydrogen is a very important step. The transportation of hydrogen from source to end user can be divided into two parts, as follows:
- Large volume, cross country transmission from source to Singapore; and
- Distribution from landing point to various end users within Singapore.
The methods of transportation can be divided into two major methods, namely:
- High pressure hydrogen gas transmission pipeline; and
- Transportation through different carriers.
The method of transportation through different carriers can be sub-divided into four major methods, namely:
- Compressed hydrogen (CH2). Hydrogen is typically compressed to 700 barg to increase the volume by about 700 times and stored in cylinders built for the transportation of extra high-pressure hydrogen.
- Liquefied hydrogen (LH2). Hydrogen is liquefied to -253 degrees Celsius under cryogenic conditions, which will increase the volume by about 848 times and stored in cryogenic tanks suitable for extremely low temperatures.
- Chemically bonded hydrogen carriers such as ammonia, methanol and Liquid Organic Hydrogen Carrier (LOHC). The hydrogen is bonded to these chemical carriers through a hydrogenation process before its transportation to Singapore. The hydrogen is extracted from its carrier upon reaching the destination through a dehydrogenation process. In most cases, heat is released during hydrogenation process and heat is required during dehydrogenation process.
- Solid-state hydrogen carrier such as metal hydrides and other nanomaterial carriers through physio-absorption. They normally operate within a low pressure of 30-50 barg at room temperature. The solid-state hydrogen carriers are not chemically bonded and thus will require only minimum energy for extraction of hydrogen. However, the current commercially available solid-state hydrogen carriers are low volume or still at low Technology Readiness Level. Thus, these are not widely brought up in discussions for commercial implementation.
Considerations for Transportation Selection
The following factors should be considered when selecting a transportation method prior to adoption:
Based on the above considerations, the most suitable carrier for hydrogen import to Singapore may be the hydrogen gas transmission pipeline. However, there are numerous drawbacks in the adaptation of hydrogen gas transmission pipeline for the import of hydrogen to Singapore, which include the following:
- The hydrogen supply is limited to the source country. In consideration of logistical security and uninterrupted hydrogen supply, this may not be the best option. For the security of supply, the gas pipeline option should be combined with other shipping carrier options to diversify the sources of hydrogen globally.
- Based on extensive studies, the CAPEX and OPEX of gas pipelines beyond 1,000km will increase exponentially, making it less economical when the source of supply is farther than 1,000km from Singapore.
- The pipeline must be well protected against third-party damage, particularly near the shore area. In recent years, it has been observed that well-protected pipeline in deep waters can also be sabotaged by a third party in times of emergency.
Existing Natural Gas Transmission Pipeline in Singapore
Based on the data from Singapore’s Energy Market Authority (EMA), the amount of Natural Gas (NG) imported to Singapore in year 2021 was 10.6 Mtoe (more specifically, 7.4 Mtoe through submarine gas pipeline and 3.2 Mtoe from LNG ships). The import growth from 2020 to 2021 was 4.1%. The total import of 10.6 Mtoe worked out to about 1,190 mmscfd (i.e., 830 mmscfd from PNG and 360 mmscfd from LNG). The main NG injection points in Singapore are as shown in the map below.
The NG injection points are as follows:
- Sakra NG Station from Sumatra PNG;
- Sakra ORF from West Natuna PNG;
- Attap Valley ORF from Malaysia PNG; and
- SLNG Terminal from various sources in the world.
From the map above, it can be seen that:
- Other than Senoko Power Station in the north of Singapore, all power stations are located in Jurong Island and Tuas area.
- All gas transmission pipelines are within Jurong Island and Tuas area and concentrated in the western region for gas supply to Senoko Power Station and Senoko Gasworks.
Based on the reports in local news, PNG supply from Sumatra and West Natuna will be terminated in year 2028. Thereafter, NG supply in Singapore will need to be supported by the SLNG Terminal or a new injection point to be developed within next five years.
Consideration for Green Hydrogen Gas Supply to Singapore via Transmission Pipeline
Prior to embarking on the laying of hydrogen gas transmission pipeline in Singapore, the potential end users, existing infrastructures and other factors will have to be taken into consideration for the implementation of hydrogen gas transmission pipeline in Singapore:
- Source of hydrogen supply: Singapore’s hydrogen supply is projected to be sourced from Southeast Asian countries such as Malaysia, Indonesia, Thailand, Cambodia, Laos and Vietnam, based on an optimum distance of 1,000km of submarine gas pipeline and taking into consideration CAPEX and OPEX. This projection is premised on the source country being fitted with a stable and continuous 24/7 supply of renewable power, such as hydropower, to ensure a continuous supply of green hydrogen.
- Landing point for submarine hydrogen gas transmission pipeline: The landing point for the hydrogen gas pipeline should preferably be close to Singapore’s existing LNG Terminal so that pure hydrogen can be imported and distributed to the new hydrogen network or blended with natural gas from the SLNG terminal to transmit through the existing natural gas supply network. This landing point is recommended in consideration of the imminent termination of two PNG gas supply sources from Sumatra and West Natuna in 2028.
- Hydrogen distribution gas supply network in Singapore: The existing NG gas transmission pipelines as shown in the Network Map above were designed for NG transmission. It is very unlikely that they are suitable for transmission of 100 per cent pure hydrogen. However, it is likely to be suitable for transmission of blended NG:H2 ranging from 10-30 per cent hydrogen blending ratio, as practiced in many countries globally. In view of the above constraint, a new hydrogen transmission pipeline could be laid alongside these existing NG pipelines to give end users the choice to tap either NG or hydrogen or do their own blending within their premises to suit their equipment requirements.
Challenges to lay hydrogen transmission pipeline for distribution in Singapore:
The following challenges should be taken into consideration prior to laying a hydrogen gas transmission pipeline to and within Singapore:
- High population density: Singapore is a very small and densely populated city-state country. Almost every part of the country is either within the urban zone now or in the near future. Thus, the design of the hydrogen gas transmission pipeline must be extra stringent and over and above code requirements, as not many internationally accepted codes will allow high pressure hydrogen gas transmission pipeline to be laid and cut across densely populated areas due to its potential embrittlement and gas leak potential.
- Congested underground services: Almost all utility services are laid under public roads as Singapore has limited land space. This leads to challenges for the hydrogen gas transmission pipeline to be laid according to the required bending radius to allow for the pigging of the pipeline. Besides posing difficulties in pipe laying, works by other services providers within the same road width could lead to third party damage to the hydrogen gas pipeline.
- Frequent diversion for other infrastructure development: Due to limited land space in Singapore, underground services are frequently planned to be diverted to allow for other mega infrastructure projects, such as the construction of new expressways, subways and rapid transit developments. Unlike NG, the Minimum Ignition Energy (MIE) of hydrogen is extremely low at about 0.019 mJ and the Flammable Limit is extra wide at 4 – 75% (LFL ~ UFL). This results in an extra high risk for hot tapping and line stopping for the diversion of hydrogen pipeline during the welding of saddle tee and hot tap cutting. A slight mistake through human error could potentially cause a catastrophic accident. An alternative to hot tapping, line stopping and bypassing for diversion works is to shutdown the pipeline and purge all hydrogen in the pipeline, although that will cause major disruption to end users.
- Requirement for odorisation: To protect the public, odorisation of flammable and explosive gases is required in Singapore. However, odorised hydrogen will not be suitable for fuel cell users, as the purity of hydrogen must be at least 99.970-99.999 per cent pure. This will eliminate mobility vehicles and other industrial users who need fuel cells to be adopted for their power generation from using hydrogen as a fuel.
Research today focuses on overcoming technical concerns such as:
- The potential for hydrogen to embrittle the steel and welds used
- to fabricate the pipelines
- The need to control hydrogen permeation and leaks
- The need for lower cost, more reliable, and more durable hydrogen compression technology
One possibility for rapidly expanding the hydrogen delivery infrastructure is to adapt part of the natural gas delivery infrastructure to accommodate hydrogen. Converting natural gas pipelines to carry a blend of natural gas and hydrogen (up to about 15-20 per cent hydrogen) appears to be the most cost effective option, with modest modifications to the pipeline. Converting existing natural gas pipelines to deliver pure hydrogen may require more substantial modifications, and therefore be costly. Whether operators choose a complete conversion of an existing asset to transport hydrogen or introduce a hydrogen blend, regulatory requirements dictate a series of preparatory actions, such as conducting hazard analyses, risk assessments and safety evalutions.
The safety aspects of hydrogen are naturally related to the properties of hydrogen: ignition limits, diffusion rates, leak rates and interaction of hydrogen with materials. Regarding the degradation of and interaction with other materials, it is important to be aware of the influence of any trace elements that are present, intended or not, and the purity and composition of the hydrogen.
International standardisation organisations include the International Hydrogen Technical Committee (ISO/TC197), the European Industrial Gas Association (EIGA) – Hydrogen Transportation Pipelines, the American Society of Mechanical Engineers (ASME) ASMEB31.12-2014 “Hydrogen Pipelines”, and CGAG-5.6-2005 “Hydrogen Pipeline Systems”. These organisations specify standards for the production, storage, transportation, testing and use of hydrogen energy.