Hydrogen Blending Projects

Hydrogen can be directly blended into existing natural gas systems, offsetting fossil fuel energy with low carbon energy – provided the hydrogen source is clean, of course. This can create a massive demand for low carbon hydrogen in the near term, supporting the development of local production markets. It also allows for connecting the electric and gas networks, as hydrogen can be produced from excess electricity instead of curtailing renewables and can subsequently be blended into the natural gas grid instead of stored above or underground.

Hydrogen blending offers a near-term decarbonization solution for hard to decarbonize sectors like building and industrial heating, which can be difficult to electrify. What’s more, there are efforts around the world to develop membrane technology that can separate the hydrogen and natural gas components into individual streams of high purity, which would offer the opportunity of using the gas network to store and transport pure hydrogen from production source to end-user.

Hydrogen blending is a solution with enormous potential for societal significance and community impact, but there are still technical, safety, regulatory, public acceptance, and economic challenges that need to be overcome before it can be widely implemented. There is close to a hundred hydrogen blending pilot & demonstration projects around the world addressing these challenges and advancing the industry.

Hydrogen burns fast, has a wide flammable region, high diffusivity, and low ignition energy when compared to natural gas. Admixing hydrogen in natural gas will impact various properties of the fuel, including key safety properties such as explosivity, dispersion, ignition, and flammability.

The following summarizes some of the key safety challenges and ongoing research for hydrogen blending in natural gas systems:

Hydrogen is a much smaller molecule than methane with lower viscosity and a lower kinetic diameter, so it is more difficult to prevent hydrogen systems from developing leaks, even in pipework that was ‘leak tight’ when tested with nitrogen. Hydrogen is also difficult to detect, with an invisible flame that generally cannot be detected from typical infrared flame detectors, requiring ultraviolet detection.

Natural gas is odorized for commercial and residential use, typically using sulfur-based odorants, to aid in the detection of leaks and operator safety during repairs. Pure hydrogen, which is also naturally odorless, is not odorized as it has historically been strictly for industrial use. At this time, there is no known odorant suitable for pure hydrogen that is light enough to “travel with” hydrogen at an equal dispersion rate, meaning the hydrogen will eventually separate from the odorant. However, for hydrogen blending projects at least up to 20% by volume, typical natural gas odorants can be used as research has shown that hydrogen is not expected to separate from the natural gas in this range. Further research and development will be required for greater blend levels and particularly for the potential transition to a 100% hydrogen network.

Hydrogen can cause metal embrittlement and subsequent failure in high-strength steels, or can leak through joints and connections in piping. Generally, plastic piping (e.g., polyethylene) is more suited to hydrogen blending as there are limited concerns with materials integrity. Metal embrittlement is driven by the partial pressure of hydrogen in the blend, which increases with system pressure and hydrogen content, making embrittlement more of a concern for high-pressure transmission systems than low-pressure distribution systems.

Accurate measurement of gas composition and flow rates are essential to ensure correct transactions and billings for local distribution companies (LDCs). Since the addition of hydrogen into natural gas changes the properties of the gas, for example the calorific value gas and Wobbe number, accuracy and compatibility of existing metering equipment with the presence of hydrogen needs to be understood. Gas quality and accurate measurement challenges can be summarized into the following sub-topics:

Current gas chromatographs generally are not compatible with hydrogen blending. Alternatives are available for measuring the hydrogen content and calorific value of blended gas.

As hydrogen blending changes the energy content of the delivered gas, this needs to be accounted for in customer billing to ensure accurate transactions based on energy delivered.

Some meters may contain materials incompatible with hydrogen service that are susceptible to fatigue cracking or leaking.

In the race to transform our energy systems, a greener hydrogen economy is emerging at an exponential rate. Hydrogen blending is no longer a distant dream; it’s here - happening now, with accelerating advancements from around the world. There are a range of topics that are important to system planning and network management for local distribution companies (LDCs) pursuing or interested in pursuing hydrogen blending projects in their natural gas distribution systems, including:

• Energy resiliency and reliability of renewables
• Emissions reductions from hydrogen blending
• Network capacity and management
• Injection and blending stations
• Compression and pressure management
• Standards and codes

Hydrogen burns fast, has a wide flammable region, high diffusivity, and low ignition energy when compared to natural gas. The effects of added hydrogen in methane on combustion properties are well understood, and many original equipment manufacturers (OEM’s) already have considerable experience with other hydrogen rich fuels, such as town gas.

The sensitivity of any particular end-use network or customer to hydrogen blending should be evaluated on a case-by-case basis to evaluate risk and mitigation measures. Most studies show that impacted properties can be controlled using more robust control systems or mitigation strategies.

State-of-the-art knowledge, opportunities, and risks with the various end-uses of hydrogen-natural gas blends can be divided into the following subtopics:

The calorific value of hydrogen-natural gas blends is lower than natural gas alone due to the lower energy content by volume of hydrogen, meaning that the rating of end-use equipment is decreased due to the lower energy content provided by the same volume of fuel. Properties such as flame velocity and temperature increase with increasing hydrogen addition, effecting flame stability and pollutant emissions. The increase in flame velocity and temperature causes a higher risk of flashback and elevated NOx emissions which must be mitigated.

Generally, demonstration has shown that existing low pressure residential and commercial end use appliances, including water and space heating, cooking stoves and ovens, fireplaces, etc., are compatible with hydrogen blending at least up to 20% by volume and potentially higher. Several organizations have tested blending up to 40% or more in typical residential appliances with no issues. Going forward, new appliances should be designed with hydrogen blending and potential 100% future conversion in mind.

Hydrogen blending can pose higher concerns for industrial end-use customers depending on their equipment and processes. Generally, gas turbines, engines, compressors, and boilers can handle up to 5% hydrogen blending with no issue due to allowable gas purity ranges, while restaging or full replacement may be required for higher blends. Equipment manufacturers today are producing equipment capable of handling much higher blends of hydrogen.

Due to the use of high strength steels and high pressures for CNG storage tanks, hydrogen blending is generally incompatible with CNG applications as hydrogen poses safety and integrity concerns for these materials.

A technology rapidly being advanced, hydrogen-natural gas separation provides an opportunity to (1) use the natural gas network as a storage and transport system for delivering pure hydrogen to end users, and (2) protect end users sensitive to hydrogen. This technology is not quite commercial or proven, however there are efforts globally to advance this solution and lower the costs.