February 21, 2024
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By Hannah Tennent, former Port Maritime Environment and Sustainability Intern
Hydrogen is the most abundant element in the world, found in the sun, in water, and in our own bodies. While hydrogen has been around since the dawn of the universe, it is now growing in popularity as a promising carbon-emission-free future fuel that can help minimize the effects of climate change. Hydrogen engines and fuel cells can propel all types of vehicles, from cars to heavy-duty trucks, shipping containers, and maritime vessels. When used, it doesn’t emit any greenhouse gases. Because of these attributes, hydrogen could be a key component of how the Port of Seattle will reach the goal of being carbon neutral or better by 2050. Currently, the cost of production is still high and the infrastructure to produce and distribute enough hydrogen for widespread use doesn’t yet exist. Strategies such as developing a regional clean hydrogen hub in the Pacific Northwest, hope to increase supplies of green hydrogen in our area.
The Port is studying how hydrogen might fit into maritime operations and support Seattle City Light’s power distribution system. The outcomes of these studies will provide more information on hydrogen’s potential role in the decarbonization of the Seattle waterfront. Learn more about this “fuel of the stars” and why the Port considers it a worthwhile investment.
Hydrogen (H) is the lightest chemical element. It consists of only one proton and one unpaired electron. This unpaired electron is eager to join with another so hydrogen rarely exists in the world on its own; it is usually part of a compound. Some of the most common compounds are water (H2O), ammonia (NH3), methane (CH4), and table sugar (C12H22O11). When two hydrogen atoms bond to each other, they create molecular hydrogen (H2). At room temperature, molecular hydrogen is a non-toxic, colorless, and odorless gas.
Because hydrogen doesn’t often exist by itself, it must be separated from a compound to create hydrogen fuel. There are a variety of production methods, differentiated by color labels, and each has a varying environmental impact. 95% of the hydrogen produced in the world today is grey hydrogen. (Source: "Use of Hydrogen" at U.S. Energy Information Administration (EIA)). It is used in petroleum refining, food processing, and fertilizer production. Grey hydrogen is made by heating natural gas with high-temperature steam to separate the hydrogen atoms from the carbon atoms in a process called steam reforming. This process releases carbon emissions. To curb the effects of climate change, we need to be using green hydrogen. This process uses electricity produced by renewable sources, like wind or solar, to split hydrogen from oxygen in water. No harmful greenhouse gases (GHGs) are emitted at any point in this process, from production to use.
You may also hear about additional colors in the hydrogen rainbow, including black, brown, blue, and pink. Black and brown hydrogen use oil and coal, meaning they also release GHGs. Blue hydrogen uses the same process as grey hydrogen but the carbon emissions would be captured and stored instead of being released into the atmosphere. This is a developing technology that isn’t yet available at scale. Finally, pink hydrogen is produced by using nuclear fission-powered reactors to generate electricity for electrolysis.
Once green hydrogen is produced, it is versatile. It can be used in both gas and liquid form. Hydrogen can be burned in internal combustion engines or used to create electricity in fuel cells. Fuel cells convert the energy stored in hydrogen into electricity through an electrochemical reaction with oxygen. The negative electrons in hydrogen create an electrical current while the positive protons combine with oxygen to produce water. Heat, electricity, and water are the only byproducts from hydrogen used in fuel cells, unlike fossil fuels used in engines that emit carbon dioxide, other GHGs, and particulate matter. Additionally, because water is both the feedstock and the byproduct, our hydrogen production is not limited, unlike finite reservoirs of fossil fuels.
Fuel cells have many benefits. They can continuously produce electricity as long as they are provided with hydrogen and they are much quieter than internal combustion engines. Reduced noise is good news for marine life if fuel cells replace traditional engines in maritime vessels. Fuel cells can power anything that uses electricity, as well as vehicles specially designed to use them, like cars, heavy-duty trucks, backup power systems, and ships. (Sources: "Hydrogen Fuel Cells Explained" at Airbus; and "Why We Need Green Hydrogen" at Columbia Climate School ). Some example vehicles exist while others, like ferries and tugs, are quickly developing.
Energy density is the amount of energy stored per unit of mass or a given weight for a certain amount of fuel. The higher the energy density of a fuel, the more energy it releases when used and the further a vehicle could travel on a smaller amount of fuel. Diesel has an energy density of 45 megajoules per kilogram (MJ/kg) while marine gas oil, a fuel commonly used by ships, is 42.7 MJ/kg. Hydrogen blows them out of the water at 120.2 MJ/kg. This high energy density is why NASA relies on hydrogen to get rockets into space.
However, hydrogen has a low volumetric energy density, or the amount of energy in a certain volume or amount of the fuel, because it is so light and exists as a gas at room temperature. 1kg of gasoline is about 1/3 of a gallon of gasoline which would be stored in a small container. 1kg of hydrogen gas, at room temperature, would have to be stored in 100 big balloons. (Source: "Scientists Seek to Solve Hydrogen Storage Problems" at Washington University in St. Louis). This isn’t practical so hydrogen gas must be compressed 300-700 times atmospheric pressure to move it in gas form or made into a liquid by cooling it down to cryogenic temperatures. This low volumetric energy density means the direct use of hydrogen is likely to be specific to the differing needs of different types of vehicles and vessels. Perhaps most importantly, hydrogen is a key ingredient in future marine fuels such as ammonia and methanol.
Hydrogen is 14 times lighter than air. (Source: "Hydrogen Compared with Other Fuels" at Hydrogen Tools). This, plus the molecule’s small size, makes it prone to leaking. If the leak occurs in an open area, the small particles will quickly dissipate. However, in confined spaces, the hydrogen can collect. Hydrogen is flammable like many other fuels commonly used today. For a hydrogen fire to start, there must be enough hydrogen pooled together, as well as an ignition source, and the right amount of oxygen. A low concentration of hydrogen requires about the same amount of energy to ignite as natural gas or gasoline. But, as the amount of hydrogen increases, it becomes easier to ignite. (Source: "Hydrogen Safety" at Department of Energy).
Industries that currently use hydrogen fuel, like NASA and fertilizer producers, already have safety protocols in place. Standards and best practices will be established along with new hydrogen projects. While it is critical to advance hydrogen safety, proponents argue that hydrogen’s other characteristics make it safer than traditional fuels. Because hydrogen is non-toxic, a spill would not contaminate the environment. If a hydrogen leak is not contained, it will disperse rapidly, making fires at ground level rare. If propane or gasoline vapor leaks, it is heavier than air, making it much more likely a fire could happen around people and buildings. (Source: "Hydrogen Safety" at National Resources Defense Council).
This recent increase in funding and attention is because renewable energy is declining in cost. Hydrogen has immense potential to help decrease carbon emissions while also being an effective energy carrier, especially for industrial sectors that are difficult to decarbonize. Because renewable resources are available around the globe in more places than fossil fuels, hydrogen would also allow countries that produce it to become more energy-independent.
All these aspects make hydrogen a promising contender and the research funds will lead to the development needed to make a hydrogen industry a reality. We don’t currently have widespread infrastructure that can transport hydrogen. Green hydrogen currently costs more than grey or blue hydrogen because electrolysis is expensive. More investment can encourage innovation, scale up manufacturing, and help bring down this cost.
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