HYDROGEN TRANSPORTATION AND ENERGY STORAGE
Transportation and electric power generation represent the two biggest sources of greenhouse gas (GHG) emissions worldwide, and they continue to rely in large part on finite fossil fuel resources found only in select regions of the world. Hydrogen, by comparison, is a potentially inexhaustible clean resource that could be available anywhere electricity and water exist. Today, hydrogen is widely used to support chemical and refining processes, as well as other industrial uses. However, the surface has barely been scratched of its potential as an energy storage mechanism and as a transportation and power generation fuel.
The use of hydrogen fuel cells for transportation is not new. However, significant research and development is underway to advance these technologies and establish a more reliable, efficient and widespread infrastructure to support them. Unlike natural gas, hydrogen fuel is viewed as a viable alternative to diesel because its energy density is approximately three times greater than any traditional hydrocarbon-based fuel while only emitting water vapor. Hydrogen fuel cell electric drivetrains can be a good alternative to pure electric vehicles, which might have limited range and require longer charging durations. Hydrogen fuel cell vehicles are ideal for drayage operations in which trucks may have continuous duty cycles and require short-duration refueling.
Another opportunity is the use of hydrogen as an energy storage option for supporting electric power. Once processed, large quantities of hydrogen can be stored in fairly small volumes, as compared to the amount of liquefied natural gas needed to achieve the same energy output. Using stored hydrogen as a fuel source for generation could provide an alternate energy storage method to put power back onto the electric grid, in times of low generation from other renewable resources.
The key challenge to moving forward with widespread hydrogen-fueled transportation and electric power generation is the production of pure hydrogen. Although it is the most abundant element on Earth, elemental hydrogen does not exist in abundance naturally. Rather, it must be extracted from compounds that contain it, such as water.
According to the U.S. Department of Energy (DOE), 95% of hydrogen production in the United States is through a process called natural gas reforming, which produces carbon emissions and other GHGs. A more sustainable production opportunity is through electrolysis, which uses electricity to split water into hydrogen and oxygen. Although electrolysis is normally very inefficient, if the electricity used in the electrolysis process comes from renewable resources, then hydrogen production becomes virtually emission-free. Per the DOE, reforming low-cost natural gas provides for a steppingstone today for hydrogen production, but hydrogen production is expected to be augmented by renewables and low-carbon domestic energy sources over the long term.
Renewable energy resources can be used to produce hydrogen locally, particularly during times of curtailment. For example, wind energy in the Upper Midwest of the U.S. is largely curtailed at night. A hydrogen production facility could use this wind power to produce and store hydrogen for power generation needs. Co-locating generation units on-site with renewables and hydrogen production also enables the use of existing electric transmission interconnections, reducing the need for additional delivery infrastructure.