Centrally produced hydrogen must be transported to markets. The development of a large hydrogen transmission and distribution infrastructure is a key challenge to be faced if the United States is to move toward a hydrogen economy. A variety of hydrogen transmission and distribution methods are likely to be used. Larger industrial users rely on pipelines and compressors to move the hydrogen gas.

Pipeline Systems

Currently, more than 99 percent of all the hydrogen gas transported in the United States is transported by pipeline as a compressed gas. Pipeline transmission of hydrogen dates back to the late 1930s. The pipelines that carry hydrogen generally have operated at pressures less than 1,000 pounds per square inch (psi), with a good safety record. As of 2006, the U.S. hydrogen pipeline network totaled over 1,200 miles in length, excluding on-site and in-plant hydrogen piping More than 93 percent of the U.S. hydrogen pipeline infrastructure is located in just two States, Texas and Louisiana, where large chemical users of hydrogen, such as refineries and ammonia and methanol plants, are concentrated.

The existing U.S. hydrogen pipeline network is only one-third of 1 percent of the natural gas network in length and has less than 200 delivery points. Also, because of concerns over potential leakage, the hydrogen pipes tend to be much smaller in diameter and have fewer interconnections. Special positive displacement compressors are also required to move hydrogen through the pipelines. The length of hydrogen gas piping tends to be short, because it is usually less expensive to transport the hydrogen feedstock, such as natural gas, through the existing pipeline network than to move the hydrogen itself through new piping systems. Historically, welded hydrogen pipelines have been relatively expensive to construct (approximately $1.2 million per transmission mile and $0.3 million per distribution mile). Consequently, the pipelines have required a high utilization rate to justify their initial capital costs. More recently, polyethylene sleeves and tubing systems have emerged as a possible low-cost alternative solution for new hydrogen distribution systems, with total capital investments for transmission piping potentially dropping to just under $0.5 million per mile (in 2005 dollars) by 2017 and with commensurately lower costs for distribution lines.

How a centralized hydrogen transmission and distribution system will evolve is unknown, and therefore the costs cannot be estimated with a high degree of confidence. The costs will depend on where the pipelines are sited, rights-of-way, pipeline diameter, quality and nature of the pipeline materials required to address the special properties of hydrogen, operating pressures, contractual arrangements with hydrogen distributors, financing and loan guarantees, the locations of dispensing stations relative to distributors, and how applicable environmental and safety issues in the production, transmission, distribution, and dispensing of hydrogen are addressed. Because all hydrogen gas has to be manufactured, hydrogen production facilities may be located in ways that minimize overall production and delivery costs.

Liquid Hydrogen (Cryogenic) Transport

Hydrogen can be cooled and liquefied in order to increase its storage density and lower its delivery cost. There are currently four liquid hydrogen suppliers and seven production plants in the United States with a total production capacity of about 76,495 metric tons per day. Those facilities support about 10,000 to 20,000 bulk shipments of liquid hydrogen per year to more than 300 locations. Most long-distance transfers of hydrogen use large cryogenic barges, tanker trucks, and railcars to transport the liquid hydrogen. NASA is the largest consumer of liquid hydrogen. The chief constraints to widespread use of this hydrogen transportation mode relate to the energy losses associated with liquefying hydrogen and the storage losses associated with boil-off.

Compressed Hydrogen Gas Cylinders

Hydrogen is also distributed in high-pressure compressed gas “tube trailer” trucks and cylinder bottles. This delivery method is relatively expensive, and typically it is limited to small quantities and distances of less than 200 miles.

Alternative Chemical Carriers

Hydrogen also can be transported using hydrogen-rich carrier compounds, such as ethanol, methanol, gasoline, and ammonia. Such carriers offer lower transportation costs, because they are liquids at room temperature and usually are easier to handle than cryogenic hydrogen; however, they also require an extra transformation step, with costs that must be weighed against the cost savings associated with transporting low-pressure liquids. Hydrogen carriers such as methanol and ammonia may also present some additional safety and handling challenges.

Hydrogen Fuel Distribution

The most economical methods for distributing hydrogen depend on the quantities and distances involved. For distribution of large volumes of hydrogen at high utilization rates, pipeline delivery is almost always cheaper than other methods—except in the case of long-distance transportation, e.g., over an ocean, in which case liquid hydrogen transport is cheaper.

Source: U.S. Energy Information Administration