Hydrogen - Energy Policy Analysis: A Conceptual Framework - page 195

composed of substantial amounts of hydrogen and other elements: for example, ethanol (C 2 H 5 OH)
and ammonia (NH 3 ).
Transmission by pipeline is the least expensive way to transport large amounts of hydrogen;
several lines have been built in the United States, near large petroleum refineries and chemical
plants in Illinois, California, and along the Gulf Coast. However, in comparison with the more
than 1 million miles of natural gas pipelines, the current hydrogen pipeline infrastructure in the
United States is very small, less than 1,200 miles in length (USDOE 2010). Moreover, natural gas
pipelines are not suited for hydrogen transport because high-pressure hydrogen leaks easily through
the smallest of holes and embrittles the mild steel used for gas pipeline construction. Pipelines for
hydrogen require different materials, welding procedures, and designs for valves, compressors,
sensors, and safety devices than those used for natural gas (Armaroli and Balzani 2011, 290).
Compressed hydrogen can be transported over highways in high-pressure tube trailers. This
option is used primarily to move modest amounts of hydrogen over relatively short distances. It
tends to become cost prohibitive for distances greater than about 200 miles from the location of
production (USDOE 2010). By comparison, for a given volume, liquefied hydrogen that has been
cooled to -253°C is denser and contains greater energy content than gaseous hydrogen. In the
absence of an existing pipeline, shipping liquefied hydrogen is a preferred method of transporting
hydrogen over long distances because a tanker truck can carry more than a tube truck, at lower
cost (Ekins, Hawkins, and Hughes 2010, 44). However, liquefaction is costly because it requires
a substantial amount of energy. Nonetheless, due to the limited amount of pipeline available, hy-
drogen is often transported as a liquid in superinsulated, cryogenic tank trucks and later vaporized
for use at the receiving site (USDOE 2010).
For a given volume, hydrogen contains a smaller amount of usable energy than other fuels such
as natural gas and gasoline. Because of its low volumetric energy density, hydrogen is comparatively
more costly to transport and store. Principally, this is due to the large initial capital investment
required to construct a new pipeline infrastructure. There are also a number of technical concerns
with pipeline transmission of hydrogen over long distances, including the potential for hydrogen
embrittlement of steel and welds used for pipeline construction, the need for lower-cost, higher-
reliability hydrogen compression technology, and the desire to prevent hydrogen permeation and
leakage from pipeline and other containment materials (USDOE 2010). No ship tankers exist yet
for liquefied hydrogen, but presumably could be built similar to those for liquefied natural gas
(Ekins, Hawkins, and Hughes 2010, 43).
The method by which hydrogen is produced also affects the cost and method of transportation.
Distributed production at the point of use, such as directly at refueling stations or at stationary
power sites, eliminates long-distance transportation costs. Conversely, production in large central
plants results in lower production costs due to greater economies of scale, but requires long-distance
transport that increases transportation costs. Consequently, the costs of hydrogen production and
transportation must be analyzed together (USDOE 2010).
Efforts are being made to better understand the options and trade-offs for hydrogen transporta-
tion from central and decentralized production sites under various delivery scenarios. In the United
States, research is also focused on developing:
s,OWERCOSTMORERELIABLEHYDROGENCOMPRESSIONTECHNOLOGY
s-ORECOSTEFFECTIVEBULKHYDROGENSTORAGETECHNOLOGY
s.EWMATERIALSFORLOWERCOSTHYDROGENPIPELINES
s-OREENERGYEFlCIENTANDLOWERCOSTHYDROGENLIQUEFACTIONPROCESSES
s)NTEGRATEDPRODUCTIONDELIVERYANDENDUSETECHNOLOGIES