|
Trains have long been considered a more fuel efficient way
to haul freight than trucks, but now hybrid locomotives look to make them an
even more efficient option.
Martin Schroeder, Chief Engineer of the American Public
Transportation Association states, "Reducing fuel use, improving efficiency and reducing CO2 pollution have been technical challenges in the transportation industry for many decades. The advancements we see today in energy storage, clean propulsion and hybrid vehicles had their start in the automotive industry back in the 1970's."
In 1980, the average train used four liters of fuel to move
one ton of freight 380 kilometers, by 2007 the average distance traveled had
increased to 700 kilometers. Over the past 25 years, fuel efficiency in diesel
locomotives has increased 85%.
Mr. Schroeder explains, "The type of hybrid depends on the type of rail service and the type of vehicle. Passenger light rail and heavy rail vehicles electrified by overhead or third-rail contact systems may incorporate energy storage. Most light rail and heavy rail vehicles are capable of regenerative braking through their electrical drive... Energy recovered during braking can be stored in batteries or returned to the electrical distribution system for later use."
Hybrid trains use an onboard rechargeable energy storage
system (RESS). Surplus energy from regenerative braking is stored and when
needed transferred directly to the transmission system. Storage systems can use
dynamic breaking or even shutdown the main power source while idling to
conserve more power. Reducing energy consumption is a main draw of the switch
to Hybrid trains as well as achieving cost reductions. Various battery
technologies including lithium-ion, nickel-cadmium and sodium/iron chloride
have also been suggested and are currently being tested in rail applications.
Large freight railway grew 47 percent between 1990 and 2007
and rail shipping has been more fuel-efficient than trucking for at least the
past few decades. With electric trains having no other carbon emissions than
what was generated at the utility and electric diesel hybrids having cut
emissions by 20%, the efficiency of rail continues to grow. The most efficient
hybrid rail option would appear to be Hydrail or Hydrogen Rail. Emitting only water
as a byproduct of combustion, hybrid trains also are able to store the massive
storage tanks required of Hydrogen implementation.
Mr. Schroeder feels that, "The challenge of energy storage and design is providing enough energy density to minimize weight, size and cost increases. Current storage devices typically have less than ten percent the energy density of diesel fuel."
Challenges arising in the development of hybrid locomotives
mirror those found in the auto industry. Utilizing technologies created in the
auto industry such as regenerative braking, hybrid power train and fuel cell
power allow hybrid trains to operate more efficiently. The issues of power
density and durability are increased in scale with the size of rail
applications. Also like their automotive counterparts, hybrid trains are
considerably more expensive up front yet allow for rapid return of investment
through lower operational fuel usage.
http://www.scientificamerican.com
http://en.wikipedia.org/wiki/hybrid_train
http://www.airwaterland.ca/article.asp?id=485
http://www.enn.com/sci-tech/article/24048
http://www.gereports.com
http://www.hydrogencarsnow.com | 
