NyOrka Page 6 12/18/2008The weight <strong>of</strong> <strong>the</strong> full hydrogen tank is still higher than that <strong>of</strong> <strong>the</strong> gasoline fuel tankbecause <strong>of</strong> <strong>the</strong> material and safety requirements <strong>of</strong> <strong>the</strong> container; Materials mustwithstands corrosive attack from hydrogen and oxygen and can hold extreme pressure aswell as prevent diffusion through walls and system connection. Whereas hydrogen ishighly volatile, disperses extremely fast, burns with an invisible flame and must beextremely pure to make fuel cells work properly, <strong>the</strong>n hydrogen production, storage anddistribution must be optimised along every step within <strong>the</strong> <strong>energy</strong> conversion path.Fur<strong>the</strong>r conversion factors have been issued in tables and explained in variouslanguages 3 .2.1 Methods and pathways for productionThree main methods exist for <strong>the</strong> mass production <strong>of</strong> hydrogen; Steam reforming, partialoxidation, and electrolysis. Emerging technologies are <strong>the</strong>rmolysis and <strong>the</strong>rmo-chemicalcycles, which have not been built yet and operate at temperatures above 1000°C. Theclassic methods are described in text books such as CJ Winter’s: Hydrogen as an <strong>energy</strong><strong>carrier</strong> 4 .Approximately 95 percent <strong>of</strong> hydrogen is currently produced via steam reforming.Steam reforming is a <strong>the</strong>rmal process that involves reacting natural gas or o<strong>the</strong>r lighthydrocarbons with steam. This is a three-step process that results in a mixture <strong>of</strong>hydrogen and carbon dioxide, which is <strong>the</strong>n separated by pressure swing adsorption, toproduce pure hydrogen. Steam reforming is considered <strong>the</strong> most <strong>energy</strong> efficientcommercialized technology currently available (η = 75-82%), and is most cost-effectivewhen applied to large, constant loads. <strong>In</strong> this case <strong>the</strong> hydrogen must be transported to <strong>the</strong>market and purified to fit <strong>the</strong> use within PEM fuel cells. Research is being conducted onimproving catalyst life and heat integration, which would lower <strong>the</strong> temperature neededfor <strong>the</strong> reformer and make <strong>the</strong> process even more efficient and economical. Recentdemonstrations where hydrogen vehicles, especially buses have been tested in realtransport service, difficulties have arisen with small scale gas-reformers <strong>of</strong> <strong>the</strong> size thatwould fit hydrogen refuelling stations 5 These problems have not been defined properlywithin <strong>the</strong> industry but refer to both operational and purity problems. Due to <strong>the</strong>sediscoveries <strong>the</strong> reforming technology that has been referred to as straight forwardexercise <strong>of</strong> down-scaling an established technology before broad on site applications <strong>the</strong>reforming procedures will not be addressed within this chapter <strong>of</strong> future technologypathways.Partial oxidation (auto-<strong>the</strong>rmal production) <strong>of</strong> fossil fuels is ano<strong>the</strong>r method <strong>of</strong> <strong>the</strong>rmalproduction. It involves <strong>the</strong> reaction <strong>of</strong> fuel with a limited supply <strong>of</strong> oxygen to produce ahydrogen mixture, which is <strong>the</strong>n purified. Partial oxidation can be applied to a wide range<strong>of</strong> hydrocarbon feedstock, including light hydrocarbons as well as heavy oils andhydrocarbon solids. However, it has a higher capital cost because it requires pure oxygen3 An Icelandic/english version is to be found on www.new<strong>energy</strong>.is/publications.4 Winter, Carl-Jochen & Joachim Nitsch eds 1988; Hydrogen as an <strong>energy</strong> <strong>carrier</strong>, technologies, systems, economy(translation from: Wasserst<strong>of</strong>f als Energieträger) Springer Verlag, Berlin, New York.5 HyFleetCute; <strong>the</strong> hydrogen bus demonstrations in Berlin, Nov 2008, presentation by Total;
NyOrka Page 7 12/18/2008to minimize <strong>the</strong> amount <strong>of</strong> gas that must later be treated. <strong>In</strong> order to make partialoxidation cost effective for <strong>the</strong> specialty chemicals market, lower cost fossil fuels must beused. Current research is aimed to improve membranes for better separation andconversion processes in order to increase efficiency, and thus decrease <strong>the</strong> consumption<strong>of</strong> fossil fuels.The direct use <strong>of</strong> natural gas in <strong>the</strong> <strong>energy</strong> mix is growing rapidly, not <strong>the</strong> least as fuel fortransport and is <strong>the</strong>refore in direct competition with hydrogen on <strong>the</strong> market. Centralproduction <strong>of</strong> hydrogen from natural gas demands a different approach to distribution andinfrastructure as compared with hydrogen that is made in a distributed manner; mainlywith electrolysis from water or directly from solar power plants.Figure 1 Overview <strong>of</strong> <strong>energy</strong> streams, from source to user phase. Any source <strong>of</strong> <strong>energy</strong> can become asource <strong>of</strong> hydrogen and <strong>the</strong>refore it may give all regions an opportunity for local production andspecific local use.
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