Generation, of the energy carrier HYDROGEN In context ... - needs

NyOrka Page 23 12/18/20084.2 Criteria for hydrogen applicationsThe production pathway selected for further analysis emphasises the electrolytichydrogen production in as competitive and secure operation as possible and thenadjusting these to optimal efficiency. The current bulk production method; steamreformation from gas will also be used as reference.4.2.1 Efficency of productionCurrent electrolysers show an efficiency of about 65 - 75% but the goal is to raise it up to87% by 2020. In future models the technology may allow for electrolysis to be carriedout under high pressure and partial substitution (up to 20%) of the electric energy withhigh heat. As a rule the efficiency of low pressure electrolysers is given with thefollowing function:ηsystem=m * H 2HH 2EElectrwhere m H2 : Mass of produced hydrogenH H2 : Heat value of hydrogenE Electr : Amount of electricity 24If the pressure in the electrolyser is raised this is done only to reduce the volume ofhydrogen and therefore the space of hydrogen stations. When high heat is added to theprocess the voltage can be lowered from 1,48Volt to 1,23Volt.4.2.2 Quality criteriaModern PEM fuel cells are sensitive to impurities carried in hydrogen. The purity issometimes simplified to four, five or six nines (99,99%; 99,999% and 99,9999%), but thetolerance is not equal for all impurities. Within the HyFLEET:CUTE project, the brakedown of cost components of hydrogen revealed that monitoring and analysing the qualityas well as purification of hydrogen has significant impact on its price. The PEM fuel cellsare mostly applied in vehicles but for stationary applications other types are more costeffective and they can use a range of fuel types. The proportional in-stallation of fuel celltypes is presented in the fuel cell chapter.From electrolytic hydrogen the impurities consist mainly of O 2 that damages the coatingsof PEM fuel cells. Impurities from gas-reformation can be H 2 O, CO, CO 2 or N-compounds and those can harm PEM fuel cells but types of stationary FCs can withstandmore impurity (see section on fuel cells). International standards for purity have not beenset but are rather negotiated along the delivery chain. Drying and purification can raiseprices and can become energy intensive within the reformation or gasification methods(see section on hydrogen costs). Whereas the NEEDS project is dedicated to hydrogen in24 Faltenbacher Michael, PE International 2006, report on LCA of hydrogen production within CUTE cities