Production of electrolytic hydrogen

Table 4. Cost comparison for the hybrid CPV production of electrolytic hydrogen. Note that 1 kg of hydrogen has the energy equivalent of one U.S. gallon of gasoline.

Norway is gaining its energy exclusively from hydro power and was able up to now to to refrain from using oil, gas, coal, or nuclear power. Large-scale production of electrolytic hydrogen is made since 1949 with a peak capacity peaking at 100,000 Nm /h (which corresponds to 450 MW of hydro power). It has been discontinued, however, since it could not compete with the hydrogen produced from hydrocarbons. 

J. Ivy, Summary of Electrolytic Hydrogen Production, NREL/MP-560-36734, September 2004. Available at www.nrel.gov... 

Carpetis C (1984) An assessment of electrolytic hydrogen production hy means of photovoltaic energy conversion. Int J Hydrogen Energy 9 969-991... 

S. Trasatti provides a detailed review of the advances in the production of cathodes with favorable characteristics for the manufacture of electrolytic hydrogen. A careful analysis is given of performance characteristics on the basis of electrode reaction kinetics and catalysis. 

Production and Application of Electrolytic Hydrogen Present and Future... 

Finally, the indirect dehalogenation, via electrolytic production of atomic hydrogen, represents a possible alternative, especially when operating in protonated solvents, under background current conditions, on cathodes activated with noble metal particles (e.g. Pd, Ru, Rh, Ir, Au) (Cheng et al. 1997 Tsyganok et al. 1998 Tsyganok and Otsuka 1999 Iwakura et al. 2004). 

Levene, J., and Ramsden, T. Summary of Electrolytic Hydrogen Production . National Renewable Energy Laboratory, Golden, CO, MP-560-41099, (2007). 

The nature of the electrolyte sometimes has an important influence on the products of electrolytic reduction. The alkalinity or acidity, for example, plays an essential part in determining the nature of the substance obtained in the reduction of nitrobenzene in this case the effect is mainly due to the influence of the hydrogen ion concentration on various possible side reactions. The formation of azoxybenzene, for example, in an alkaline electrolyte is due to the reaction between phenyl-hydroxylamine and nitrosobenzene, viz.,... 

Because water can be used directly in the liquid form, there is a considerable saving in capital and operating costs. Because of combination with electrolysis, a is large, which bestows many advantages. But CECE involves production of a huge amount of electrolytic hydrogen and unless there is a direct market for this hydrogen, the process remains uneconomical for primary enrichment. 

The cost of hydrogen production by both electrolysis and SMR is dominated by the cost of their energy inputs. Around 300 /t H2 is associated with capital costs and operation of an SMR while electrolysis cells costing 300 /kW require produce capital costs of about 400 /t H2. Electricity from Generation 111+ nuclear reactors (such as Westinghouse s AP-1000, AECL s ACR-1000 , or the European EPR) is expected to cost 3 to 5 e/kW.h - 1 500 to 2 500 /t H2. This is without credits for co-production of oxygen (300 /t H2) and heavy water (120 /t H2 net of production costs). On this basis, the total cost of electrolytic hydrogen would be comparable to that from an SMR. 

Fig 4. Daily variation of electrolytic hydrogen production rate (1), the solar array temperature (2) and radiation power density (3). Single crystalline silicon solar cells, SPE electrolyzer, location Cape Canaveral, FA. The time scale denotes minutes elapsed from 5 a.m. [23],... 

Bulk production of hydrogen via electrolysis appears improbable until renewable or nuclear electricity becomes widely available and considerably cheaper than at present. The principal attribute of electrolytic hydrogen is its ultra-purity, which is an important requirement for proton-exchange membrane fuel cells. Nevertheless, the use of valuable electricity to electrolyze water and then feeding the resultant hydrogen to a fuel cell is intrinsically wasteful by virtue of the combined inefficiencies of the two devices involved. This really only makes sense in situations where there is more electricity than can be consumed as such, or where there are reasons for wanting hydrogen that transcend considerations of efficiency and cost. 

The generation of electrolytic hydrogen is achieved by selecting an MHR system in the electricity generation mode [72]. The two major safety aspects, higher operating temperatures and tritium permeation to the product gas, were evaluated and shown not to be a serious concern for the nuclear process heat plant [63]. 

Ivy, J. (2004) Summary of electrolytic hydrogen production . Report NREL/ MP-560-36734, National Renewable Energy Laboratory, Golden, USA, available at http //www.nrel.gov/docs/fy04osti/36734.pdf (accessed March 2008). 

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