High-temperature electrolysis system

Housley, G.K., J.E. O Brien, G.L. Hawkes (2008), Design of a Compact Heat Exchanger for Heat Recuperation from a High Temperature Electrolysis System , 2008 ASME International Congress and Exposition, Boston, MA, USA, November, paper IMECE2008-68917. 

While there are large unknowns about the cost of high temperature electrolysis systems, an economic assessment can be made of the peak electricity market underlying the potential system economics. The distinguishing characteristic of this system is that the electricity is sold to meet the needs of three premium markets (US DOE, 2007b), in which the value and price of electricity are far above the price of base-load electricity. These three markets (Table 1) determine the technical requirements and economic viability of the concept. 

Stoots, C.M. (2005), Engineering Process Model for High-temperature Electrolysis System Performance Evaluation, Idaho National Laboratory, June. 

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Matsunaga, K. et al., Hydrogen production system with high temperature electrolysis for nuclear power plant, Paper 6282 in Proc. ICAPP 06, Reno, NV, June 4-8,2006. 

Figure 1 Peak power production system using high temperature electrolysis...

CEA has chosen to focus on a limited number of potentially interesting processes, namely the high temperature electrolysis, the iodine/sulphur cycle and the hybrid sulphur cycle (Figure 1). Other options are evaluated on a more limited basis. Rather than building expensive large scale demonstration loops, emphasis is placed on experiments their goals are to better understand the thermodynamic behaviour of the chemical system to implement more reliable models. 

The coupled nuclear-hydrogen plant investigated in this paper was studied in earlier work (Vilim, 2007). There the full power condition and the combined plant efficiency were estimated. The plant appears in Figures 1 through 3 as three modules - the primary system, the power conversion system and the high-temperature electrolysis plant. The interface between the nuclear side and the chemical plant appears in these figures in the form of the flow paths that connect these three modules. 

Fig. 9. Schematic of high-temperature electrolysis in a solid-oxide cell. The geometry can be planar or tubular as in the case of the first demonstration of the hybrid solar concentrator PV system. Operating the electrolysis cell in reverse corresponds to electricity and heat production...

A partnership between universities, private industry and national laboratories has been established to identify and test high temperature materials and designs for NHI heat exchangers and other system interface components. Tlie work performed by this partnership will identify candidate materials, and perform corrosion and physical property tests necessary for NHI heat exchangers and process equipment needed for thermochemical cycles and high temperature electrolysis. 

A lower cost system is achieved if electricity and steam is generated from a coal-fired power plant and then routed to a high-temperature electrolysis plant for steam decomposition with an overall thermal efficiency of 35 - 38 % (based on 35 % efficiency of electricity production from coal) [55]. 

An advanced hybrid system combines high temperature electrolysis with coal gasification. The latter produces synthesis gas plus steam at a high temperature which is used... 

For several decades, commercial alkaline electrolyzers have been available in a variety of series with outputs of up to approximately 750 Nm h hydrogen. Product development for PEM electrolysis only began around 25 years ago, and thus there are fewer commercial systems (<30 Nm h ) available compared to alkaline electrolysis. However, aU major manufacturers of PEM electrolyzers are currently developing and constructing 1 MW systems (see Table 11.4). High-temperature electrolysis is currently being pursued only sporadically by industry, which means that some demonstration systems exist, but no commercial products are yet available. 

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