Sulzer Hexis

Sulzer Hexis went into bankruptcy in late 2005, so the following account is history. The Sulzer Hexis fuel cell was exclusively aimed at the domestic market (Batawi 1996 1999 2001 Schuler, 2001 Ballhausen, 2001). After a long development history the project matured as the Sulzer Hexis Premiere, an incomplete fuel cell, calculated using calorific value theory. 

It should be remembered that the Hexis SOEC was yet another incomplete cell, without circulators, and with doubtful published performance assessment in terms of the calorific value of the fuel, in contrast to the chemical exergy. 

A process is on-going whereby the German firm H C Starck of Goslar, a member of the major Bayer group, is acquiring a large stake in the 

C Heat exchanger D Heat storage tank E Control E Auxiliaiy burner G DC/AC converter H Gas desulphurisation unit I Water treatment J Exhaust 

Energy Centrum Netherlands (ECN) and in the SOEC/MEA producer Innovative Dutch Electroceramics (InDEC), jointly sited at Petten. Starck will acquire SOEC research, operational and manufacturing capability, and will contribute worldwide marketing strength. 

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Batawi E, Weissen U, Schuler A, Keller M, and Voisard C. Cell Manufacturing Processes at Sulzer Hexis. In Yokokawa H, Singhal SC, editors. Proceedings of the Seventh International Symposium on Solid Oxide Fuel Cells (SOFC-VII), Pennington, NJ The Electrochemical Society, 2001 2001(16) 140-147. 

The Austrian gas utility companies Energie AC Oberosterreich, Wienstrom, ESTAC and SAFE are testing PEM and SOFC residential fuel cell power plants from Sulzer Hexis and Vaillant companies. 

Research on SOFC is concentrated at Sulzer Hexis, in close collaboration with the Federal Laboratory for Materials Research and the Federal Institutes of Technology Zurich and Lausanne. 

Fuel cells. Topics include both SOFC and PEM type fuel cells. Also R D for DMFC has been investigated. Emphasis was given to solving problems related to fulfilling the market requirements of the Sulzer Hexis SOFC. The main goal is to increase both reliability, lifetime, and the power conversion rate, while reducing costs. Considerable efforts were also invested in the development and demonstration of the PEM. Outcomes of this work include a 60 kW stack for cars demonstrated successfully in 2002 in the VW Bora and recently in a much improved car. The 1 kW-unit "Power Pac" is a standalone unit its PEM-stack has been demonstrated in various applications like boats and small cars (SAM). 

Enet Swiss Energy www.energy-research.ch Paul Scherrer Institute www.psi.ch Sulzer Hexis www.hexis.ch... 

Typically, TSOFC use co- and counter-flow configurations whereas planar stacks sometimes favour cross flow simplifying manifolds attachment. The flow of air usually provides cooling to a stack in either design as does internal reforming (Sulzer Hexis). The flow regime strongly affects the distribution of gas composition, mechanical stress, stack temperature and ultimately current density. 

However, the mechanical self support of cells is basically provided by the thickest PEN layer either one of the electrodes or the electrolyte (Sulzer Hexis, MHI, RR, CFCL). Thick porous ceramic (RR, MHI) and metallic substrates and interconnects (Ceres Power) onto which a thin PEN is applied have also been suggested to provide the mechanical support required. The electrolyte and anode supported cells are nowadays preferred in tubular and planar stacks. 

Despite the many problems that still exist with these perovskite cathodes, several commercial developers including Siemens Westinghouse, Rolls Royce, and Sulzer Hexis have adopted the LSM material for use in current devices and they are hkely to be incorporated in first generation conunercial SOFCs. 

EnBW (2004). Sulzer-Hexis SOFC-field test. Energie Baden-Wurtemburg AG. Website http / / WWW.enbw.com. 

Figure 12.18 Example of SOFC geometries, (a) Tubular geometry ofthe Siemens-Westinghouse system (b) Planar structure ofthe Sulzer-Hexis SOFC (for details, see the text).

In the Sulzer-Hexis prototype (shown schematically in Figure 12.18b), which runs on natural gas, the key component is the ceramic/metal hybrid stack with circular planar elements. The inner round aperture (2.2 cm diameter) is used as a channel for the fuel supply, while the metallic interconnect ensures an electrical contact between the individual segments of the stack, and also distributes the gases onto the surface of the electrodes. The fuel pours radially out of the channel at the anode end ofthe cell to the outside. Simultaneously, preheated air is fed from the outside to the interior of the stack through four channels, and then redirected so as to flow radially over the cathode end of the cell to the outside. The fuel, which is not converted on the anode, is burned off at the edge of the stack. This fuel cell has been developed to supply, simultaneously, an electrical power of 1 kW and a thermal capacity of approximately 2.5 kW. 

The special steel developed by Siemens together with the Austrian company Plansee is still used by Sulzer Hexis within their electrolyte supported stack design. Fuel is supplied to the centre of circular cells with a diameter of 120 mm and flows in parallel with the air to the outer rim of the cell, where the fuel gas that has not reacted within the cell, is burned. Air is supplied from the outside and heats up, while flowing towards the centre (see fig. 4). The stack is typically operated at 950°C. Up to 70 cells are stacked together, delivering 1.1 kW. 

Switzerland Sulzer Hexis >60 metallic IC, electrolyte substrate anode substrate materials, cells, stack, manufacturing, system... 

Recently, the Swiss company Sulzer Hexis AG has developed the concept of an SOFC for small-scale domestic application to provide heating on demand and to cover peak power requirements. This so-called Hexis (Heat Exchanger Integrated Stack) cell consists of circular zirconia electrolyte disks of about 12 cm diameter that carry the anode and cathode (Figure 7.38). The individual cells are... 

Fig. 18.2 Cell performance degradation of (a) the first generation sealless tubular cells by Westlnghouse (Currently Siemens, From [13, 14]) and (b) the second generation planar cells by Sulzer Hexis (Currently Hexis, From [17])...

Sulzer Hexis built 110 1 kW demonstration units based on its electrolyte-supported technology with superalloy interconnects. The latest version of the units, integrated into a hot water/heating appliance, has shown a degradation rate of around 1 to 2 percent per 1000 hrs in continuous operation, and about 2x higher with thermal cycling (69). 

Sulzer Hexis Switzerland IkW 1998- 2002 Planar SOFC, field trails of many testing... 

Schuler, A. An Intermediate Report on the Way to a Near-Series Sulzer Hexis Fuel Cell System, in Sixth European Solid Oxide Fuel Cell Forum. 2004. Luzern, der Schweiz European Fuel Cell Forum. 

Planar SOFC, in particular, monolithic designs (MHI) are capable of high (volumetric) power densities most favoured by direct and short current paths across the stack components. The PEN is principally square, rectangular and circular (Ceramic Fuel Cells Limited (CFCL), Mitsubishi Materials Corp., Sulzer Hexis) in shape with active surface areas of 100-200 cm (15.5-31 in ). A drawback of this design is that it often necessitates the use of high temperature sealants for application at the in-... 

Figure 7.30 Ring-type solid oxide fuel cell with metal cell interconnects. The fuel gas comes up the central tube and out over the anode. Air is blown in from the outside over the cathode. After passing over both electrodes the gas streams mix, and the remaining fuel is burnt to provide more heat. (Diagram reproduced by kind permission of Sulzer Hexis Ltd).

From a publication by Huijsmans et it is also evident that the Netherlands Energy Research Foundation (ECN) has upscaled planar SOECs with a CeogCdo jOi 95 electrolyte and that these cells have been evaluated in the Sulzer Hexis concept. 

Thermal expansion coefficients For high-temperature utilization, Ni-Cr-based alloys are excellent from the anticorrosion point of view. Even so, such Ni-Cr alloys have high thermal expansion coefficients dictating a larger match with YSZ. Cr-based alloys developed by Siemens/Plansee have an essentially similar thermal expansion coefficient as YSZ. This alloy was utilized by Sulzer Hexis. Alternatively, Fe-Cr ferritic alloys are frequently utilized. Although complete matching in thermal expansion coefficient with YSZ is not obtained, Ni-Cr alloys provide considerable improvement. 

Sulzer Hexis CrSFelYaOs High-velocity oxygen flame (HVOF)-sprayed coating of (Y,Ca)Mn03 66... 

Table 13.2 lists the major SOFC system manufacturers worldwide this list does not include research institutes, universities, and manufacturers of solely ceramic components. Many of these manufacturers have built and tested SOFC stacks in their own facilities. Only Siemens Westinghouse, Sulzer Hexis and a few other companies have built fully integrated SOFC systems, and operated them at customer sites these systems are described in this section. 

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