Stack Module Research Articles

Operation of High Temperature Steam Electrolyzer Module

A nominally 4-kW planar solid oxide stack module was operated in electrolysis mode. The module consisted of two 60-cell stacks with an integrated steam generator. The tests included both steam electrolysis to produce hydrogen and steam-carbon dioxide co-electrolysis to produce syngas. The initial performance of the module matched the performance of a 10-cell short stack. Fairly rapid initial degradation, attributed primarily to thermal imbalance from the heat duty of steam generator was noted. Reducing the heat duty of the steam generator within the thermal enclosure significantly improved the performance stability. The production of hydrogen and syngas was verified using dew point sensor and gas chromatograph.

Fabrication and characterization of micro tubular SOFCs for advanced ceramic reactors

Abstract Realization of micro tubular solid oxide fuel cell (SOFC) modules, which are robust and low temperature operable, is expected to accelerate the commercialization of SOFC systems. “Advanced ceramic reactor” project targets on realizing such a high-efficient micro ceramic reactor, especially a novel SOFC module. The goal of this research/development project is to develop electrode and electrolyte materials for low temperature operation, and to establish manufacturing process technology for micro tubular SOFCs and integrated modules, as well as demonstration of cell stack modules. In this paper, the concept of advanced ceramic reactor project and recent achievement will be presented.

Solid Oxide Fuel Cell (SOFC) Development in Denmark

The SOFC technology under development at Risø National Laboratory (RISØ) and Topsoe Fuel Cell A/S (TOFC) is based on an integrated approach ranging from basic materials research on single component level over development of cell and stack manufacturing technology to system studies and modelling. The effort also comprises an extensive cell and stack testing program. Systems design, development and test is pursued by TOFC in collaboration with various partners. The standard cells are thin and robust with dimensions of 12 x 12 cm2 and cell stacks are based on internal manifolding. Production of cells is being up-scaled continuously. The durability of the standard stack design with standard cells has been tested for more than 13000 hours including nine full thermal cycles with an overall voltage degradation rate of about 1% per 1000 hours. Recently, the degradation rate has been significantly reduced by introduction of improved stack component materials. 75-cell stacks in the 1+ kW power range have been tested successfully. Stacks have been delivered in a pre-reduced state to partners and tested successfully in test systems with natural gas as fuel. The consortium of TOFC and RISØ has an extended program to develop the SOFC technology all the way to a marketable product. Stack and system modelling including cost optimisation analysis is used to develop multi kW stack modules for operation in the temperature range 700-850oC. To ensure the emergence of cost-competitive solutions, a special effort is focused on larger anode-supported cells as well as a new generation of SOFCs based on porous metal supports and new electrode and electrolyte materials. The SOFC program comprises development of next generation of cells and multi stack modules for operation at lower temperature with increased durability and mechanical robustness in order to ensure long-term competitiveness.

Quantization of complex Lagrangian submanifolds

Let Λ be a smooth Lagrangian submanifold of a complex symplectic manifold X . We construct twisted simple holonomic modules along Λ in the stack of deformation-quantization modules on X .

Effect of spectral irradiance distribution on the outdoor performance of amorphous Si//thin-film crystalline Si stacked photovoltaic modules

Effects of spectral irradiance distributions on the outdoor performance of amorphous Si//thin-film crystalline Si stacked photovoltaic (PV) modules installed at Shiga-prefecture in Japan have been investigated. Outdoor solar spectrum measurements revealed that more than 95% of annual total spectra were blue-rich compared to AM1.5 standard solar spectrum. The outdoor performance of the modules had a higher spectral dependence than that of polycrystalline Si modules. Also, the peak of the histogram of annual spectral indexes well corresponded to the peak of the outdoor performance. The results indicate that the actual spectral irradiance distribution is important in designing stacked PV modules.

Characteristics and performance of 10 kW class all-vanadium redox-flow battery stack

A kW class all-vanadium redox-flow battery (VRB) stack, which was composed of 14 cells each with an electrode geometric surface area of 875 cm 2, with an average output power of 1.14 kW, at the charge–discharge current density of 70 mA cm −2, was successfully assembled by filter press type. Then, a 10 kW class VRB stack was manufactured with a configuration of 4 × 2 (serial × parallel) of the improved aforementioned kW class stack modules, which produced a direct output of 10.05 kW (current density 85 mA cm −2). The energy efficiency of more than 80%, at an average output power of 10.05 kW, for the 10 kW class VRB stack was achieved, indicating VRB is a promising high efficiency technology for electric storage.

Solid oxide fuel cell development at Topsoe Fuel Cell and Risø

The consortium of Topsoe Fuel Cell A/S and Riso National Laboratory has scaled up its production capacity of anode-supported cells to about 1100 per week. The consortium has an extended program to develop the SOFC technology all the way to a marketable product. Standard stacks have been tested for more than 13 000 h. Post-mortem analysis has revealed the dominating degradation mechanisms. Recently, the degradation rate has been reduced to below 0.5% per 1000 h by introduction of improved stack component materials, including improved metallic interconnects. Several 50- or 75-cell stacks in the 1 kWe and above power range have been tested successfully on methane-rich reformate gas at a fuel utilization up to 92%. Stack and system modeling – including cost optimization analysis – is used to develop 5–25 kWe stack modules for operation in the 700–850°C temperature range. A special effort is focused on manufacturing and testing of larger anode-supported cells and stacks with a footprint of 18 × 18 cm 2 . The SOFC program comprises the development of next-generation cells with metallic supports for operation at lower temperature with increased durability, lower cost, and high mechanical robustness. A range of fuels have been studied including natural gas, LPG, methanol, DME, diesel and ammonia. A multi-stack design study for a 24-stack module prototype has been finalized, and stack construction is under way for a 20 kWe prototype running on natural gas. The studies predict system electrical efficiencies from 50% to 56% (AC out/LHV fuel in) depending on the fuel used and the size of the system.

The modeling of a standalone solid-oxide fuel cell auxiliary power unit

In this research, a Simulink model of a standalone vehicular solid-oxide fuel cell (SOFC) auxiliary power unit (APU) is developed. The SOFC APU model consists of three major components: a controller model; a power electronics system model; and an SOFC plant model, including an SOFC stack module, two heat exchanger modules, and a combustor module. This paper discusses the development of the nonlinear dynamic models for the SOFC stacks, the heat exchangers and the combustors. When coupling with a controller model and a power electronic circuit model, the developed SOFC plant model is able to model the thermal dynamics and the electrochemical dynamics inside the SOFC APU components, as well as the transient responses to the electric loading changes. It has been shown that having such a model for the SOFC APU will help design engineers to adjust design parameters to optimize the performance. The modeling results of the SOFC APU heat-up stage and the output voltage response to a sudden load change are presented in this paper. The fuel flow regulation based on fuel utilization is also briefly discussed.

Fabrication and characterization of micro tubular SOFCs for operation in the intermediate temperature

Tubular SOFC systems appear to be well-suited to accommodate repeated cycling under rapid changes in electrical load and in cell operating temperatures. Our goal is to develop innovative processing method to fabricate new micro tubular SOFCs with sub-millimeter diameter and its stack module which enable to generate high volumetric power density. In this study, micro tubular SOFCs under 1 mm diameter have been successfully fabricated and tested in the intermediate temperature region (550 °C or under). The cell consists of NiO–Gd doped ceria (GDC) as an anode (support tube), GDC as an electrolyte and (La, Sr)(Fe, Co)O 3 (LSCF)–GDC as a cathode. The single tubular cell with 0.8 mm diameter and 12 mm length generated over 70 mW at 550 °C with H 2 fuel, which indicates that the cell generated over 0.3 W cm −2 at 550 °C.

Engineering aspects and hardware verification of a volume producable solid oxide fuel cell stack design for diesel auxiliary power units

A solid oxide fuel cell (SOFC) stack module is presented that is designed for operation on diesel reformate in an auxiliary power unit (APU). The stack was designed using a top-down approach, based on a specification of an APU system that is installed on board of vehicles. The stack design is planar, modular and scalable with stamped sheet metal interconnectors. It features thin membrane electrode assemblies (MEAs), such as electrolyte supported cells (ESC) and operates at elevated temperatures around 800 °C. The stack has a low pressure drop in both the anode and the cathode to facilitate a simple system layout. An overview of the technical targets met so far is given. A stack power density of 0.2 kW l −1 has been demonstrated in a fully integrated, thermally self-sustaining APU prototype running with diesel and without an external water supply.

Thermodynamic analysis of a PEM fuel cell power system

This study deals with the thermodynamic modeling of a polymer electrolyte membrane (PEM) fuel cell power system for transportation applications. The PEM fuel cell performance model developed previously by two of the authors is incorporated into the present model. The analysis includes the operation of all the components in the system, which consists of two major modules: PEM fuel cell stack module and system module and a cooling pump. System module includes air compressor, heat exchanger, humidifier and a cooling loop. A parametric study is performed to examine the effect of varying operating conditions (e.g., temperature pressure and air stoichiometry) on the energy and exergy efficiencies of the system. Further, thermodynamic irreversibilities in each component of the system are determined. It is found that, with the increase of external load (current density), the difference between the gross stack power and net system power increases. The largest irreversibility rate occurs in the fuel cell stack. Thus, minimization of irreversibility rate in the fuel cell stack is essential to enhance the performance of the system, which in turn reduces the cost and helps in commercialization of fuel cell power system in transportation applications.

Microlocal Riemann–Hilbert Correspondence

We construct the global microlocal Riemann–Hilbert correspondence as an explicit equivalence between the abelian stack of microlocal perverse sheaves defined in [W] and the abelian stack of regular holonomic microdifferential modules of [KK]. The theory of analytic ind-sheaves and its microlocalization is crucial for our construction since it allows us to define solution complexes with values in the (ind-)ring of microlocal holomorphic functions (resp. microlocal tempered holomorphic functions).

Status and Recent Progress in SOFC Development at Haldor Topsøe A/S and Risø

The SOFC technology under development at Haldor Topsoe A/S and Riso National Laboratory is based on an integrated approach ranging from manufacturing of planar anode-supported cells and compact stacks to analysis of total systems. The standard cells are thin and robust with dimensions of 12 x 12 cm 2 and cell stacks are based on internal manifolding. Production of cells is being up-scaled continuously. The durability of the standard stack design with standard cells has been tested for more than 13000 hours including nine full thermal cycles with an overall voltage degradation rate of about 1% per 1000 hours. Recently, the degradation rate has been significantly reduced by introduction of improved stack component materials. 75-cell stacks in the 1+ kW power range have been tested successfully, so far for several hundred hours. Stacks have been delivered in a pre-reduced state to partners and tested successfully in test systems with natural gas as fuel. The consortium of Haldor Topsoe A/S and Riso has an extended program to develop the SOFC technology all the way to a marketable product. Stack and system modelling including cost optimisation analysis is used to develop 5 kW stack modules for operation in the temperature range 700-850°C. To ensure the emergence of cost-competitive solutions, a special effort is focused on manufacturing and testing of larger anode-supported cells. The SOFC program comprises development of next generation cells and multi stack modules for operation at lower temperature with increased durability and mechanical robustness. Development of cells with porous metallic support and new electrode materials is in progress in order to ensure long-term competitiveness.

Single-Wavelength 5.6 kW Direct Diode Laser with a High-Efficiency Beam Combination

Our group developed a new optical system equipped with a slit mirror to combine the output power from two LD stack modules (30 bars each) and focus them into a single beam. The new device realized a CW output power of more than 3 kW with a transfer efficiency of 92%. Furthermore, by combining beams from two added stack modules to the main optical path using polarization coupling, we have achieved a CW output power of 5.6 kW with a single wavelength of 808 nm. The focused spot size was 2.4 mm×0.5 mm (the power intensity was 467 kW/cm2) at a practical focal length of 100 mm. The transfer efficiency from the LD output to the focal spot was estimated to be 86.5%. The total energy efficiency against the input electricity was approximately 45%. This value is the highest ever reported in a high-power LD applied to material processing, and a full threefold higher than that of the diode-pumped Nd:YAG laser, a device heretofore known to be highly efficient (at around 15%).

Study of the Gas Flow Distribution and Heat Transfer for Externally Manifolded Fuel Cell Stack Module Using Computational Fluid Dynamics Method

Uniform gas flow distribution in a fuel cell system is desired to attain maximum power operation potential. Two types of manifold systems are often used in fuel cell stacks; they are internal manifold system and external manifold system. This paper presents the modeling approach using the Computational Fluid Dynamics (CFD) method in analyzing fluid flow and heat transfer for the external manifold fuel cell stacks and stack module design. Computational models based on a Megawatt carbonate fuel cell stack module have been developed for investigating the fuel and oxidant flow distributions through the external manifold systems. This paper presents the modeling approaches and flow and temperature distribution results for externally manifolded fuel cell stack and stack module.

Stacks of quantization-deformation modules on complex symplectic manifolds

On a complex symplectic manifold X, we construct the stack of quantization-deformation modules, that is, (twisted) modules of microdifferential operators with an extra central parameter τ, a substitute to the lack of homogeneity. We also quantize involutive submanifolds of contact manifolds.

Fuel cell minivan from Mitsubishi Motors

Japan’s Mitsubishi Motors Corporation (MMC) has developed a fuel cell vehicle based on its recently launched Grandis minivan. The FCV is powered by the fuel cell system developed by Germany’s DaimlerChrysler, MMC’s strategic alliance partner and largest shareholder, and incorporates a fuel cell stack and power module from Ballard Power Systems in Canada and hydrogen storage cylinders. Visit www.re-focus.net for the latest renewable energy news

The Direct FuelCell™ stack engineering

FuelCell Energy (FCE) has developed power plants in the size range of 300 kW to 3 MW for distributed power generation. Field-testing of the sub-megawatt plants is underway. The FCE power plants are based on its Direct FuelCell™ (DFC) technology. This is so named because of its ability to generate electricity directly from a hydrocarbon fuel, such as natural gas, by reforming it inside the fuel cell stack itself. All FCE products use identical 8000 cm 2 cell design, approximately 350–400 cells per stack, external gas manifolds, and similar stack compression systems. The difference lies in the packaging of the stacks inside the stack module. The sub-megawatt system stack module contains a single horizontal stack whereas the MW-class stack module houses four identical vertical stacks. The commonality of the design, internal reforming features, and atmospheric operation simplify the system design, reduce cost, improve efficiency, increase reliability and maintainability. The product building-block stack design has been advanced through three full-size stack operations at company’s headquarters in Danbury, CT. The initial proof-of-concept of the full-size stack design was verified in 1999, followed by a 1.5 year of endurance verification in 2000–2001, and currently a value-engineered stack version is in operation. This paper discusses the design features, important engineering solutions implemented, and test results of FCE’s full-size DFC stacks.

Completion of the ITER toroidal field model coil

In the scope of the ITER EDA a Toroidal Field Model Coil (TFMC) has been manufactured accompanied by a thorough Quality Assurance (QA) test program. This large superconducting coil has been conceptually designed by the ITER European Home Team (EUHT) and manufactured by European industry. The coil is being completed and will be tested at the Forschungszentrum Karlsruhe in spring 2001. The race track shaped winding is made of a cable-in-conduit conductor in a circular 316LN stainless steel jacket. From this conductor five double pancake (DP) modules were fabricated. Results of conductor and DP manufacture were already presented at previous conferences and are therefore only summarized here. The paper concentrates on the subsequent manufacturing steps, namely the stacking of the DP modules, the insulation and impregnation of the winding pack, the outer joint manufacture by electron beam welding, the assembly of the winding pack with the stainless steel case, the mounting of the helium pipes, the sensors and the busbars. To assemble the coil into the TOSKA facility and to fit it to the EU-LCT coil a heavy Inter-Coil Structure (ICS) has been built, in which the TFMC will rest on four wedges.

Plagiotropic architectural development of four tree species of the temperate forest

Four tree species of the temperate deciduous forests of south-western Québec have an architectural development that corresponds to Troll's model. Two of these species, American elm (Ulmus americana L.) and American basswood (Tilia americana L.), are mid-successional and the two others, American beech (Fagus grandifolia Ehrh.) and Eastern hemlock (Tsuga canadensis (L.) Carr.), are late successional. In the four species, the main stem is the result of the stacking of modules with plagiotropic development and secondary straightening. Nevertheless, the architectural analysis of these four species reveals that two growth patterns are present. In elm and basswood, the modules are differentiated from one another and are integrated into the hierarchical structure of the tree. In beech and hemlock, the modules are mixed and their apical meristems possess an autodifferentiation potential, which provides for a greater individuality within the tree structure. In spite of belonging to the same architectural model, differences in the development pattern favour a greater efficiency in stem growth for elm and basswood versus a greater shape plasticity, including a greater lateral branch development if required, in beech and hemlock.Key words: tree architecture, organization plan, Troll's model, plagiotropy, morphological differentiation of axes.