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Fuel Cell Housing for Rapid Start-Up Auxiliary Power and Gas Separation
IB-1942, IB-2189
APPLICATIONS:
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In tests of the new fuel cell stack design, Berkeley Lab scientists have attained 0.85 kW/l at 0.4 W/cm2 and project volumetric power density of >2 kW/l . |
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- Assembling planar SOFCs into stacks for power generation
- Auxiliary power for autos and RV
- Individualized oxygen production for use in homes or hospitals
ADVANTAGES:
- Start-up temperatures reached in 3.5 minutes for 400 thermal cycles without failure
- Survives the most extreme thermal shocks of any fuel cell to date
- Tolerates large thermal gradients across the stack
- Demonstrated peak power density of 0.45W/cm2 at 720°C
- Enables the use of conventional fuel cell materials
ABSTRACT:
Berkeley Lab scientists have designed a fuel cell housing unit that enables rapid thermal cycling of planar SOFCs made of conventional fuel cell materials. The invention makes strides towards enabling the use of SOFCs for portable applications such as auxiliary automotive power or the use of related electrochemical gas separators for single-user oxygen production for health purposes.
The open circuit voltage of SOFCs employing the design remained stable after more than 400 cycles between room temperature and 700°C, demonstrating that the seals maintained excellent quality. The fuel cells also survived instantaneous heating rates of over 1200°C per minute without failure, by far the most extreme temperature history for a planar SOFC. The new design achieves a peak power density of 0.45W/cm2 at 720°C.
The cell holder consists of a stainless steel casing with window frames to accommodate SOFC membranes comprising the anode chamber. Fuel is fed through a gas inlet and undergoes oxidation at the anodes before exhausting out the gas outlet. This design uses efficient edge current collection.
STATUS:
REFERENCE NUMBERS: IB-1942 and 2189
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Durable Joining of Dissimilar Materials
IB-2065
APPLICATIONS:
- Metal/ceramic joints in SOFCs
- Thermal barrier coatings
- Metal/ceramic bonding
ADVANTAGES:
- Survives rapid thermal cycling
- Thinner than graded joint
- Eliminates the need to introduce a third material into the joint
- High strength over a wide range of joint porosities
- Unlike graded joints, preserves contrast in material properties at the interface
ABSTRACT:
One barrier to solid oxide fuel cell manufacturing is forming robust joints between materials that don’t chemically bond with each other and/or differ greatly in form or particle size, such as metals and ceramics. Berkeley Lab scientists solve this problem by decorating the surface of the more ductile material with particles of the less ductile material via milling and then sinter-bonding this composite to the less ductile materials and/or another material that will sinter with either of the first two materials.
This technique is especially useful in devices where the utility of the joint is derived from a sharp interface between the two materials or where a third bonding material might be incompatible with system requirements. Joints made using this method have proven more durable during rapid thermal cycling than bonds relying on mechanical interlocking of articles or fibers and are more compact than graded joints.
STATUS:
REFERENCE NUMBERS: IB-2065
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Single-step Infiltration for Improved Low Temperature Cathode Performance
IB-2107
APPLICATIONS:
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Berkeley Lab scientists sinter a porous YSZ layer onto an electrolyte and then use a new method to create a continuous monolayer of nanoscale LSM particles with high surface area inside the pores. |
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- Optimizing cathode or anode performance in SOFCs and oxygen generators/gas separators
- Improving catalysts for hydrocarbon formation
- Generating protective coatings for metals, polymers, and ceramics
ADVANTAGES:
- One step instead of ten reduces processing costs
- Creates a connected network of nanoscale particles with minimal reduction in gas flow
- Lower infiltration sintering temperatures enable a wider choice of materials
- At 650°C, cathode performance exceeds 350 mW per cm2
ABSTRACT:
Scientists at Berkeley Lab have invented a one-step method for infiltrating porous structures with a continuous, electronically conducting monolayer or several continuous monolayers using only 3-5 weight percent of ceramic. The technique enables high SOFC cathode performance at lower temperatures where less expensive and more pliable metals can replace ceramics for some cells parts.
In this method the porous structure is sintered separately from the coating, allowing the firing temperatures of each material to be optimized. If the coating is fired at lower temperatures, the result is desirably small particle sizes that provide a higher surface area for electrochemical reactions, without blocking gas flow through the ceramic pores. The fine scale of the coating particles also allows the use of materials whose thermal expansions aren’t well matched with each other, without the risk of cracking.
The technique was used to prepare a LSM-YSZ composite cathode for a SOFC. Operating at 650°C, the cathode performance exceeds 350 mW per cm2. The LSM particles are between 30 and 100 nm.
STATUS:
- Patent pending. Available for licensing or collaborative research.
REFERENCE NUMBERS: IB-2107
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Robust, Multifunctional Joint for Large Scale Power Production Stacks
IB-2064
APPLICATIONS:
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DIAGRAM OF BERKELEY LAB'S MULTIFUNCTIONAL JOINT |
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Sealing/joining for:
- electrochemical devices, especially metal supported tubular SOFC cells
- electronic devices operating at elevated temperatures
ADVANTAGES:
- Robust, gas-tight, and compact
- Provides electrical management over a wide range of temperature
- Promises to be inexpensive and easy to manufacture
- Enables rapid thermal cycling and endures thermal shock
ABSTRACT:
Berkeley Lab scientists have developed a multifunctional joint for metal supported, tubular SOFCs that divides various joint functions so that materials and methods optimizing each function can be chosen without sacrificing space. The functions of the joint include joining neighboring fuel cells in series, sealing cells so that distinct atmospheres don’t interact, providing electrical connections between neighboring cells, and insulating electrodes in the same cell.
The design takes advantage of highly conductive metal cell supports and edge current collection to ensure efficient power production. Traditionally, the various functions performed by the Berkeley Lab joint require physical separation, which complicates the manufacturing process and produces a less robust cell. The new joint demonstrates excellent structural integrity and is expected to be inexpensive and easy to manufacture. Novel Berkeley Lab brazing techniques make the innovative design possible. (See “Braze for Robust Seals with Ceramic”, IB-2066, above.)
STATUS:
- Patent pending. Available for licensing or collaborative research.
REFERENCE NUMBERS: IB-2064
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