The present invention pertains to fuel cells, and more particularly to an array of direct methanol fuel cells and a method of fabricating the array of fuel cells, in which electrical energy is produced through the consumption of gaseous or liquid fuels.
Fuel cells in general, are xe2x80x9cbattery replacementsxe2x80x9d, and like batteries, produce electricity through an electrochemical process without combustion. The electrochemical process utilized provides for the combining of hydrogen with oxygen from the air. The process is accomplished utilizing a proton exchange membrane (PEM) sandwiched between two electrodes, namely an anode and a cathode. Fuel cells, as known, can provide perpetual electricity as long as fuel and oxygen is supplied. Hydrogen is typically used as the fuel for producing the electricity and can be processed from methanol, natural gas, petroleum, or stored as pure hydrogen. Direct methanol fuel cells (DMFCs) utilize methanol, in a gaseous or liquid form as fuel, thus eliminating the need for expensive reforming operations. DMFCs provide for a simpler PEM cell system, lower weight, streamlined production, and thus lower costs.
In a standard DMFC, a dilute aqueous solution of methanol is fed as the fuel on the anode side (first electrode) and the cathode side (second electrode) is exposed to forced or ambient air (or O2). A nafion type proton conducting membrane typically separates the anode and the cathode sides. The flow streams must be kept separate in the design of the fuel cell. Several of these fuel cells can be connected in series or parallel depending on the power requirements.
Typically DMFCs designs are large stacks with forced airflow at elevated temperatures. Smaller air breathing DMFC designs are more complicated. In conventional PEM fuel cells, stack connections are made between the fuel cell assemblies with conductive plates, machined with channels or grooves for gas distribution. A typical conventional fuel cell is comprised of an anode (H2 or methanol side) current collector, anode backing, membrane electrode assembly (MEA) (anode/ion conducting membrane/cathode), cathode backing, and cathode current collector. Each fuel cell generates approximately 1.0 V, although the typical operating voltage is lower. To obtain higher voltages, fuel cells are typically stacked in series (bi-polar mannerxe2x80x94positive to negative) one on top another. Conventional fuel cells can also be stacked in parallel (positive to positive) to obtain higher current, but typically, larger fuel cells are simply used. When stacking fuel cells, the fuel and oxidant must remain separated. This requires creative management of the gas flows.
DMFCs typically operate between 0.2-0.8 volts. To power a device requiring greater potentials, multiple fuel cells need to be connected in series for bipolar voltage adding. However, a device capable of higher voltages is sought in which a small single planar surface, thus a smaller area, is utilized. In this instance, multiple DMFCs are formed on a single planar surface. Each fuel cell will include a fuel inlet and a fuel outlet. There is a need to form the array of fuel cells to share components, such as microfluidic channels that feed the multiple fuel cells simultaneously.
Accordingly, it is a purpose of the present invention to provide for a planar array design in which multiple direct methanol fuel cells can be xe2x80x9cstackedxe2x80x9d in a planar array, so that higher voltages can be obtained.
It is a purpose of the present invention to provide for a planar stack design for a plurality of direct methanol fuel cells in which a planar array of direct methanol fuel cells is achieved on a single planar surface.
It is a further purpose of the present invention to provide for a planar stack design for direct methanol fuel cells in which a plurality of microfluidic channels are utilized to equivalently and simultaneously feed the plurality of direct methanol fuel cells, remove the exhaust, namely carbon dioxide, and recirculate the methanol/water mixture.
It is yet a further purpose of the present invention to provide for method of fabricating a planar stack of direct methanol fuel cells in which a planar array of direct methanol fuel cells is achieved on a single planar surface including a plurality of microfluidic channels to feed a fuel-bearing fluid, remove carbon dioxide exhaust, and recirculate the methanol/water mixture.
The above problems and others are at least partially solved and the above purposes and others are realized in a fuel cell array apparatus and method of forming the fuel cell array apparatus including a base portion, formed of a singular body, and having a major surface. At least two spaced apart membrane electrode assemblies are formed on the major surface of the base portion. A fluid supply channel is defined in the base portion and communicating with each of the at least two spaced apart membrane electrode assemblies for supplying a fuel-bearing fluid to each of the at least two spaced apart membrane electrode assemblies. An exhaust channel is defined in the base portion and communicating with each of the at least two spaced apart membrane electrode assemblies. The exhaust channel is spaced apart from the fluid supply channel for exhausting fluid from each of the at least two spaced apart membrane electrode assemblies. Each of the two spaced apart membrane electrode assemblies and the cooperating fluid supply channel and cooperating exhaust channel forms a single fuel cell assembly. There is additionally included a top portion which includes a plurality of electrical components for electrical integration of the plurality of formed fuel cell assemblies.