Plug Power Inc.

Mechanical Technology Incorporated

William D Ernst

Michael M Walsh

Gary Mittleman

A fuel cell system includes a fuel cell stack, a fuel processor, a heater and a controller. The fuel cell stack provides an output power that includes a first power that is consumed by a first load. The fuel processor furnishes a fuel flow to the fuel cell stack, and the heater furnishes heat to the fuel processor when enabled. The controller is coupled to the fuel cell stack to monitor the output power and is coupled to the heater to selectively enable the heater to provide heat to the fuel processor when the first power decreases below a predetermined threshold.

Operating a fuel cell system during low power demand

A Proton Exchange Membrane (PEM) fuel cell stack is disclosed having multiple layers between a first end plate and a second end plate. The multiple layers define multiple fuel cell sub-stacks disposed in parallel and electrically isolated from each other intermediate the end plates. At the end plates, the fuel cell sub-stacks are electrically connected in series. At least some layers of the fuel cell stack comprise shared layers shared between multiple sub-stacks, and at least some layers of the multiple layers comprise dedicated layers for corresponding fuel cell sub-stacks. The shared layers include a fluid flow plate assembly and a membrane electrode assembly, while the dedicated layers comprise gas diffusion layers. The fluid flow plate assembly is fabricated of a non-conductive material and has multiple conductive fluid flow sub-plates, each of which aligns to a respective sub-stack of the fuel cell stack.

PEM-type fuel cell assembly having multiple parallel fuel cell

Isolator(s) include isolating material and optionally gasketing material strategically positioned within a fuel cell assembly. The isolating material is disposed between a solid electrolyte and a metal flow field plate. Reactant fluid carried by flow field plate channel(s) forms a generally transverse electrochemical gradient. The isolator(s) serve to isolate electrochemically a portion of the flow field plate, for example, transversely outward from the channel(s), from the electrochemical gradient. Further, the isolator(s) serve to protect a portion of the solid electrolyte from metallic ions.

Gradient isolator for flow field of fuel cell assembly

A lubricated piston rod seal which inhibits gas leaking from a high pressure chamber on one side of the seal to a low pressure chamber on the other side of the seal. A liquid is supplied to the surface of the piston rod on the low pressure side of the seal. This liquid acts as lubricant for the seal and provides cooling for the rod. The seal, which can be a plastic, elastomer or other material with low elastic modulus, is designed to positively pump lubricant through the piston rod/seal interface in both directions when the piston rod is reciprocating. The capacity of the seal to pump lubricant from the low pressure side to the high pressure side is less than its capacity to pump lubricant from the high pressure side to the low pressure side which ensures that there is zero net flow of lubricant to the high pressure side of the seal. The film of lubricant between the seal and the rod minimizes any sliding contact and prevents the leakage of gas. Under static conditions gas leakage is prevented by direct contact between the seal and the rod.

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Troy, NY, United States of America

William D Ernst