The Department of Energy’s National Energy Technology Laboratory (NETL) is seeking licensing partners interested in implementing United States Patent Number 7,159,841 entitled "Piezoelectric Axial Flow Microvalve."
Disclosed in this patent are the design and functionality of NETL’s piezo-electrically operated microvalves and their use in fuel cell systems, which consist of an assembly of individual fuel cells into a stack. The microvalve improves flow control over the entire fuel cell system by integrating flow distribution and controlling of individual fuel cells within the stack. By controlling fuel flow in each individual cell, the microvalve system can prevent the overheating and under-performing of a portion of the stack, thereby avoiding reduced efficiency and energy output for the entire stack.
Both the PEFC and the SOFC types of fuel cells use a fixed flow field and inlet fuel flow manifold design. The cell geometry within a fuel cell stack provides many flow paths for reactants to flow, which inherently creates flow distribution problems that can potentially cause inefficiencies or even damage to individual cells. Currently, the flow of reactants (hydrogen and oxygen) through the individual fuel cells in a stack is controlled by imposing relatively large pressure drops across the total stack, thereby attempting to ensure adequate flow in each individual fuel cell in the stack.
This invention integrates small micro-valves along the fuel feed manifold of the stack to control the fuel flow to each cell within the stack. By providing cell-to-cell flow control, the additional flow required for stack operation can potentially be reduced below the stated 1.3 times the stoichiometry, which improves fuel efficiency. More importantly, the overall efficiency can be improved by optimizing the performance of each cell within the stack. Using MEMS technology, this microvalve can be made small enough to fit within the limited confines of a fuel cell. It draws its minimal operating power from the fuel cell itself, eliminating the need for an external power source. Also, the microvalve has been designed to operate under the chemical, temperature, and pressure conditions typical in fuel cells. Protection from degradation by hydrogen gas is achieved by the application of a diffusion barrier coating.
The piezoelectric microvalve helps to:
U.S. Patent No: 7,159,841
Title: Piezoelectric Axial Flow Microvalve
Inventors: Randall Gemmen, Jimmy Thornton, Jeffrey Vipperman, William Clark
NETL Reference No: 02N-08
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