Abstract: A fuel cell system includes a fuel cell and a fuel system. The fuel cell includes a housing and a fuel cell stack positioned in the housing. The fuel cell stack is configured to produce an electrochemical reaction from a fuel and air to output electricity. The fuel system includes a fuel source, a fuel vaporizer, and fuel lines through which fuel flows from the fuel source to the fuel vaporizer and from the fuel vaporizer to the fuel cell stack. The fuel vaporizer includes a conductive tube through which the fuel flows, the conductive tube being in contact with the housing to conduct heat from the housing to the fuel to vaporize the fuel.

Abstract: Circuits (20, 220, 320, 420) are provided for applying electrical charge collected from a piezoelectric device (22) to a charge storage device (24, 224, 424). The circuits comprise a peak detector (32, 232) and a switch(es) (34, 134, 234, 434) which is/are operated to initiate transfer of the electrical charge from the piezoelectric device to the charge storage device upon detection by the peak detector (32, 232) of a peak voltage across the piezoelectric device (22). In an example embodiment, the peak detector (32, 232) comprises a peak-detection capacitance (C4); a gain element (42, 242); and a non-linear PN junction circuit (40). The circuits can also comprise charge multiplier circuit (300) configured to continue application of the electrical charge to the charge storage device (224) after the switch (262) has been turned off and/or after a point in time when magnitude of the voltage across the charge storage device (224) equals the magnitude of the voltage across the piezoelectric device (22).