Abstract: An apparatus for heating fluid includes a tank for holding fluid to be heated, and a fuel wafer in fluid communication with the fluid. The fuel wafer includes a fuel mixture including reagents and a catalyst, and an electrical resistor or other heat source in thermal communication with the fuel mixture and the catalyst.

Abstract: A reactor device includes a sealed vessel defining an interior, a fuel material within the interior of the vessel, and a heating element proximal the vessel. The fuel material may be a solid including nickel and hydrogen. The sealed vessel may be sealed against gas ingress or egress and may contain no more than a trace amount of gaseous hydrogen. The sealed vessel is heated with an input amount of energy without ingress or egress of material into or out of the sealed vessel. An output amount of thermal energy exceeding the input amount of energy is received from the sealed vessel. The fuel material has a specific energy greater than that of any chemical reaction based energy source.