TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Component: Each fuel cell is metal fuel cell or hydrogen fuel cell. It is preferably a metal fuel cell, e.g. zinc fuel cell (preferably), aluminum fuel cell, lithium fuel cell, magnesium fuel cell, or iron fuel cell. It further comprises a regeneration unit; a reaction product storage unit; and a second reactant storage unit.The system further comprises a power conversion unit for converting the power output from the fuel cells into another form; and a controller for sensing outage of primary power to the loads, and responsive to, operatively engaging the fuel cells to provide power to the loads and the cooling unit. The power conversion unit is configured to convert a direct current (DC) power from the fuel cells into an alternating current (AC) power, or into another form of DC power. The controller is configured to sense resumption of primary power to the loads, and, responsive to, disengage the fuel cells from providing power to the loads and the cooling unit.The system is configured not to utilize or produce significant quantities of flammable fuel or reactant product. It is configured to provide backup power to the loads for 0.5-650 hours. It is configured to have an energy density of 35 Watt-hours/kg of combined fuel and electrolyte added to the system to 400 Watt-hours/kg of combined fuel and electrolyte added to the system. It further comprises an energy requirement. The combined volume of fuel and electrolyte added to the system is 0.0028-0.025 L/Watt-hour of the system's energy requirement. The energy requirement is 50-500000 or 5-5000000 Watt-hours.The fuel storage unit is configured to store fuel at a pressure of -5 - 200 psi. The power sources comprise fuel that is present in cell cavities of the power source prior to the controller sensing the outage of primary power to the loads; and one or more second reactants that are present in the power source at a pressure of 0.01-200 psi gauge pressure prior to operative engagement of the fuel cells. The amount of fuel present in the cell cavities of the power source prior to controller sensing the outage of the primary power to the loads is to permit engagement of the fuel cells by the controller for 0.001-100 minutes or more without additional fuel being added. The system is also configured to expel no reaction products outside of the system.The fuel and second storage units have a selected volume of 0.001-10000 L. The cooling unit is configured to remove from the vicinity of the system, heat generated by the loads and/or the fuel cells. It is configured to circulate a cooling fluid (8a, 8b) past the fuel cells and/or the loads. It comprises an open loop system configured to cool a first cooling fluid by circulating a second cooling fluid through a heat exchange, and to circulate the cooled first cooling fluid past the fuel cells and/or the loads; and a closed loop system configured to cool a first cooling fluid by circulating a second cooling fluid from a reservoir through the heat exchange and then back to the reservoir, and to circulate the cooled first cooling fluid past the fuel cells and/or the loads. A rack (18) is provided to physically support the fuel cells and the loads.