Auxiliary power is electric power that is provided by an alternate source and that serves as backup for the primary power source at the station main bus or prescribed sub-bus. An offline unit provides electrical isolation between the primary power source and the critical technical load whereas an online unit does not. A Class A power source is a primary power source, i.e., a source that assures an essentially continuous supply of power. Types of auxiliary power services include Class B, a standby power plant to cover extended outages of the order of days; Class C, a 10-to-60-second quick-start unit to cover short-term outages of the order of hours; and Class D, an uninterruptible non-break unit using stored energy to provide continuous power within specified voltage and frequency tolerances. History Uses/Implementations Many uses and implementations of auxiliary power are experimented with to increase its efficiency. One such experimentation was to find a better way to operate a diesel engine with fuel cell based auxiliary power units. The method of which is to separate hydrogen-rich gas from the diesel fuel to generate electricity separately in an auxiliary power unit. With this process, an effective reduction in emissions can be achieved by lowering the consumed volume of gas per hour. However, upon power demands reaching 60% a sharp decrease in performance occurs, which can be solved by using a diesel or kerosine fuel with a maximum CO concentration of 1.5%. There are a variety of other implementations of auxiliary power units in energy systems. This explains for how a significant portion of emissions come from commercial vehicles. Diesel engines operating within densely populated areas, running within an ineffective range in order to power their auxiliary systems, such as refrigeration, are contributors to a large portion of the emissions from automobiles. Using a model with a diesel powered four-stroke engine on a truck with 100% load capacity driving a combination of typical urban and city road cycles, emissions and auxiliary power demand were recorded. Then by using the calculated auxiliary power demand, a source was developed to support the demand for the auxiliary systems in the form of a PEM fuel cell. The end product of the PEM fuel cell was able to support the auxiliary systems of the truck using a maximum of 5 kW of power. This input was able to sustain the cooling chamber, cabin air-conditioning, radio unit, etc. The