All generation is provided by the solar electric array. Load autonomy during inclement periods is provided by energy stored in the battery and the solar array is sized to meet the load requirement for the month with the least sunshine. Stand-alone PV systems are designed to provide excess energy for the rest of the year, and may still be more cost effective than other generator technologies.
TEGs continuously consume fuel and require frequent maintenance.
For applications where the daily load is large or in areas where winter sunlight is scant, the PV and batteries required to maintain a site's entire electrical design load may render a stand-alone PV system too costly. In such cases a solar-hybrid system can help reduce the initial system cost while maintaining low operating costs and required liability. By integrating a back-up charging system into the design, the photovoltaic array can be sized so that its output is used by the load for most of the year. In a PV -generator set hybrid systems, the generator is allowed to operate only at its optimum level, so when the genset runs, it is producing power at its lowest possible cost per KWh. Hybrid systems of this sort allow the solar array and the battery bank to be reduced substantially.