Effect of small continuous loads on inverter and system efficiency

This paper presents the effects of inverter efficiency drop at part-load condition on system performance and cost. The goal is to create a stand-alone system with 95% availability that has a small continuous load and large intermittent load. The system is composed of photovoltaic (PV) panels, batteries, an inverter, charge controller, wiring, and loads. Incandescent lights are used to represent the small continuous load, and fluorescent lights are employed as the large intermittent load. The system performance is analyzed as a function of various parameters such as number of batteries, PV panels, and inverter efficiency. It is shown that having two inverters is beneficial to power small and large loads separately if the inverter efficiency drop at part-load condition is large. This avoids the inverter efficiency drop at part-load condition and lowers the system lifecycle cost.