In order to achieve full independence in power supply, many families have considered installing battery to store energy generated by their residential PV power devices but a study by Stanford University shows that investment returns for residential PV device with an auxiliary battery is 21% lower than that the same device without it.

The outcome results from analysis based on EROI (energy return on investment), the amount of usable energy (the exergy) delivered from a particular energy source to the amount of exergy used to obtain that energy source. The higher the EROI the higher the development value.

The study looked into the EROI of residential PV power devices in five U.S. states, finding that EROI of the devices dropped by over 20% after installation of batteries.

The research team blamed the phenomenon on increase in self-consumption, due to difference in energy loss during charging and discharging of battery. As a result, energy loss for consumption of power generated by residential PV power devices via an auxiliary battery is much higher than transmission of the power to grid. However, battery is still desirable, should residences don't have feed line for transmission of excess power to grid.

Moreover, from a macro perspective, installation of auxiliary batteries for residential PV power devices can enhance maneuverability and stability of overall power supply, as existing grids cannot accommodate influx of PV power generated by residential devices and utilities in short term. The research team also points to the need of continuing R&D on improving the output, charging/discharging efficiency, and life of batteries.

(Collaborative media: TechNews, first photo courtesy of pixabay)