Lifetime Evaluation of a Battery Storage System used for Residential Electricity Supply in East Africa

In this work, we have evaluated the lifetime of a Lithium-ion (Li-ion) battery, which is used for providing electricity for a residential home located in East Africa. The battery is recharged at least once per week from a PVpanel. The lifetime of the Li-ion battery was evaluated under different scenarios, where the battery-recharging interval, the load power profile, and the maximum and minimum allowed battery state-of-charge (SOC) were varied. Thus, 23 different study cases were considered. Furthermore, for this analysis, the monthly temperature profile for the city of Nairobi was used.
The battery lifetime can be related to the battery capacity fade, the battery resistance increase (i.e., power degradation), or to both. Nevertheless, in this work we have assumed that the capacity of the battery is the performance parameter, which limits the battery lifetime. For an accurate lifetime estimation, both calendar and cycle life of the batteries were considered by means of lifetime models, which were developed based on accelerated aging tests carried out on a lithium cobalt oxide-based battery
The inputs of the algorithm, which was used to estimate the Li-ion battery lifetime, were the battery temperature and the power profile. Because the mission profile corresponds to a period of one to seven days, it was continuously applied until the battery reached the EOL (i.e., 20% capacity fade). Furthermore, as it is well known, the battery degradation is a non-linear function of time / number of cycles. Thus, the available capacity was updated periodically, after each month of simulation.
For the considered battery scenarios, lifetime expectancy between 21 and 56 months were obtained. Furthermore, it was observed that the maximum and minimum allowed battery SOC interval and the battery recharging interval have a non-linear effect on the lifetime of the considered battery.