End of life estimation for storage systems used in photovoltaic residential installation

The availability of grid storage for photovoltaic residential installation can play an important role in both the scenarios of managing excess energy and of stabilizing transient frequency. Starting from these considerations, the estimation of battery lifetime is an essential issue in energy system planning, operation and maintenance. Major degradation mechanisms related to batteries determine an overall item aging: their effects determine a reduction of the battery capacity and an increase of the internal resistance of the cells. The degradation can be considered unacceptable when the capacity of the battery is below the 80% of the nominal one and when its State of Health (SOH) is considered 0%. This work presents an algorithm to manage in a satisfying economical way the storage battery system for residential photovoltaic plants. The novelty of this study is the addition of degradation mechanisms that unavoidably affects the battery, in an economical optimization, so that the consumer can exploit the best theoretical trade-off between minimum cash flow and maximization of the battery lifetime. In the proposed algorithm, degradation mechanisms are considered taking into account two aging typologies: cycle aging and calendar aging.