Correct sizing of a storage unit for a residential PV plant

In recent years the use of batteries in parallel to photovoltaic generators are often proposed to increase the self-consumption of residential plants reducing the losses related to energy transfer to the grid. For PV stand-alone plants, the use of storage systems is necessary to ensure the feedings of the loads during night-time and when the sun is not enough to cover the power demand. The choice of the optimal size of a storage unit to be coupled with a residential PV plant is not a trivial problem. Indeed, increasing the size implies a higher initial cost but also a greater lifetime of the battery pack. Moreover, the increase of the battery lifetime could allow to avoid a substitution of the battery pack reducing the operating costs along the plant lifetime. In this paper, a novel procedure to evaluate the optimal size of a battery coupled with a PV plant is applied to a residential unit taking into account aging phenomena of the battery that are influenced by their operating conditions and, consequently, by their size.