Integrating renewable energy resources into electrical distribution networks necessitates using battery energy storage systems (BESSs) to manage intermittent energy generation, enhance grid reliability, and prevent reverse power flow. Thus, this study focuses on the optimal sizing of BESS in electrical power distribution networks, considering, cost, grid reliability, and environmental impact. The adapted electrical power distribution network in this research has a 25 MVA/33 kV capacity with 7 MWp photovoltaic power plants. The variability of renewable energy sources and the ampacity limitations of the adapted electrical power network are analyzed first. After that, a linear optimization approach is applied to minimize the storage system's cost subject to a specific grid's reliability. In addition to that, a life cycle assessment approach that evaluates the environmental impacts of different BESS technologies is used to evaluate the options of BESSs. Results indicate that integrating an optimally sized BESS significantly improves grid reliability, reduces energy deficits, and lowers operational costs. Moreover, the environmental impact assessment reveals that Lithium Iron Phosphate batteries are the most environmentally friendly option due to their high cycle life and moderate efficiency. The study concludes that the optimal BESS size for the adapted network is 120 Ah/33 kV, with a loss of load probability of 1% and annual savings of $0.367 million.