As data centers rapidly expand and pursue decarbonization goals, integrating on-site renewable energy systems and Battery Energy Storage Systems (BESS) is critical for reducing grid stress and minimizing renewable energy curtailment. This technical talk presents how PLEXOS, a leading power system modelling tool, can be used to design and optimize data center energy infrastructure through the integration of on-site renewable generation and Battery Energy Storage Systems (BESS). The session focuses on managing renewable energy curtailment, alleviating transmission congestion, and determining the optimal sizing and technology selection for both generation and storage assets. It can also touch on Islanding operation of data centres with RTC for investing and operations.