Large-scale photovoltaic power plants have rapidly expanded due to the growing demand for sustainable energy alternatives. The techno-economic design and optimisation of a grid-connected photovoltaic plant is presented in this thesis, with an emphasis on cost-effectiveness and energy production maximisation. With a focus on the importance of renewables in reaching decarbonisation objectives, the study starts with an examination of Italian energy policies and climate goals. The basics of PV technology are then examined, including several module technologies, the properties of solar radiation, and how site selection affects system performance. System sizing, the choice of inverter and transformer, and an analysis of module voltage ranges and string topologies are all included in the engineering design phase.