Energy security is a complex issue that arises as one of the main concerns for most of the countries when regarding the future. In this sense, given the acknowledged lack of future-oriented studies in this field, this article performs a prospective analysis of the energy security of a national energy system. This is done through a novel methodological framework combining Life Cycle Assessment and Energy Systems Modelling. In particular, the recently proposed Renewable Energy Security Index (RESI) is endogenously integrated into a national power generation model in order to prospectively evaluate the energy security of the Spanish electricity production mix. This facilitates the exploration of alternative energy security scenarios based on RESI targets and focused on the penetration of renewables. The results show that, despite the relatively high renewable contribution reached in a business-as-usual scenario, a significantly higher and faster renewable penetration is attained when implementing RESI targets of 70%, 80% and 90% by 2030 in Spain. This is found to be associated with a large deployment of (onshore and offshore) wind power generation technology. Finally, a favourable life-cycle climate change performance is found when pursuing ambitious energy security targets.