Scenario-based techno-reliability optimization of an off-grid hybrid renewable energy system: A multi-city study framework

With the intrinsic volatile nature of renewable resources, it is necessary to evaluate the reliability aspect of renewable energy systems to withstand unexpected events in intensely loaded power systems. However, most of the studies mainly considered the loss of supply probability as a reliability criterion but neglected the effect of required operating reserve that is critical for the system's reliability under unexpected events. In this paper, a techno-reliability optimization framework is proposed to incorporate the impact of reliability constraints during the operation and planning phase of hybrid renewable energy systems. This multi-objective framework considers a scenario-based approach under different levels of peak load and load reserves that are further evaluated by a unified weightage index (techno-economic-reliability index) to find out the optimal reliability level while considering the trade-off between techno-economic and reliability indicators. As a case study, the proposed framework is implemented in multiple locations in Pakistan to investigate the correlation between system evaluation indicators and the variation of available resources for different system configurations. The results indicate that the load reserve-based scenario (52) is the most feasible operating reserve strategy to obtain the optimal system configuration in terms of techno-economic-reliability nexus. The sensitivity analysis of various system and economic evaluation indicators shows that the levelized cost of energy is more sensitive to the available site resources and discount rate. Moreover, the system reliability level has the least effect on the size of battery storage. This paper provides a concept of the micro-grid value proposition for the energy policymakers to select the appropriate multi-objective constraints while prioritizing the trade-off between techno-economic and reliability indicators.