Evaluating the impact of adding energy storage on the performance of a hybrid power system

Hybrid power systems have the capability to incorporate significant renewable energy penetration for a small autonomous system while still maintaining reliable grid stability. While there are many papers covering the optimization of component size and dispatch strategy, far fewer papers contain experimental performance data from hybrid systems. Mercy Hospital in Bo, Sierra Leone is converting their power system into a photovoltaic (PV)–diesel hybrid system, thus providing an opportunity to examine the change in system performance before, during, and after the conversion. Due to the seasonal availability of electric power in Sierra Leone, two datasets representing two distinct load profiles are analyzed: Wet Season and Dry Season. The difference in generation efficiency, cost per kW h, generator runtime, and fuel consumption are calculated between a diesel-only generation baseline and the recorded hybrid system performance. The results indicated that the hybrid system significantly reduces operation costs; approximately 37% less during Dry Season and 64% reduction in the Wet Season than a diesel-only generator serving the same load.

Research highlights
► A photovoltaic–diesel hybrid power system is compared to a diesel-only system.
► The efficiency, cost, generator runtime, and fuel consumption are calculated.
► Overall efficiency of two systems is very similar.
► Reduced operation and maintenance costs for hybrid system gave bigger cost savings.
► The hybrid system is more advantageous in serving the same load.