Optimising mixed-portfolio hybrid Renewable systems with no or constrained grid connectivity

Abstract

We present a method to optimise a hybrid renewable energy system design under various grid constraints, from entirely off-grid to strongly interconnected. The optimisation procedure is a simplified downward gradient method, and the variable used as the objective function is the equivalent annual cost of the system installation and operation. The results show how a good interconnection provides the opportunity to use renewable energy technology as an income stream without a need for energy storage. A balance of energy storage and local backup generation emerges as the optimum if the grid is severely constrained or without grid connection. It is always a balance of storage and backup, as the storage is most cost effective to balance supply and demand over short time scales of less than a week while back-up generation is better able to meet longer periods of insufficient renewable generation. Another key results is that a combination of renewable technologies, PV and wind, is always better here than one technology alone.