Study of optimization design criteria for stand-alone hybrid renewable power systems

Hybrid renewable power systems integrate two or more sources of energy, one of which is renewable, optionally a storage system and typically work in stand-alone mode. They are being considered more and more and we should increment their usage taking advantage of their positive benefits: free of charge resource availability, CO2 emissions reductions and subsidies. Dealing with their inconveniences: variability of renewable resources availability and cost acquisition, through the optimization of the design and the control of the system. The optimal design of hybrid renewable power systems is usually defined by economic criteria. But there are also technical and environmental criteria to be taken into account to improve decision-making. In this paper a discussion on different criteria will introduce the non-economical perspectives in addition to the economic criteria. A case study of a PV-Wind-Diesel-Battery system for a Telecommunication station in Catalonia is discussed. Availability of renewable energy sources is obtained with RETScreen and PVSyst. Analysis and simulations of various hybrid power systems have been done in HOMER resulting on a comparison of different scenarios. Optimal scenario taking into account the best results of all three types of criteria: economic, technical and environmental, is a trade-off of the economic optimum.