Least cost planning for autonomous energy supply systems

TALCO (Technical And Least Cost Optimisation) is a new optimisation tool made to develop technical system designs for autonomous energy supply systems on the basis of a lifetime least cost calculation. TALCO is based on detailed technical models for all components used in autonomous energy supply systems. The models describe the electrical characteristics and the component ageing under operating conditions. Further on all economic parameters (investments, interest rates, maintenance, exchange of components, fuel) of the components are taken into account. Coupled with powerful optimisation algorithms the calculation of the optimum system design is possible. The result are minimum lifetime costs for a given energy demand at a specific location and under given boundary conditions like interest rates or a certain solar fraction. To get a basis for parameters on operating costs, maintenance and repair in autonomous energy supply systems 30 PV hybrid systems were analysed in detail. Data on these systems was collected over more than 120 years of accumulated operation time. Some results of this analysis will be presented within this paper. It turned out from the analysis of the real systems as well as from systematic studies with the least cost optimisation tool TALCO that the costs depend heavily on the boundary conditions (technical, usage and size, economical). But it is obvious from the studies that for systems with less than 15000 kWh annual energy consumption PV-hybrid systems are the most cost effective solution for most applications.